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  • 1. Agarwala, Hemlata
    Correspondence of RuIIIRuII and RuIVRuIII Mixed Valent States in a SmallDinuclear Complex2012In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, p. 5667-5675Article in journal (Refereed)
    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.

  • 2. 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)2013In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, p. 7384-7394Article in journal (Refereed)
  • 3.
    Akkarasamiyo, Sunisa
    et al.
    Stockholm Univ, Dept Organ Chem, S-10691 Stockholm, Sweden..
    Sawadjoon, Supaporn
    Stockholm Univ, Dept Organ Chem, S-10691 Stockholm, Sweden..
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Samec, Joseph S. M.
    Stockholm Univ, Dept Organ Chem, S-10691 Stockholm, Sweden..
    Tsuji-Trost Reaction of Non-Derivatized Allylic Alcohols2018In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, no 14, p. 3488-3498Article in journal (Refereed)
    Abstract [en]

    Palladium-catalyzed allylic substitution of non-derivatized enantioenriched allylic alcohols with a variety of uncharged N-, S-, C- and O-centered nucleophiles using a bidentate BiPhePhos ligand is described. A remarkable effect of the counter ion (X) of the XPd[kappa(2)-BiPhePhos][kappa(3)-C3H5] was observed. When ClPd[kappa(2)-BiPhePhos][eta(3)-C3H5] (complexI) was used as catalyst, non-reproducible results were obtained. Study of the complex by X-ray crystallography, (PNMR)-P-31 spectroscopy, and ESI-MS showed that a decomposition occurred where one of the phosphite ligands was oxidized to the corresponding phosphate, generating ClPd[kappa(1)-BiPhePhosphite-phosphate][eta(3)-C3H5] species (complexII). When the chloride was exchanged to the weaker coordinating OTf- counter ion the more stable Pd[kappa(2)-BiPhePhos][eta(3)-C3H5](+)+[OTf] (-) (complexIII) was formed. ComplexIII performed better and gave higher enantiospecificities in the substitution reactions. ComplexIII was evaluated in Tsuji-Trost reactions of stereogenic non-derivatized allylic alcohols. The desired products were obtained in good to excellent yields (71-98%) and enantiospecificities (73-99%) for both inter- and intramolecular substitution reactions with only water generated as a by-product. The methodology was applied to key steps in total synthesis of (S)-cuspareine and (+)-lentiginosine. A reaction mechanism involving a palladium hydride as a key intermediate in the activation of the hydroxyl group is proposed in the overall transformation.

  • 4.
    Ali, Md. Ehesan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Oppeneer, Peter M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Unraveling the Electronic Structure, Spin States, Optical and Vibrational Spectra of Malaria Pigment2015In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, no 23, p. 8544-8553Article in journal (Refereed)
    Abstract [en]

    A detailed knowledge of the electronic structure and magnetic and optical properties of hemozoin, the malaria pigment, is essential for the design of effective antimalarial drugs and malarial diagnosis. By employing state-of-the-art electronic structure calculations, we have performed an in-depth investigation of the malaria pigment. Specifically, molecular bond lengths and spin states of the two Fe-III heme centers and their exchange interaction, the UV/Vis absorption spectrum, and the IR vibrational spectra were calculated and compared with available experimental data. Our density functional theory (DFT)-based calculations predict a singlet ground spin state that stems from an S=5/2 spin state on each of the Fe heme centers with a very weak antiferromagnetic exchange interaction between them. Our theoretical UV/Vis and IR spectra provide explanations for various spectroscopic studies of hemozoin and -hematin (a synthetic analogue of hemozoin). A good comparison of calculated and measured properties demonstrates the convincing unveiling of the electronic structure of the malaria pigment. Based on the predicted vibrational spectra, we propose a unique spectral band from the nuclear resonance vibrational spectroscopy (NRVS) results that could be used as a key fingerprint for malarial detection.

  • 5. Amorati, Riccardo
    et al.
    Valgimigli, Luca
    Dinér, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Bakhtiari, Khadijeh
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Saeedi, Mina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Engman, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Multi-faceted reactivity of alkyltellurophenols towards peroxyl radicals: Catalytic antioxidant versus thiol-depletion effect2013In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, no 23, p. 7510-7522Article in journal (Refereed)
    Abstract [en]

    Hydroxyaryl alkyl tellurides are effective antioxidants both in organic solution and aqueous biphasic systems. They react by an unconventional mechanism with ROO. radicals with rate constants as high as 107M1s1 at 303K, outperforming common phenols. The reactions proceed by oxygen atom transfer to tellurium followed by hydrogen atom transfer to the resulting RO. radical from the phenolic OH. The reaction rates do not reflect the electronic properties of the ring substituents and, because the reactions occur in a solvent cage, quenching is more efficient when the OH and TeR groups have an ortho arrangement. In the presence of thiols, hydroxyaryl alkyl tellurides act as catalytic antioxidants towards both hydroperoxides (mimicking the glutathione peroxidases) and peroxyl radicals. The high efficiency of the quenching of the peroxyl radicals and hydroperoxides could be advantageous under normal cellular conditions, but pro-oxidative (thiol depletion) when thiol concentrations are low.

  • 6.
    Andaloussi, Mounir
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Lindh, Jonas
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry. ORGFARM.
    Sävmarker, Jonas
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Sjöberg, Per J.R.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Larhed, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Microwave-promoted palladium(II)-catalyzed C-P bond formation by using arylboronic acids or aryltrifluoroborates.2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 47, p. 13069-13074Article in journal (Refereed)
    Abstract [en]

    The first Pd-II-catalyzed P arylation has been performed by using palladium acetate, the rigid bidentate ligand dmphen (dmphen=2,9-dimethyl-1,10-phenanthroline), and without the addition of base or acid. Couplings of arylboronic acids or aryl trifluoroborates with H-phosphonate dialkyl esters were conducted in 30 min with controlled microwave (MW) heating under non-inert conditions. Aryl phosphites were also synthesized at room temperature with atmospheric air as the sole reoxidant. The arylated phosphonates were isolated in 44-90% yields. The excellent chemoselectivity of the method was illustrated in the synthesis of a Mycobacterium tuberculosis glutamine synthetase (MTB-GS) inhibitor. Online ESIMS was used to detect cationic palladium species in ongoing reactions directly, and a catalytic cycle has been proposed based on these results.

  • 7.
    Appukkuttan, Prasad
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry.
    Dehaen, Wim
    Van der Eycken, Erik
    Microwave-assisted transition-metal-catalyzed synthesis of N-shifted and ring-expanded buflavine analogues2007In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 13, no 22, p. 6452-6460Article in journal (Other academic)
    Abstract [en]

    Two novel and efficient strategies for the synthesis of hitherto unknown N-shifted and ring-expanded buflavine analogues are presented. Construction of the medium-sized ring system of the title molecules, a difficult task due to the high activation energy needed for the ring-closure with the additional rigidity imposed by the biaryl skeleton, was achieved by using Suzuki-Miyaura biaryl coupling and a ring-closing metathesis reaction as the key steps. The combination of a second-generation Grubbs catalyst and microwave irradiation proved to be highly useful in generating the otherwise difficult to obtain medium-sized ring system of the buflavine analogues.

  • 8.
    Arkhypchuk, Anna I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Mijangos, Edgar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Redox Switching in Ethenyl- Bridged Bisphospholes2014In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, no 49, p. 16083-16087Article in journal (Refereed)
    Abstract [en]

    A 2e(-)/2H(+) redox platform has been implemented in the ethenyl-bridged bisphosphol-3-ol 1 to afford the first phospholes that feature chemically reversible oxidations. Oxidation of the title compounds to the corresponding bisphosphol-3-one 2 leads to a change in conjugation topology and a concomitant hypsochromic shift of the lowest-energy absorption maximum by 100nm. Electrochemical oxidation proceeds without any detectable intermediates, whereas the deprotonated form of 1 can be observed in an aprotic medium during the reduction of 2. This dianionic intermediate 3 is characterized by end absorptions that are bathochromically shifted by circa 200nm compared to those of 2.

  • 9.
    Arkhypchuk, Anna I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mihali, Viorica Alina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ehlers, Andreas
    Lammertsma, Koop
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Oxaphospholes and Bisphospholes from Phosphinophosphonates and alpha,beta-Unsaturated Ketones2013In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, no 41, p. 13692-13704Article in journal (Refereed)
    Abstract [en]

    The reaction of a {W(CO)(5)}-stabilized phosphinophosphonate 1, (CO)(5)WPH(Ph)P(O)(OEt)(2), with ethynyl- (2a-f) and diethynylketones (7-11, 18, and 19) in the presence of lithium diisopropylamide (LDA) is examined. Lithiated 1 undergoes nucleophilic attack in the Michael position of the acetylenic ketones, as long as this position is not sterically encumbered by bulky (iPr)(3)Si substituents. Reaction of all other monoacetylenic ketones with lithiated 1 results in the formation of 2,5-dihydro-1,2-oxaphospholes 3 and 4. When diacetylenic ketones are employed in the reaction, two very different product types can be isolated. If at least one (Me)(3)Si or (Et)(3)Si acetylene terminus is present, as in 7, 8, and 19, an anionic oxaphosphole intermediate can react further with a second equivalent of ketone to give cumulene-decorated oxaphospholes 14, 15, 24, and 25. Diacetylenic ketones 10 and 11, with two aromatic acetylene substituents, react with lithitated 1 to form exclusively ethenyl-bridged bisphospholes 16 and 17. Mechanisms that rationalize the formation of all heterocycles are presented and are supported by DFT calculations. Computational studies suggest that thermodynamic, as well as kinetic, considerations dictate the observed reactivity. The calculated reaction pathways reveal a number of almost isoenergetic intermediates that follow after ring opening of the initially formed oxadiphosphetane. Bisphosphole formation through a carbene intermediate G is greatly favored in the presence of phenyl substituents, whereas the formation of cumulene-decorated oxaphospholes is more exothermic for the trimethylsilyl-containing substrates. The pathway to the latter compounds contains a 1,3-shift of the group that stems from the acetylene terminus of the ketone substrates. For silyl substituents, the 1,3-shift proceeds along a smooth potential energy surface through a transition state that is characterized by a pentacoordinated silicon center. In contrast, a high-lying transition state TS(E-F)(R=Ph) of 37kcalmol(-1) is found when the substituent is a phenyl group, thus explaining the experimental observation that aryl-terminated diethynylketones 10 and 11 exclusively form bisphospholes 16 and 17.

  • 10.
    Ayub, Rabia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Papadakis, Raffaello
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Jorner, Kjell
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. uppsala university.
    Zietz, Burkhard
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. uppsala university.
    Cyclopropyl Group: An Excited-State Aromaticity Indicator?2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 55, p. 13684-13695Article in journal (Refereed)
    Abstract [en]

    The cyclopropyl (cPr) group, which is a well-known probe for detecting radical character at atoms to which it is connected, is tested as an indicator for aromaticity in the first * triplet and singlet excited states (T-1 and S-1). Baird's rule says that the -electron counts for aromaticity and antiaromaticity in the T-1 and S-1 states are opposite to Huckel's rule in the ground state (S-0). Our hypothesis is that the cPr group, as a result of Baird's rule, will remain closed when attached to an excited-state aromatic ring, enabling it to be used as an indicator to distinguish excited-state aromatic rings from excited-state antiaromatic and nonaromatic rings. Quantum chemical calculations and photoreactivity experiments support our hypothesis; calculated aromaticity indices reveal that openings of cPr substituents on [4n]annulenes ruin the excited-state aromaticity in energetically unfavorable processes. Yet, polycyclic compounds influenced by excited-state aromaticity (e.g., biphenylene), as well as 4n-electron heterocycles with two or more heteroatoms represent limitations.

  • 11.
    Biswas, Srijit
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Synthetical Organic Chemistry.
    Dahlstrand, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Watile, Rahul A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Synthetical Organic Chemistry.
    Kalek, Marcin
    Himo, Fahmi
    Samec, Joseph S. M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Synthetical Organic Chemistry.
    Atom-Efficient Gold(I)-Chloride-Catalyzed Synthesis of alpha-Sulfenylated Carbonyl Compounds from Propargylic Alcohols and Aryl Thiols: Substrate Scope and Experimental and Theoretical Mechanistic Investigation2013In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, no 52, p. 17939-17950Article in journal (Refereed)
    Abstract [en]

    Gold(I)-chloride-catalyzed synthesis of -sulfenylated carbonyl compounds from propargylic alcohols and aryl thiols showed a wide substrate scope with respect to both propargylic alcohols and aryl thiols. Primary and secondary aromatic propargylic alcohols generated -sulfenylated aldehydes and ketones in 60-97% yield. Secondary aliphatic propargylic alcohols generated -sulfenylated ketones in yields of 47-71%. Different gold sources and ligand effects were studied, and it was shown that gold(I) chloride gave the highest product yields. Experimental and theoretical studies demonstrated that the reaction proceeds in two separate steps. A sulfenylated allylic alcohol, generated by initial regioselective attack of the aryl thiol on the triple bond of the propargylic alcohol, was isolated, evaluated, and found to be an intermediate in the reaction. Deuterium labeling experiments showed that the protons from the propargylic alcohol and aryl thiol were transferred to the 3-position, and that the hydride from the alcohol was transferred to the 2-position of the product. Density functional theory (DFT) calculations showed that the observed regioselectivity of the aryl thiol attack towards the 2-position of propargylic alcohol was determined by a low-energy, five-membered cyclic protodeauration transition state instead of the strained, four-membered cyclic transition state found for attack at the 3-position. Experimental data and DFT calculations supported that the second step of the reaction is initiated by protonation of the double bond of the sulfenylated allylic alcohol with a proton donor coordinated to gold(I) chloride. This in turn allows for a 1,2-hydride shift, generating the final product of the reaction.

  • 12.
    Biswas, Srijit
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Synthetical Organic Chemistry.
    Watile, Rahul A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Synthetical Organic Chemistry.
    Samec, Joseph S. M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Synthetical Organic Chemistry.
    Tandem Pd/Au-Catalyzed Route to alpha-Sulfenylated Carbonyl Compounds from Terminal Propargylic Alcohols and Thiols2014In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, no 8, p. 2159-2163Article in journal (Refereed)
    Abstract [en]

    An efficient and highly atom-economical tandem Pd/Au-catalyzed route to -sulfenylated carbonyl compounds from terminal propargylic alcohols and thiols has been developed. This one-step procedure has a wide substrate scope with respect to substituents at the -position of the alcohol. Both aromatic and aliphatic thiols generated the -sulfenylated carbonyl products in good to excellent yields. A mechanism is proposed in which the reaction proceeds through a Pd-catalyzed regioselective hydrothiolation at the terminal triple bond of the propargyl alcohol followed by an Au-catalyzed 1,2-hydride migration.

  • 13. Brandt, Peter
    et al.
    Norrby, Per-Ola
    Daly, Adrian M
    Gilheany, Declan G
    Chromium-salen-mediated alkene epoxidation: a theoretical and experimental study indicates the importance of spin-surface crossing and the presence of a discrete intermediate.2002In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 8, no 18, p. 4299-307Article in journal (Refereed)
    Abstract [en]

    The mechanism of alkene epoxidation by chromium(v) oxo salen complexes has been studied by DFT and experimental methods. The reaction is compared to the closely related Mn-catalyzed process in an attempt to understand the dramatic difference in selectivity between the two systems. Overall, the studies show that the reactions have many similarities, but also a few critical differences. In agreement with experiment, the chromium system requires a change from low- to high-spin in the catalytic cycle, whereas the manganese system can proceed either with spin inversion or entirely on the high-spin surface. The low-spin addition of metal oxo species to an alkene leads to an intermediate which forms epoxide either with a barrier on the low-spin surface or without a barrier after spin inversion. Supporting evidence for this intermediate was obtained by using vinylcyclopropane traps. The chromium(v) oxo complexes can adopt a stepped shape or form a more concave surface, analogous to previous results on manganese salen complexes.

  • 14.
    Butorin, Sergei M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Kvashnina, Kristina O.
    European Synchrotron Radiat Facil, CS40220, F-38043 Grenoble 9, France.;Helmholtz Zentrum Dresden Rossendorf, Inst Resource Ecol, POB 510119, D-01314 Dresden, Germany..
    Smith, Anna L.
    Delft Univ Technol, Dept Radiat Sci & Technol, Mekelweg 15, NL-2629 JB Delft, Netherlands..
    Popa, Karin
    European Commiss, Joint Res Ctr, Inst Transuranium Elements, POB 2340, D-76125 Karlsruhe, Germany..
    Martin, Philippe M.
    CEA Marcoule, CEA, DEN, DTEC,SECA,LCC, F-30207 Bagnols Sur Ceze, France..
    Crystal-Field and Covalency Effects in Uranates: An X-ray Spectroscopic Study2016In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 28, p. 9693-9698Article in journal (Refereed)
    Abstract [en]

    The electronic structure of U-V- and U-VI-containing uranates NaUO3 and Pb3UO6 was studied by using an advanced technique, namely X-ray absorption spectroscopy (XAS) in high-energy-resolution fluorescence-detection (HERFD) mode. Due to a significant reduction in core-hole lifetime broadening, the crystal-field splittings of the 5f shell were probed directly in HERFD-XAS spectra collected at the U3d edge, which is not possible by using conventional XAS. In addition, the charge-transfer satellites that result from U5f-O2p hybridization were clearly resolved. The crystal-field parameters, 5f occupancy, and degree of covalency of the chemical bonding in these uranates were estimated by using the Anderson impurity model by calculating the U3d HERFD-XAS, conventional XAS, core-to-core (U 4f-3d transitions) resonant inelastic X-ray scattering (RIXS), and U4f Xray photoelectron spectra. The crystal field was found to be strong in these systems and the 5f occupancy was determined to be 1.32 and 0.84 electrons in the ground state for NaUO3 and Pb3UO6, respectively, which indicates a significant covalent character for these compounds.

  • 15.
    Chi, Celestine N.
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Strotz, Dean
    Riek, Roland
    Vögeli, Beat Rolf
    NOE-derived methyl distances from a 360 kDa proteasome complex2018In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, no 9, p. 2270-2276Article in journal (Refereed)
    Abstract [en]

    Nuclear magnetic resonance spectroscopy is the prime tool to probe structure and dynamics of biomolecules at atomic resolution. A serious challenge for that method is the size limit imposed on molecules to be studied. Standard studies are typically restricted to ca. 30-40 kDa. More recent developments lead to spin relaxation measurements in methyl groups in single proteins or protein complexes as large as a mega-Dalton, which directly allow the extraction of angular information or experiments with paramagnetic samples. However, these probes are all of indirect nature in contrast to the most intuitive and easy-to-interpret structural/dynamics restraint, the internuclear distance, which can be measured by nuclear Overhauser enhancement (NOE). Here, we demonstrate time-averaged distance measurements on the 360 kDa half proteasome from Thermoplasma acidophilium. The approach is based on exact quantification of the NOE (eNOE). Our findings open up an avenue for such measurements on very large molecules. These restraints will help in a detailed determination of conformational changes upon perturbation such as ligand binding.

  • 16.
    Chow, Shiao Y.
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Stevens, Marc Y.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Åkerbladh, Linda
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Bergman, Sara
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Odell, Luke R.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Mild and Low-Pressure fac-Ir(ppy)3-Mediated Radical Aminocarbonylation of Unactivated Alkyl Iodides through Visible-Light Photoredox Catalysis2016In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 27, p. 9155-9161Article in journal (Refereed)
    Abstract [en]

    A novel, mild and facile preparation of alkyl amides from unactivated alkyl iodides employing a fac-Ir(ppy)(3)-catalyzed radical aminocarbonylation protocol has been developed. Using a two-chambered system, alkyl iodides, fac-Ir(ppy)(3), amines, reductants, and CO gas (released ex situ from Mo(CO)(6)), were combined and subjected to an initial radical reductive dehalogenation generating alkyl radicals, and a subsequent aminocarbonylation with amines affording a wide range of alkyl amides in moderate to excellent yields.

  • 17.
    Dinér, Peter
    et al.
    Center for Catalysis, Department of Chemistry, Aarhus University.
    Kjaersgaard, Anne
    Lie, Mette Alstrup
    Jørgensen, Karl Anker
    On the origin of the stereoselectivity in organocatalysed reactions with trimethylsilyl-protected diarylprolinol2008In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 14, no 1, p. 122-127Article in journal (Refereed)
    Abstract [en]

    The origin of the enantioselectivity in the TMS-protected (TMS=trimethylsilyl) prolinol-catalysed alpha-heteroatom functionalisation of aldehydes has been investigated by using density functional theory calculations. Eight different reaction paths have been considered which are based on four different conformers of the TMS-protected prolinol-enamine intermediate. Optimisation of the enamine structures gave two intermediates with nearly the same energy. These intermediates both have an E configuration at the C==C bond and the double bond is positioned anti or syn, relative to the 2-substituent in the pyrrolidine ring. For the four intermediates, the chiral TMS-protected-diaryl substituent effectively shields one of the faces of the reacting C==C bond in the enamine intermediate. A number of transition states have been calculated for the enantioselective fluorination by N-fluorobenzenesulfonimide (NFSI) and based on the transition-state energies it has been found that the enantioselectivity depends on the orientation of the C==C bond, being anti or syn, relative to the 2-substituent on the pyrrolidine ring, rather than the approach of the electrophilic fluorine to the face of the reacting carbon atom in the enamine which is less shielded relative to the face with the highest shielding. The calculated enantiomeric excess of 96 % ee (ee=enantiomeric excess) for the fluorination reaction corresponds well with the experimentally found enantiomeric excess-97 % ee. The transition state for the alpha-amination reaction with the same type of intermediate has also been calculated by using diethyl azodicarboxylate as the amination reagent. The implication of the intermediate structures on the stereoselection of alpha-functionalisation of aldehydes is discussed.

  • 18. Dourado, Daniel F A R
    et al.
    Fernandes, Pedro Alexandrino
    Mannervik, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Ramos, Maria João
    Glutathione transferase: new model for glutathione activation2008In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 14, no 31, p. 9591-8Article in journal (Refereed)
    Abstract [en]

    Glutathione transferases are enzymes of the cellular detoxification system that metabolize a vast spectrum of xenobiotic and endobiotic toxic compounds. They are homodimers or heterodimers and each monomer has an active center composed of a G-site in which glutathione (GSH) binds and an H-site for the electrophilic substrate. When GSH binds to the G-site, the pKa value of its thiol group drops by 2.5 units; this promotes its deprotonation and, therefore, produces a strong nucleophilic thiolate that is able to react with the electrophilic substrate. The mechanism behind the deprotonation of the thiol group is still unknown. Some studies point to the fact that the GSH glutamyl alpha-carboxylate group is essential for GSH activation, whereas others indicate the importance of the active-center water molecules. On the basis of QM/MM calculations, we propose a mechanism of GSH activation in which a water molecule, acting as a bridge, is able to assist in the transfer of the proton from the GSH thiol group to the GSH glutamyl alpha-carboxylate group, after an initial GSH conformational rearrangement. We calculated the potential of mean force of this GSH structural rearrangement that would be necessary for the approach of both groups and we then performed a QM/MM ONIOM scan of water-assisted proton transfer. The overall free-energy barrier for the process is consistent with experimental studies of the enzyme kinetics.

  • 19. Dreiser, Jan
    et al.
    Westerström, Rasmus
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Zhang, Yang
    Popov, Alexey A.
    Dunsch, Lothar
    Kraemer, Karl
    Liu, Shi-Xia
    Decurtins, Silvio
    Greber, Thomas
    The Metallofullerene Field-Induced Single-Ion Magnet HoSc2N@C-802014In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, no 42, p. 13536-13540Article in journal (Refereed)
    Abstract [en]

    The low-temperature magnetic properties of the endohedral metallofullerene HoSc2N@C-80 have been studied by superconducting quantum interference device (SQUID) magnetometry. Alternating current (ac) susceptibility measurements reveal that this molecule exhibits slow relaxation of magnetization in a small applied field with timescales in the order of milliseconds. The equilibrium magnetic properties of HoSc2N@C-80 indicate strong magnetic anisotropy. The large differences in magnetization relaxation times between the present compound and the previously investigated DySc2N@C-80 are discussed.

  • 20. Drescher, Simon
    et al.
    Meister, Annette
    Blume, Alfred
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Almgren, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Dobner, Bodo
    General Synthesis and Aggregation Behaviour of a Series of Single-Chain 1,ω-Bis(phosphocholines)2007In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 13, no 18, p. 5300-5307Article in journal (Refereed)
    Abstract [en]

    The synthesis and physicochem. characterization of a series of polymethylene-1,w-bis(phosphocholines) with even-numbered chain lengths between 22 and 32 carbon atoms is described. Two new synthetic strategies for the prepn. of long-chain 1,wo-diols as hydrocarbon building blocks are presented. The temp.-dependent self-assembly of the single-chain bolaamphiphiles was investigated by cryo transmission electron microscopy (cryo-TEM), differential scanning calorimetry (DSC), and Fourier transform IR spectroscopy (FTIR).

  • 21.
    Durbeej, Bo
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Sandala, Gregory M.
    Bucher, Denis
    Smith, David M.
    Radom, Leo
    On the importance of ribose orientation in the substrate activation of the coenzyme B12-dependent mutases2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 34, p. 8578-8585Article in journal (Refereed)
    Abstract [en]

    The degree to which the corrin ring portion of coenzyme B-12 can   facilitate the H-atom-abstraction step in the glutamate mutase   (GM)-catalyzed reaction of (S)-glutamate has been investigated with   density functional theory. The crystal structure of GM identifies two   possible orientations of the ribose portion of coenzyme B-12. In one orientation (A), the OH groups of the ribose extend away from the   corrin ring, whereas in the other orientation (B) the OH groups, especially that involving O3', are instead directed towards the corrin   ring. Our calculations identify a sizable stabilization amounting to   about 30kJ mol(-1) in the transition structure (TS) complex   corresponding to orientation B (TS(B)Corlm). In the TS complex where   the ribose instead is positioned in orientation A, no such effect is   manifested. The observed stabilization in TS(B)CorIm appears to be the   result of favorable interactions involving O3' and the corrin ring,   including a C-H center dot center dot center dot O hydrogen bond. We   find that the degree of stabilization is not particularly sensitive to   the Co-C distance. Our calculations show that any potential   stabilization afforded to the H-atom-abstraction step by coenzyme B12   is sensitive to the orientation of the ribose moiety.

  • 22.
    Eilers, Gerriet
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Schwartz, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Stein, Matthias
    Zampella, Giuseppe
    de Gioia, Luca
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Ligand versus metal protonation of an iron hydrogenase active site mimic2007In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 13, no 25, p. 7075-7084Article in journal (Refereed)
    Abstract [en]

    The protonation behavior of the iron hydrogenase active-site mimic [Fe2(u-adt)(CO)4(PMe3)2] (1; adt=N-benzyl-azadithiolate) has been investigated by spectroscopic, electrochemical, and computational methods. The combination of an adt bridge and electron-donating phosphine ligands allows protonation of either the adt nitrogen to give [Fe2(μ-Hadt)(CO)4(PMe3)2]+ ([1H]+), the Fe-Fe bond to give [Fe2-(μ-adt)(μ-H)(CO)4(PMe3)2]+ ([1Hy]+), or both sites simultaneously to give [Fe2(μ-Hadt)(μ-H)(CO)4(PMe3)2]2+ ([1HHy]2+). Complex 1 and its protonation products have been characterized in acetonitrile solution by IR, 1H, and 31PNMR spectroscopy. The solution structures of all protonation states feature a basal/basal orientation of the phosphine ligands, which contrasts with the basal/apical structure of 1 in the solid state. Density functional calculations have been performed on all protonation states and a comparison between calculated and experimental spectra confirms the structural assignments. The ligand protonated complex [1H]+ (pKa =12) is the initial, metastable protonation product while the hydride [1Hy]+ (pKa=15) is the thermodynamically stable singly protonated form. Tautomerization of cation [1H]+ to [1Hy]+ does not occur spontaneously. However, it can be catalyzed by HCl (k=2.2M-1s-1), which results in the selective formation of cation [1Hy]+. The protonations of the two basic sites have strong mutual effects on their basicities such that the hydride (pKa=8) and the ammonium proton (pKa=5) of the doubly protonated cationic complex [1HHy]2+ are considerably more acidic than in the singly protonated analogues. The formation of dication [1HHy]2+ from cation [1H]+ is exceptionally slow with perchloric or trifluoromethanesulfonic acid (k= 0.15 M-1s-1), while the dication is formed substantially faster (k > 102 M-1 s-1) with hydrobromic acid. Electrochemically, 1 undergoes irreversible reduction at -2.2V versus ferrocene, and this potential shifts to -1.6, - 1.1, and -1.0 V for the cationic complexes [1H]+, [1Hy]+, and [1HHy]2+, respectively, upon protonation. The doubly protonated form [1HHy]2+ is reduced at less negative potential than all previously reported hydrogenase models, although catalytic proton reduction at this potential is characterized by slow turnover.

  • 23.
    El Nahhas, Amal
    et al.
    Lund Univ, Dept Chem Phys, Lund, Sweden..
    Shameem, Muhammad Anwar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Chabera, Pavel
    Lund Univ, Dept Chem Phys, Lund, Sweden..
    Uhlig, Jens
    Lund Univ, Dept Chem Phys, Lund, Sweden..
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Synthesis and Characterization of Cyclopentadithiophene Heterofulvenes: Design Tools for Light-Activated Processes2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 24, p. 5673-5677Article in journal (Refereed)
    Abstract [en]

    The development of new materials for solar-to-energy conversion should consider stability, ease of fabrication, and beneficial photophysical properties. In this context, a set of novel -conjugated building blocks, with phospha- and arsaalkenes possessing a unique dithienyl annulated heterofulvenoid core, have been prepared as air- and moisture-stable sensitizers. These compounds unify electron-donor and -acceptor moieties, making them potential candidates for light-harvesting applications. Optical characterization of these systems was performed by steady-state and time-resolved absorption spectroscopy, supported by time-dependent DFT calculations. Tuning of the optical properties of these systems can be achieved by varying the pnictogen element at the bridgehead position, giving a bathochromic shift of approximate to 40nm and coordinating the phosphaalkene towards gold Au-I centers. The latter results in a approximate to 2000-fold extension of the approximate to 10ps lifetime of uncoordinated systems well into the ns regime.

  • 24.
    Emanuelsson, Rikard
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Löfås, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Wallner, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry. Institut für Anorganische Chemie, Technische Universität Graz.
    Nauroozi, Djawed
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Baumgartner, Judith
    Institut für Anorganische Chemie, Technische Universität Graz.
    Marschner, Christoph
    Institut für Anorganische Chemie, Technische Universität Graz.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Grigoriev, Anton
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Configuration- and Conformation-Dependent Electronic Structure Variations in 1,4-Disubstituted Cyclohexanes Enabled by a Carbon-to-Silicon Exchange2014In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, no 30, p. 9304-9311Article in journal (Other academic)
    Abstract [en]

    Cyclohexane, with its well-defined conformers, could be an ideal force-controlled molecular switch if it were to display substantial differences in electronic and optical properties between its conformers. We utilize sigma conjugation in heavier analogues of cyclohexanes (i.e. cyclohexasilanes) and show that 1,4-disubstituted cyclohexasilanes display configuration-and conformation-dependent variations in these properties. Cis- and trans-1,4-bis(trimethylsilylethynyl)-cyclohexasilanes display a 0.11 V difference in their oxidation potentials (computed 0.11 V) and a 0.34 eV difference in their lowest UV absorption (computed difference between first excitations 0.07 eV). This is in stark contrast to differences in the corresponding properties of analogous all-carbon cyclohexanes (computed 0.02 V and 0.03 eV, respectively). Moreover, the two chair conformers of the cyclohexasilane trans isomer display large differences in electronic-structure-related properties. This enables computational design of a mechanically force-controlled conductance switch with a calculated single-molecule ON/OFF ratio of 213 at zero-bias voltage.

  • 25. Erdem, Özlen F
    et al.
    Stein, Matthias
    Kaur-Ghumaan, Sandeep
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Reijerse, Edward J
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Lubitz, Wolfgang
    Effect of cyanide ligands on the electronic structure of [FeFe] hydrogenase active-site model complexes with an azadithiolate cofactor2013In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, no 43, p. 14566-14572Article in journal (Refereed)
    Abstract [en]

    A detailed characterization of a close synthetic model of the [2 Fe]H subcluster in the [FeFe] hydrogenase active site is presented. It contains the full primary coordination sphere of the CO-inhibited oxidized state of the enzyme including the CN(-) ligands and the azadithiolate (adt) bridge, [((μ-SCH2 )2 NR)Fe2 (CO)4 (CN)2 ](2-) , R=CH2 CH2 SCH3 . The electronic structure of the model complex in its Fe(I) Fe(II) state was investigated by means of density functional theory (DFT) calculations and Fourier transform infrared (FTIR) spectroscopy. By using a combination of continuous-wave (CW) electron paramagnetic resonance (EPR) and hyperfine sublevel correlation (HYSCORE) experiments as well as DFT calculations, it is shown that, for this complex, the spin density is delocalized over both iron atoms. Interestingly, we found that the nitrogen hyperfine coupling, which represents the interaction between the unpaired electron and the nitrogen at the dithiolate bridge, is slightly larger than that in the analogous complex in which the CN(-) ligands are replaced with PMe3 ligands. This reveals, first, that the CN(-) /PMe3 ligands coordinated to the iron core are electronically coupled to the amine in the adt bridge. Second, the CN(-) ligands in this complex are somewhat stronger σ-donor ligands than the PMe3 ligand, and thereby enable more spin density to be transferred from the Fe core to the adt unit, which might in turn affect the reactivity of the bridging amine.

  • 26. Finke, Aaron D.
    et al.
    Jahn, Burkhard O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Saithalavi, Anas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Dahlstrand, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Nauroozi, Djawed
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Haberland, Sophie
    Gisselbrecht, Jean-Paul
    Boudon, Corinne
    Mijangos, Edgar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Schweizer, W. Bernd
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Diederich, Francois
    The 6,6-Dicyanopentafulvene Core: A Template for the Design of Electron-Acceptor Compounds2015In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, no 22, p. 8168-8176Article in journal (Refereed)
    Abstract [en]

    The electron-accepting ability of 6,6-dicyanopentafulvenes (DCFs) can be varied extensively through substitution on the five-membered ring. The reduction potentials for a set of 2,3,4,5-tetraphenyl-substituted DCFs, with varying substituents at the para-position of the phenyl rings, strongly correlate with their Hammett sigma(p)-parameters. By combining cyclic voltammetry with DFT calculations ((U)B3LYP/6-311+G(d)), using the conductor-like polarizable continuum model (CPCM) for implicit solvation, the absolute reduction potentials of a set of twenty DCFs were reproduced with a mean absolute deviation of 0.10eV and a maximum deviation of 0.19eV. Our experimentally investigated DCFs have reduction potentials within 3.67-4.41eV, however, the computations reveal that DCFs with experimental reduction potentials as high as 5.3eV could be achieved, higher than that of F-4-TCNQ (5.02eV). Thus, the DCF core is a template that allows variation in the reduction potentials by about 1.6eV.

  • 27. Fortage, Jerome
    et al.
    Boixel, Julien
    Blart, Errol
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Becker, Hans Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Odobel, Fabrice
    Single-step electron transfer on the nanometer scale: Ultra-fast charge shift in strongly coupled zinc porphyrin-gold porphyrin dyads2008In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 14, no 11, p. 3467-3480Article in journal (Refereed)
    Abstract [en]

    The synthesis, electrochemical properties, and photoinduced electron transfer processes of a series of three novel zinc (II)-gold (III) bisporphyrin dyads (ZnP-S-AuP+) are described. The systems studied consist of two trisaryl porphyrins connected directly in the meso position via an alkyne unit to tert-(phenylenethynylene) or penta(phenylenethynylene) spacers. In these dyads, the estimated center to center interporphyrin separation distance varies from 32 to 45 A. The absorption, emission, and electrochemical data indicate that there are strong electronic interactions between the linked elements, thanks to the direct attachment of the spacer on the porphyrin ring through the alkyne unit, At room temperature in toluene, light excitation of the zinc porphyrin results in almost quantitative formation of the charge shifted state center dot+ZnP-S-AuP center dot, whose lifetime is in the order of hundreds of picoseconds. In this solvent, the charge-separated state decays to the ground state through the intermediate population of the zinc porphyrin triplet excited state. Excitation of the gold porphyrin leads instead to rapid energy transfer to the triplet ZnP. In dichloromethane the charge shift reactions are even faster, with time constants down to 2 ps, and may be induced also by excitation of the gold porphyrin. In this latter solvent, the longest charge-shifted lifetime (tau= 2.3ns) was obtained with the penta(phenylenethynylene) spacer. The charge shift reactions are discussed in terms of bridge-mediated super-exchange mechanisms as electron or hole transfer. These new bis-porphyrin arrays, with strong electronic coupling, represent interesting molecular systems in which extremely fast and efficient long-range photoinduced charge shift occurs over a long distance. The rate constants are two to three orders of magnitude larger than for corresponding ZnP-AuP+ dyads linked via meso-phenyl groups to oligo-phenyleneethynylene spacers. Ibis study demonstrates the critical impact of the attachment position of the spacer on the porphyrin on the electron transfer rate, and this strategy can represent a useful approach to develop molecular photonic devices for long-range charge separations.

  • 28. Fortage, Jerome
    et al.
    Scarpaci, Annabelle
    Viau, Lydie
    Pellegrin, Yann
    Blart, Errol
    Falkenström, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Asselberghs, Inge
    Kellens, Ruben
    Libaers, Wim
    Clays, Koen
    Eng, Mattias P.
    Odobel, Fabrice
    Charge-Transfer State and Large First Hyperpolarizability Constant in a Highly Electronically Coupled Zinc and Gold Porphyrin Dyad2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 36, p. 9058-9067Article, review/survey (Refereed)
    Abstract [en]

    We report the synthesis and the characterizations of a novel dyad composed of a zinc porphyrin (ZnP) linked to a gold porphyrin (AuP) through an ethynyl spacer. The UV/Vis absorption spectrum and the electrochemical properties clearly reveal that this dyad exhibits a strong electronic coupling in the ground state as evidenced by shifted redox potentials and the appearance of an intense charge-transfer band localized at lambda = 739 nm in dichloromethane. A spectroelectrochemical study of the dyad along with the parent homometallic system (i.e., ZnP-ZnP and AuP-AuP) was undertaken to determine the spectra of the reduced and oxidized porphyrin units. Femtosecond transient absorption spectroscopic analysis showed that the photoexcitation of the heterometallic dyad leads to an ultrafast formation of a charge-separated state (+ZnP-AuP center dot) that displays a particularly long lifetime (tau=4 ns in toluene) for such a short separation distance. The molecular orbitals of the dyad were determined by DFT quantum-chemical calculations. This theoretical study confirms that the observed intense band at lambda = 739 nm corresponds to an interporphyrin charge-transfer transition from the HOMO orbital localized on the zinc porphyrin to LUMO orbitals localized on the gold porphyrin. Finally, a Hyper-Rayleigh scattering study shows that the dyad possesses a large first molecular hyperpolarizability coefficient (beta = 2100 x 10(-30) esu at lambda = 1064 nm), thus highlighting the valuable nonlinear optical properties of this new type of push-pull porphyrin system.

  • 29.
    Garcia-Bennett, Alfonso E
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Xiao, Changhong
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm.
    Zhou, Chunfang
    Nanologica AB, Stockholm.
    Castle, Toen
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm.
    Miyasaka, Keiichi
    Graduate School of EEWS WCU Energy Science & Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea.
    Terasaki, Osamu
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm and Graduate School of EEWS WCU Energy Science & Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea.
    Bicontinuous cubic mesoporous materials with biphasic structures2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 48, p. 13510-13516Article in journal (Refereed)
    Abstract [en]

    The replication of amphiphilic systems within an inorganic silica matrix allows the study of the fundamental properties of mesostructural changes, that is, kinetic and structural parameters. Herein we report a detailed study of the transition between cubic bicontinuous mesostructure with space groups Ia$\bar 3$d and Pn$\bar 3$m symmetry, which are associated with the minimal G and D surfaces, respectively. The transition may be induced through micellar swelling of the anionic amphiphilic surfactant N-lauroyl alanine by trimethylbenzene. Rich kinetic behaviour is observed and has been exploited to prepare particles with biphasic structures. Transmission electron microscopy evidence indicates that there is epitaxial growth from one mesostructure to the other involving the [111] and [110] orientations of the Ia$\bar 3$d and Pn$\bar 3$m symmetry structures, respectively. From kinetic studies, we show that the formation of the Ia$\bar 3$d mesophase is preceded by a hexagonal phase (plane group p6mm) and an epitaxial relationship has been observed involving the sixfold or $\bar 3$ axis orientations of both structures. Our data suggests that the Pn$\bar 3$m mesostructure is kinetically stable at low temperatures whereas the Ia$\bar 3$d mesostructure is the more stable structure after prolonged periods of hydrothermal treatment. We present evidence from transmission electron microscopy and small-angle X-ray diffractograms and also electron crystallography modelling of the unit cells at particular points in the structural change.

  • 30.
    Geng, Xue-Li
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Acetylene-Expanded Dendralene Segments with Exotopic Phosphaalkene Units2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 43, p. 12153-12162Article in journal (Refereed)
    Abstract [en]

    Bis-TMS protected C, C-diacetylenic phosphaalkene (A(2)PA) 1 (Mes*P=C(C CTMS)(2); Mes*=2,4,6-tBu(3)Ph) has been used as a building block for the construction of butadiyne-expanded dendralene fragments in which phosphaalkenes feature as exotopic double bonds. Treatment of 1 with CuCl gives rise to a Cu(I) acetylide that is selectively formed at the acetylene trans to the Mes* group. The cis-TMS-acetylene engages in similar chemistry, albeit at higher temperatures and longer reaction times. The differentiation between the two acetylene termini of 1 allows for the controlled synthesis of the title compounds by a variety of different Cu- and Pd-catalyzed oxidative acetylene homo- and heterocoupling protocols. Crystallographic characterization of A(2)PA 1 and dimeric Mes*P=C(C CR(1))C(4)(R(2)C C)C=PMes* (3b, R(1)=R(2)=Ph; 6, R(1)=R(2)=TMS), and 10 (R(1)=R(2)=C CPh) verifies that the stereochemistry across the P=C bond is conserved during the coupling reactions, whereas spectroscopic evidence reveals cis/trans isomerization in an iodo-substituted A(2)PA intermediate 4 (Mes*P=C(C CTMS)(C CI). UV/Vis spectroscopic and electrochemical studies reveal that efficient pi conjugation operates through the entire acetylenic phosphaalkene framework, even in the cross-conjugated dimeric structures. The P centers contribute considerably to the frontier molecular orbitals of the compounds, thereby leading to smaller HOMO-LUMO gaps than in all-carbon-based congeners. Phenyl- and/or ethynylphenyl substituents at the A(2)PA framework influence the HOMO and LUMO to a varying degree depending on their relationship to the Mes* group, thus enabling a fine-tuning of the frontier molecular orbitals of the compounds.

  • 31.
    Glas, Adrian
    et al.
    Max Planck Gesell, Chem Genom Ctr, Otto Hahn Str 15, D-44227 Dortmund, Germany..
    Wamhoff, Eike-Christian
    Max Planck Inst Colloids & Interfaces, Dept Biomol Syst, Muhlenberg 1, D-14424 Potsdam, Germany.;Free Univ Berlin, Dept Biol Chem & Pharm, Takustr 3, D-14195 Berlin, Germany..
    Krüger, Dennis M.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Structure and Molecular Biology. Max Planck Gesell, Chem Genom Ctr, Otto Hahn Str 15, D-44227 Dortmund, Germany..
    Rademacher, Christoph
    Max Planck Inst Colloids & Interfaces, Dept Biomol Syst, Muhlenberg 1, D-14424 Potsdam, Germany.;Free Univ Berlin, Dept Biol Chem & Pharm, Takustr 3, D-14195 Berlin, Germany..
    Grossmann, Tom N.
    Max Planck Gesell, Chem Genom Ctr, Otto Hahn Str 15, D-44227 Dortmund, Germany.;Vrije Univ Amsterdam, Dept Chem & Pharmaceut Sci, Boelelaan 1083, NL-1081 HV Amsterdam, Netherlands..
    Increased Conformational Flexibility of a Macrocycle-Receptor Complex Contributes to Reduced Dissociation Rates2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 64, p. 16157-16161Article in journal (Refereed)
    Abstract [en]

    Constraining a peptide in its bioactive conformation by macrocyclization represents a powerful strategy to design modulators of challenging biomolecular targets. This holds particularly true for the development of inhibitors of protein-protein interactions which often involve interfaces lacking defined binding pockets. Such flat surfaces are demanding targets for traditional small molecules rendering macrocyclic peptides promising scaffolds for novel therapeutics. However, the contribution of peptide dynamics to binding kinetics is barely understood which impedes the design process. Herein, we report unexpected trends in the binding kinetics of two closely related macrocyclic peptides that bind their receptor protein with high affinity. Isothermal titration calorimetry, F-19 NMR experiments and molecular dynamics simulations reveal that increased conformational flexibility of the macrocycle-receptor complex reduces dissociation rates and contributes to complex stability. This observation has impact on macrocycle design strategies that have so far mainly focused on the stabilization of bioactive ligand conformations.

  • 32. Goeppert, Alain
    et al.
    Dinér, Peter
    Organic Chemistry Department of Chemistry Göteborg University.
    Ahlberg, Per
    Sommer, Jean
    Methane activation and oxidation in sulfuric acid2002In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 8, no 14, p. 3277-3283Article in journal (Refereed)
    Abstract [en]

    The H/D exchange observed when methane is contacted with D(2)SO(4) at 270-330 degrees C shows that the alkane behaves as a sigma base and undergoes rapid and reversible protonation at this temperature. DFT studies of the hydrogen exchange between a monomer and a dimer of sulfuric acid and methane show that the transition states involved in the exchange are bifunctional, that is one hydrogen atom is transferred from a hydroxy group in sulfuric acid to methane, while one hydrogen atom is abstracted from methane by a non-hydroxy oxygen atom in sulfuric acid. All the transition states include a CH(5) moiety, which shows similarities to the methanium ion CH(5) (+). The calculated potential activation energy of the hydrogen exchange for the monomer is 174 kJ mol(-1), which is close to the experimental value (176 kJ mol(-1)). Solvation of the monomer and the transition state of the monomer with an extra sulfuric acid molecule, decrease the potential activation energy by 6 kJ mol(-1). The acid-base process is in competition, however, with an oxidative process involving methane and sulfuric acid which leads to CO(2), SO(2), and water, and thus to a decrease of acidity and loss of reactivity of the medium.

  • 33.
    Gupta, Arvind Kumar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Alkynyl Coinage Metal Clusters and Complexes-Syntheses, Structures, and Strategies2018In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, no 30, p. 7536-+Article in journal (Refereed)
    Abstract [en]

    In this Concept we discuss how the chemistry of coinage metal complexes based on alkynyl ligands has developed over the past decades. The rich coordination of alkynyl, that exhibit both (1) (end-on) and (2) (side on) modes, includes non-bridged systems, as well as bridging of up to four (or six) metal centres. Resulting metal clusters often exhibit highly regular structures and typical coordination motifs forming fascinating assemblies exploiting this versatile coordination. Metallophilic interactions are often an important driving force for the formation of large clusters. In addition, the use of co-ligands as well the possibility to encapsulate counter ions greatly increases the chemical and structural diversity. Herein we attempt to summarize and highlight design principles towards multinuclear homo and hetero-bi-metallic coinage metal clusters of alkynyl ligands.

  • 34.
    Hall, James P.
    et al.
    Univ Reading, Dept Chem, Reading RG6 6AD, Berks, England.;Diamond Light Source, Harwell Sci & Innovat Campus,Fermi Ave, Didcot OX11 0QX, Oxon, England..
    Gurung, Sarah P.
    Univ Reading, Dept Chem, Reading RG6 6AD, Berks, England.;Diamond Light Source, Harwell Sci & Innovat Campus,Fermi Ave, Didcot OX11 0QX, Oxon, England..
    Henle, Jessica
    Univ Reading, Dept Chem, Reading RG6 6AD, Berks, England..
    Poidl, Patrick
    Univ Reading, Dept Chem, Reading RG6 6AD, Berks, England..
    Andersson, Johanna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC. Chalmers, Dept Chem & Chem Engn, S-41296 Gothenburg, Sweden..
    Lincoln, Per
    Chalmers, Dept Chem & Chem Engn, S-41296 Gothenburg, Sweden..
    Winter, Graeme
    Diamond Light Source, Harwell Sci & Innovat Campus,Fermi Ave, Didcot OX11 0QX, Oxon, England..
    Sorensen, Thomas
    Diamond Light Source, Harwell Sci & Innovat Campus,Fermi Ave, Didcot OX11 0QX, Oxon, England..
    Cardin, David J.
    Univ Reading, Dept Chem, Reading RG6 6AD, Berks, England..
    Brazier, John A.
    Univ Reading, Dept Pharm, Reading RG6 6AD, Berks, England..
    Cardin, Christine J.
    Univ Reading, Dept Chem, Reading RG6 6AD, Berks, England..
    Guanine Can Direct Binding Specificity of Ru-dipyridophenazine (dppz) Complexes to DNA through Steric Effects2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 21, p. 4981-4985Article in journal (Refereed)
    Abstract [en]

    X-ray crystal structures of three -[Ru(L)(2)dppz](2+) complexes (dppz=dipyridophenazine; L=1,10-phenanthroline (phen), 2,2-bipyridine (bpy)) bound to d((5BrC)GGC/GCCG) showed the compounds intercalated at a 5-CG-3 step. The compounds bind through canted intercalation, with the binding angle determined by the guanine NH2 group, in contrast to symmetrical intercalation previously observed at 5-TA-3 sites. This result suggests that canted intercalation is preferred at 5-CG-3 sites even though the site itself is symmetrical, and we hypothesise that symmetrical intercalation in a 5-CG-3 step could give rise to a longer luminescence lifetime than canted intercalation.

  • 35. Huber, Stefan M.
    et al.
    Ertem, Mehmed Z.
    Aquilante, Francesco
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Gagliardi, Laura
    Tolman, William B.
    Cramer, Christopher J.
    Generating Cu-II-oxyl/Cu-III-oxo species from Cu-I-alpha-ketocarboxylate complexes and O-2: in silico studies on ligand effects and C-H-activation reactivity.2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 19, p. 4886-4895Article in journal (Refereed)
    Abstract [en]

    A mechanism for the oxygenation of Cu-I complexes with alpha-keto-carboxylate ligands that is based on a combination of density functional theory and multireference second-order perturbation theory (CASSCF/CASPT2) calculations is elaborated. The reaction proceeds in a manner largely analogous to those of similar Fe-II-alpha-ketocarboxylate systems, that is, by initial attack of a coordinated oxygen molecule on a ketocarboxylate ligand with concomitant decarboxylation. Subsequently, two reactive intermediates may be generated, a Cu-peracid structure and a [CuO](+) species, both of which are capable of oxidizing a phenyl ring component of the supporting ligand. Hydroxylation by the [CuO](+) species is predicted to proceed with a smaller activation free energy. The effects of electronic and steric variations on the oxygenation mechanisms were studied by introducing substituents at several positions of the ligand backbone and by investigating various N-donor ligands. In general, more electron donation by the N-donor ligand leads to increased stabilization of the more Cu-II/Cu-III-like intermediates (oxygen adducts and [CuO](+) species) relative to the more Cu-I-like peracid intermediate. For all ligands investigated the [CuO](+) intermediates are best described as Cu-II-O center dot(-) species with triplet ground states. The reactivity of these compounds in C-H abstraction reactions decreases with more electron-donating N-donor ligands, which also increase the Cu-O bond strength, although the Cu-O bond is generally predicted to be rather weak (with a bond order of about 0.5). A comparison of several methods to obtain singlet energies for the reaction intermediates indicates that multireference second-order perturbation theory is likely more accurate for the initial oxygen adducts, but not necessarily for subsequent reaction intermediates.

  • 36. Jarikote, Dilip Venkatrao
    et al.
    Krebs, Nils
    Tannert, Sebastian
    Röder, Beate
    Seitz, Oliver
    Exploring base-pair-specific optical properties of the DNA stain thiazole orange.2007In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 13, no 1, p. 300-10Article in journal (Refereed)
    Abstract [en]

    Double-stranded DNA offers multiple binding sites to DNA stains. Measurements of noncovalently bound dye-nucleic acid complexes are, necessarily, measurements of an ensemble of chromophores. Thus, it is difficult to assign fluorescence properties to base-pair-specific binding modes of cyanine dyes or, vice versa, to obtain information about the local environment of cyanines in nucleic acids by using optical spectroscopy. The feasibility to stain DNA and simultaneously probe local perturbations by optical spectroscopy would be a valuable asset to nucleic acid research. So-called FIT probes (forced intercalation probes) were used to pinpoint the location of the DNA stain thiazole orange (TO) in PNADNA duplexes. A detailed analysis of the base-pair dependence of optical properties is provided and enforced binding of TO is compared with "classical" binding of free TO-PRO1. UV-visible absorbance, circular dichroism (CD) and fluorescence spectroscopy, and melting-curve analyses confirmed site-specific TO intercalation. Thiazole orange exhibited base-specific responses that are not observed in noncovalent dye-nucleic acid complexes, such as an extraordinary dependence of the TO extinction coefficient (+/-60 % variation of the averaged epsilon(max) of 57,000 M(-1) cm(-1)) on nearest-neighbor base pairs. TO signals hybridization, as shown by increases in the steady-state fluorescence emission. Studies of TO fluorescence lifetimes in FIT-PNA and in DNADNA and PNADNA complexes highlighted four different fluorescence-decay processes that may be closed or opened in response to matched or single-mismatched hybridization. A very fast decay process (0.04-0.07 ns) and a slow decay process (2.33-3.95 ns) provide reliable monitors of hybridization, and the opening of a fast decay channel (0.22-0.48 ns) that resulted in an attenuation of the fluorescence emission is observed upon the formation of mismatched base pairs.

  • 37. Jena, Naresh K.
    et al.
    Josefsson, Ida
    Eriksson, Susanna Kaufmann
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Odelius, Michael
    Solvent-Dependent Structure of the I-3(-) Ion Derived from Photoelectron Spectroscopy and Ab Initio Molecular Dynamics Simulations2015In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, no 10, p. 4049-4055Article in journal (Refereed)
    Abstract [en]

    Ab initio molecular dynamics (MD) simulations of the solvation of LiI3 in four different solvents (water, methanol, ethanol, and acetonitrile) are employed to investigate the molecular and electronic structure of the I-3(-) ion in relation to X-ray photoelectron spectroscopy (XPS). Simulations show that hydrogen-bond rearrangement in the solvation shell is coupled to intramolecular bond-length asymmetry in the I-3(-) ion. By a combination of charge analysis and I 4d core-level XPS measurements, the mechanism of the solvent-induced distortions has been studied, and it has been concluded that charge localization mediates intermolecular interactions and intramolecular distortion. The approach involving a synergistic combination of theory and experiment probes the solvent-dependent structure of the I-3(-) ion, and the geometric structure has been correlated with the electronic structure.

  • 38.
    Johansson, Olof
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Johannissen, Linus O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Bistable Molecular Switches Based on Linkage Isomerization in Ruthenium Polypyridyl Complexes with a Ligand-Bound Ambidentate Motif2009In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 5, p. 1195-1204Article in journal (Refereed)
    Abstract [en]

    Electron-transfer-induced linkage isomerization was investigated in a series of bis-tridentate Ru polypyridyl complexes [Ru(L-X-OH)(Y-tpy)](2+) with ambidentate ligand L-X-OH bpy-C(R)(OH)-py (bpy-2,2'-bipyridine py-pyridine; R-H, Me, Ph, or tBu) and spectator ligand Y-tpy (tpy 2.2':6',2 ''-terpyridine, Y-p-tolyl, p-PhCO2Me, Cl, OEt, N-pyrrolidine). The ligand-bound ambidentate motif switches reversibly between N and O coordination in the Ru-II and Ru-III state,respectively. The potentials of the Ru-III/II couple differ by about 0.5 V between the isomers, and this results in a bistable electrochemical response of the molecular switches. The effects of structural modifications in form of substituents on the linking carbon atom of the ambidentate ligand and on the central pyridine moiety of the spectator ligand were investigated by electrochemical and computational methods. Differences in isomerization behavior span six orders of magnitude in rate constants and two orders of magnitude in equilibrium constants. The results can be interpreted in terms of steric and electronic substituent effects and their influence on rotational barriers, ligation geometry, and electron deficiency of the metal center.

  • 39.
    Johnson, Ben A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Agarwala, Hemlata
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    White, Travis A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mijangos, Edgar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Maji, Somnath
    Indian Inst Technol Hyderabad, Dept Chem, Sangareddy 502285, Telangana, India..
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Judicious Ligand Design in Ruthenium Polypyridyl CO2 Reduction Catalysts to Enhance Reactivity by Steric and Electronic Effects2016In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 42, p. 14870-14880Article in journal (Refereed)
    Abstract [en]

    A series of Ru-II polypyridyl complexes of the structural design [Ru-II(R-tpy)(NN)(CH3CN)](2+) (R-tpy= 2,2': 6', 2''-terpyridine (R= H) or 4,4', 4''-tri-tert-butyl-2,2': 6', 2''-terpyridine (R= tBu); NN= 2,2'-bipyridine with methyl substituents in various positions) have been synthesized and analyzed for their ability to function as electrocatalysts for the reduction of CO2 to CO. Detailed electrochemical analyses establish how substitutions at different ring positions of the bipyridine and terpyridine ligands can have profound electronic and, even more importantly, steric effects that determine the complexes' reactivities. Whereas electron-donating groups para to the heteroatoms exhibit the expected electronic effect, with an increase in turnover frequencies at increased overpotential, the introduction of a methyl group at the ortho position of NN imposes drastic steric effects. Two complexes, [Ru-II(tpy)(6-mbpy)(CH3CN)](2+) (trans-[3](2+); 6-mbpy= 6-methyl- 2,2'-bipyridine) and [Ru-II(tBu-tpy)(6-mbpy)(CH3CN)](2+) (trans-[4](2+)), in which the methyl group of the 6-mbpy ligand is trans to the CH3CN ligand, show electrocatalytic CO2 reduction at a previously unreactive oxidation state of the complex. This low overpotential pathway follows an ECE mechanism (electron transfer-chemical reaction-electron transfer), and is a direct result of steric interactions that facilitate CH3CN ligand dissociation, CO2 coordination, and ultimately catalytic turnover at the first reduction potential of the complexes. All experimental observations are rigorously corroborated by DFT calculations.

  • 40. Johnston, Eric V.
    et al.
    Verho, Oscar
    Karkas, Markus D.
    Shakeri, Mozaffar
    Tai, Cheuk-Wai
    Palmgren, Pål
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Eriksson, Kristofer
    Oscarsson, Sven
    Backvall, Jan-E.
    Highly Dispersed Palladium Nanoparticles on Mesocellular Foam: An Efficient and Recyclable Heterogeneous Catalyst for Alcohol Oxidation2012In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 39, p. 12202-12206Article in journal (Refereed)
  • 41.
    Jorner, Kjell
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Emanuelsson, Rikard
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Dahlstrand, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Tong, Hui
    Denisova, Aleksandra V.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Impact of Ground- and Excited-State Aromaticity on Cyclopentadiene and Silole Excitation Energies and Excited-State Polarities2014In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, no 30, p. 9295-9303Article in journal (Refereed)
    Abstract [en]

    A new qualitative model for estimating the properties of substituted cyclopentadienes and siloles in their lowest pi pi* excited states is introduced and confirmed through quantum chemical calculations, and then applied to explain earlier reported experimental excitation energies. According to our model, which is based on excited-state aromaticity and antiaromaticity, siloles and cyclopentadienes are cross-hyperconjugated "aromatic chameleons" that adapt their electronic structures to conform to the various aromaticity rules in different electronic states (Huckel's rule in the pi(2) electronic ground state (S-0) and Baird's rule in the lowest pi pi* excited singlet and triplet states (S-1 and T-1)). By using pen-and-paper arguments, one can explain polarity changes upon excitation of substituted cyclopentadienes and siloles, and one can tune their lowest excitation energies by combined considerations of ground-and excited-state aromaticity/antiaromaticity effects. Finally, the "aromatic chameleon" model can be extended to other monocyclic compound classes of potential use in organic electronics, thereby providing a unified view of the S-0, T-1, and S-1 states of a range of different cyclic cross-pi-conjugated and cross-hyperconjugated compound classes.

  • 42.
    Jorner, Kjell
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Feixas, Ferran
    Univ Girona, IQCC, Campus Montilivi S-N, Girona 17071, Catalonia, Spain.;Univ Girona, Dept Quim, Campus Montilivi S-N, Girona 17071, Catalonia, Spain..
    Ayub, Rabia
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. Uppsala Univ, Uppsala Ctr Computat Chem UC3, Box 518, S-75120 Uppsala, Sweden..
    Sola, Miquel
    Univ Girona, IQCC, Campus Montilivi S-N, Girona 17071, Catalonia, Spain.;Univ Girona, Dept Quim, Campus Montilivi S-N, Girona 17071, Catalonia, Spain..
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Analysis of a Compound Class with Triplet States Stabilized by Potentially Baird Aromatic [10]Annulenyl Dicationic Rings2016In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 8, p. 2793-2800Article in journal (Refereed)
    Abstract [en]

    The low-lying triplet state of a recently published compound (TMTQ) was analyzed quantum chemically in light of suggestions that it is influenced by Baird aromaticity. Two mesomeric structures describe this state: 1)a zwitterionic Baird aromatic structure with a triplet diradical 8-electron methano[10]annulene (M10A) dicationic ring and 2)a Huckel aromatic with a neutral closed-shell 10-electron ring. According to charge and spin density distributions, the Huckel aromatic structure dominates the triplet state (the Baird aromatic contributes at most 12%), and separation of the aromatic fluctuation index (FLU) into and electron contributions emphasizes this finding. The small singlet-triplet energy gap is due to Huckel aromaticity of the M10A ring, clarified by comparison to the smaller analogues of TMTQ. Yet, TMTQ and its analogues are Huckel-Baird hybrids allowing for tuning between closed-shell 4n+2 Huckel aromaticity and open-shell 4n Baird aromaticity.

  • 43. Karlsson, Karl Martin
    et al.
    Jiang, Xiao
    Eriksson, Susanna Kaufman
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Gabrielsson, Erik
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Sun, Licheng
    Phenoxazine Dyes for Dye-Sensitized Solar Cells: Relationship Between Molecular Structure and Electron Lifetime2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 23, p. 6415-6424Article in journal (Refereed)
    Abstract [en]

    A series of metal-free organic dyes with a core phenoxazine chromophore have been synthesized and tested as sensitizers in dye-sensitized solar cells. Overall conversion efficiencies of 6.03-7.40% were reached under standard AM 1.5G illumination at a light intensity of 100 mW cm(-2). A clear trend in electron lifetime could be seen; a dye with a furan-conjugated linker showed a shorter lifetime relative to dyes with the acceptor group directly attached to the phenoxazine. The addition of an extra donor unit, which bore insulating alkoxyl chains, in the 7-position of the phenoxazine could increase the lifetime even further and, together with additives in the electrolyte to raise the conduction band, an open circuit voltage of 800 mV could be achieved. From photoelectron spectroscopy and X-ray absorption spectroscopy of the dyes adsorbed on TiO2 particles, it can be concluded that the excitation is mainly of cyano character (i.e., on average, the dye molecules are standing on, and pointing out, from the surface of TiO2 particles).

  • 44.
    Kathiravan, Subban
    et al.
    Linnaeus Univ, Ctr Biomat Chem, Dept Chem & Biomed Sci, S-39182 Kalmar, Sweden..
    Nicholls, Ian A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry. Linnaeus Univ, Ctr Biomat Chem, Dept Chem & Biomed Sci, S-39182 Kalmar, Sweden..
    Monoprotected L-Amino Acid (L-MPAA), Accelerated Bromination, Chlorination, and Iodination of C(sp²)-H Bonds by Iridium(III) Catalysis2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 29, p. 7031-7036Article in journal (Refereed)
    Abstract [en]

    Halogenated arenes are important structural motifs commonly found in biologically active molecules and used for a variety of transformations in organic synthesis. Herein, we report the mono-protected L-amino acid (L-MPAA) accelerated iridium(III)-catalyzed halogenation of (hetero)anilides at room temperature. This reaction constitutes the first example of an iridium(III)/L-MPAA-catalyzed general halogenation of (hetero)arenes through C(sp²)-H activation. Furthermore, we demonstrate the potential utility of our method through its use in the synthesis of a quinolone derivative.

  • 45.
    Kjeldsen, Frank
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Ion Physics.
    Silivra, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Ion Physics.
    Zubarev, Roman
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Ion Physics.
    Zwitterionic States in Gas-Phase Polypeptide Ions Revealed by 157-nm Ultra-Violet Photodissociation2006In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 12, no 30, p. 7920-7928Article in journal (Refereed)
    Abstract [en]

    A new method of detecting the presence of deprotonation and determining its position in gas-phase polypeptide cations is described. The method involves 157-nm ultra-violet photodissociation (UVPD) and is based on monitoring the losses of CO2 (44 Da) from electronically excited deprotonated carboxylic groups relative to competing COOH losses (45 Da) from neutral carboxylic groups. Loss of CO2 is a strong indication of the presence of a zwitterionic [(+)center dot center dot center dot(-)center dot center dot center dot(+)] salt bridge in the gas-phase polypeptide cation. This method provides a tool for studying, for example, the nature of binding within polypeptide clusters. Collision-activated dissociation (CAD) of decarboxylated cations localizes the position of deprotonation. Fragment abundances can be used for the semi-quantitative assessment of the branching ratio of deprotonation among different acidic sites, however, the mechanism of the fragment formation should be taken into account. Cations of Trp-cage proteins exist preferentially as zwitterions, with the deprotonation position divided between the Asp(9) residue and the C terminus in the ratio 3:2. The majority of dications of the same molecule are not zwitterions. Furthermore, 157-nm UVPD produces abundant radical cations M center dot+ from protonated molecules through the loss of a hydrogen atom. This method of producing M center dot+ ions is general and can be applied to any gas-phase peptide cation. The abundance of the molecular radical cations M center dot+ produced is sufficient for further tandem mass spectrometry (MS/MS), which, in the cases studied, yielded side-chain loss of a basic amino acid as the most abundant fragmentation channel together with some backbone cleavages.

  • 46. Krogh, J W
    et al.
    Barone, G
    Lindh, Roland
    Department of Theoretical Chemistry, Lund University.
    The prediction of the nuclear quadrupole splitting of Sn-119 Mossbauer spectroscopy data by scalar relativistic DFT calculations2006In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 12, no 19, p. 5116-5121Article in journal (Refereed)
    Abstract [en]

    The electric field gradient components for the tin nucleus of 34 tin compounds of experimentally known structures and Sn-119 Mossbauer spectroscopy parameters were computed at the scalar relativistic density functional theory level of approximation. The theoretical values of the electric field gradient components were used to determine a quantity, V, which is proportional to the nuclear quadrupole splitting parameter (Delta E). In a subsequent linear regression analysis the effective nuclear quadrupole moment, Q, was evaluated. The value of (11.9 +/- 0.1) fm(2) is a significant improvement over the non-relativistic result of (15.2 +/- 4.4) fm(2) and is in agreement with the experimental value of (10.9 +/- 0.8) fm(2). The average mean square error Delta E-calcd-Delta E-exptl = +/- 0.3 mm s(-1) is a factor of two smaller than in the non-relativistic case. Thus, the approach has a quality which provides accurate support for the structure interpretation by Sn-119 spectroscopy. It was noted that geometry optimization at the relativistic level does not significantly increase the quality of the results compared with non-relativistic optimized structures. The accuracy in the approach called on us to consider the singlet-triplet state nature of the electronic structure of one of the investigated compounds.

  • 47. Kumar, Bhupendra
    et al.
    Beyler, Maryline
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Kubiak, Clifford P.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Photoelectrochemical Hydrogen Generation by an [FeFe] Hydrogenase Active Site Mimic at a p-Type Silicon/Molecular Electrocatalyst Junction2012In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 5, p. 1295-1298Article in journal (Refereed)
  • 48.
    Kumar, Rohan J
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Karlsson, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Streich, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Rolandini Jensen, Alice
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Jäger, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Becker, Hans-Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Johansson, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Vectorial Electron Transfer in Donor-Photosensitizer-Acceptor Triads Based on Novel Bis-tridentate Ruthenium Polypyridyl Complexes2010In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 16, no 9, p. 2830-2842Article in journal (Refereed)
    Abstract [en]

    The first examples of rodlikedonor–photosensitizer–acceptor arrays based on bis-2,6-di(quinolin-8-yl)pyridineRuII complexes 1a and 3a for photoinduced electron transfer have been synthesized and investigated. The complexes are synthesized in a convergent manner and are isolated as linear, single isomers. Time-resolved absorption spectroscopy reveals long-lived, photoinduced charge-separated states(tCSS (1a)=140 ns, tCSS (3a)=200 ns) formed by stepwise electron transfer.The overall yields of charge separation (Yield 50% for complex 1a and Yield 95% for complex 3a) are unprecedented for bis-tridentate RuII polypyridyl complexes.This is attributed to the longlived excited state of the [Ru(dqp)2]2+ complex combined with fast electron transfer from the donor moiety following the initial charge separation. The rodlike arrangement of donor and acceptor gives controlled, vectorial electron transfer, free from the complications of stereoisomeric diversity. Thus, such arrays provide an excellent system for the study of photoinduced electron transfer and, ultimately, the harvesting of solar energy.

  • 49. Kärkäs, Markus D.
    et al.
    Johnston, Eric V.
    Karlsson, Erik A.
    Lee, Bao-Lin
    Åkermark, Torbjörn
    Shariatgorji, Mohammadreza
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Ilag, Leopold
    Hansson, Örjan
    Bäckvall, Jan-E.
    Åkermark, Björn
    Light-Induced Water Oxidation by a Ru complex Containing a Bio-Inspired Ligand2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 28, p. 7953-7959Article in journal (Refereed)
    Abstract [en]

    The new Ru complex 8 containing the bio-inspired ligand 7 was successfully synthesized and characterized. Complex 8 efficiently catalyzes water oxidation using Ce(IV) and Ru(III) as chemical oxidants. More importantly, this complex has a sufficiently low overpotential to utilize ruthenium polypyridyl-type complexes as photosensitizers.

  • 50.
    Larsson, Per-Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Salhi-Benachenhou, Nessima
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Lunell, Sten
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Quadricyclane Radical Cation Rearrangements: A Computational Study of the Transformations to 1,3,5-Cycloheptatriene and Norbornadiene2004In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 10, no 3, p. 681-688Article in journal (Refereed)
    Abstract [en]

    An alternative skeletal rearrangement of the quadricyclane radical cation (Q.+) explains the side products formed in the one-electron oxidation to norbornadiene. First, the bicyclo[2.2.1]hepta-2-ene-5-yl-7-ylium radical cation, with an activation energy of 14.9 kcal mol-1, is formed. Second, this species can further rearrange to 1,3,5-cycloheptatriene through two plausible paths, that is, a multistep mechanism with two shallow intermediates and a stepwise path in which the bicyclo[3.2.0]hepta-2,6-diene radical cation is an intermediate. The multistep rearrangement has a rate-limiting step with an estimated activation energy of 16.5 kcal mol-1, which is 2.8 kcal mol-1 lower in energy than the stepwise mechanism. However, the lowest activation energy is found for the Q.+ cycloreversion to norbornadiene that has a transition structure, in close correspondence with earlier studies, and an activation energy of 10.1 kcal mol-1, which agrees well with the experimental estimate of 9.3 kcal mol-1. The computational estimates of activation energies were done using the CCSD(T)/6-311+G(d,p) method with geometries optimized on the B3LYP/6-311+G(d,p) level, combined with B3LYP/6-311+G(d,p) frequencies.

12 1 - 50 of 97
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