Syntheses and coordination chemistry of methylpyridylphosphine oxide ligands with copper(II)

The coordination properties of three heterofunctional phosphine oxide ligands, 2-methylpyridyldiphenylphosphine oxide (L1), phenylphosphino-bis-2-methylpyridine oxide (L2) and phenylphosphino-bis-2-methylpyridine N,N',P-trioxide (L3) with Cu(II) is described. The X-ray crystal structures of the compounds display a distorted octahedral geometry, which exhibit Jahn-Teller distortions. In compounds 1 and 2, the L1 and 12 ligands react with Cu(BF4)(2) in a 2:1 ligand to metal ratio, respectively, with the BF4 anions interacting with the metal center. L3 reacts with Cu(BF4)(2) in 1:1 and 2:1 ligand/metal ratios to form compounds 3 and 4, respectively. Addition of either 2,2'-bipyridine or 4,4'-bipyridine to reaction solutions containing Cu(BF4)(2) and U produces a discrete molecule (5) and a polymeric structure (7), respectively. The reaction of both bipyridines in the presence of Cu(BF4)(2) and L3 gives rise to a discrete molecule (6) characterized by two octahedral coppers interconnected by the 4,4'-bipyridine. The electrochemical and photophysical properties of all compounds were investigated by cyclic voltammetry (CV) and UV-Vis, as they exhibited no emission or excitation in fluorimetric experiments. (C) 2010 Elsevier Ltd. All rights reserved.