Synthesis, spectroscopy and electroluminescence of cadmium(II) polypyridyl complexes

Five new complexes [Cd(ptpy-R)2](PF6)2 (ptpy = 4′-phenyl-2,2′:6′,2″-terpyridine; R = tert-Butyl (1), hexyloxy (2), carbozole-9-yl (3), naphthalene-1-yl-phenylamine-N-yl (4) and diphenylamine-N-yl (5)) were synthesized and characterized by 1H NMR, elemental analyses, UV–vis spectroscopy and cyclic voltammetry. The emission color of resultant complex molecules has been tuned effectively, from violet (397 nm) for 1 to orange (602 nm) for 5 in film, by modifying the electron-donating ability of the substituent R. The UV–vis spectroscopy and the solution-state luminescence showing remarkable solvatochromism suggests the emission involves the intra-ligand charge transfer (1ILCT) excited state, occurring from the substituent R moiety to Cd(II) coordinated terpyridine. The electroluminescence (EL) properties for these organic materials were also studied and complexes 3, 4 and 5 exhibit EL wavelength at 548 nm, 596 nm and 604 nm with maximum current efficiency of 3.25 cd/A, 3.15 cd/A and 2.16 cd/A, respectively.