Since the initial report by Lehn et al. in 1979, ruthenium tris(bipyridine) ([Ru(bpy) 3 ] 2+ ) and its numerous derivatives were applied as photosensitizers (PSs) in a large panel of photocatalytic conditions while the bis(terpyridine) analogues were disregarded because of their low quantum yields and short excited-state lifetimes. In this study, we prepared a new terpyridine ligand, 4′-(4-bromophenyl)-4,4‴:4″,4‴′-dipyridinyl-2,2′:6′,2″-terpyridine (Bipytpy) and used it to prepare the heteroleptic complex [Ru(Tolyltpy)(Bipytpy)](PF 6 ) 2 (1; Tolyltpy = 4′tolyl-2,2′:6′,2′-terpyridine). Complex 1 exhibits enhanced photophysical properties with a higher quantum yield (7.4 × 10 -4 ) and a longer excited-state lifetime (3.8 ns) compared to those of [Ru(Tolyltpy) 2 ](PF 6 ) 2 (3 × 10 -5 and 0.74 ns, respectively). These enhanced photophysical characteristics and the potential for PS-catalyst interaction through the peripheral pyridines led us to apply the complex for visible-light-driven hydrogen evolution.The photocatalytic system based on 1 as the PS, triethanolamine as a sacrificial donor, and cobaloxime as a catalyst exhibits sustained activity over more than 10 days under blue-light irradiation (light-emitting diode centered at 450 nm). A maximum turnover number of 764 was obtained after 12 days.

The structure−properties relationship in a series of carbonyl rhenium(I) complexes based on substituted terpyridine ligands of general formula [Re(κ x N-Rtpy)(CO) y L] n+ is explored by both experimental and theoretical methods. In these compounds, the terpyridine ligands adopt both bidentate (κ 2 N) and terdentate (κ 3 N) coordination modes associated with three or two carbonyls, respectively. Conversion from the κ 2 N to the κ 3 N coordination mode leads to large changes in the absorption spectra and oxidation potentials due to destabilization of the HOMO level of each complex. The absorption profiles of the κ 3 N complexes cover the whole visible spectra with lower maxima around 700 nm, tailing out to 800 nm, while no emission is observed with Br − as the axial ligand L. When the axial ligand is modified from the native halide to pyridine or triphenylphosphine, the lowest absorption band is blue-shifted by 60 and 90 nm, respectively. These cationic complexes are near-infrared emitters with emission maxima between 840 and 950 nm for the pyridine compounds and 780−800 nm for the triphenylphosphine compounds.

The synthesis of a Ir(III)-Co(III) dyad with vectorial electron transfer afforded a novel supramolecular system that photocatalytically produces hydrogen in a range extending from the blue region of the spectrum to the red region with higher turnover number and frequency compared to other bimetallic dyads.

A new class of cationic iridium(III) complexes of the form [(C(∧)N)2Ir(N(∧)N)][PF6] is reported, where C(∧)N = cyclometallating 2-phenylpyridinato, ppy, or 2-(2,4-difluorophenyl)-5'-methylpyridinato, dFMeppy, and N(∧)N = guanidyl-pyridine, gpy, or -pyrazine, gpz, as the ancillary ligand. A large blue-shift in the emission coupled with a 7-to-9 fold enhancement in photoluminescence quantum yield and microsecond emission lifetimes were observed for the complexes containing the partially saturated gpy ligand as compared to the benchmark complex [(ppy)2Ir(bpy)][PF6], C1, where bpy is 2,2'-bipyridine.