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.Financial support from the Russian Foundation for Basic Research (grant numbers 12-03-00305a and 12-03-33028a) is gratefully acknowledged. M. G. H. thanks the Australian Research Council for financial support and M. S. thanks the Foundation for Polish Science for a Laureate Fellowship of the Welcome progra