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  • 1. Aabloo, A
    et al.
    Klintenberg, M
    Thomas, John Oswald
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Strukturkemi. strukturkemi.
    Molecular dynamics simulation of a polymer-inorganic interface.2000Inngår i: Electrochim.Acta, Vol. 45, s. 1425-Artikkel i tidsskrift (Fagfellevurdert)
  • 2. Aabloo, A.
    et al.
    Thomas, John Oswald
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Strukturkemi. strukturkemi.
    Molecular dynamics simulation of lithium ion mobility in a PEO surface.2001Inngår i: Solid State Ionics, Vol. 143, s. 83-Artikkel i tidsskrift (Fagfellevurdert)
  • 3.
    Aabloo, A
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Strukturkemi. strukturkemi.
    Thomas, John Oswald
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Strukturkemi. strukturkemi.
    Molecular dynamics simulation of Nd3+ ions in a crystalline PEO surface1998Inngår i: ELECTROCHIMICA ACTA, ISSN 0013-4686, Vol. 43, nr 10-11, s. 1361-1364Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Poly(ethylene oxide) based electrolytes are systems in which ionic salts are dissolved into an amorphous EO matrix. Potentials developed earlier to model crystalline and amorphous bulk PEO systems are here used for the MD simulation at 400 K of the behavi

  • 4.
    Aabloo, A
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Strukturkemi. strukturkemi.
    Thomas, John Oswald
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Strukturkemi. strukturkemi.
    Molecular dynamics simulations of a poly(ethylene oxide) surface1997Inngår i: POLYMER, ISSN 0032-3861, Vol. 38, nr 18, s. A47-A51Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Potentials developed earlier for crystalline and amorphous bulk PEO systems have been used for the MD simulation of a PEO surface model. The surface comprises the outer region of a 122 Angstrom-thick sheet of PEO in which the PEO, -(CH2-CH2-O)(n)- chains

  • 5.
    Aarik, J.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi. oorganisk kemi.
    Aidla, A.
    Mändar, H.
    Uustare, T.
    Schuisky, M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi. oorganisk kemi.
    Hårsta, A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi. oorganisk kemi.
    Atomic layer growth of epitaxial TiO2 thin films from TiCl4 and H2O on a-Al2O3 substrates2002Inngår i: J. Cryst. Growth, nr 242, s. 189-198Artikkel i tidsskrift (Fagfellevurdert)
  • 6.
    Aarik, J.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi. oorganisk kemi.
    Sundqvist, J.
    Aidla, A.
    Lu, J.
    Sajavaara, T.
    Kukli, K.
    Hårsta, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi. oorganisk kemi.
    Hafnium tetraiodide and oxygen as precursors for atomic layer deposition of hafnium oxide thin films2002Inngår i: Thin Solid Films, Vol. 418, s. 69-72Artikkel i tidsskrift (Fagfellevurdert)
  • 7.
    Abbas, Alaa
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
    Palladium-Catalysed Carbonylative Synthesis of Acylamidines2014Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
  • 8. Abbrent, S
    et al.
    Plestil, J
    Hlavata, D
    Lindgren, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Strukturkemi. strukturkemi.
    Tegenfeldt, Jörgen
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Strukturkemi. strukturkemi.
    Wendsjö, Å
    Crystallinity and morphology of PVdF-HFP based gel electrolytes.2001Inngår i: Polymer, Vol. 42, s. 1407-Artikkel i tidsskrift (Fagfellevurdert)
  • 9.
    Abbrent, Sabina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Kemiska institutionen.
    Lithium ion interactions in polymer gel electrolytes: Effect on structure, dynamics and morphology2000Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Polymer electrolytes are an essential part of the modern all-solid lithium battery. Several properties, such as mechanical and thermal stability, good ionic conductivity and compatibility with other materials used in the battery are necessary for a successful material.

    This thesis is focused on the ionic interactions in two electrolyte systems, based on a cross-linked polyethylene oxide (nona(ethylene oxide)dimethacrylate) or a fluorinated copolymer (polyvinylidene fluoride-hexafluoropropylene). Changes of thermal properties and morphology of and coordination in the electrolyte on addition of a lithium salt (LiTFSI) and different types and concentrations of solvents are studied. These properties are shown to control the ionic conductivity of the resulting material, influencing the conductivity mechanism.

    The presumably inert polyvinylidene fluoride is shown to undergo large structural changes, where polar conformations of the polymer backbone appear on salt addition, inducing a different crystalline phase. The lithium cation in the polyethylene oxide based electrolyte can coordinate either to the polymer chain or to the solvent. In for example systems containing propylene carbonate, the lithium ion binds more strongly to the polymer than to the solvent. This is in contrast to the systems with dimethyl sulphoxide where the ion prefers the solvent. This variation in coordination also strongly affects the mobility of the cation, reflected both in diffusion constants and in conductivity data.

    A combination of techniques was necessary to use for a deeper understanding of these complex materials. Coordination has been studied by FTIR and high resolution NMR, dynamics by NMR diffusion measurements and impedance spectroscopy, and morphology by diffraction techniques and DSC.

  • 10. Abdala, Paula M
    et al.
    Safonova, Olga V
    Wiker, Geir
    van Beek, Wouter
    Emerich, Herman
    van Bokhoven, Jeroen A
    Sá, Jacinto
    Szlachetko, Jakub
    Nachtegaal, Maarten
    Scientific opportunities for heterogeneous catalysis research at the SuperXAS and SNBL beam lines.2012Inngår i: Chimia (Basel), ISSN 0009-4293, Vol. 66, nr 9, s. 699-705Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this short review, we describe the complementary experimental capabilities for catalysis research at two beam lines available to the Swiss community, SuperXAS at SLS (Swiss Light Source, Villigen) and SNBL (Swiss Norwegian Beam lines) at ESRF (European Synchrotron Radiation Facility, Grenoble). Over the years, these two facilities have been developed to provide powerful techniques for structural studies under in situ and operando conditions. These techniques, X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and X-ray emission spectroscopy (XES) in combination with Raman or infrared spectroscopy provide new avenues for structure-performance studies of catalysts. Several exemplary studies are used to demonstrate the capability of these facilities.

  • 11.
    Abdelhamid, Hani Nasser
    et al.
    Stockholm Univ, Inorgan & Struct Chem, SE-10691 Stockholm, Sweden;Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden.
    Huang, Zhehao
    Stockholm Univ, Inorgan & Struct Chem, SE-10691 Stockholm, Sweden;Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden.
    El-Zohry, Ahmed
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Zheng, Haoquan
    Stockholm Univ, Inorgan & Struct Chem, SE-10691 Stockholm, Sweden;Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden.
    Zou, Xiaodong
    Stockholm Univ, Inorgan & Struct Chem, SE-10691 Stockholm, Sweden;Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden.
    A Fast and Scalable Approach for Synthesis of Hierarchical Porous Zeolitic Imidazolate Frameworks and One-Pot Encapsulation of Target Molecules2017Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 56, nr 15, s. 9139-9146Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A trimethylamine (TEA)-assisted synthesis approach that combines the preparation of hierarchical porous zeolitic, imidazolate framework ZIF-8, nanoparticles and one-pot encapsulation of target molecules is presented. Two dye molecules, rhodamine B (RhB) and methylene blue (MB), and one protein (bovine serum albumin, BSA) were, tested as the target molecules. The addition of TEA into the solution of zinc nitrate promoted the formation of ZnO nanocrystals, which rapidly transformed to ZIF-8 nanoparticles after the addition of the linker 2-methylimidazole (Hmim): Hierarchical porous dye@ZIF-8 nanoparticles with high crystallinity, large BET surface areas (1300-2500 m(2)/g), and large pore Volatiles (0.5-1.0 cm(3)/g) could be synthesized. The synthesis procedure was fast (down to 2 min) and scalable. The Hmim/Zn ratio could be greatly reduced (down to 2:1) compared to previously reported ones. The surface areas, and the mesopore size, structure, and density could be modified by changing the TEA or dye concentrations, or by postsynthetic treatment using reflux in methanol. This synthesis and one-pot encapsulation approach is simple and can be readily scaled Up. The photophysical properties such as lifetime and photostability of the dyes could be tuned via encapsulation. The lifetimes of the encapsulated dyes were increased by 3-27-fold for RhB@ZIF-8 and by 20-fold for MB@ZIF-8, compared to those of the corresponding free dyes. The synthesis approach is general, which was successfully applied for encapsulation of protein BSA. It could also be extended for the synthesis of hierarchical porous cobalt-based ZIP (dye@ZIF-67).

  • 12. Abdel-Hamid, Mohammed K
    et al.
    Macgregor, Kylie A
    Odell, Luke R
    Chau, Ngoc
    Mariana, Anna
    Whiting, Ainslie
    Robinson, Phillip J
    McCluskey, Adam
    1,8-Naphthalimide derivatives: new leads against dynamin I GTPase activity.2015Inngår i: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 13, nr 29Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fragment-based in silico screening against dynamin I (dynI) GTPase activity identified the 1,8-naphthalimide framework as a potential scaffold for the design of new inhibitors targeting the GTP binding pocket of dynI. Structure-based design, synthesis and subsequent optimization resulted in the development of a library of 1,8-naphthalimide derivatives, called the Naphthaladyn™ series, with compounds 23 and 29 being the most active (IC50 of 19.1 ± 0.3 and 18.5 ± 1.7 μM respectively). Compound 29 showed effective inhibition of clathrin-mediated endocytosis (IC50(CME) 66 μM). The results introduce 29 as an optimised GTP-competitive lead Naphthaladyn™ compound for the further development of naphthalimide-based dynI GTPase inhibitors.

  • 13.
    Abdellah, Mohamed
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. South Valley Univ, Qena Fac Sci, Dept Chem, Qena 83523, Egypt..
    El-Zohry, Ahmed M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Antila, Liisa J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Windle, Christopher D.
    Univ Cambridge, Dept Chem, Christian Doppler Lab Sustainable SynGas Chem, Lensfield Rd, Cambridge CB2 1EW, England..
    Reisner, Erwin
    Univ Cambridge, Dept Chem, Christian Doppler Lab Sustainable SynGas Chem, Lensfield Rd, Cambridge CB2 1EW, England..
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Time-Resolved IR Spectroscopy Reveals a. Mechanism with TiO2 as a Reversible Electron Acceptor in a TiO2-Re Catalyst System for CO2 Photoreduction2017Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 139, nr 3, s. 1226-1232Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Attaching the phosphonated molecular catalyst [(ReBr)-Br-I(bpy)-(CO)(3)](0) to the wide-bandgap semiconductor TiO2 strongly enhances the rate of visible-light-driven reduction of CO2 to CO in dimethylformamide with triethanolamine (TEOA) as sacrificial electron donor. Herein, we show by transient mid-IR spectroscopy that the mechanism of catalyst photoreduction is initiated by ultrafast electron injection into TiO2, followed by rapid (ps-ns) and sequential two-electron oxidation of TEOA that is coordinated to the Re center. The injected electrons can be stored in the conduction band of TiO2 on an ms-s time scale, and we propose that they lead to further reduction of the Re catalyst and completion of the catalytic cycle. Thus, the excited Re catalyst gives away one electron and would eventually get three electrons back. The function of an electron reservoir would represent a role for TiO2 in photocatalytic CO2 reduction that has previously not been considered. We propose that the increase in photocatalytic activity upon heterogenization of the catalyst to TiO2 is due to the slow charge recombination and the high oxidative power of the Re-II species after electron injection as compared to the excited MLCT state of the unbound Re catalyst or when immobilized on ZrO2, which results in a more efficient reaction with TEOA.

  • 14.
    Abdellah, Mohamed
    et al.
    Lund Univ, Div Chem Phys, Box 124, S-22100 Lund, Sweden.;Lund Univ, NanoLund, Box 124, S-22100 Lund, Sweden.;South Valley Univ, Qena Fac Sci, Dept Chem, Qena 83523, Egypt..
    Poulsen, Felipe
    Univ Copenhagen, Dept Chem, DK-2100 Copenhagen, Denmark..
    Zhu, Qiushi
    Lund Univ, Div Chem Phys, Box 124, S-22100 Lund, Sweden.;Lund Univ, NanoLund, Box 124, S-22100 Lund, Sweden..
    Zhu, Nan
    Tech Univ Denmark, Dept Chem, Kemitorvet Bldg 207, DK-2800 Lyngby, Denmark.;Dalian Univ Technol, Zhang Dayu Sch Chem, Dalian 116024, Peoples R China..
    Zidek, Karel
    Acad Sci Czech Republ, Inst Plasma Phys, Reg Ctr Special Opt & Optoelect Syst TOPTEC, Za Slovankou 1782-3, Prague 18200 8, Czech Republic..
    Chabera, Pavel
    Lund Univ, Div Chem Phys, Box 124, S-22100 Lund, Sweden.;Lund Univ, NanoLund, Box 124, S-22100 Lund, Sweden..
    Corti, Annamaria
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hansen, Thorsten
    Univ Copenhagen, Dept Chem, DK-2100 Copenhagen, Denmark..
    Chi, Qijin
    Tech Univ Denmark, Dept Chem, Kemitorvet Bldg 207, DK-2800 Lyngby, Denmark..
    Canton, Sophie E.
    DESY, Attosecond Sci Grp, Notkestr 85, D-22607 Hamburg, Germany.;ELI HU Nonprofit Ltd, ELI ALPS, Dugonics Ter 13, H-6720 Szeged, Hungary..
    Zheng, Kaibo
    Lund Univ, Div Chem Phys, Box 124, S-22100 Lund, Sweden.;Lund Univ, NanoLund, Box 124, S-22100 Lund, Sweden.;Qatar Univ, Coll Engn, Gas Proc Ctr, POB 2713, Doha, Qatar..
    Pullerits, Tonu
    Lund Univ, Div Chem Phys, Box 124, S-22100 Lund, Sweden.;Lund Univ, NanoLund, Box 124, S-22100 Lund, Sweden..
    Drastic difference between hole and electron injection through the gradient shell of CdxSeyZn1−xS1−y quantum dots2017Inngår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 9, nr 34, s. 12503-12508Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ultrafast fluorescence spectroscopy was used to investigate the hole injection in CdxSeyZn1-xS1-y gradient core-shell quantum dot (CSQD) sensitized p-type NiO photocathodes. A series of CSQDs with a wide range of shell thicknesses was studied. Complementary photoelectrochemical cell measurements were carried out to confirm that the hole injection from the active core through the gradient shell to NiO takes place. The hole injection from the valence band of the QDs to NiO depends much less on the shell thickness when compared to the corresponding electron injection to n-type semiconductor (ZnO). We simulate the charge carrier tunneling through the potential barrier due to the gradient shell by numerically solving the Schrodinger equation. The details of the band alignment determining the potential barrier are obtained from X-ray spectroscopy measurements. The observed drastic differences between the hole and electron injection are consistent with a model where the hole effective mass decreases, while the gradient shell thickness increases.

  • 15.
    Abdellah, Mohamed
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. South Valley Univ, Qena Fac Sci, Dept Chem, Qena 83523, Egypt.
    Zhang, Shihuai
    Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Wang, Mei
    Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Competitive Hole Transfer from CdSe Quantum Dots to Thiol Ligands in CdSe-Cobaloxime Sensitized NiO Films Used as Photocathodes for H-2 Evolution2017Inngår i: ACS Energy Letters, ISSN 2380-8195, Vol. 2, nr 11, s. 2576-2580Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Quantum dot (QD) sensitized NiO photocathodes rely on efficient photoinduced hole injection into the NiO valence band. A system of a mesoporous NiO film co-sensitized with CdSe QDs and a molecular proton reduction catalyst was studied. While successful electron transfer from the excited QDs to the catalyst is observed, most of the photogenerated holes are instead quenched very rapidly (ps) by hole trapping at the surface thiols of the capping agent used as linker molecules. We confirmed our conclusion by first using a thiol free capping agent and second varying the thiol concentration on the QD's surface. The later resulted in faster hole trapping as the thiol concentration increased. We suggest that this hole trapping by the linker limits the H-2 yield for this photocathode in a device.

  • 16.
    Abdelmoniem, Amr M.
    et al.
    Cairo Univ, Dept Chem, Fac Sci, Giza, Egypt.
    Elnagdi, Mohamed H.
    Cairo Univ, Giza, Egypt;Kuwait Univ, Safat, Kuwait.
    Elsehemy, Mohamed S.
    Cairo Univ, Dept Chem, Fac Pharm, Giza, Egypt.
    El-Seedi, Hesham R.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Farmakognosi. Menoufia Univ, Dept Chem, Fac Sci, Shibin Al Kawm 32512, Egypt.
    Abdelhamid, Ismail A.
    Cairo Univ, Dept Chem, Fac Sci, Giza, Egypt.
    Synthesis, Chemistry and Utilities of Diaminoazoles with Special Reference to 3,5-Diaminopyrazoles2018Inngår i: Current Organic Synthesis, ISSN 1570-1794, E-ISSN 1875-6271, Vol. 15, nr 4, s. 487-514Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Background: Although the chemistry of heteroaromatic monoamino azoles has been surveyed more than once in the last decade, the chemistry of the di- and triaminoazoles has not been reviewed. In this article we will survey the synthesis, chemistry and utility of the diaminoazoles. In this review, the chemistry of the diaminoazoles as well as their most important utilities will be surveyed. Objective: The review focuses on recent progress in diaminoazoles (i.e. diaminopyrazoles, diaminoimidazoles, diaminotriazoles and diaminothiazole) with especial references to diaminopyrazoles. The synthesis as well as pharmaceutical utilities are reported. There are several methods for synthesis of diaminopyrazoles. 3,5-Diaminopyrazole and its derivatives are prepared through the reaction of malononitrile or arylhydrazononitrile with hydrazine derivatives. 3,4-Diaminopyrazoles are prepared via nitration of 3-aminopyrazole with subsequent reduction of the produced compound. The diaminopyrazoles have several applications in cosmetic and pharmaceutical industries. They also have useful utilities as a constituent in oxidative hair dyes. Conclusion: We managed to report the common methods for the synthesis of diaminoazoles with especial reference to aminopyrazoles that are prepared through the reaction of malononitrile or hydrazononitriles with hydrazine derivatives. Some important applications that include pharmaceutical utilities such as hair dye constituents are reported.

  • 17. Abdi-Jalebi, Mojtaba
    et al.
    Andaji-Garmaroudi, Zahra
    Cacovich, Stefania
    Stavrakas, Camille
    Philippe, Bertrand
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Richter, Johannes M.
    Alsari, Mejd
    Booker, Edward P.
    Hutter, Eline M.
    Pearson, Andrew J.
    Lilliu, Samuele
    Savenije, Tom J.
    Rensmo, Håkan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Divitini, Giorgio
    Ducati, Caterina
    Friend, Richard H.
    Stranks, Samuel D.
    Maximizing and stabilizing luminescence from halide perovskites with potassium passivation2018Inngår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 555, s. 497-501Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability2 (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield—a quantity that must be maximized to obtain high efficiency—remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can approach the efficiency limits in tandem solar cells, coloured-light-emitting diodes and other optoelectronic applications.

  • 18.
    Abdi-Jalebi, Mojtaba
    et al.
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge, England.
    Pazoki, Meysam
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Philippe, Bertrand
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Dar, M. Ibrahim
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, Lausanne, Switzerland.
    Alsari, Mejd
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge, England.
    Sadhanala, Aditya
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge, England.
    Diyitini, Giorgio
    Univ Cambridge, Dept Mat Sci & Met, Charles Babbage Rd, Cambridge, England.
    Imani, Roghayeh
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Lilliu, Samuele
    Univ Sheffield, Dept Phys & Astron, Sheffield, S Yorkshire, England; UAE Ctr Crystallog, Dubai, U Arab Emirates.
    Kullgren, Jolla
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Rensmo, Håkan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Gratzel, Michael
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, Lausanne, Switzerland.
    Friend, Richard H.
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge, England.
    Dedoping of Lead Halide Perovskites Incorporating Monovalent Cations2018Inngår i: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, nr 7, s. 7301-7311Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report significant improvements in the optoelectronic properties of lead halide perovskites with the addition of monovalent ions with ionic radii close to Pb2+. We investigate the chemical distribution and electronic structure of solution processed CH3NH3PbI3 perovskite structures containing Na+, Cu+, and Ag+, which are lower valence metal ions than Pb2+ but have similar ionic radii. Synchrotron X-ray diffraction reveals a pronounced shift in the main perovskite peaks for the monovalent cation-based films, suggesting incorporation of these cations into the perovskite lattice as well as a preferential crystal growth in Ag+ containing perovskite structures. Furthermore, the synchrotron X-ray photoelectron measurements show a significant change in the valence band position for Cu- and Ag-doped films, although the perovskite bandgap remains the same, indicating a shift in the Fermi level position toward the middle of the bandgap. Such a shift infers that incorporation of these monovalent cations dedope the n-type perovskite films when formed without added cations. This dedoping effect leads to cleaner bandgaps as reflected by the lower energetic disorder in the monovalent cation-doped perovskite thin films as compared to pristine films. We also find that in contrast to Ag+ and Cu+, Na+ locates mainly at the grain boundaries and surfaces. Our theoretical calculations confirm the observed shifts in X-ray diffraction peaks and Fermi level as well as absence of intrabandgap states upon energetically favorable doping of perovskite lattice by the monovalent cations. We also model a significant change in the local structure, chemical bonding of metal-halide, and the electronic structure in the doped perovskites. In summary, our work highlights the local chemistry and influence of monovalent cation dopants on crystallization and the electronic structure in the doped perovskite thin films.

  • 19. Abdin, Amir
    et al.
    Feyzabi, Kaveh
    Hellman, Oskar
    Nordström, Henrietta
    Rasa, Dilman
    Thaung Tolförs, Gustav
    Öqvist, Per-Olof
    Methods to create compressive stress in high strength steel components2018Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Residual compressive stresses can be used to increase the lifetime of parts under cyclic stress as they negate the applied tensile stresses that cause crack initiation and propagation in the material. The goal of this project was to investigate methods to induce stresses, their advantages and disadvantages as well as depth and magnitude of induced stresses, and also to find methods of analyzing the induced residual stresses. This was done on behalf of Epiroc Drilling Tools AB in order for them to induce stresses on the insides of their long, narrow and hollow rods, where stress induction is difficult. Shot peening was used as a reference as that is the method currently in use by the company. The results show that the two most promising methods are cavitation peening and laser shock peening; two relatively new methods with large magnitudes and depth of induced stress as well as a great capability of inducing stresses on the hard-to-reach insides of the rods. Ultrasonic needle peening, ultrasonic shot peening as well as induction hardening, cryogenic treatment and friction stir processing were also investigated. Methods of analyzing the stresses include X-ray diffraction and slitting, hole drilling and ultrasonic methods.

  • 20. Abdissa, Negera
    et al.
    Fangfang, Pan
    Gruhonjic, Amra
    Gräfenstein, Jürgen
    Fitzpatrick, Paul A
    Landberg, Göran
    Rissanen, Kari
    Yenesew, Abiy
    Erdelyi, Mate
    Naphthalene Derivatives from the Roots of Pentas parvifolia and Pentas bussei.2016Inngår i: Journal of natural products (Print), ISSN 0163-3864, E-ISSN 1520-6025, Vol. 79, nr 9, s. 2181-2187Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The phytochemical investigation of the CH2Cl2/MeOH (1:1) extract of the roots of Pentas parvifolia led to the isolation of three new naphthalenes, parvinaphthols A (1), B (2), and C (3), two known anthraquinones, and five known naphthalene derivatives. Similar investigation of the roots of Pentas bussei afforded a new polycyclic naphthalene, busseihydroquinone E (4), a new 2,2'-binaphthralenyl-1,1'-dione, busseihydroquinone F (5), and five known naphthalenes. All purified metabolites were characterized by NMR and MS data analyses, whereas the absolute configurations of 3 and 4 were determined by single-crystal X-ray diffraction studies. The E-geometry of compound 5 was supported by DFT-based chemical shift calculations. Compounds 2-4 showed marginal cytotoxicity against the MDA-MB-231 human triple-negative breast cancer cell line with IC50 values ranging from 62.3 to 129.6 μM.

  • 21. Abdissa, Negera
    et al.
    Induli, Martha
    Fitzpatrick, Paul
    Alao, John Patrick
    Sunnerhagen, Per
    Landberg, Göran
    Yenesew, Abiy
    Erdelyi, Mate
    Cytotoxic quinones from the roots of Aloe dawei.2014Inngår i: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 19, nr 3, s. 3264-3273Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Seven naphthoquinones and nine anthraquinones were isolated from the roots of Aloe dawei by chromatographic separation. The purified metabolites were identified by NMR and MS analyses. Out of the sixteen quinones, 6-hydroxy-3,5-dimethoxy-2-methyl-1,4-naphthoquinone is a new compound. Two of the isolates, 5,8-dihydroxy-3-methoxy-2-methylnaphthalene-1,4-dione and 1-hydroxy-8-methoxy-3-methylanthraquinone showed high cytotoxic activity (IC₅₀ 1.15 and 4.85 µM) on MCF-7 breast cancer cells, whereas the others showed moderate to low cytotoxic activity against MDA-MB-231 (ER Negative) and MCF-7 (ER Positive) cancer cells.

  • 22. Abdurahman, Samir
    et al.
    Youssefi, Masoud
    Höglund, Stefan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Vahlne, Anders
    Characterization of the invariable residue 51 mutations of human immunodeficiency virus type 1 capsid protein on in vitro CA assembly and infectivity2007Inngår i: Retrovirology, ISSN 1742-4690, E-ISSN 1742-4690, Vol. 4, s. 69-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    BACKGROUND: The mature HIV-1 conical core formation proceeds through highly regulated protease cleavage of the Gag precursor, which ultimately leads to substantial rearrangements of the capsid (CAp24) molecule involving both inter- and intra-molecular contacts of the CAp24 molecules. In this aspect, Asp51 which is located in the N-terminal domain of HIV-1 CAp24 plays an important role by forming a salt-bridge with the free imino terminus Pro1 following proteolytic cleavage and liberation of the CAp24 protein from the Pr55Gag precursor. Thus, previous substitution mutation of Asp51 to alanine (D51A) has shown to be lethal and that this invariable residue was found essential for tube formation in vitro, virus replication and virus capsid formation. RESULTS: We extended the above investigation by introducing three different D51 substitution mutations (D51N, D51E, and D51Q) into both prokaryotic and eukaryotic expression systems and studied their effects on in vitro capsid assembly and virus infectivity. Two substitution mutations (D51E and D51N) had no substantial effect on in vitro capsid assembly, yet they impaired viral infectivity and particle production. In contrast, the D51Q mutant was defective both for in vitro capsid assembly and for virus replication in cell culture. CONCLUSION: These results show that substitutions of D51 with glutamate, glutamine, or asparagine, three amino acid residues that are structurally related to aspartate, could partially rescue both in vitro capsid assembly and intra-cellular CAp24 production but not replication of the virus in cultured cells.

  • 23.
    Aboye, Teshome L.
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för farmakognosi.
    Burman, Robert
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för farmakognosi.
    Göransson, Ulf
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för farmakognosi.
    Synthesis, Cyclization and Oxidative folding of backbone engineered Cyclotides2010Konferansepaper (Fagfellevurdert)
  • 24.
    Aboye, Teshome Leta
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för farmakognosi.
    Clark, Richard J.
    University of Queensland, Institute for Molecular Bioscience.
    Burman, Robert
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för farmakognosi.
    Craik, David J.
    University of Queensland, Institute for Molecular Bioscience.
    Göransson, Ulf
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för farmakognosi.
    Synthesis and Oxidative Folding of Cyclic Cystine Knot Peptides: Towards Backbone Engineering2010Inngår i: Peptides 2010: Tales of Peptides Proceedings of the Thirty-First European Peptide Symposium / [ed] Michal Lebl, Morten Meldal, Knud J. Jensen, Thomas Høeg-Jensen, European Peptide Society , 2010, s. 142-143Konferansepaper (Fagfellevurdert)
  • 25.
    Aboye, Teshome Leta
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för farmakognosi.
    Clark, Richard J.
    University of Queensland, Institute for Molecular Bioscience.
    Craik, David J.
    University of Queensland, Institute for Molecular Bioscience.
    Göransson, Ulf
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för farmakognosi.
    Synthesis and folding of the circular cystine knotted cyclotide cycloviolacin O22008Inngår i: Peptides 2008: Chemistry of Peptides in Life Science Technology and MedicineProceedings of The Thirtieth European Peptide Symposium / [ed] Hilkka Lankinen, The Finnish Peptide Society and The European Peptide Society , 2008, s. 280-281Konferansepaper (Fagfellevurdert)
  • 26.
    Abrahamsson, Malin L. A.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    Berglund Baudin, Helena
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    Tran, A.
    Philouze, C.
    Berg, K.
    Raymond-Johansson, Mary Katherine
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    Sun, L.
    Åkermark, B.
    Styring, S.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    Ruthenium-Manganese Complexes for Artificial Photosynthesis: Factors Controlling Intramolecular Electron Transfer and Excited State Quenching Reactions2002Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 41, nr 6, s. 1534-1544Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Continuing our work toward a system mimicking the electron-transfer steps from manganese to P(680)(+) in photosystem II (PS II), we report a series of ruthenium(II)-manganese(II) complexes that display intramolecular electron transfer from manganese(II) to photooxidized ruthenium(III). The electron-transfer rate constant (k(ET)) values span a large range, 1 x 10(5)-2 x 10(7) s(-1), and we have investigated different factors that are responsible for the variation. The reorganization energies determined experimentally (lambda = 1.5-2.0 eV) are larger than expected for solvent reorganization in complexes of similar size in polar solvents (typically lambda approximately 1.0 eV). This result indicates that the inner reorganization energy is relatively large and, consequently, that at moderate driving force values manganese complexes are not fast donors. Both the type of manganese ligand and the link between the two metals are shown to be of great importance to the electron-transfer rate. In contrast, we show that the quenching of the excited state of the ruthenium(II) moiety by manganese(II) in this series of complexes mainly depends on the distance between the metals. However, by synthetically modifying the sensitizer so that the lowest metal-to-ligand charge transfer state was localized on the nonbridging ruthenium(II) ligands, we could reduce the quenching rate constant in one complex by a factor of 700 without changing the bridging ligand. Still, the manganese(II)-ruthenium(III) electron-transfer rate constant was not reduced. Consequently, the modification resulted in a complex with very favorable properties.

  • 27.
    Abrahamsson, Maria
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström.
    Becker, Hans-Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Microsecond (MLCT)-M-3 excited state lifetimes in bis-tridentate Ru(II)-complexes: significant reductions of non-radiative rate constants2017Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, nr 39, s. 13314-13321Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper we report the photophysical properties of a series of bis-tridentate Ru-II-complexes, based on the dqp-ligand (dqp = 2,6-di(quinolin-8-yl) pyridine), which display several microsecond long excited state lifetimes for triplet metal-to-ligand charge transfer ((MLCT)-M-3) at room temperature. Temperature dependence of the excited state lifetimes for [Ru(dqp)(2)](2+) and [Ru(dqp)(ttpy)](2+) (ttpy = 4'-tolyl-2,2': 6', 2 ''-terpyridine) is reported and radiative and non-radiative rate constants for the whole series are reported and discussed. We can confirm previous assumptions that the near-octahedricity of the bis-dqp complexes dramatically slows down activated decay at room temperature, as compared to most other and less long-lived bis-tridentate RuII-complexes, such as [Ru(tpy)(2)](2+) with tau = 0.25 ns at room temperature (tpy = 2,2': 6', 2 ''-terpyridine). Moreover, the direct non-radiative decay to the ground state is comparatively slow for similar to 700 nm room-temperature emission when considering the energy-gap law. Analysis of the 77 K emission spectra suggests that this effect is not primarily due to smaller excited state distortion than that for comparable complexes. Instead, an analysis of the photophysical parameters suggests a weaker singlet-triplet mixing in the MLCT state, which slows down both radiative and non-radiative decay.

  • 28.
    Abrahamsson, Maria
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Kemisk fysik.
    Becker, Hans-Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Kemisk fysik.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Kemisk fysik.
    Bonnefous, Celine
    Chamchoumis, Charles
    Thummel, Randolph
    Six-membered Ring Chelate Complexes of Ru(II): Structural and photophysical effects2007Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 46, nr 24, s. 10354-10364Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structural and photophysical properties of Ru(II)−polypyridyl complexes with five- and six-membered chelate rings were studied for two bis-tridentate and two tris-bidentate complexes. The photophysical effect of introducing a six-membered chelate ring is most pronounced for the tridentate complex, leading to a room-temperature excited-state lifetime of 810 ns, a substantial increase from 180 ns for the five-membered chelate ring model complex. Contrasting this, the effect is the opposite in tris-bidentate complexes, in which the lifetime decreases from 430 ns to around 1 ns in going from a five-membered to six-membered chelate ring. All of the complexes were studied spectroscopically at both 80 K and ambient temperatures, and the temperature dependence of the excited-state lifetime was investigated for both of the bis-tridentate complexes. The main reason for the long excited-state lifetime in the six-membered chelate ring bis-tridentate complex was found to be a strong retardation of the activated decay via metal-centered states, largely due to an increased ligand field splitting due to the complex having a more-octahedral geometry.

  • 29.
    Abrahamsson, Maria
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Kemisk fysik.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap, Kemisk fysik.
    Tocher, Derek
    Nag, Samik
    Datta, Dipankar
    Modulation of the lowest metal-to-ligand charge-transfer state in [Ru(bpy)(2)(N-N)](2+) systems by changing the N-N from hydrazone to azine: Photophysical Consequences2006Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 45, nr 23, s. 9580-9586Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two Ru( II) complexes, [ Ru( bpy) L-2]( ClO4) 2 ( 1) and [ Ru( bpy)(2)L']( BF4) 2 ( 2), where bpy is 2,2'-bipyridine, L is diacetyl dihydrazone, and L' 1: 2 is the condensate of L and acetone, are synthesized. From X-ray crystal structures, both are found to contain distorted octahedral RuN62+ cores. NMR spectra show that the cations in 1 and 2 possess a C-2 axis in solution. They display the expected metal-to-ligand charge transfer ( (MLCT)-M-1) band in the 400 - 500 nm region. Complex 1 is nonemissive at room temperature in solution as well as at 80 K. In contrast, complex 2 gives rise to an appreciable emission upon excitation at 440 nm. The room-temperature emission is centered at 730 nm ( lambda(max)(em)) with a quantum yield ( em) of 0.002 and a lifetime ( tau(em)) of 42 ns in an air-equilibrated methanol - ethanol solution. At 80 K, Phi(em) = 0.007 and tau(em)= 178 ns, with a lambda(max)(em) of 690 nm, which is close to the 0 - 0 transition, indicating an (MLCT)-M-3 excited-state energy of 1.80 eV. The radiative rate constant ( 5 x 10(4) s(-1)) at room temperature and 80 K is almost temperature independent. From spectroelectrochemistry, it is found that bpy is easiest to reduce in 2 and that L is easiest in 1. The implications of this are that in 2 the lowest (MLCT)-M-3 state is localized on a bpy ligand and in 1 it is localized on L. Transient absorption results also support these assignments. As a consequence, even though 2 shows a fairly strong and long-lived emission from a Ru( II) -> bpy CT state, the Ru( II) -> L CT state in 1 shows no detectable emission even at 80 K.

  • 30.
    Abrahamsson, Maria
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Acceleratormasspektrometrigruppen. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Jäger, Michael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Kumar, Rohan J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Österman, Tomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kvantkemi.
    Persson, Petter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kvantkemi.
    Becker, Hans-Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Johansson, Olof
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kvantkemi.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Bistridentate Ruthenium(II)polypyridyl-Type Complexes with Microsecond 3MLCT State Lifetimes: Sensitizers for Rod-Like Molecular Arrays2008Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, nr 46, s. 15533-15542Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of bistridentate ruthenium(II) polypyridyl-type complexes based on the novel 2,6-di(quinolin-8-yl)pyridine (dqp) ligand have been synthesized and their photophysical properties have been studied. The complexes are amenable to substitution in the 4-position of the central pyridine with conserved quasi-C2v symmetry, which allows for extension to isomer-free, rod-like molecular arrays for vectorial control of electron and energy transfer. DFT calculations performed on the parent [Ru(dqp) 2](2+) complex (1) predicted a more octahedral structure than in the typical bistridentate complex [Ru(tpy)2](2+) (tpy is 2,2':6',2"-terpyridine) thanks to the larger ligand bite angle, which was confirmed by X-ray crystallography. A strong visible absorption band, with a maximum at 491 nm was assigned to a metal-to-ligand charge transfer (MLCT) transition, based on time-dependent DFT calculations. 1 shows room temperature emission (Phi = 0.02) from its lowest excited ((3)MLCT) state that has a very long lifetime (tau = 3 micros). The long lifetime is due to a stronger ligand field, because of the more octahedral structure, which makes the often dominant activated decay via short-lived metal-centered states insignificant also at elevated temperatures. A series of complexes based on dqp with electron donating and/or accepting substituents in the 4-position of the pyridine was prepared and the properties were compared to those of 1. An unprecedented (3)MLCT state lifetime of 5.5 micros was demonstrated for the homoleptic complex based on dqpCO2Et. The favorable photosensitizer properties of 1, such as a high extinction coefficient, high excited-state energy and long lifetime, and tunable redox potentials, are maintained upon substitution. In addition, the parent complex 1 is shown to be remarkably photostable and displays a high reactivity in light-induced electron and energy transfer reactions with typical energy and electron acceptors and donors: methylviologen, tetrathiofulvalene, and 9,10-diphenylanthracene. This new class of complexes constitutes a promising starting point for the construction of linear, rod-like molecular arrays for photosensitized reactions and applications in artificial photosynthesis and molecular electronics.

  • 31.
    Abrahamsson, Maria
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Acceleratormasspektrometrigruppen. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Jäger, Michael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Österman, Tomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kvantkemi.
    Eriksson, Lars
    Persson, Petter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kvantkemi.
    Becker, Hans-Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Johansson, Olof
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    A 3.0 mu s room temperature excited state lifetime of a bistridentate Ru-II-polypyridine complex for rod-like molecular arrays2006Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 128, nr 39, s. 12616-12617Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A bistridentate RuII-polypyridine complex [Ru(bqp)2]2+ (bqp = 2,6-bis(8'-quinolinyl)pyridine) has been prepared, which has a coordination geometry much closer to a perfect octahedron than the typical Ru(terpyridine)2-type complex. Thus, the complex displays a 3.0 mus lifetime of the lowest excited metal-to-ligand charge transfer (3MLCT) state at room temperature. This is, to the best of our knowledge, the longest MLCT state lifetime reported for a RuII-polypyridyl complex at room temperature. The structure allows for the future construction of rod-like, isomer-free molecular arrays by substitution of donor and acceptor moieties on the central pyridine units. This makes it a promising photosensitizer for applications in molecular devices for artificial photosynthesis and molecular electronics.

  • 32.
    Abrahamsson, Maria
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Lundqvist, Maria
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kvantkemi.
    Wolpher, Henriette
    Johansson, Olof
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Eriksson, Lars
    Bergquist, Jonas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Analytisk kemi.
    Rasmussen, Torben
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Becker, Hans-Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fotokemi och molekylärvetenskap.
    Norrby, Per-Ola
    Åkermark, Björn
    Persson, Petter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kvantkemi.
    Steric influence on the excited-state lifetimes of ruthenium complexes with bipyridyl-alkanylene-pyridyl ligands.2008Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 47, nr 9, s. 3540-3548Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structural effect on the metal-to-ligand charge transfer (MLCT) excited-state lifetime has been investigated in bis-tridentate Ru(II)-polypyridyl complexes based on the terpyridine-like ligands [6-(2,2'-bipyridyl)](2-pyridyl)methane (1) and 2-[6-(2,2'-bipyridyl)]-2-(2-pyridyl)propane (2). A homoleptic ([Ru(2)(2)](2+)) and a heteroleptic complex ([Ru(ttpy)(2)](2+)) based on the new ligand 2 have been prepared and their photophysical and structural properties studied experimentally and theoretically and compared to the results for the previously reported [Ru(1)(2)](2+). The excited-state lifetime of the homoleptic Ru-II complex with the isopropylene-bridged ligand 2 was found to be 50 times shorter than that of the corresponding homoleptic Ru-II complex of ligand 1, containing a methylene bridge. A comparison of the ground-state geometries of the two homoleptic complexes shows that steric interactions involving the isopropylene bridges make the coordination to the central Ru-II ion less octahedral in [Ru(2)(2)](2+) than in [Ru(1)(2))(2+). Calculations indicate that the structural differences in these complexes influence their ligand field splittings as well as the relative stabilities of the triplet metal-to-ligand charge transfer ((MLCT)-M-3) and metal-centered ((MC)-M-3) excited states. The large difference in measured excited-state lifetimes for the two homoleptic Ru-II complexes is attributed to a strong influence of steric interactions on the ligand field strength, which in turn affects the activation barriers for thermal conversion from (MLCT)-M-3 states to short-lived (MC)-M-3 states.

  • 33.
    Abrahamsson, Maria
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Acceleratormasspektrometrigruppen. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    Wolpher, Henriette
    Johansson, Olof
    Larsson, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    Kritikos, Mikael
    Eriksson, Lars
    Norrby, Per-Ola
    Bergquist, Jonas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Kemiska institutionen, Avdelningen för analytisk kemi.
    Sun, Licheng
    Åkermark, Björn
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    A New Strategy for the Improvement of Photophysical Properties in Ruthenium(II) Polypyridyl Complexes: Synthesis and Photophysical and Electrochemical Characterization of Six Mononuclear Ruthenium(II) Bisterpyridine-Type Complexes2005Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 44, nr 9, s. 3215-3225Artikkel i tidsskrift (Fagfellevurdert)
  • 34.
    Abramsson, Mia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
    Production and characterization of Acetylcholine Binding Protein2018Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
  • 35. Abu-samha, M.
    et al.
    Børve, K. J.
    Harnes, J.
    Bergersen, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    What Can C1s Photoelectron Spectroscopy Tell about Structure and Bonding in Clusters of Methanol and Methyl Chloride?2007Inngår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 111, nr 37, s. 8903-8909Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Single-component clusters of methanol and methyl chloride have been produced by adiabatic expansion, and their carbon Is photoelectron spectra were recorded using synchrotron radiation and a high-resolution electron analyzer. The experimental spectra are interpreted by means of theoretical models based on molecular dynamics simulations. The data are used to explore to what extent core-level photoelectron spectra may provide information on the bonding mechanism and the geometric structure of clusters of polar molecules. The results indicate that the cluster-to-monomer shift in ionization energy and also the width of the cluster peak may be used to distinguish between hydrogen bonding and weaker electrostatic interactions. Moreover, the larger width of the cluster peak in methanol clusters as compared to methyl chloride clusters is partly due to the structured surface of methanol clusters. Theoretical modeling greatly facilitates the analysis of core-level photoelectron spectra of molecular clusters.

  • 36. Abuzooda, Thana
    et al.
    Amini, Ahmad
    Swedish Drug Agency,751 03 Uppsala, Sweden.
    Abdel-Rehim, Mohamed
    Graphite-based microextraction by packed sorbent for online extraction of β-blockers from human plasma samples2015Inngår i: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 992, s. 86-90Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work a new graphitic material (Carbon-XCOS) was used as a sorbent for microextraction by packed sorbent (MEPS). The β-blockers metoprolol and acebutolol in plasma samples were extracted and detected online using Carbon-MEPS syringe and liquid chromatography and tandem mass spectrometry (LC-MS/MS). Factors affecting the MEPS performance such as conditioning, washing and elution solutions were investigated. The validation of the bioanalytical method was performed using human plasma. The standard curve ranged from 10 to 2000nM and the lower limit of quantification (LLOQ) was set to 10nM. The method validation showed good accuracy and precision for the quality control (QC) samples at three concentration levels (30, 800 and 1600nM). The accuracy values of the QC samples were in the range of 86-108% (n=18). The precision values of intra- and inter-day for QC samples ranged from 4.4% to 14.4% (RSD) for the both studied analytes. The coefficient of determination (R(2)) values were ≥0.999 (n=3).

  • 37.
    Acharya, P
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Chattopadhyaya, J
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för bioorganisk kemi.
    The Hydrogen Bonding and Hydration of 2'-OH in Adenosine and Adenosine 3'-ethylphosphate.2002Inngår i: J. Org. Chem., Vol. 67, s. 1852-1865Artikkel i tidsskrift (Fagfellevurdert)
  • 38.
    Acharya, Parag
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Studies on the Non-covalent Interactions (Stereoelectronics, Stacking and Hydrogen Bonding) in the Self-assembly of DNA and RNA2003Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis is based on ten publications (Papers I-X). The phosphodiester backbone makes DNA or RNA to behave as polyelectrolyte, the pentose sugar gives the flexibility, and the aglycones promote the self-assembly or the ligand-binding process. The hydrogen bonding, stacking, stereoelectronics and hydration are few of the important non-covalent forces dictating the self-assembly of DNA/RNA. The pH-dependent thermodynamics clearly show (Papers I and II) that a change of the electronic character of aglycone modulates the conformation of the sugar moiety by the tunable interplay of stereoelectronic anomeric and gauche effects, which are further transmitted to steer the sugar-phosphate backbone conformation in a cooperative manner. 3'-anthraniloyl adenosine (a mimic of 3'-teminal CCAOH of the aminoacyl-tRNAPhe) binds to EF-Tu*GTP in preference over 2'-anthraniloyl adenosine, thereby showing (Paper III) that the 2’-endo sugar conformation is a more suitable mimic of the transition state geometry than the 3’-endo conformation in discriminating between correctly and incorrectly charged aminoacyl-tRNAPhe by EF-Tu during protein synthesis. The presence of 2'-OH in RNA distinguishes it from DNA both functionally as well as structurally. This work (Paper IV) provides straightforward NMR evidence to show that the 2'-OH is intramolecularly hydrogen bonded with the vicinal 3'-oxygen, and the exposure of the 3'-phosphate of the ribonucleotides to the bulk water determines the availability of the bound water around the vicinal 2'-OH, which then can play various functional role through inter- or intramolecular interactions. The pH-dependent 1H NMR study with nicotinamide derivatives demonstrates (Paper V) that the cascade of intramolecular cation (pyridinium)-π(phenyl)-CH(methyl) interaction in edge-to-face geometry is responsible for perturbing the pKa of the pyridine-nitrogen as well as for the modulation of the aromatic character of the neighboring phenyl moiety, which is also supported by the T1 relaxation studies and ab initio calculations. It has been found (Papers VI-IX) that the variable intramolecular electrostatic interaction between electronically coupled nearest neighbor nucleobases (steered by their respective microenvironments) can modulate their respective pseudoaromatic characters. The net result of this pseudoaromatic cross-modulation is the creation of a unique set of aglycones in an oligo or polynucleotide, whose physico-chemical properties are completely dependent upon the propensity and geometry of the nearest neighbor interactions (extended genetic code). The propagation of the interplay of these electrostatic interactions across the hexameric ssDNA chain is considerably less favoured (effectively up to the fourth nucleobase) compared to that of the isosequential ssRNA (up to the sixth nucleobase). The dissection of the relative strength of basepairing and stacking in a duplex shows that stability of DNA-DNA duplex weakens over the corresponding RNA-RNA duplexes with the increasing content of A-T/U base pairs, while the strength of stacking of A-T rich DNA-DNA duplex increases in comparison with A-U rich sequence in RNA-RNA duplexes (Paper X).

    Delarbeid
    1. The Transmission of the Electronic Character of Guanin-9-yl Drives the Sugar-phosphate Backbone Torsions in Guanosine 3',5'-bisphosphate.
    Åpne denne publikasjonen i ny fane eller vindu >>The Transmission of the Electronic Character of Guanin-9-yl Drives the Sugar-phosphate Backbone Torsions in Guanosine 3',5'-bisphosphate.
    Vise andre…
    1999 Inngår i: Angew. Chem. Int. Ed., Vol. 38, nr 24, s. 3645-3650Artikkel i tidsskrift (Fagfellevurdert) Published
    Identifikatorer
    urn:nbn:se:uu:diva-91143 (URN)
    Tilgjengelig fra: 2003-11-26 Laget: 2003-11-26bibliografisk kontrollert
    2. The RNA Molecular Wire: The pH-Dependent Change in Electronic Character of Adenine-9-yl is Transmitted to Drive the Sugar-Phosphate Backbone Torsions in Adenosine 3', 5'-bisphosphate
    Åpne denne publikasjonen i ny fane eller vindu >>The RNA Molecular Wire: The pH-Dependent Change in Electronic Character of Adenine-9-yl is Transmitted to Drive the Sugar-Phosphate Backbone Torsions in Adenosine 3', 5'-bisphosphate
    Vise andre…
    2000 Inngår i: J. Phys. Org. Chem., Vol. 13, s. 300-305Artikkel i tidsskrift (Fagfellevurdert) Published
    Identifikatorer
    urn:nbn:se:uu:diva-91144 (URN)
    Tilgjengelig fra: 2003-11-26 Laget: 2003-11-26bibliografisk kontrollert
    3. The Strength of the 3'-gauche effect Dictates the Structure of 3'-anthraniloyladenosine and its 5'-phosphate, Two Analogues of the 3'-end of Aminoacyl tRNA
    Åpne denne publikasjonen i ny fane eller vindu >>The Strength of the 3'-gauche effect Dictates the Structure of 3'-anthraniloyladenosine and its 5'-phosphate, Two Analogues of the 3'-end of Aminoacyl tRNA
    Vise andre…
    1999 Inngår i: J. Chem. Soc. Perkin 2, s. 1531-1536Artikkel i tidsskrift (Fagfellevurdert) Published
    Identifikatorer
    urn:nbn:se:uu:diva-91145 (URN)
    Tilgjengelig fra: 2003-11-26 Laget: 2003-11-26bibliografisk kontrollert
    4. The Hydrogen Bonding and Hydration of 2'-OH in Adenosine and Adenosine 3'-ethylphosphate
    Åpne denne publikasjonen i ny fane eller vindu >>The Hydrogen Bonding and Hydration of 2'-OH in Adenosine and Adenosine 3'-ethylphosphate
    2002 Inngår i: J. Org. Chem., Vol. 67, nr 6, s. 1852-1865Artikkel i tidsskrift (Fagfellevurdert) Published
    Identifikatorer
    urn:nbn:se:uu:diva-91146 (URN)
    Tilgjengelig fra: 2003-11-26 Laget: 2003-11-26bibliografisk kontrollert
    5. A Repertoire of Pyridinium-Phenyl-Methyl Cross-Talk through a Cascade of Intramolecular Electrostatic Interactions
    Åpne denne publikasjonen i ny fane eller vindu >>A Repertoire of Pyridinium-Phenyl-Methyl Cross-Talk through a Cascade of Intramolecular Electrostatic Interactions
    Vise andre…
    2003 Inngår i: J. Org. Chem., Vol. 68, nr 4, s. 1529-1538Artikkel i tidsskrift (Fagfellevurdert) Published
    Identifikatorer
    urn:nbn:se:uu:diva-91147 (URN)
    Tilgjengelig fra: 2003-11-26 Laget: 2003-11-26bibliografisk kontrollert
    6. Cross-Modulation of Physicochemical Character of Aglycones in Dinucleoside (3'→5') monophosphates by the Nearest Neighbor Interaction in the Stacked State
    Åpne denne publikasjonen i ny fane eller vindu >>Cross-Modulation of Physicochemical Character of Aglycones in Dinucleoside (3'→5') monophosphates by the Nearest Neighbor Interaction in the Stacked State
    2002 Inngår i: J. Am. Chem. Soc., Vol. 124, nr 46, s. 13722-13730Artikkel i tidsskrift (Fagfellevurdert) Published
    Identifikatorer
    urn:nbn:se:uu:diva-91148 (URN)
    Tilgjengelig fra: 2003-11-26 Laget: 2003-11-26bibliografisk kontrollert
    7. Tandem Electrostatic Effect From the First to the Third Aglycon in the Trimeric RNA Owing to the Nearest-neighbor Stacking
    Åpne denne publikasjonen i ny fane eller vindu >>Tandem Electrostatic Effect From the First to the Third Aglycon in the Trimeric RNA Owing to the Nearest-neighbor Stacking
    2003 Inngår i: J. Am. Chem. Soc., Vol. 125, nr 8, s. 2094-2100Artikkel i tidsskrift (Fagfellevurdert) Published
    Identifikatorer
    urn:nbn:se:uu:diva-91149 (URN)
    Tilgjengelig fra: 2003-11-26 Laget: 2003-11-26bibliografisk kontrollert
    8. Cross-Modulation of the pKa of Nucleobases in a Single-Stranded Hexameric-RNA Due to Tandem Electrostatic Nearest-Neighbor Interactions
    Åpne denne publikasjonen i ny fane eller vindu >>Cross-Modulation of the pKa of Nucleobases in a Single-Stranded Hexameric-RNA Due to Tandem Electrostatic Nearest-Neighbor Interactions
    Vise andre…
    2003 (engelsk)Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 125, nr 33, s. 9948-9961Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The pH titration studies (pH 6.7-12.1) in a series of dimeric, trimeric, tetrameric, pentameric, and hexameric oligo-RNA molecules [GpA (2a), GpC (3a), GpApC (5), GpA(1)pA(2)pC (6), GpA(1)pA(2)pA(3)pC (7), GpA(1)pA(2)pA(3)pA(4)pC (8)] have shown that the pK(a) of N(1)-H of 9-guaninyl could be measured not only from its own deltaH8G, but also from the aromatic marker protons of other constituent nucleobases. The relative chemical shift differences [Deltadelta((N)(-)(D))] between the protons in various nucleotide residues in the oligo-RNAs at the neutral (N) and deprotonated (D) states of the guanine moiety show that the generation of the 5'-(9-guanylate ion) in oligo-RNAs 2-8 reduces the stability of the stacked helical RNA conformation owing to the destabilizing anion(G(-))-pi/dipole(Im(delta)(-)) interaction. This destabilizing effect in the deprotonated RNA is, however, opposed by the electrostatically attractive atom-pisigma (major) as well as the anion(G(-))-pi/dipole(Py(delta)(+)) (minor) interactions. Our studies have demonstrated that the electrostatically repulsive anion(G(-))-pi/dipole(Im(delta)(-)) interaction propagates from the first to the third nucleobase quite strongly in the oligo-RNAs 6-8, causing destacking of the helix, and then its effect is gradually reduced, although it is clearly NMR detectable along the RNA chain. Thus, such specific generation of a charge at a single nucleobase moiety allows us to explore the relative strength of stacking within a single-stranded helix. The pK(a) of 5'-Gp residue from its own deltaH8G in the hexameric RNA 8 is found to be 9.76 +/- 0.01; it, however, varies from 9.65 +/- 0.01 to 10.5 +/- 0.07 along the RNA chain as measured from the other marker protons (H2, H8, H5, and H6) of 9-adeninyl and 1-cytosinyl residues. This nucleobase-dependent modulation of pK(a)s (DeltapK(a) +/- 0.9) of 9-guaninyl obtained from other nucleobases in the hexameric RNA 8 represents a difference of ca. 5.1 kJ mol(-)(1), which has been attributed to the variable strength of electrostatic interactions between the electron densities of the involved atoms in the offset stacked nucleobases as well as with that of the phosphates. The chemical implication of this variable pK(a) for guanin-9-yl deprotonation as obtained from all other marker protons of each nucleotide residue within a ssRNA molecule is that it enables us to experimentally understand the variation of the electronic microenvironment around each constituent nucleobase along the RNA chain in a stepwise manner with very high accuracy without having to make any assumption. This means that the pseudoaromaticity of neighboring 9-adeninyl and next-neighbor nucleobases within a polyanionic sugar-phosphate backbone of a ssRNA can vary from one case to another due to cross-modulation of an electronically coupled pi system by a neighboring nucleobase. This modulation may depend on the sequence context, spatial proximity of the negatively charged phosphates, as well as whether the offset stacking is ON or OFF. The net outcome of this electrostatic interaction between the neighbors is creation of new sequence-dependent hybrid nucleobases in an oligo- or polynucleotide whose properties are unlike the monomeric counterpart, which may have considerable biological implications.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-91150 (URN)10.1021/ja034651h (DOI)12914458 (PubMedID)
    Tilgjengelig fra: 2003-11-26 Laget: 2003-11-26 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    9. The Nucleobases in Single-stranded DNA are Better Stacked and Yet Their Pseudoaromatic Characters are More Poorly Cross-modulated Than in the RNA Counterparts Due to Variable Tandem Nearest-neighbour Electrostatic Interactions
    Åpne denne publikasjonen i ny fane eller vindu >>The Nucleobases in Single-stranded DNA are Better Stacked and Yet Their Pseudoaromatic Characters are More Poorly Cross-modulated Than in the RNA Counterparts Due to Variable Tandem Nearest-neighbour Electrostatic Interactions
    Vise andre…
    Inngår i: J. Am. Chem. Soc.Artikkel i tidsskrift (Fagfellevurdert) Submitted
    Identifikatorer
    urn:nbn:se:uu:diva-91151 (URN)
    Tilgjengelig fra: 2003-11-26 Laget: 2003-11-26bibliografisk kontrollert
    10. Measurement of nucleobase pKa values in model mononucleotides shows RNA-RNA duplexes to be more stable than DNA-DNA duplexes
    Åpne denne publikasjonen i ny fane eller vindu >>Measurement of nucleobase pKa values in model mononucleotides shows RNA-RNA duplexes to be more stable than DNA-DNA duplexes
    Vise andre…
    2004 (engelsk)Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 126, nr 9, s. 2862-2869Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    To understand why the RNA-RNA duplexes in general has a higher thermodynamic stability over the corresponding DNA-DNA duplexes, we have measured the pK(a) values of both nucleoside 3',5'-bis-ethyl phosphates [Etp(d/rN)pEt] and nucleoside 3'-ethyl phosphates [(d/rN)pEt] (N = A, G, C, or T/U), modeling as donors and acceptors of base pairs in duplexes. While the 3',5'-bis-phosphates, Etp(d/rN)pEt, mimic the internucleotidic monomeric units of DNA and RNA, in which the stacking contribution is completely absent, the 3'-ethyl phosphates, (d/rN)pEt, mimic the nucleotide at the 5'-end. The pK(a) values of the nucleobase in each of these model nucleoside phosphates have been determined with low pK(a) error (sigma = +/-0.01 to 0.02) by (1)H NMR (at 500 MHz) with 20-33 different pH measurements for each compound. This study has led us to show the following: (1) All monomeric DNA nucleobases are more basic than the corresponding RNA nucleobases in their respective Etp(d/rN)pEt and (d/rN)pEt. (2) The pK(a) values of the monomeric nucleotide blocks as well as Delta pK(a) values between the donor and acceptor can be used to understand the relative base-pairing strength in the oligomeric duplexes in the RNA and DNA series. (3) The Delta G*(pKa) of the donor and acceptor of the base pair in duplexes enables a qualitative dissection of the relative strength of the base-pairing and stacking in the RNA-RNA over the DNA-DNA duplexes. (4) It is also found that the relative contribution of base-pairing strength and nucleobase stacking in RNA-RNA over DNA-DNA is mutually compensating as the % A-T/U content increases or decreases. This interdependency of stacking and hydrogen bonding can be potentially important in the molecular design of the base-pair mimics to expand the alphabet of the genetic code.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-91152 (URN)10.1021/ja0386546 (DOI)14995203 (PubMedID)
    Tilgjengelig fra: 2003-11-26 Laget: 2003-11-26 Sist oppdatert: 2017-12-14bibliografisk kontrollert
  • 39.
    Acharya, Sandipta
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Barman, Jharna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Cheruku, Pradeep
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Chatterjee, Subhrangsu
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Acharya, Parag
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Isaksson, Johan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Chattopadhyaya, Jyoti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för bioorganisk kemi.
    Significant pKa Perturbation of Nucleobases Is an Intrinsic Property of the Sequence Context in DNA and RNA2004Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 126, nr 28, s. 8674-8681Artikkel i tidsskrift (Fagfellevurdert)
  • 40. Adamska-Venkatesh, Agnieszka
    et al.
    Mirmohades, Mohammad
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Sommer, Constanze
    Reijerse, Edward
    Lubitz, Wolfgang
    Lomoth, Reiner
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Following [FeFe] Hydrogenase Active Site Intermediates by Flash Photolysis/Mid-IR ProbingManuskript (preprint) (Annet vitenskapelig)
  • 41.
    Adeyemi, Ahmed
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för organisk farmaceutisk kemi.
    Bergman, Joakim
    AstraZeneca, Dept Med Chem Cardiovasc & Metab Dis, Innovat Med & Early Dev Biotech Unit, Pepparedsleden 1, S-43183 Molndal, Sweden..
    Branalt, Jonas
    AstraZeneca, Dept Med Chem Cardiovasc & Metab Dis, Innovat Med & Early Dev Biotech Unit, Pepparedsleden 1, S-43183 Molndal, Sweden..
    Sävmarker, Jonas
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi.
    Larhed, Mats
    Uppsala universitet, Science for Life Laboratory, SciLifeLab. Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi.
    Continuous Flow Synthesis under High-Temperature/High-Pressure Conditions Using a Resistively Heated Flow Reactor2017Inngår i: Organic Process Research & Development, ISSN 1083-6160, E-ISSN 1520-586X, Vol. 21, nr 7, s. 947-955Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A cheap, easy-to-build, and effective resistively heated reactor for continuous flow synthesis at high temperature and pressure is herein presented. The reactor is rapidly heated directly using, an electric current and is capable of rapidly delivering temperatures and pressures up to 400 degrees C and 200 bar, respectively. High-temperature and high-pressure applications of this reactor were safely performed and demonstrated by selected transformations such as esterifications, transesterifications, and direct carboxylic acid to nitrile reactions using supercritical ethanol, methanol, and acetonitrile. Reaction temperatures were between 300 and 400 degrees C with excellent conversions and good to excellent isolated product yields. Examples of Diels-Alder reactions were also carried out at temperatures up to 300 degrees C in high yield. No additives or catalysts were used in the reactions.

  • 42.
    Afifi, Hala
    et al.
    Institute of Pharmaceutical Science, King’s College London, UK.
    Karlsson, Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Heenan, Richard K.
    ISIS-CCLRC, Rutherford Appleton Laboratory, Chilton, UK.
    Dreiss, Cécile A.
    Institute of Pharmaceutical Science, King’s College London, UK.
    Structural transitions in cholesterol-based wormlike micelles induced by encapsulating alkyl ester oils with varying architecture2012Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 378, nr 1, s. 125-134Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of encapsulating oils on the phase behaviour and the microstructure of wormlike micelles formed by polyoxyethylene cholesteryl ether (ChEO10) and triethylene glycol monododecyl ether co-surfactant (C12EO3) was investigated using rheology, Cryo-TEM and small-angle neutron scattering measurements. Six alkyl ester oils bearing small, systematic variations in their molecular structure were encapsulated: ethyl butyrate (EB24), ethyl caproate (ECO26), ethyl caprylate (EC28), methyl enanthate (ME17), methyl caprylate (MC18) and butyl butyrate (BB44), where the subscripts refer to the length of the alkyl chain and fatty acid chain, respectively, on either sides of the ester link. The addition of alkyl ester oils to ChEO10/C12EO3 solutions promotes the longitudinal growth of the surfactant aggregates into wormlike micelles possessing an elliptical cross-section, with rminor 31 Â± 2 Ã… and rmajor varying from 45 to 70 Ã…. At fixed alkyl chain length, oils with longer fatty acid chains were found to be more efficient in inducing wormlike micelle formation or their elongation, following the order: EC28 > ECO26 > EB24. Instead, at fixed fatty acid chain length, increasing the alkyl chain has a negative effect on the longitudinal micellar growth (MC18 > EC28 and EB24 > BB44). At high co-surfactant concentrations and in the presence of EB24, an unusual phase of ring-like micelles was detected. Overall, the orientation of the oil molecules within the micelles enables them to act as co-surfactants with a small head-group, decreasing the average cross-section area and promoting longitudinal growth of the micelles into worms.

  • 43. Agarwala, Hemlata
    Bidirectional non-​innocence of the β-​diketonato ligand 9-​oxidophenalenone (L-​) in [Ru([9]​aneS3)​(L)​(dmso)​]​n, [9]​aneS3 = 1,​4,​7-​trithiacyclononane2014Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 43, s. 3939-3948Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The new compound [RuII([9]aneS3)(L)(dmso)]ClO4 ([1]ClO4) ([9]aneS3 = 1,4,7-trithiacyclononane, HL =9-hydroxyphenalenone, dmso = dimethylsulfoxide) has been structurally characterised to reveal almostequal C–O bond distances of coordinated L−, suggesting a delocalised bonding situation of the β-diketonatoligand. The dmso ligand is coordinated via the sulfur atom in the native (1+) and reduced states(1 and 1−) as has been revealed by X-ray crystallography and by DFT calculations. Cyclic voltammetry of1+ exhibits two close-lying one-electron oxidation waves at 0.77 V and 0.94 V, and two similarly closeone-electron reduction processes at −1.43 V and −1.56 V versus SCE in CH2Cl2. The electronic structuresof 1n in the accessible redox states have been analysed via experiments (EPR and UV-vis-NIR spectroelectrochemistry)and by DFT/TD-DFT calculations, revealing the potential for bidirectional non-innocent behaviourof coordinated L•/−/•2−. Specifically, the studies establish significant involvement of L basedfrontier orbitals in both the oxidation and reduction processes: [([9]aneS3)(dmso)RuIII–L•]3+ (13+) ⇌ [([9]-aneS3)(dmso)RuIII–L−]2+/[([9]aneS3)(dmso)RuII–L•]2+ (12+) ⇌ [([9]aneS3)(dmso)RuII–L−]+ (1+) ⇌ [([9]aneS3)-(dmso)RuII–L•2−] (1) ⇌ [([9]aneS3)(dmso)RuII–L3−]−/[([9]aneS3)(dmso)RuI–L•2−]− (1−).

  • 44. Agarwala, Hemlata
    Correspondence of RuIIIRuII and RuIVRuIII Mixed Valent States in a SmallDinuclear Complex2012Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, s. 5667-5675Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The dirutheniumACHTUNGTRENUNG(III) compound[(m-oxa){RuACHTUNGTRENUNG(acac)2}2] [1, oxa2=oxamidato(2), acac=2,4-pentanedionato]exhibits an S=1 ground statewith antiferromagnetic spin-spin coupling(J=40 cm1). The molecularstructure in the crystal of 1·2C7H8 revealedan intramolecular metal–metaldistance of 5.433 and a notableasymmetry within the bridging ligand.Cyclic voltammetry and spectroelectrochemistry(EPR, UV/Vis/NIR) of thetwo-step reduction and of the two-stepoxidation (irreversible second step)produced monocation and monoanionintermediates (Kc=105.9) with broadNIR absorption bands (e ca.2000m1cm1) and maxima at 1800 (1)and 1500 nm (1+). TD-DFT calculationssupport a RuIIIRuII formulationfor 1 with a doublet ground state. The1+ ion (RuIVRuIII) was calculated withan S=3/2 ground state and the doubletstate higher in energy (DE=694.6 cm1). The Mulliken spin densitycalculations showed little participationof the ligand bridge in the spin accommodationfor all paramagnetic species[(m-oxa){RuACHTUNGTRENUNG(acac)2}2]n, n=+1, 0, 1,and, accordingly, the NIR absorptionswere identified as metal-to-metal (intervalence)charge transfers. Whereasonly one such NIR band was observedfor the RuIIIRuII (4d5/4d6) system 1,the RuIVRuIII (4d4/4d5) form 1+ exhibitedextended absorbance over the UV/Vis/NIR range.

  • 45. Agarwala, Hemlata
    Electronic structure and catalytic aspects of [Ru(tpm)​(bqdi)​(Cl​/H2O)​]​n, tpm = tris(1-​pyrazolyl)​methane and bqdi = o-​benzoquinonediimine2013Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 42, s. 3721-3734Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The diamagnetic complexes [Ru(tpm)(bqdi)(Cl)]ClO4 ([1]ClO4) (tpm = tris(1-pyrazolyl)methane, bqdi =o-benzoquinonediimine) and [Ru(tpm)(bqdi)(H2O)](ClO4)2 ([2](ClO4)2) have been synthesized. Thevalence state-sensitive bond distances of coordinated bqdi [C–N: 1.311(5)/1.322(5) Å in [1]ClO4;1.316(7)/1.314(7) Å in molecule A and 1.315(6)/1.299(7) Å in molecule B of [2](ClO4)2] imply its fullyoxidised quinonediimine (bqdi0) character. DFT calculations of 1+ confirm the {RuII–bqdi0} versus the antiferromagneticallycoupled {RuIII–bqdi˙−} alternative. The 1H NMR spectra of [1]ClO4 in different solventsshow variations in chemical shift positions of the NH (bqdi) and CH (tpm) proton resonances due to theirdifferent degrees of acidity in different solvents. In CH3CN/0.1 mol dm−3 Et4NClO4, [1]ClO4 undergoesone reversible RuII ⇌ RuIII oxidation and two reductions, the reversible first electron uptake being bqdibased (bqdi0/bqdi˙−). The electrogenerated paramagnetic species {RuIII–bqdi0}(12+) and {RuII–Q˙−}(1)exhibit RuIII-type (12+: <g> = 2.211/Δg = 0.580) and radical-type (1: g = 1.988) EPR signals, respectively, asis confirmed by calculated spin densities (Ru: 0.767 in 12+, bqdi: 0.857 in 1). The aqua complex [2](ClO4)2exhibits two one-electron oxidations at pH = 7, suggesting the formation of {RuIVvO} species. The electronicspectral features of 1n (n = charge associated with the different redox states of the chloro complex:2+, 1+, 0) in CH3CN and of 22+ in H2O have been interpreted based on the TD-DFT calculations. The applicationpotential of the aqua complex 22+ as a pre-catalyst towards the epoxidation of olefins has beenexplored in the presence of the sacrificial oxidant PhI(OAc)2 in CH2Cl2 at 298 K, showing the desiredselectivity with a wide variety of alkenes. DFT calculations based on styrene as the model substratepredict that the epoxidation reaction proceeds through a concerted transition state pathway.IntroductionThe well recognized mixing of ruthenium dπ orbitals andπ orbitals of redox non-innocent quinonoid moieties introducesseveral manifestations with respect to the valence distributionat the metal–quinonoid interface, as depicted in Scheme 1.1This makes the electronic structure of such complexes sensitiveto the molecular frameworks, and in many occasions theexperimental results

  • 46. Agarwala, Hemlata
    Electronic structures and selective fluoride sensingfeatures of Os(bpy)2(HL2−) and [{Os(bpy)2}2(μ-HL2−)]2+(H3L: 5-(1H-benzo[d]imidazol-2-yl)-1H-imidazole-4-carboxylic acid)2014Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 43, s. 13932-13947Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The article deals with the newly designed mononuclear and asymmetric dinuclear osmium(II) complexesOsII(bpy)2(HL2−) (1) and [(bpy)2OsII(μ-HL2−)OsII(bpy)2](Cl)2 ([2](Cl)2)/[(bpy)2OsII(μ-HL2−)OsII(bpy)2](ClO4)2([2](ClO4)2), respectively, (H3L = 5-(1H-benzo[d]imidazol-2-yl)-1H-imidazole-4-carboxylic acid and bpy = 2,2’-bipyridine). The identity of 1 has been established by its single crystal X-ray structure. The ligand (HL2−)-basedprimary oxidation process (E°298, 0.23 V versus SCE) along with the partial metal contribution (∼20%) in 1 hasbeen revealed by the ligand-dominated HOMO of 1 (HL2−: 88%, Os: 8%), as well as by the Mulliken spindensity distribution of 1+ (HL2−: 0.878, Os: 0.220). Accordingly, 1+ exhibits a free radical type EPR at 77 K witha partial metal-based anisotropic feature (g1 = 2.127, g2 = 2.096, g3 = 2.046; <g> = 2.089; Δg = 0.08).1H-NMR of the dinuclear 22+ in CDCl3 suggests an intimate mixture of two diastereomeric forms in a 1 : 1ratio. The DFT-supported predominantly Os(II)/Os(III)-based couples of asymmetric 22+ at 0.24 V and 0.50 Vversus SCE result in a comproportionation constant (Kc) value of 8.2 × 104. The class I mixed valent state of23+ (S = 1/2) has, however, been corroborated by the Mulliken spin density distribution of Os1: 0.887, Os2:0.005, HL2−: 0.117, as well as by the absence of a low-energy IVCT (intervalence charge transfer) band in thenear-IR region (up to 2000 nm). The appreciable spin accumulation on the bridge in 23+ or 24+ (S = 1, Os1:0.915, Os2: 0.811 and HL2−: 0.275) implies a mixed electronic structural form of [(bpy)2OsIII(μ-HL2−)-OsII(bpy)2]3+(major)/[(bpy)2OsII(μ-HL•−)OsII(bpy)2]3+(minor) or [(bpy)2OsIII(μ-HL2−)OsIII(bpy)2]4+(major)/[(bpy)2-OsIII(μ-HL•−)OsII(bpy)2]4+ (minor), respectively. The mixed valent {OsIII(μ-HL2−)OsII} state in 23+, however, fails toshow EPR at 77 K due to the rapid spin relaxation process. The DFT-supported bpy-based two reductions forboth 1+ and 22+ appear in the potential range of −1.5 V to −1.8 V versus SCE. The electronic transitions in 1nand 2n are assigned by the TD-DFT calculations. Furthermore, the potential anion sensing features of 1 and22+ via the involvement of the available N–H proton in the framework of coordinated HL2− have been evaluatedby different experimental investigations, in conjunction with the DFT calculations, using a wide variety ofanions such as F−, Cl−, Br−, I−, OAc−, SCN−, HSO4− and H2PO4−. This, however, establishes that both 1 and 22+are equally efficient in recognising the F− ion selectively, with log K values of 6.83 and 5.89, respectively.

  • 47. Agarwala, Hemlata
    Four-Center Oxidation State Combinations and Near-Infrared Absorption in[Ru(pap)(Q)2]n (Q=3,5-Di-tert-butyl-N-aryl-1,2-benzoquinonemonoimine,pap=2-Phenylazopyridine)2013Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, s. 7384-7394Artikkel i tidsskrift (Fagfellevurdert)
  • 48. Agarwala, Hemlata
    Probing valence and spin situations in selective ruthenium–iminoquinonoidframeworks. An experimental and DFT analysis2011Inngår i: Inorganica Chimica Acta, ISSN 0020-1693, E-ISSN 1873-3255, Vol. 374, s. 216-225Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ruthenium–iminoquinone complexes, [Ru(tpm)(Cl)(Q)]+ [tpm = tris(1-pyrazolyl)methane, Q = 3,5-di-tert-butyl-N-aryl-1,2-benzoquinonemonoimine, where aryl = C6H5, [1]+; m-(OCH3)2C6H3, [2]+;m-(Cl)2C6H3, [3]+] have been synthesized. The sensitive bond distances of ‘‘Q’’ in [1](ClO4) and[2](ClO4), C–O: 1.294(8), 1.281(2) Å; C–N: 1.352(8), 1.335(2) Å; and C–C(meta): 1.366(10)/1.367(9) Å,1.364(2)/1.353(2) Å, respectively, and other analytical as well as theoretical (DFT) events suggest thevalence configuration of [RuIII(tpm)(Cl)(QSq)]+ for [1]+–[3]+. The paramagnetic [1]+–[3]+ show sharp1H NMR spectra with strikingly small J of 1.8–3.0 Hz. The DFT calculations on [1]+ predict that the triplet(S = 1) state exists above (1004 cm1) the singlet (S = 0) ground state. [1]+ exhibits l = 2.2 BM at 300 Kwhich diminishes to 0.3 BM near 2 K due to the steady decrease in the ratio of triplet to singlet populationwith the lowering of temperature. [1]+–[3]+ exhibit one oxidation and two successive reductions each inCH3CN. Experimental and DFT analyses collectively establish the valence configurations at thenon-innocent {Ru–Q} interface along the redox chain as [(tpm)(Cl)RuIII(QQo)]2+ ([1]2+–[3]2+)?[(tpm)(Cl)RuIII(QSq)]+ ([1]+–[3]+)?[(tpm)(Cl)RuII(QSq)]M[(tpm)(Cl)RuIII(QCat)] (1–3)?[(tpm)(Cl)-RuII(QCat)] ([1]–[3]). The spectral features of [1]n–[3]n (n = +2, +1, 0) have been addressed based onthe TD-DFT calculations on [1]n.

  • 49. Agarwala, Hemlata
    Sensitivity of a Strained C−C Single Bond to Charge Transfer: RedoxActivity in Mononuclear and Dinuclear Ruthenium Complexes ofBis(arylimino)acenaphthene (BIAN) Ligands2014Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 53, s. 7389-7403Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The new compounds [Ru(acac)2(BIAN)], BIAN = bis(arylimino)-acenaphthene (aryl = Ph (1a), 4-MeC6H4 (2a), 4-OMeC6H4 (3a), 4-ClC6H4 (4a), 4-NO2C6H4 (5a)), were synthesized and structurally, electrochemically, spectroscopically,and computationally characterized. The α-diimine sections of the compoundsexhibit intrachelate ring bond lengths 1.304 Å < d(CN) < 1.334 and 1.425 Å < d(CC)< 1.449 Å, which indicate considerable metal-to-ligand charge transfer in the groundstate, approaching a RuIII(BIAN•−) oxidation state formulation. The particularstructural sensitivity of the strained peri-connecting C−C bond in the BIAN ligandstoward metal-to-ligand charge transfer is discussed. Oxidation of [Ru(acac)2(BIAN)]produces electron paramagnetic resonance (EPR) and UV−vis−NIR (NIR = near infrared) spectroelectrochemically detectableRuIII species, while the reduction yields predominantly BIAN-based spin, in agreement with density functional theory (DFT)spin-density calculations. Variation of the substituents from CH3 to NO2 has little effect on the spin distribution but affects theabsorption spectra. The dinuclear compounds {(μ-tppz)[Ru(Cl)(BIAN)]2}(ClO4)2, tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine;aryl (BIAN) = Ph ([1b](ClO4)2), 4-MeC6H4 ([2b](ClO4)2), 4-OMeC6H4 ([3b](ClO4)2), 4-ClC6H4 ([4b](ClO4)2), were alsoobtained and investigated. The structure determination of [2b](ClO4)2 and [3b](ClO4)2 reveals trans configuration of thechloride ligands and unreduced BIAN ligands. The DFT and spectroelectrochemical results (UV−vis−NIR, EPR) indicateoxidation to a weakly coupled RuIIIRuII mixed-valent species but reduction to a tppz-centered radical state. The effect of the πelectron-accepting BIAN ancillary ligands is to diminish the metal−metal interaction due to competition with the acceptor bridgetppz.

  • 50. Agarwala, Hemlata
    Sensitivity of the Valence Structure in Diruthenium Complexes As aFunction of Terminal and Bridging Ligands2014Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 53, s. 6082-6093Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The compounds [(acac)2RuIII(μ-H2L2−)RuIII(acac)2] (rac, 1, and meso, 1′) and[(bpy)2RuII(μ-H2L•−)RuII(bpy)2](ClO4)3 (meso, [2](ClO4)3) have been structurally, magnetically,spectroelectrochemically, and computationally characterized (acac− = acetylacetonate, bpy= 2,2′-bipyridine, and H4L = 1,4-diamino-9,10-anthraquinone). The N,O;N′,O′-coordinated μ-H2Ln− forms two β-ketiminato-type chelate rings, and 1 or 1′ are connected via NH···Ohydrogen bridges in the crystals. 1 exhibits a complex magnetic behavior, while [2](ClO4)3 is aradical species with mixed ligand/metal-based spin. The combination of redox noninnocentbridge (H2L0 → → → →H2L4−) and {(acac)2RuII} → →{(acac)2RuIV} or {(bpy)2RuII} →{(bpy)2RuIII} in 1/1′ or 2 generates alternatives regarding the oxidation state formulations for the accessible redox states (1n and2n), which have been assessed by UV−vis−NIR, EPR, and DFT/TD-DFT calculations. The experimental and theoretical studiessuggest variable mixing of the frontier orbitals of the metals and the bridge, leading to the following most appropriate oxidationstate combinations: [(acac)2RuIII(μ-H2L•−)RuIII(acac)2]+ (1+) → [(acac)2RuIII(μ-H2L2−)RuIII(acac)2] (1) → [(acac)2RuIII(μ-H2L•3−)RuIII(acac)2]−/[(acac)2RuIII(μ-H2L2−)RuII(acac)2]− (1−) → [(acac)2RuIII(μ-H2L4−)RuIII(acac)2]2−/[(acac)2RuII(μ-H2L2−)RuII(acac)2]2− (12−) and [(bpy)2RuIII(μ-H2L•−)RuII(bpy)2]4+ (24+) → [(bpy)2RuII(μ-H2L•−)RuII(bpy)2]3+/[(bpy)2RuII(μ-H2L2−)RuIII(bpy)2]3+ (23+) → [(bpy)2RuII(μ-H2L2−)RuII(bpy)2]2+ (22+). The favoring of RuIII by σ-donatingacac− and of RuII by the π-accepting bpy coligands shifts the conceivable valence alternatives accordingly. Similarly, theintroduction of the NH donor function in H2Ln as compared to O causes a cathodic shift of redox potentials with correspondingconsequences for the valence structure.

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