Zinc and copper complexes of stilbene iminopyridine ligands with η2-Olefin binding mode

Abstract

Two stilbene based iminopyridine ligands (L1-L2) synthesized by a condensation reaction between N,N-Dimethyl-4,4′-azodianiline and 2-pyridinecarboxaldehyde or 2,6-pyridinedicarboxaldehyde, with 73% and 65% yield, are described. The two ligands have been characterized by elemental analysis and spectroscopic techniques. The complexation of ligand L1 with ZnCl2 afforded neutral tetrahedral zinc(II) metal complex C1 formulated as [ZnL1Cl2] with a 2D supramolecular architecture reinforced by π···π stacking and hydrogen bonding in the solid state. Interestingly in the case of copper(I) complex C2, ligand L1 acts as a ditopic ligand since it coordinates one Cu(I) with an iminopyridyl fragment and a second metal center with an η2-olefin binding mode giving rise to a 1D-polymeric structure. The coordination sphere is completed with an acetonitrile solvent molecule leading to a distorted tetrahedral geometry around copper cation and the resulting coordination polymer can be formulated as {[Cu(L1)2CH3CN]BF4}. In addition complexation of L2 with zinc chloride afforded complex C3 formulated as [ZnL2Cl2]. DFT and TDDFT computations permitted to investigate the frontier MOs of all species and to assign their UV–visible absorption bands.