Synthesis and structural characterization of new transition metal complexes of a highly luminescent amino-terpyridine ligand

The synthesis, NMR and UV-Vis spectroscopy measurements and X-ray diffraction analysis of four new metal complexes of the amino terpyridine ligand 4́-[4-(4-aminophenyl)phenyl]-2,2́:6́,2́́-terpyridine L, namely [FeL2](ClO4)2 (1), [ZnL2](ClO4)2 (2), [CdL2](ClO4)2 (3) and [PtMe3IL] (4), are reported. The X-ray crystal structures of complexes 1-3 are 1:2 metal:ligand structures with tridentate ligands decorated around the octahedral metal centers. In complex 4, with L in a bidentate coordination mode, the Pt(IV) coordinated methyl and iodine groups form a fac-arrangement. The 1H NMR spectrum of 4 shows three 195Pt-1H resonances for the methyl groups incorporating the fac-arrangement, which confirms the bidentate coordination mode of L in solution. The X-ray crystal structure of L shows a transoid conformation of the pyridine ring nitrogen atoms along the interannular bond in the terpyridine core. Ligand L exhibits a bright blue emission in dichloromethane [fluorescence quantum yield (ΦF) = 68%] and its emission maxima shows significant solvatochromism (461 nm in dichloromethane to 533 nm in N,N-dimethylformamide), while its complexes 2 and 3 are only very weakly emissive and 1 and 4 are found to be non-emissive.