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Photoinduced electron transfer in non-covalent free-base octaethylporphyrin and 2-nitrofluorene donor-acceptor system: A combined experimental and quantum chemical study
摘要： Photosynthetic reaction center functions through non-covalent incorporation into a well-defined transmembrane proteins. In the context of exploring photoinduced electron transfer (PET) in non-covalent donor-acceptor systems, we have investigated electron transfer from free-base octaethylporphyrin (OEP) donor to 2-nitrofluorene (2NF) acceptor in acetonitrile (ACN), a polar solvent. Steady-state and time-resolved emission spectroscopic studies in conjunction with density functional theory (DFT) calculations were employed to explore the electron transfer process. Quenching of the fluorescence emission intensity as well as fluorescence lifetime of the OEP upon excitation at the Q band of OEP at 300 K, is attributed to the PET from OEP to 2NF. Our DFT [wB97XD functional and 6-31G (d,p) basis set] calculations also support the interaction between donor and acceptor and also reveals the co-facial π-π interaction energy of ?24.6 kcal/mol with intermolecular distance b4 ?. Our results are expected to shed light on PET in non-covalent donor acceptor systems.
关键词： Marcus theory,Photoinduced electron transfer,Octaethylporphyrin,Second-order bimolecular fluorescence quenching constant,2-Nitrofluorene,DFT study by wB97XD/6-31G(d,p),Time-resolved emission spectroscopy
更新于2025-09-23 15:22:29
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Defect Density-Dependent Electron Injection From Excited-State Ru(II) Tris-Diimine Complexes Into Defect- Controlled Oxide Semiconductors
摘要： Dye-sensitized solar cells and photocatalysts that consist of a light absorbing dye and a wide gap oxide semiconductor substrate have been studied extensively as a means of solar energy conversion. Although defects existing at an oxide surface have a significant impact on the electron injection efficiency from the excited state dye-molecule into the oxide, the effects of defects on the electron injection process has not been fully understood in any dye-sensitized system. In this study, we present a systematic evaluation of electron injection into defects using emissive Ru(II) complexes adsorbed on oxide substrates (HCa2Nb3O10 nanosheets and nonstoichiometric SrTiO3—"), which had different defect densities. Using these oxides, electron injection from adsorbed Ru(II) complexes was observed by time-resolved emission spectroscopy. It was shown that electron injection from the excited state Ru(II) complex into an oxide was influenced by the defect density of the oxide as well as by the excited state oxidation potential (Eox*) of the Ru(II) complex. Electron injection was clearly accelerated with increasing defect density of the oxide, and was inhibited with increasing electron density of the oxide because of a trap-filling effect. Even though the Eox* of the Ru(II) complex was more positive than the conduction band edge potential of the oxide, electron injection into defects could be identified when a defective oxide was employed. The electron injection event is discussed in detail, on the basis of the defect density and the energy levels of oxides as well as the Eox* values of Ru(II) complexes. Overall the results suggest that it is possible to estimate the potential of surface defect states in an oxide by changing Eox* of an emissive complex dye.
关键词： Dye-sensitized solar cells,defect density,electron injection,Ru(II) complexes,time-resolved emission spectroscopy,photocatalysts
更新于2025-09-11 14:15:04