Studies On Preparation And Photoelectrochemical Properties Of A Cobaloxime-Based Photoactive Molecular Device And A TPA-Ru Photosensitizer Unit

A photosensitizer containing triphenylamine and pyridine functional group was designed and synthesized as a light capturing unit for a molecular device. An axial coordination of the pyridine group of the photosensitizer to a cobaloxime complex results in construction of a new noble-metal-free molecular device. The structures of the photosensitizer and the molecular device were characterized by MS and1H NMR spectroscopy. The UV-vis and fluorescence spectra, electrochemistry of the molecular device, and photoinduced hydrogen production with the device were studied. On the basis of the apparent quenching of the fluorescence emission in the molecular device as compared to that of the free photosensitizer and the redox potentials of the molecular device, photosensitizer, and triethylamine, the intramolecular photoinduced electron transfer from the photosensitizer unit to the cobaloxime unit is thermodynamically feasible. But no H2 was detected by GC analysis in the photocatalytic reaction with the molecular device, presumably due to fast electron recombination and/or a short life of charge-separated state of the molecular device.Two lignds containing triphenylamine and phenanthroline functional group were prepared (L1=4-[4-((4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenyl)(phenyl)amino) phenyl]-benzoic acid, L2=4-[(4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenyl) (phenyl)amino]-phenylphosphonic acid diethyl ester). Coordination of the ligands to [Ru(bpy)2Cl2] results in construction of two new photosensitizers. The structures of the ligands and photosensitizers were characterized by MS and1H NMR spectroscopy. The UV-vis and fluorescence spectra, as well as electrochemistry of photosensitizers were studied. The electron transfer was verified by transient absorption spectroscopy and kinetic traces obtained from laser flash photolysis.