A dinuclear extension to constrained heteroleptic Cu(I) systems

Abstract

This article reports the synthesis and optical properties of three dinuclear, cationic copper complexes [Cu2(?-dppm)2(?-L)](NO3)2 (dppm diphenyldiphosphinomethane, L: LA 3,6-bis(2-pyridyl)-4,5-diphenyl-pyridazine, LB 3,6-bis(2-pyridyl)-4,5-di(4-pyridyl)-pyridazine and LC 3,6-bis(2-pyridyl)-8,9-diazafluoranthene). These were formed on the reaction of [Cu(?-dppm)(NO3)]2 with a series of N-donor (bppn) ligands L. The single crystal X-ray structures of [Cu2(?-dppm)2(?-L)](NO3)2?CH2Cl2 were determined and revealed that in both, the two copper atoms are held by three bridging ligands, two dppm ligands and one bppn ligand acting as a tetradentate bridge. The absorption spectra of the complexes present a MLCT [Cu ??*(N[logical and]N)] band in the ? 370?425 nm region. These new complexes exhibit red-orange MLCT-based emission in the solid-state with lifetimes in the microsecond range. In oxygen-free dichloromethane solution, the complex [Cu2(?-dppm)2(?-LC)]2+ has a long lifetime of 22.8 ?s. The long emission lifetimes are attributed to a rigid conformation that precludes the possible distortion of the copper in the excited state.