Effect of Ligand Spacer on Metallosupramolecular Architectures: From a Dinuclear Copper(II) Double Helicate to a Tetranuclear Copper(II) Complex

Abstract

AbstractTwo new bis(N,O‐bidentate) Schiff base ligands with asymmetric spacers between the donor sites have been synthesized. The asymmetric ligand H2L1 self‐assembles with copper(II) ions to give rise to a dinuclear copper(II) complex [Cu2L12] (1), while a more flexible ligand H2L2, having an additional methylene group in the spacer, forms a tetranuclear copper(II) cluster [Cu4L24] (2). Both complexes have been characterized by different analytical and spectroscopic techniques. Single‐crystal X‐ray diffraction study of 1 shows a dinuclear copper(II) double‐stranded helicate with the two heterotopic ligands oriented head‐to‐head (HH), with a separation of 7.687(3) Å between the distorted tetrahedral copper(II) centers. The bis(bidentate) ligand strands wrap around the copper centers with a similar relative orientation (HH) to give rise to a double‐helical structure. The intramolecular face‐to‐face π–π interaction stabilizes the double‐helical structure of the molecule. In the tetranuclear complex 2, the four copper(II) centers, separated by 7.288(2)–8.239(2) Å, define a slightly distorted tetrahedron.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)