Donor-bridge-acceptor complexes (D-B-A) are important model systems for understanding of light-induced processes. Here, we apply two-color two-dimensional infrared (2D-IR) spectroscopy to D-B-A complexes with a -Pt(II) acetylide bridge (D-C≡C-Pt-C≡C-A) to uncover the mechanism of vibrational energy redistribution (IVR). Site-selective C isotopic labeling of the bridge is used to decouple the acetylide modes positioned on either side of the Pt-center.
View Article and Find Full Text PDFThere is a growing interest in developing dye-sensitized photocatalytic systems (DSPs) to produce molecular hydrogen (H ) as alternative energy source. To improve the sustainability of this technology, we replaced the sacrificial electron donor (SED), typically an expensive and polluting chemical, with an alcohol oxidation catalyst. This study demonstrates the first dye-sensitized system using a diketopyrrolopyrrole dye covalently linked to 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) based catalyst for simultaneous H evolution and alcohol-to-aldehyde transformation operating in water with visible irradiation.
View Article and Find Full Text PDFOver the last decades, photoreceptive proteins were extensively studied with biophysical methods to gain a fundamental understanding of their working mechanisms and further guide the development of optogenetic tools. Time-resolved infrared (IR) spectroscopy is one of the key methods to access their functional non-equilibrium processes with high temporal resolution but has the major drawback that experimental data are usually highly complex. Linking the spectral response to specific molecular events is a major obstacle.
View Article and Find Full Text PDFVibrational energy transfer (VET) between two isotopologues of [Re(dcb)(CO)Br] immobilized on a TiO surface is studied with the help of 2D IR spectroscopy in dependence of surface coverage. To dilute the molecules on the surface, and thereby control the intermolecular distances, two different diluents have been used: a third isotopologue of the same molecule and 4-cyanobenzoic acid. As expected, the VET rate decreases with dilution.
View Article and Find Full Text PDFThe ground- and excited-state properties of six rhenium(I) κ-tricarbonyl complexes with 4'-(4-substituted-phenyl)terpyridine ligands bearing substituents of different electron-donating abilities were evaluated. Significant modulation of the electrochemical potentials and a nearly 4-fold variation of the triplet metal-to-ligand charge-transfer (MLCT) lifetimes were observed upon going from CN to OMe. With the more electron-donating NMe group, we observed in the κ complex the appearance of a very strong absorption band, red-shifted by ca.
View Article and Find Full Text PDFCycloruthenation is a well known process in organometallic ruthenium chemistry. In this work, we report unprecedented cycloruthenated rhenium bis-arene compounds with planar chirality. In a two-step process, the reaction of acetyl-pyridine with [Re(η6-C6H6)2]+ introduced a pyridinyl-methanol ligand at one of the arene rings.
View Article and Find Full Text PDFHydridocarbonyl complexes, a class of industrially relevant catalysts, contain both the M-H and M-CO moieties. Here, using two-dimensional infrared spectroscopy, we examine the coupling of the typically weak M-H stretching mode and the intense M(C≡O) mode. By studying a series of Ir(I)- and Ir(III)-based hydridocarbonyl complexes, we show that the arrangement of the H and CO ligands in a configuration leads to strong vibrational coupling and mode delocalization.
View Article and Find Full Text PDFProton-coupled electron transfer (PCET) was studied in a series of tungsten hydride complexes with pendant pyridyl arms ([(PyCHCp)WH(CO)], PyCHCp = pyridylmethylcyclopentadienyl), triggered by laser flash-generated Ru--bipyridine oxidants, in acetonitrile solution. The free energy dependence of the rate constant and the kinetic isotope effects (KIEs) showed that the PCET mechanism could be switched between concerted and the two stepwise PCET mechanisms (electron-first or proton-first) in a predictable fashion. Straightforward and general guidelines for how the relative rates of the different mechanisms depend on oxidant and base are presented.
View Article and Find Full Text PDFThe response of water re-solvating a charge-transfer dye (deprotonated Coumarin 343) after photoexcitation has been measured by means of transient THz spectroscopy. Two steps of increasing THz absorption are observed, a first ∼10 ps step on the time scale of Debye relaxation of bulk water and a much slower step on a 3.9 ns time scale, the latter of which reflecting heating of the bulk solution upon electronic relaxation of the dye molecules from the S back into the S state.
View Article and Find Full Text PDFA covalently linked organic dye-cobaloxime catalyst system based on mesoporous NiO is synthesized by a facile click reaction for mechanistic studies and application in a dye-sensitized solar fuel device. The system is systematically investigated by photoelectrochemical measurements, density functional theory, time-resolved fluorescence, transient absorption spectroscopy, and photoelectron spectroscopy. The results show that irradiation of the dye-catalyst on NiO leads to ultrafast hole injection into NiO from the excited dye, followed by a fast electron transfer process to reduce the catalyst.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
September 2016
For the first time, organic semiconducting polymer dots (Pdots) based on poly[(9,9'-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3} thiadiazole)] (PFBT) and polystyrene grafting with carboxyl-group-functionalized ethylene oxide (PS-PEG-COOH) are introduced as a photocatalyst towards visible-light-driven hydrogen generation in a completely organic solvent-free system. With these organic Pdots as the photocatalyst, an impressive initial rate constant of 8.3 mmol h(-1) g(-1) was obtained for visible-light-driven hydrogen production, which is 5-orders of magnitude higher than that of pristine PFBT polymer under the same catalytic conditions.
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