Synthesis,structures and properties of two novel copper(II) complexes with hydrogen bonding supramolecular networks

Two novel complexes, [Cu(HL)₂(H₂O)]₂(OH)₂(ClO₄)₂·1.5H₂O (1) and [Cu(HL)₂]Cl₂·4H₂O (2), have been prepared by reacting copper salts with the 4-amino-3-ethyl-1,2,4-triazole-5-thione (HL) ligand in neutral solution and in HCl (6 mol L^–1) medium, respectively. They were characterized by FT-IR and u.v.–vis. spectra, and the structures were determined by single crystal X-ray diffraction techniques. In both complexes, the triazole ligand chelated the metal ions through the amine and thione substituents on the five-membered ring. Complex (1) has a square-pyramidal copper(II) ion coordinated by two triazole ligands and one water molecule. Unlike (1), the Cu²⁺ ion in (2) displays its characteristic Jahn–Teller distortion with the distance of the Cl^– anions to metal ion further away than that of the triazole ligands. The most intriguing structural features of the title complexes are that the HL ligands chelate copper(II) ions through the N(1) and S(1) atoms, in a cis mode in (1) and a trans mode in (2). In both cases, self-assembled crystals, by supramolecular contacts simultaneously, form two multi-dimensional frameworks.