Synthesis and luminescence properties of platinum(II) complexes of 4′-chloro-2,2′:6′,2″-terpyridine and 4,4′,4″-trichloro-2,2′:6′,2″-terpyridine

The complex [Pt(Cl3terpy)Cl]PF6 has been prepared from cis-[Pt(dimethylsulfoxide)2Cl2] and 4,4′,4″-trichloro-2,2′:6′,2″-terpyridine (Cl3terpy). The complex [Pt(Clterpy)Cl]Cl has been prepared from cis-[Pt(1,5-cyclooctadiene)Cl2] and 4′-chloro-2,2′:6′,2″-terpyridine (Clterpy). Complexes have been characterized by 1H NMR, IR and UV–Vis spectroscopies and elemental analysis. The lowest energy excited state for these complexes is metal-to-ligand charge transfer (MLCT) in character. UV–Vis and low-temperature luminescence spectroscopy indicate that the MLCT state energy is lowered by chlorination of the terpy ligand. Chlorination also has substantial effects on the luminescent properties in fluid solution at 298 K. Unlike the related ‘parent’ complex [Pt(terpy)Cl]+, the chlorinated terpy complexes are luminescent in ambient fluid solution at 298 K. The 1.9 μs 3MLCT emission lifetime for [Pt(Cl3terpy)Cl]PF6 is unusually long for a platinum(II) complex in fluid solution.