Syntheses, structures, and luminescent properties of [bis(iminoalkyl)pyridine]cadmium(II) complexes

Four new Cd-II complexes of 2,6-bis[1-(phenylimino)ethyl]-pyridine (L-1), 2,6-bis [1-(2,6-diisopropylphenylimino)ethyl]-pyridine (L-2), 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]- pyridine (L-3), 2,6-bis[1-(2-methylphenylimino)ethyl]-pyridine (L-4) have been synthesized. These complexes have the formulas [Cd(L-1)Cl-2].1.5CH3CN (1), [Cd(L-2)Cl-2] (2), [Cd(L-3)Cl-2].CH3CN (3), and [Cd(L-4)Cl-2].CH3CN (4). The molecular structures of complexes 1-4 were determined by single-crystal X-ray diffraction. Crystallographic studies of 1-4 reveal all four complexes to be five-coordinate with geometries that can be best described as distorted trigonal-bi-pyramidal. All eight compounds (L-1-L-4 and 1-4) are luminescent at room temperature in solution and the solid state. At 298 K in dichloromethane solution, all compounds have fluorescent emissions at about 368-409 rim. The fluorescent emission of these compounds originates from ligand-centered pi*-pi transitions. The Cd-II centers play a key role in enhancing the fluorescent emission of the ligands. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).