Synthetic Applications of Photocatalytic Oxidation and Reduction Reactions of Organic Reactants on Irradiated Semiconductor Surfaces

Fox, Marye Anne

doi:10.1002/9783527618248.ch8

Cited by 9 publications

(5 citation statements)

References 162 publications

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“…Photoexcited states of molecules are vehicles for solar energy conversion and storage, photosensitization, photocatalysis, and molecular devices. − However, structural information for excited state molecules has been sparse and indirect, in comparison with abundant and sophisticated kinetics information obtained by time-resolved optical spectroscopy. The recent development of time-domain X-ray structural techniques begins to enable molecular structure determination of highly energetic transient species with limited lifetimes in both crystalline and disordered forms, using similar pump−probe techniques employed in optical spectroscopy but with X-ray pulses as the probe. − …”

Section: Introductionmentioning

confidence: 99%

MLCT State Structure and Dynamics of a Copper(I) Diimine Complex Characterized by Pump−Probe X-ray and Laser Spectroscopies and DFT Calculations

et al. 2003

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The molecular structure and dynamics of the photoexcited metal-to-ligand-charge-transfer (MLCT) state of [Cu(I)(dmp)(2)](+), where dmp is 2,9-dimethyl-1,10-phenanthroline, in acetonitrile have been investigated by time-domain pump-probe X-ray absorption spectroscopy, femtosecond optical transient spectroscopy, and density functional theory (DFT). The time resolution for the excited state structural determination was 100 ps, provided by single X-ray pulses from a third generation synchrotron source. The copper ion in the thermally equilibrated MLCT state has the same oxidation state as the corresponding copper(II) complex in the ground state and was found to be penta-coordinate with an average nearest neighbor Cu-N distance 0.04 A shorter than that of the ground state [Cu(I)(dmp)(2)](+). The results confirm the previously proposed "exciplex" structure of the MLCT state in Lewis basic solvents. The evolution from the photoexcited Franck-Condon MLCT state to the thermally equilibrated MLCT state was followed by femtosecond optical transient spectroscopy, revealing three time constants of 500-700 fs, 10-20 ps, and 1.6-1.7 ns, likely related to the kinetics for the formation of the triplet MLCT state, structural relaxation, and the MLCT excited-state decay to the ground state, respectively. DFT calculations are used to interpret the spectral shift on structural relaxation and to predict the geometries of the ground state, the tetracoordinate excited state, and the exciplex. The DFT calculations also indicate that the amount of charge transferred from copper to the dmp ligand upon photoexcitation is similar to the charge difference at the copper center between the ground-state copper(I) and copper(II) complexes.

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Section: Introductionmentioning

confidence: 99%

MLCT State Structure and Dynamics of a Copper(I) Diimine Complex Characterized by Pump−Probe X-ray and Laser Spectroscopies and DFT Calculations

et al. 2003

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“…Photoinduced charge-transfer processes have been among the most studied chemical reactions because of their relevance to molecular devices, photocatalysis, and solar energy conversion/storage. – Understanding the molecular structures and dynamics of both photoexcited states and charge-separated intermediates is crucial not only for their broad applications, but also for their fundamental importance in gaining insight into the nature of photochemical reactions. It enables one to develop theoretical models for predicting the reaction mechanisms and dynamics for photoinduced processes.…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Local Structure of Photoexcited Cu Diimine Complex Refined by Quantitative XANES Analysis

2008

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The structural details of [Cu(dmp) 2] (+) (dmp = 2,9-dimethyl-1,10-phenanthroline) at its metal-to-ligand charge-transfer (MLCT) excited-state in acetonitrile were extracted using quantitative analysis of Cu K-edge X-ray adsorption near edge structure (XANES). The study combines two techniques: fitting experimental XANES spectra with a multidimensional interpolation approximation, and calculating theoretical XANES spectra with molecular potentials beyond the muffin-tin approximation. The results of the study show that the best fit of the experimental XANES data must include a solvent molecule binding to the Cu with a short Cu-N distance of 2.00 A. This confirms that the formation of an exciplex is responsible for the excited-state quenching in coordinating solvents, such as acetonitrile. Moreover, the calculations suggest that the formation of this exciplex state is accompanied by significant rocking distortions of the dmp ligands resulting in a 108 degrees angle between the N(solvent)-Cu bond and the C 2 symmetry axis of the dmp ligand. This combined approach allows us to extract molecular configurations that would otherwise be missed in a conventional qualitative XANES analysis.

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“…The utilization of semiconductor photocatalysts in the chemical reactions is an important research area in photochemistry during the last two decades 15,16 . Photocatalytic reactions have been considered from both technological and economical viewpoints due to providing a short, clean, and direct route 17 .…”

Section: Introductionmentioning

confidence: 99%

Polyelectrolyte‐controlled visible light catalytic reduction of nitrobenzene

Mardani

Kazemi

Mohamadnia

2020

Polymers for Advanced Techs

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To study the effect of cationic polyelectrolytes on the photoreduction of nitrobenzene over TiO2, a sequence of synthetic cationic polyelectrolytes (SCPs) containing acrylamide (AAm) and 2‐(dimethylamino)ethyl acrylate methochloride (DAEA) using various AAm:DAEA molar ratios (50:50, 55:45, 60:40, 70:30, and 85:15) were synthesized and named as PEA, PEB, PEC, PED, and PEE, respectively. According to the obtained monomer reactivity ratios, the SCPs with a range from medium to high molecular weights (2.11×105 ≤ Mv ≤ 1.22 ×106 g/mol) were obtained. Then the influence of the SCPs and the other polyelectrolytes such as Zetag 7563 (a commercial grade of cationic polyelectrolyte) and poly(vinylsulfate) potassium salt (PVSK) as an anionic polyelectrolyte on the photoreduction of nitrobenzene over TiO2 under 400 nm LED irradiation was investigated. Zetag 7563 was not an appropriate polyelectrolyte to enhance the photoreduction of nitrobenzene due to its high Mv, and having high entanglement of polymer chains. By the addition of PVSK anionic polyelectrolyte, the conversion of nitrobenzene to aniline decreased; the PVSK has a probably greater tendency than nitrobenzene to be absorbed on the surface of TiO2 (PVSK reduces the adsorption of nitrobenzene on the surfaces of TiO2 due to the electrostatic interactions with TiO2). Simultaneous use of TiO2 with 0.01 g of PEB (with medium Mv and 4.4 meq/g charge density), led to an increase in the nitrobenzene photoreduction (95% conversion) in comparison with application of bare TiO2 (53% conversion). It supposes that the selection of appropriate SCPs can facilitate the access of reactants to each other and enhance the nitrobenzene photoreduction.

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Synthetic Applications of Photocatalytic Oxidation and Reduction Reactions of Organic Reactants on Irradiated Semiconductor Surfaces

Cited by 9 publications

References 162 publications

MLCT State Structure and Dynamics of a Copper(I) Diimine Complex Characterized by Pump−Probe X-ray and Laser Spectroscopies and DFT Calculations

MLCT State Structure and Dynamics of a Copper(I) Diimine Complex Characterized by Pump−Probe X-ray and Laser Spectroscopies and DFT Calculations

Three-Dimensional Local Structure of Photoexcited Cu Diimine Complex Refined by Quantitative XANES Analysis

Polyelectrolyte‐controlled visible light catalytic reduction of nitrobenzene

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