title: Combining topological and steric constraints for the preparation of heteroleptic copper(I) complexes.
abstract: Heteroleptic copper(I) complexes have been prepared from a macrocyclic ligand incorporating a 2,9-diphenyl-1,10-phenanthroline subunit (M30) and two bis-phosphines, namely bis[(2-diphenylphosphino)phenyl] ether (POP) and 1,3-bis(diphenylphosphino)propane (dppp). In both cases, the diphenylphosphino moieties of the PP ligand are too bulky to pass through the 30-membered ring of M30 during the coordination process, hence the formation of C2v-symmetrical pseudo-rotaxanes is prevented. When POP is used, X-ray crystal structure analysis shows the formation of a highly distorted [Cu(M30)(POP)](+) complex in which the POP ligand is only partially threaded through the M30 unit. This compound is poorly stable as the Cu(I) cation is not in a favorable coordination environment due to steric constraints. By contrast, in the case of dppp, the bis-phosphine ligand undergoes both steric and topological constraints and adopts a nonchelating coordination mode to generate [Cu2(M30)2(μ-dppp)](BF4)2. This compound exhibits metal-to-ligand charge transfer (MLCT) emission characterized by a very large Stokes' shift (≈200 nm) that is not attributed to a dramatic structural distortion between the ground and the emitting states but to very weak MLCT absorption transitions at longer wavelengths. Accordingly, [Cu2(M30)2(μ-dppp)](BF4)2 shows unusually high luminescence quantum yields for Cu(I) complexes, both in solution and in the solid state (0.5 and 7 %, respectively).
authors: Laboratoire de Chimie des Matériaux Moléculaires, Université de Strasbourg et CNRS (UMR 7509), Ecole Européenne de Chimie, Polymères et Matériaux, 25 rue Becquerel, 67087 Strasbourg Cedex 2 (France).
authors: Meera
authors: M
authors: Mohankumar
authors: Filippo
authors: F
authors: Monti
authors: Michel
authors: M
authors: Holler
authors: Frédéric
authors: F
authors: Niess
authors: Béatrice
authors: B
authors: Delavaux-Nicot
authors: Nicola
authors: N
authors: Armaroli
authors: Jean-Pierre
authors: JP
authors: Sauvage
authors: Jean-François
authors: JF
authors: Nierengarten
keywords: bis-phosphine ligands; copper; phenanthroline ligands; photophysical properties; self-assembly