Effect of non-covalent interaction on the diastereoselective self-assembly of Cu(ii) complexes containing a racemic Schiff base in a chiral self-discriminating process?

New Journal of Chemistry Pub Date: 2014-01-30 DOI: 10.1039/C3NJ01547E

Abstract

The diastereoselective self-assembly of five Cu(II) heterochiral complexes containing a racemic Schiff base ligand LH (where LH = (R,S) 2-((1-(2-pyridyl)ethylimino)methyl)phenol in a chiral self-discriminating process is reported. Complexes 1–5 are synthesized using ligand LH, Cu(NO3)2·3H2O, Cu(ClO4)2·6H2O, and co-ligands such as N3?, NCS?, NCO?, and are conclusively structurally characterized. Determination of the molecular structures of 1–5 confirmed the presence of a di-copper core with an inversion centre located directly between the two copper ions. In 1–5, each ligand in the di-copper core discriminates its own chirality and results in heterochiral dimerization in a chiral self-discriminating manner. The crystal packing pattern of compounds 1–5 are analyzed in terms of non-covalent C–H?O, C–H?N, C–H?π, and parallel displaced π?π interactions. In the crystal structure of compounds 1–4, there is a parallel displaced π?π interaction between the pyridine and benzene rings in the two adjacent heterochiral dimers, which act cooperatively with other different non-covalent interactions. In 2, the coordinated water molecule acts as a bifurcated H-bond donor to phenoxo-O and perchlorate-O in a diastereoselective and enantioselective manner, respectively. The results described here address new examples of the rarely occurring chiral self-discriminating process.

Graphical abstract: Effect of non-covalent interaction on the diastereoselective self-assembly of Cu(ii) complexes containing a racemic Schiff base in a chiral self-discriminating process
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