Synthesis, structure, thermal and magnetic properties of new tetranuclear copper(II) complex supported by multidentate ligand and glutarate functionality

Abstract

A new tetranuclear Cu(II) complex, [Cu(H2O)4][Cu4(cpdp)2(glut)]Cl2·6H2O (1) was successfully constructed by utilization of carboxylate-based multidentate ligand N,N'-bis[2-carboxybenzomethyl]-N,N'-bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol (H3cpdp), in combination with glutarate (glut) and Cu(II) ions, and characterized systematically. Originally, the symmetrical flexible ligand cpdp3− is capable to bind two Cu(II) ions, leaving behind accessible binding sites for further coordination of exogenous glutarate anion which facilitates the assembly of two ligand-bound Cu(II) pairs. In MeOH/H2O, the reaction of CuCl2·2H2O with H3cpdp and sodium glutarate in the presence of NaOH results in the formation of 1. Complex 1 was characterized by different analytical techniques, including single crystal X-ray structure investigation. Analysis of single crystal X-ray structure shows that 1 is a self-assembled tetranuclear copper complex in which two dinuclear [Cu2(cpdp)]+ species are exclusively bridged by one glutarate functionality through μ4:η1:η1:η1:η1 manner, acting as a coligand. Thermoanalytical methods (TGA/DTA) were used to examine the thermal stability and it was observed that 1 is stable up to ∼190°C. Variable temperature (2-300 K) magnetic susceptibility studies show the weak antiferromagnetic interactions among the copper centers with the value of magnetic exchange coupling constant (J) of -0.5 cm−1.