The first water-soluble hexarhenium cluster complexes with a heterocyclic ligand environment: synthesis, luminescence, and biological properties.

The hexarhenium cluster complexes with benzotriazolate apical ligands [{Re6(μ3-Q)8}(BTA)6](4-) (Q = S, Se; BTA = benzotriazolate ion) were obtained by the reaction of [{Re6(μ3-Q)8}(OH)6](4-) with molten 1H-BTA (1H-benzotriazole). The clusters were crystallized as potassium salts and characterized by X-ray single-crystal diffraction, elemental analyses, and UV-vis and luminescence spectroscopy. In addition, their cellular uptake and toxicity were evaluated. It was found that both clusters exhibited luminescence with high lifetimes and quantum yield values; they were taken up by the cells illuminating them under UV irradiation and, at the same time, did not exhibit acute cytotoxic effects.