uu.seUppsala University Publications
Change search
Link to record
Permanent link

Direct link
BETA
Mirmohades, Mohammad
Publications (10 of 10) Show all publications
Aster, A., Wang, S., Mirmohades, M., Esmieu, C., Berggren, G., Hammarström, L. & Lomoth, R. (2019). Metal vs. ligand protonation and the alleged proton-shuttling role of the azadithiolate ligand in catalytic H-2 formation with FeFe hydrogenase model complexes. Chemical Science, 10(21), 5582-5588
Open this publication in new window or tab >>Metal vs. ligand protonation and the alleged proton-shuttling role of the azadithiolate ligand in catalytic H-2 formation with FeFe hydrogenase model complexes
Show others...
2019 (English)In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 10, no 21, p. 5582-5588Article in journal (Refereed) Published
Abstract [en]

Electron and proton transfer reactions of diiron complexes [Fe(2)adt(CO)(6)] (1) and [Fe(2)adt(CO)(4)(PMe3)(2)] (4), with the biomimetic azadithiolate (adt) bridging ligand, have been investigated by real-time IR- and UV-vis-spectroscopic observation to elucidate the role of the adt-N as a potential proton shuttle in catalytic H-2 formation. Protonation of the one-electron reduced complex, 1(-), occurs on the adt-N yielding 1H and the same species is obtained by one-electron reduction of 1H(+). The preference for ligand vs. metal protonation in the Fe-2(i,0) state is presumably kinetic but no evidence for tautomerization of 1H to the hydride 1Hy was observed. This shows that the adt ligand does not work as a proton relay in the formation of hydride intermediates in the reduced catalyst. A hydride intermediate 1HHy(+) is formed only by protonation of 1H with stronger acid. Adt protonation results in reduction of the catalyst at much less negative potential, but subsequent protonation of the metal centers is not slowed down, as would be expected according to the decrease in basicity. Thus, the adtH(+) complex retains a high turnover frequency at the lowered overpotential. Instead of proton shuttling, we propose that this gain in catalytic performance compared to the propyldithiolate analogue might be rationalized in terms of lower reorganization energy for hydride formation with bulk acid upon adt protonation.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2019
National Category
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-390686 (URN)10.1039/c9sc00876d (DOI)000474412700015 ()31293742 (PubMedID)
Funder
Swedish Research Council, 621-2014-5670Swedish Research Council, 2016-04271Swedish Research Council Formas, 213-2014-880
Available from: 2019-08-16 Created: 2019-08-16 Last updated: 2019-08-16Bibliographically approved
Jain, S. M., Qiu, Z., Häggman, L., Mirmohades, M., Johansson, M. B., Edvinsson, T. & Boschloo, G. (2016). Frustrated Lewis pair-mediated recrystallization of CH3NH3PbI3 for improved optoelectronic quality and high voltage planar perovskite solar cells. Energy & Environmental Science, 9(12), 3770-3782
Open this publication in new window or tab >>Frustrated Lewis pair-mediated recrystallization of CH3NH3PbI3 for improved optoelectronic quality and high voltage planar perovskite solar cells
Show others...
2016 (English)In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 9, no 12, p. 3770-3782Article in journal (Refereed) Published
Abstract [en]

Films of the hybrid lead halide perovskite CH3NH3PbI3 were found to react with pyridine vapor at room temperature leading to complete bleaching of the film. In dry air or nitrogen atmosphere recrystallization takes place, leading to perovskite films with markedly improved optical and photovoltaic properties. The physical and chemical origin of the reversible bleaching and recrystallization mechanism was investigated using a variety of experimental techniques and quantum chemical calculations. The strong Lewis base pyridine attacks the CH3NH3PbI3. The mechanism can be understood from a frustrated Lewis pair formation with a partial electron donation of the lone-pair on nitrogen together with competitive bonding to other species as revealed by Raman spectroscopy and DFT calculations. The bleached phase consists of methylammonium iodide crystals and an amorphous phase of PbI2( pyridine)(2). After spontaneous recrystallization the CH3NH3PbI3 thin films have remarkably improved photoluminescence, and solar cell performance increased from 9.5% for as-deposited films to more than 18% power conversion efficiency for recrystallized films in solar cells with planar geometry under AM1.5G illumination. Hysteresis was negligible and open-circuit potential was remarkably high, 1.15 V. The results show that complete recrystallization can be achieved with a simple room temperature pyridine vapor treatment of CH3NH3PbI3 films leading to high quality crystallinity films with drastically improved photovoltaic performance.

National Category
Physical Chemistry Engineering and Technology
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-311577 (URN)10.1039/c6ee02544g (DOI)000392915500017 ()
Funder
Swedish Energy AgencyStandUpSwedish Research CouncilGöran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of TechnologyKnut and Alice Wallenberg Foundation
Available from: 2016-12-29 Created: 2016-12-29 Last updated: 2017-11-29Bibliographically approved
Mirmohades, M. (2016). Insight into Catalytic Intermediates Relevant for Water Splitting. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Insight into Catalytic Intermediates Relevant for Water Splitting
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Catalysis is an important part of chemistry. This is also reflected in the chemical industry where 85-90 % of all products are made catalytically. Also nature employs catalysts, i.e. enzymes, for its reactions.

To improve on the already existing catalysts one can learn a lot from nature which often uses earth-abundant elements in the enzymes which have also been optimized and finely tuned for billions of years. To gain a deeper understanding of both enzymatic and artificial catalysis one needs to investigate the mechanism of the catalytic process. But for very efficient catalysts with turnover frequencies of several thousand per second this is not easy, since an investigation of the mechanism involves resolving intermediates in the catalytic cycle. The intermediates in these instances are short-lived corresponding to their turnover frequencies. A maximum turnover frequency of 1,000 s-1 e.g. means that each catalyst goes through the whole catalytic cycle in 1 ms. Therefore time-resolved techniques are necessary that have a faster detection speed than the turnover frequency of the catalyst.

Flash photolysis is a spectroscopic technique with an instrument response function down to 10 ns.  Coupling this technique with mid-infrared probing yields an excellent detection system for probing different redox and protonation states of carbonyl metal complexes. Since many catalysts as well as natural enzymes involved in water splitting are metal carbonyl complexes this is an ideal technique to monitor the intermediates of these catalysts.

Chapter 3 covers the investigation of [FeFe] hydrogenases, enzymes that catalyze the reduction of protons to hydrogen in nature. Chapter 4 investigates the intermediates of biomimetic complexes, resembling the active site of natural [FeFe] hydrogenases. Chapter 5 covers the insights gained from investigating other catalysts which are also involved in water splitting and artificial photosynthesis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. p. 81
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1359
Keywords
Catalysis, Artificial photosynthesis, Molecular biomimetics
National Category
Physical Chemistry
Research subject
Chemistry with specialization in Physical Chemistry; Chemistry with specialization in Chemical Physics
Identifiers
urn:nbn:se:uu:diva-281447 (URN)978-91-554-9526-8 (ISBN)
Public defence
2016-06-03, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2016-05-11 Created: 2016-03-24 Last updated: 2016-06-01
Brown, A., Antila, L., Mirmohades, M., Pullen, S., Ott, S. & Hammarström, L. (2016). Ultrafast Electron Transfer between Dye and Catalyst on a Mesoporous NiO Surface. Journal of the American Chemical Society, 26, 8060-8063
Open this publication in new window or tab >>Ultrafast Electron Transfer between Dye and Catalyst on a Mesoporous NiO Surface
Show others...
2016 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 26, p. 8060-8063Article in journal (Other academic) Published
Abstract [en]

The combination of molecular dyes and catalysts with semiconductors into dye-sensitized solar fuel devices (DSSFDs) requires control of efficient interfacial and surface charge transfer between the components. The present study reports on the light-induced electron transfer processes of p-type NiO films cosensitized with coumarin C343 and a bioinspired proton reduction catalyst, [FeFe](mcbdt)(CO)(6) (mcbdt = 3-carboxybenzene-1,2-dithiolate). By transient optical spectroscopy we find that ultrafast interfacial electron transfer (tau approximate to 200 fs) from NiO to the excited C343 ("hole injection") is followed by rapid (t(1/2) approximate to 10 ps) and efficient surface electron transfer from C343 to the coadsorbed [FeFe] (mcbdt)(CO)(6). The reduced catalyst has a clear spectroscopic signature that persists for several tens of microseconds, before charge recombination with NiO holes occurs. The demonstration of rapid surface electron transfer from dye to catalyst on NiO, and the relatively long lifetime of the resulting charge separated state, suggests the possibility to use these systems for photocathodes on. DSSFDs.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-281445 (URN)10.1021/jacs.6b03889 (DOI)000379455600005 ()27314570 (PubMedID)
Funder
Knut and Alice Wallenberg FoundationSwedish Energy AgencyCarl Tryggers foundation
Available from: 2016-03-24 Created: 2016-03-24 Last updated: 2017-11-30Bibliographically approved
Wang, L., Mirmohades, M., Brown, A., Duan, L., Li, F., Daniel, Q., . . . Hammarstrom, L. (2015). Sensitizer-Catalyst Assemblies for Water Oxidation. Inorganic Chemistry, 54(6), 2742-2751
Open this publication in new window or tab >>Sensitizer-Catalyst Assemblies for Water Oxidation
Show others...
2015 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 54, no 6, p. 2742-2751Article in journal (Refereed) Published
Abstract [en]

Two molecular assemblies with one Ru(II)-polypyridine photosensitizer covalently linked to one Ru(II)(bda)L2 catalyst (1) (bda = 2,2'-bipyridine-6,6'-dicarboxylate) and two photosensitizers covalently linked to one catalyst (2) have been prepared using a simple C-C bond as the linkage. In the presence of sodium persulfate as a sacrificial electron acceptor, both of them show high activity for catalytic water oxidation driven by visible light, with a turnover number up to 200 for 2. The linked photocatalysts show a lower initial yield for light driven oxygen evolution but a much better photostability compared to the three component system with separate sensitizer, catalyst and acceptor, leading to a much greater turnover number. Photocatalytic experiments and time-resolved spectroscopy were carried out to probe the mechanism of this catalysis. The linked catalyst in its Ru(II) state rapidly quenches the sensitizer, predominantly by energy transfer. However, a higher stability under photocatalytic condition is shown for the linked sensitizer compared to the three component system, which is attributed to kinetic stabilization by rapid photosensitizer regeneration. Strategies for employment of the sensitizer-catalyst molecules in more efficient photocatalytic systems are discussed.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-251799 (URN)10.1021/ic502915r (DOI)000351325200028 ()25700086 (PubMedID)
Available from: 2015-04-28 Created: 2015-04-24 Last updated: 2017-12-04
Hammarström, L., Brown, A., Mirmohades, M., Pullen, S., Ott, S. & Lomoth, R. (2014). Mechanistic investigations and detection of intermediates of molecular proton reduction catalysts. Paper presented at 247th National Spring Meeting of the American-Chemical-Society (ACS), MAR 16-20, 2014, Dallas, TX. Abstract of Papers of the American Chemical Society, 247, Article ID 95-INOR.
Open this publication in new window or tab >>Mechanistic investigations and detection of intermediates of molecular proton reduction catalysts
Show others...
2014 (English)In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, article id 95-INORArticle in journal, Meeting abstract (Other academic) Published
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-247723 (URN)000348457601196 ()
Conference
247th National Spring Meeting of the American-Chemical-Society (ACS), MAR 16-20, 2014, Dallas, TX
Available from: 2015-03-23 Created: 2015-03-23 Last updated: 2017-12-04
Singh, W. M., Mirmohades, M., Jane, R. T., White, T. A., Hammarström, L., Thapper, A., . . . Ott, S. (2013). Voltammetric and spectroscopic characterization of early intermediates in the Co(II)-polypyridyl-catalyzed reduction of water. Chemical Communications, 49(77), 8638-8640
Open this publication in new window or tab >>Voltammetric and spectroscopic characterization of early intermediates in the Co(II)-polypyridyl-catalyzed reduction of water
Show others...
2013 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 49, no 77, p. 8638-8640Article in journal (Refereed) Published
Abstract [en]

Early intermediates of catalytic water reduction by a Co(II)-polypyridyl species have been characterized. Electrochemical detection of the Co(III)-hydride and time-resolved spectroscopic detection of the Co(I)-ligand intermediates provide an understanding of their reactivity in electrolytic or light-driven reduction of protons to hydrogen.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-208179 (URN)10.1039/c3cc44655g (DOI)000323758900017 ()
Available from: 2013-09-24 Created: 2013-09-24 Last updated: 2017-12-06
Mirmohades, M., Pullen, S., Hammarström, L., Lomoth, R. & Ott, S.Direct Experimental Observation of Interfacial Photo-Reduction of a Molecular Proton Reduction Catalyst Incorporated in a Metal-Organic Framework.
Open this publication in new window or tab >>Direct Experimental Observation of Interfacial Photo-Reduction of a Molecular Proton Reduction Catalyst Incorporated in a Metal-Organic Framework
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-281444 (URN)
Available from: 2016-03-24 Created: 2016-03-24 Last updated: 2016-06-01
Adamska-Venkatesh, A., Mirmohades, M., Sommer, C., Reijerse, E., Lubitz, W., Lomoth, R. & Hammarström, L.Following [FeFe] Hydrogenase Active Site Intermediates by Flash Photolysis/Mid-IR Probing.
Open this publication in new window or tab >>Following [FeFe] Hydrogenase Active Site Intermediates by Flash Photolysis/Mid-IR Probing
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-281443 (URN)
Available from: 2016-03-24 Created: 2016-03-24 Last updated: 2016-06-01
Wang, S., Mirmohades, M., Hammarström, L. & Lomoth, R.IR and UV-Vis Spectroscopic Characterization of a One-Electron Reduced Intermediate of an FeFe Hydrogenase Mimic on the Nano- to Microsecond Time Scale.
Open this publication in new window or tab >>IR and UV-Vis Spectroscopic Characterization of a One-Electron Reduced Intermediate of an FeFe Hydrogenase Mimic on the Nano- to Microsecond Time Scale
(English)Manuscript (preprint) (Other academic)
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-281446 (URN)
Available from: 2016-03-24 Created: 2016-03-24 Last updated: 2018-11-08
Organisations

Search in DiVA

Show all publications