Binuclear Sulfide Niobium Clusters Coordinated by Diimine Ligands: Synthesis, Structure, Photocatalytic Activity and Optical Limiting Properties

Substitution reactions of binuclear niobium cluster anion [Nb2S4(NCS)8]4– with different types of pyridine-based diimine ligands have been carried out. In the case of 2,2′-bipyridine (bipy) and its derivatives, only monosubstituted complexes [Nb2S4(NCS)6L]2– have been isolated. In the case of 1,10-phenanthroline and 2-(2-pyridyl)benzimidazole (Hpbz), both mono- and disubstituted complexes, [Nb2S4(NCS)6L]2– and [Nb2S4(NCS)4L2], respectively, have been obtained. Crystal structures of (Et4N)2[Nb2S4(NCS)6(bipy)]·0.5bipy·0.7CH3CN and [Nb2S4(pbmz)2(NCS)4]·5DMF·0.8H2O have been determined. All compounds have been characterized by NMR, ESI mass spectrometry, IR, UV/Vis spectroscopy, and CV. TiO2 nanoparticles modified with (Et4N)2[Nb2S4(NCS)6(bipy)] show moderate photocatalytic activity in the reaction of H2 generation from water in the presence of Na2S/Na2SO3 as a sacrificial electron donor system. The linear and nonlinear optical properties of the complexes with bipyridine ligands have been studied; the complexes function as broad-band optical limiters.