Monodentate and bridging coordination of 2,5-dimercapto-1,3,4-thiadiazolate to a (2,2′:6′,2′-terpyridine)platinum(ii) center

A series of mono- and di-nuclear platinum complexes, [Pt(trpy)(McMT)](PF₆) (1), [Pt(trpy)(DMcTH)](PF₆) (2) and [(Pt(trpy))₂(DMcT)](PF₆)₂ (3) has been synthesized by the reaction of [Pt(trpy)(OH)](PF₆) with mercapto- and dimercapto-thiadiazoles (trpy = 2,2′:6′,2′-terpyridine, McMTH = 2-mercapto-5-methyl-1,3,4-thiadiazole, DMcTH₂ = 2,5-dimercapto-1,3,4-thiadiazole). The X-ray structure determinations revealed that the mercaptothiadiazoles coordinate to the platinum centers as κ¹ S-thiolate forms in all three complexes. Mononuclear DMcT–Pt complex 2 has a free thioamide group which is responsible for the formation of a hydrogen-bonded dimeric structure in the solid state. The complexes 1 and 2 show LLCT emissions in the solid state, whereas 3 is non-emissive. Cyclic voltammograms of the three complexes in DMF commonly show two reduction processes at ca. −0.7 V and −1.3 V based on the (Pt(trpy))²⁺ units. Complex 2 further shows the oxidation of a free thioamide group at 0.32 V (vs. Ag/AgCl) on the addition of Et₃N.