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Herein, we report the synthesis, and photochemical and -physical properties, as well as the catalytic performance, of a series of heteroleptic Ir III photosensitizers (IrPSs), [Ir(C^N) 2 (N^N Aryl )] + , possessing ancillary ligands that are varied with aryl-substituents on bipyridyl unit [C^N=(2-pyridyl)benzo[b]thiophen-3-yl (btp); N^N Aryl =4,4'-Y 2 -bpy (Y=-Ph or -PhSi(Ph) 3 ]. We found that the π-extension of bipyridyl ligand by aryl-substitution put bipyridyl ligand in use as an electron relay unit that performed charge accumulation before delivering to the catalytic center, greatly improving the overall CO 2 -to-CO conversion activities. In a typical run, the aryl-substituted IrPS ( tBu IrP-Ph Si )-sensitized homogeneous systems (IrPS+Re I catalyst) gave a turnover number of 1340 (Φ CO =24.2 %) at the early stage of photolysis (<5 h). This study demonstrates that the π-character modulation on the ancillary bipyridyl ligand is critical for forthcoming catalytic performance., (© 2020 Wiley-VCH GmbH.)

A series of heteroleptic iridium(III) complexes functionalized with two phosphonic acid (-PO 3 H 2 ) groups ( dfppy IrP, ppy IrP, btp IrP, and piq IrP) were prepared and anchored onto rhenium(I) catalyst (ReP)-loaded TiO 2 particles (TiO 2 /ReP) to build up a new IrP-sensitized TiO 2 photocatalyst system (IrP/TiO 2 /ReP). The photosensitizing behavior of the IrP series was examined within the IrP/TiO 2 /ReP platform for the photocatalytic conversion of CO 2 into CO. The four IrP-based ternary hybrids showed increased conversion activity and durability than that of the corresponding homo- (IrP+ReP) and heterogeneous (IrP+TiO 2 /ReP) mixed systems. Among the four IrP/TiO 2 /ReP photocatalysts, the low-energy-light (>500 nm) activated piq IrP immobilized ternary system ( piq IrP/TiO 2 /ReP) exhibited the most durable conversion activity, giving a turnover number of ≥730 for 170 h. A similar kinetic feature observed through time-resolved photoluminescence measurements of both btp IrP/TiO 2 and TiO 2 -free btp IrP films suggests that the net electron flow in the ternary hybrid proceeds dominantly through a reductive quenching mechanism, unlike the oxidative quenching route of typical dye/TiO 2 -based photolysis., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Visible-light irradiation of a ternary hybrid catalyst prepared by grafting a dye, an H 2 evolving Co III catalyst and a CO-producing Re I catalyst on TiO 2 have been found to produce both H 2 and CO (syngas) in CO 2 -saturated N,N-dimethyl formamide (DMF)/water solution containing a 0.1 m sacrificial electron donor. The H 2 /CO ratios are effectively controlled by changing either the water content of the solvent or the molar ratio of the Re I and Co III catalysts ranging from 1:2 to 15:1. The controlled syngas formation is discussed in terms of competitive electron flow from TiO 2 to each of the CO 2 -reduction and hydrogen-evolving sites depending on the efficiencies of the two catalytic reaction cycles under given reaction conditions., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Visible-light-driven H(2) evolution based on Dye/TiO(2)/Pt hybrid photocatalysts was investigated for a series of (E)-3-(5'-{4-[bis(4-R(1)-phenyl)amino]phenyl}-4,4'-(R(2))(2)-2,2'-bithiophen-5-yl)-2-cyanoacrylic acid dyes. Efficiencies of hydrogen evolution from aqueous suspensions in the presence of ethylenediaminetetraacetic acid as electron donor under illumination at λ>420 nm were found to considerably depend on the hydrophilic character of R(1), varying in the order MOD (R(1)=CH(3)OCH(2), R(2)=H)≈MO4D (R(1)=R(2)=CH(3)OCH(2))>HD (R(1)=R(2)=H)>PD (R(1)=C(3)H(7), R(2)=H). In the case of MOD/TiO(2)/Pt, the apparent quantum yield for photocatalyzed H(2) generation at 436 nm was 0.27±0.03. Transient absorption measurements for MOD- or PD-grafted transparent films of TiO(2) nanoparticles dipped into water at pH 3 commonly revealed ultrafast formation (<100 fs) of the dye radical cation (Dye(·+) ) followed by multicomponent decays, which involve minor fast decays (<5 ps) almost independent of R(1) and major slower decays with significant differences between the two samples: 1) the early decay of the major components for MOD is about 2.5 times slower than that for PD and 2) a redshift of the spectrum occurred for MOD with a time constant of 17 ps, but not for PD. The substituent effects on H(2) generation as well as on transient behavior have been discussed in terms substituent-dependent charge recombination (CR) of Dye(·+) with electrons in bulk, inner-trap, and/or interstitial-trap states, arising from different solvent reorganization., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A bright combination: a new type of donor-acceptor dyad, carbazolylaryl-substituted ortho-carboranes, which are conveniently prepared from the corresponding acetylenes and decaborane pathways, showed unique excited-state behavior associated with electron transfer unlike the meta- and para-counterparts., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)