Combining topological and steric constraints for the preparation of heteroleptic copper(I) complexes

Meera Mohankumar, Filippo Monti, Michel Holler, Frédéric Niess, Béatrice Delavaux-Nicot, Nicola Armaroli, Jean Pierre Sauvage, Jean François Nierengarten

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21 Scopus citations

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 CuI 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 CuI complexes, both in solution and in the solid state (0.5 and 7%, respectively).

Original languageEnglish
Pages (from-to)12083-12090
Number of pages8
JournalChemistry - A European Journal
Volume20
Issue number38
DOIs
StatePublished - 15 Sep 2014
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Keywords

  • bis-phosphine ligands
  • copper
  • phenanthroline ligands
  • photophysical properties
  • self-assembly

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