New dinuclear copper(I) metallacycles containing bis-Schiff base ligands fused with two 1,2,4-triazole rings: Synthesis, characterization, molecular structures and theoretical calculations

Abstract

The condensation of 4-amino-3-methyl-1H-1,2,4-triazole-5(4H)-thione (AMTT, L) with 2,2′-[1,2-phenylenebis(methyleneoxy)]dibenzaldehyde in a molar ratio 2:1 in presence of sodium hydroxide in ethanol gave the compound 4,4′-((1Z,1′Z)-((((1,2-phenylenebis(methyl-ene))bis(oxy))bis(2,1-phenylene))bis(methanylylidene))bis(azanylylidene))bis(3-methyl-1H-1,2,4-triazole-5(4H)-thione), H2L1). The reaction of H2L1 with copper(I) chloride in a molar ratio 1:1 in chloroform led to the 42-membered dinuclear metallacycle, [Cu2(H2L1)2(Cl)2]·4CHCl3 (1). The latter underwent halogen exchange reaction with sodium iodide in chloroform forming the complex [Cu2(H2L1)2(I)2]·2CHCl3 (2). All synthesized compounds were characterized by elemental analyses, IR-, 1H NMR-spectroscopy and mass spectrometry as well as X-ray single crystal diffraction analysis. On the basis of determined molecular structures, the complexes 1 and 2 are isostructural and consist of dinuclear metallacyclic units [Cu2(H2L1)2(X)2] (X=Cl (1) and I (2)), in which each ligand acts as bridging agent between two Cu–X units (X=Cl (1) and I (2)) through the sulfur atoms of their five-membered heterocycles. A topological analysis of charge density in the framework of QTAIM shows that there are various noncovalent intramolecular interactions, which control molecular architecture of the complex. The topological and energetic descriptors of the electron density distribution of all BCPs of noncovalent interactions in the complex strongly support the formulation of these interactions as hydrogen bonds and van der Waals interactions, referred to as closed-shell interactions.