Luminescent platinum(II) chloride complexes of 6-(1-alkyl-5-tetrazolyl)-4,4′-dimethyl-2,2′-bipyridine terdentate chelating ligands

Two new luminescent platinum(II) chloride complexes with N-alkylated 6-(1H-5-tetrazolyl)-4,4′-dimethyl-2,2′-bipyridine (tmbpyH), [Pt(etmbpy)Cl](BF4) (1) and [Pt(htmbpy)Cl](BF4) (2) (etmbpy = 6-(1-ethyl-5-tetrazolyl)-4,4′-dimethyl-2,2′-bipyridine; htmbpy = 6-(1-hexyl-5-tetrazolyl)-4,4′-dimethyl-2,2′-bipyridine), have been prepared and characterized. Complex 1 adopts a distorted square-planar geometry and exhibits a dimeric assembly with a head-to-tail fashion and weak Pt⋯Pt interaction. A moderately intensive broad absorption band is displayed at 350–465 nm in CH3CN solution for 1 and 2, perhaps originating from the metal-to-ligand charge-transfer (MLCT) states mixed with some halide-to-ligand charge-transfer (XLCT) and intra-ligand (IL) ππ* characters, as supported by their TD-DFT calculations. Complexes 1 and 2 show the photoluminescent properties in PMMA films and solid state at ambient temperature, which are influenced by the alkylation of the tetrazolyl-NH of tmbpyH.