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Photoregeneration of Biomimetic Nicotinamide Adenine Dinucleotide Analogues via a Dye-Sensitized Approach
摘要： Two-step photochemical reduction of an acridinium-based cation 2O+ to the corresponding anion 2O? was investigated using a dye-sensitized approach involving 2O+?COOH attached to the surface of a wide-bandgap semiconductor, p-NiO. The cation 2O+ and corresponding one-electron reduced radical form, 2O? were synthesized and characterized using steady-state UV/vis and electron paramagnectic resonance spectroscopy. The thermodynamics for the photoinduced hole injection from 2O+ and 2O? were evaluated and found to be favorable. Subsequent femtosecond transient absorption spectroscopy was utilized to evaluate the photoinduced hole injection into NiO, starting from 2O+?COOH/NiO and 2O??COOH/NiO samples. The excitation of 2O+?COOH at 620 nm initiated fast (2.8 ps) hole injection into NiO. However, 90% of the charge-separated population recombined within ～40 ps, while ～10% of the charge-separated population exhibited lifetimes longer than the time scale of our instrument (1.6 ns). In the case of 2O??COOH/NiO, the light absorption occurs predominantly by NiO (2O??COOH absorbs at 310 nm) and is associated with the electron transfer from the conduction band of NiO to the radical. The charge-separated state in this case appears to be long-lived, based on the slow (ns) growth of the trapped carriers formed on the NiO surface. The results of this work indicate that the photochemical reduction of 2O+ to the corresponding hydride form (2OH) can be achieved, opening the possibility of using such a dye-sensitized approach for regeneration of nicotinamide adenine dinucleotide analogues in enzymatic and chemical catalysis.
关键词： multiple charge accumulation,stable radical,NADH,photochemistry,NiO,dye sensitization
更新于2025-09-23 15:21:21
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Stable (BIII-Subporphyrin-5-yl)dicyanomethyl Radicals
摘要： Stable BIII-subporphyrin-substituted dicyanomethyl radicals were synthesized by SNAr reaction of meso-bromo or meso-chlorosubporphyrins with malononitrile followed by oxidation with PbO2. Different from previously reported dicyanomethyl radicals that underwent s- or π-dimer formation both in the solid state and in solutions, subporphyrin-stabilized dicyanomethyl radicals exist as monomers in solutions even at low temperature. DFT calculations revealed efficient spin delocalization over the whole subporphyrin. In the solid state, these radicals form weak π-dimers with antimagnetic interactions depending on the crystal packing structures.
关键词： porphyrinoid,dynamic covalent bond,subporphyrin,dicyanomethyl radical,stable radical
更新于2025-09-10 09:29:36