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[Cr(ttpy)2]3+ (ttpy = 4′-(4-methylphenyl)-2,2′:6,2′′-terpyridine) exhibits rich electrochemical and photophysical properties. Cyclic voltammetry performed in CH3CN shows in the cathodic part the presence of three one-electron reversible systems at −0.47, −0.85 and −1.35 V vs. Ag/AgNO3 10−2 M. These systems are attributed to the reduction of the terpyridine ligands with a partial delocalization of the charge on the tolyl for the last reduction event. The three different reduced species were generated by exhaustive electrolysis and characterized by EPR and UV-visible spectroscopy; DFT calculations were performed to locate the spin density of the electrons added during the reduction. Visible light irradiation of [Cr(ttpy)2]3+ induces the population of a luminescent metal-centered excited state with a lifetime of 270 ns in deoxygenated CH3CN. This excited state can be quenched by an electron transfer process with triphenylphosphine (PPh3) or triethanolamine (TEOA). Using TEOA as a sacrificial electron donor, the doubly reduced species (i.e.[Cr(ttpy)2] +) can be generated under continuous irradiation. In the presence of [Ru(bpy)3]2+ as an additional photosensitizer, the photoreduction of [Cr(ttpy)2]3+ towards [Cr(ttpy)2]+ is accelerated. The trinuclear [{RuII(bpy)2(bpy-O-tpy)}2CrIII]7+ complex ([Ru2Cr]7+) in which a CrIII-bis-terpyridine centre is covalently linked to two RuII-tris-bipyridine moieties by oxo bridges has been synthesised. Its electrochemical, photophysical and photochemical properties were investigated in deoxygenated CH3CN. Cyclic voltammetry indicates only a poor electronic communication between the different subunits, whereas luminescence experiments show a strong quenching of the RuII* excited state by an intramolecular process. Continuous irradiation of [Ru2Cr]7+ under visible conditions in the presence of TEOA leads to [Ru2Cr]4+ where three electrons are stored on the [Cr(ttpy)] subunit. [ABSTRACT FROM AUTHOR]

We propose in this work a stepwise approach to construct photoelectrodes. This takes advantage of the self-assembly interactions between thiol with a gold surface and terpyridine ligands with first-row transition metals. Here, a [Ru(bpy)3]2+ photosensitive center bearing a free terpyridine group has been used to construct two linear dyads on gold (Au/[ZnII-RuII]4+ and Au/[CoIII-RuII]5+). The stepwise construction was characterized by electrochemistry, quartz crystal microbalance, and atomic force microscopy imaging. The results show that the dyads behave as rigid layers and are inhomogeneously distributed on the surface. The surface coverages are estimated to be in the order of 10-11 mol cm-2. The kinetics of the heterogeneous electron transfer is determined on modified gold ball microelectrodes using Laviron's formula. The oxidation rates of the terminal Ru(II) subunits are estimated to be 700 and 2300 s-1 for Au/[ZnII-RuII]4+ and Au/[CoIII-RuII]5+, respectively. In the latter case, the rate is limited by the kinetics of electron transfer between an intermediate Co(II) center and the gold surface. For Au/[ZnII-RuII]4+, the Zn-bis-terpyridine center is not involved in the electron-transfer process and the oxidation of the Ru(II) subunit occurs through a superexchange process. In the presence of a tertiary amine in solution, the electrodes at a bias of 0.12 V behave as photoanodes when subjected to visible light irradiation. The magnitude of the photocurrent is around 10 µA cm-2 for Au/[CoIII-RuII]5+ and 5 µA cm-2 for Au/[ZnII-RuII]4+, proving the importance of an electron relay on the photon-to-current conversion. The results suggest an efficient conversion for Au/[CoIII-RuII]5+, since each bound dyad, once excited, injects an electron around 10 times per second. [ABSTRACT FROM AUTHOR]

Abstract: [Rh2(Esp)2] (Esp=α,α,α′,α′‐tetramethyl‐1,3‐benzenedipropionate) is a well‐established catalyst for intra‐ and intermolecular C(sp)3−H bond amination. We have prepared and isolated complex I, [Rh2(Esp)2(NHTces)2]2−, where the catalyst bears sulfonamidate ligands (−NHTces=−NHSO3CH2CCl3) as nitrogen sources in the coordination sphere of the rhodium centre. The possibility for light activation instead of chemical activation of the [Rh2(Esp)2] catalyst and complex I is demonstrated using [Ru(bpy)3]2+ as the photosensitizer. The oxidation of the two dinuclear Rh complexes occurs through two distinct pathways. On one hand, [Rh2(Esp)2] is oxidized in a bimolecular reaction with the RuIII species formed after excitation of the photosensitizer in the presence of an electron acceptor. In contrast, the lower oxidation potential of complex I allows for its oxidation to occur directly from the excited state of the photosensitizer, helped by ion‐pair formation between the negatively charged complex I with [Ru(bpy)3]2+. The charge‐separated state of the oxidized complex I/reduced photosensitizer had a lifetime of 50 μs. [ABSTRACT FROM AUTHOR]

The article discusses the photoelectric conversion at a bipyridine ruthenium chloride-based on metallic triad grafted on a Indium tin oxide (ITO) electrode under the visible light. Topics discussed include interaction between phosphonates with ITO and terpyridine ligands; characterization of all experiments by cyclic voltammetry in acetonitrile and tetrabutylammonium perchlorate; and the redox potential throught out the procedure.