A series of [Cu(N-N)(P-P)]BF4 complexes: Luminescence quenching caused by electron-configuration transformation in excited state

In this paper, we report a series of [Cu(N-N)(P-P)]BF4 complexes based on two phosphorous ligands and three 1,10-phenanthrolin derived diimine ligands, including their syntheses, characterizations, crystal structures. Their photophysical properties were experimentally measured and theoretically analyzed by time-dependent density functional theory (TD-DFT). It is found that the introduction of too many fused phenyl rings into diimine ligand leads to luminescence absence of corresponding [Cu(N-N)(P-P)](+) complexes at room temperature. A detailed analysis suggests that the thermal activated electron-configuration transformation between the [Cu(N-N)(P-P)]+ triplet metal-to-ligand-charge-transfer ((MLCT)-M-3) state and the lowest lying excited state of its diimine ligand ((LC)-L-3) is responsible for the luminescence quenching. (C) 2011 Elsevier B. V. All rights reserved.