A series of cationic Ir(III) complexes ([Ir(btp)(bpy-X)] (Ir-X: btp = (2-pyridyl)benzo[b]thiophen-3-yl; bpy-X = 4,4'-X-2,2'-bipyridine (X = OMe, Bu, Me, H, and CN)) were applied as visible-light photosensitizer to the CO reduction to CO using a hybrid catalyst (TiO/ReP) prepared by anchoring of Re(4,4'-Y-bpy)(CO)Cl (ReP; Y = CHPO(OH)) on TiO particles. Irradiation of a solution containing Ir-X, TiO/ReP particles, and an electron donor (1,3-dimethyl-2-phenyl-1,3-dihydrobenzimidazole) in N,N-dimethylformamide at greater than 400 nm resulted in the reduction of CO to CO with efficiencies in the order X = OMe > Bu ≈ Me> H; Ir-CN has no photosensitization effect. A notable observation is that Ir-Bu and Ir-Me are less efficient than Ir-OMe at an early stage of the reaction but reveal persistent photosensitization behavior for a much longer period of time unlike the latter. Comparable experiments showed that (1) the Ir-X sensitizers are commonly superior compared to Ru(bpy), a widely used transition-metal photosensitizer, and (2) the system comprising Ir-OMe and TiO/ReP is much more efficient than a homogeneous-solution system using Ir-OMe and Re(4,4'-Y'-bpy)(CO)Cl (Y' = CHPO(OEt)). Implications of the present observations involving reaction mechanisms associated with the different behavior of the photosensitizers are discussed in detail.

A Mn­(I)-based hybrid system (OrgD-|TiO2|-MnP) for photocatalytic CO2 reduction is designed to be a coassembly of Mn­(4,4′-Y2-bpy)­(CO)3Br (MnP; Y = CH2PO­(OH)2) and (E)-3-[5-(4-(diphenylamino)­phenyl)-2,2′-bithiophen-2′-yl]-2-cyanoacrylic acid (OrgD) on TiO2 semiconductor particles. The OrgD-|TiO2|-MnP hybrid reveals persistent photocatalytic behavior, giving high turnover numbers and good product selectivity (HCOO– versus CO). As a typical run, visible-light irradiation of the hybrid catalyst in the presence of 0.1 M electron donor (ED) and 0.001 M LiClO4 persistently produced HCOO– with a >99% selectivity accompanied by a trace amount of CO; the turnover number (TONformate) reached ∼250 after 23 h of irradiation. The product selectivity (HCOO–/CO) was found to be controlled by changing the loading amount of MnP on the TiO2 surface. In situ FTIR analysis of the hybrid during photocatalysis revealed that, at low Mn concentration, the Mn–H monomeric mechanism associated with HCOO– formation is dominant, whereas at high Mn concentration, CO is formed via a Mn–Mn dimer mechanism.

As eries of heteroleptic iridium(III) complexes functionalized with two phosphonic acid (ÀPO 3 H 2 )g roups ( dfppy IrP, ppy IrP, btp IrP,a nd piq IrP)w ere prepared and anchored onto rhenium(I) catalyst( ReP)-loadedT iO 2 particles (TiO 2 / ReP) to build up an ew 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 IrPbased ternary hybridss howed increased conversion activity and durability than that of the corresponding homo-(IrP + ReP) and heterogeneous (IrP + TiO 2 /ReP) mixed systems.Amongt he four IrP/TiO 2 /ReP photocatalysts, the lowenergy-light (> 500 nm) activated piq IrP immobilized ternary system ( piq IrP/TiO 2 /ReP) exhibitedt he most durable conversion activity,g iving at urnover number of ! 730 for 170 h. A similark inetic feature observed through time-resolved photoluminescence measurements of both btp IrP/TiO 2 and TiO 2free btp IrP films suggestst hat the net electron flow in the ternary hybrid proceeds dominantly through ar eductive quenching mechanism,u nlike the oxidative quenching route of typical dye/TiO 2 -based photolysis.[a] P.Scheme1.Schematicrepresentation of the photocatalytic IrP/TiO 2 /ReP ternary system and components used in this study.TON = turnovern umber, NP = nanoparticle.

Electron donor-acceptor (D-A) systems with a triphenylamino moiety (D) and ortho-carborane (A) show three kinds of intriguing emissions that can be attributed to the local excited state, the intramolecular charge-transfer state, and the aggregation-induced emission state. The emission behaviors depend on which positions of the carborane are substituted.