Synthesis, biological evaluation and colorimetric sensing studies of platinum group metal complexes comprising pyrazine based thiourea derivatives

Abstract

A series of complexes (1–9) were synthesized by the reaction of halide bridged metal precursors with the three pyrazine thiourea ligands L1, L2 and L3 to yield cationic as well as neutral complexes and characterized by various spectroscopic techniques. The cationic complexes are represented by the general formula [(arene)M(L)Cl] +, where L = L1, L2 and L3, arene = p-cymene, Cp* and M = Ru, Rh and Ir. All the cationic complexes were isolated with chloride/PF6 as the counter ion. Reactions of rhodium and iridium dimers with L2 yielded neutral complexes 5 and 6 with the general formula [(arene)M(L)Cl2]. The neutral complexes 5 and 6 were further reacted with NaN3 to yield azido complexes 10 and 11. These complexes were, in turn, reacted with acetylene derivatives to yield triazolo complexes 12–15 where only a few triazolo complexes of Cp* have been reported. X-ray diffraction studies revealed the complexes having a typical piano stool geometry around the metal center with the thiourea adducts binding to the metal center in a chelating (N, S) manner. Furthermore, the complexes 1–9, as well as the ligands were screened for potential anti-bacterial agents out of which complexes 3 and 5 exhibited anti-bacterial activity. Colorimetric sensing studies showed the agglomeration of the silver NPs upon addition of the ligands while the complexes were unresponsive.