Tris(2,2'-bipyridine)ruthenium Derivatives with Multiple Viologen Acceptors: Quadratic Dependence of Photocatalytic H2 Evolution Rate on the Local Concentration of the Acceptor Site.

Three Ru(bpy)3 (2+) derivatives tethered to multiple viologen acceptors, [Ru(bpy)2 (4,4'-MV2)](6+) , [Ru(bpy)2 (4,4'-MV4)](10+) , and [Ru(bpy)(4,4'-MV4)2 ](18+) [bpy=2,2'-bipyridine, 4,4'-MV2=4-ethoxycarbonyl-4'-(N-G1 -carbamoyl)-2,2'-bipyridine, and 4,4'-MV4=4,4'-bis(N-G1 -carbamoyl)-2,2'-bipyridine, where G1 =Asp(NHG2 )-NHG2 and G2 =-(CH2 )2 -N(+) C5 H4 -C5 H4 N(+) -CH3 ] were prepared as "photo-charge separators (PCSs)". Photoirradiation of these complexes in the presence of a sacrificial electron donor (EDTA) results in storage of electrons per PCS values of 1.3, 2.

Improved photocatalytic hydrogen evolution driven by chloro(terpyridine)platinum(ii) derivatives tethered to a single pendant viologen acceptor.

Three chloro(4'-(N-methylpyridinium)-2,2':6',2''-terpyridine)platinum(ii) (abbreviated as ) derivatives tethered to a single alkyl viologen unit (-(CH2)n-CH2-N(+)C5H4-C5H4N(+)-CH3; abbreviated as -, where n = 1, 3, and 4), i.e., , have been synthesized and investigated in detail.

Photochemical H2 evolution from water catalyzed by a dichloro(diphenylbipyridine)platinum(ii) derivative tethered to multiple viologen acceptors.

A new single-component photocatalyst for the reduction of water to H2, a dichloro(dpbpy)platinum(ii) derivative (dpbpy = 4,4'-diphenyl-2,2'-bipyridine) tethered to four pendant viologen acceptors (1), is shown to exhibit twice higher photocatalytic efficiency than the previously reported dichloro(bpy)-platinum(ii) analog (; bpy = 2,2'-bipyridine), consistent with the higher absorptivity of at the metal-to-ligand charge transfer ((1)MLCT) band due to the larger π-conjugation in dpbpy relative to bpy.

Pt(II)-Catalyzed photosynthesis for H2 evolution cycling between singly and triply reduced species.

A PtCl2(bpy) derivative tethered to two viologen (MV(2+)) moieties drives photochemical H2 evolution via forming a three-electron-reduced species possessing a bpy(-)˙-based (or MV(0)-based) reducing equivalent. Such species can only form after one electron reduction of both the MV(2+) sites because of rapid intramolecular electron transfer from bpy(-)˙ to MV(2+).

Pigment-acceptor-catalyst triads for photochemical hydrogen evolution.

In order to solve the problems of global warming and shortage of fossil fuels, researchers have been endeavoring to achieve artificial photosynthesis: splitting water into H2 and O2 under solar light illumination. Our group has recently invented a unique system that drives photoinduced water reduction through "Z-scheme" photosynthetic pathways. Nevertheless, that system still suffered from a low turnover number (TON) of the photocatalytic cycle (TON=4.