Luminescent mixed ligand copper(I) clusters (CuI)n(L)m (L = pyridine, piperidine):: thermodynamic control of molecular and supramolecular species

The photophysical properties of neutral adducts of CuI and the N-bound ligands pyridine (py) and piperidine (pip) of the type CunXnLm were studied as a function of the concentrations of the ligand L. For L = py, variation in the UV-Vis absorption and luminescence spectroscopic properties as a function of ligand concentration is rationalized as the result of labile equilibria involving several species, most prominently the dinuclear complex Cu2I2(py)(2) and the 'cubane' cluster Cu(4)I(4)py(4). The ease of ligand exchange in solution was exploited for the self-assembly of mixed-ligand tetrameric compounds Cu4I4(py)(n)(pip)(m) (where n + m = 4), which were identified through their photophysical properties. Factors determining these emission properties are discussed. (C) 2001 Elsevier Science B.V. All rights reserved.