Photocatalytic H₂ production by dirhodium(ii,ii) photosensitizers with red light

Photocatalytic proton reduction to generate H2 was achieved with the photosensitizers Rh2(DTolF)2(npCOO)2 (DTolF = p-ditolylformamidinate; npCOO- = 2-carboxylate-1,8-naphthyridine; 1) and [Rh2(DTolF)2(qnnp)2][BF4]2 (qnnp = 2-(quinolin-2-yl)-1,8-naphthyridine; 2) using a relay system containing the sacrificial donor BNAH (1-benzyl-1,4-dihydronicotinamide), electron acceptor MV2+ (methylviologen), and Pt nanoparticles as the catalyst with 655 nm irradiation. Comparison of the H2 evolution under similar experimental conditions show comparable activity of the Rh2(ii,ii) complexes (λirr = 655 nm) to that of the prototypical [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine; 3) with λirr = 447 nm. This work demonstrates the ability of the new panchromatic Rh2(ii,ii) complexes to achieve photocatalysis with red light.