Structure and magnetic properties of a tetranuclear Cu (II) complex containing the 2-(pyridine-2-yliminomethyl)-phenol ligand

Abstract

A tetranuclear Cu (II) complex [Cu₄L₄ (H₂O) ₄](ClO₄)₄ has been synthesized using the terdentate Schiff base 2-(pyridine-2-yliminomethyl)-phenol (HL) (the condensation product of salicylaldehyde and 2-aminopyridine) and copper perchlorate. Chemical characterizations such as IR and UV/vis of the complex have been carried out. A single-crystal diffraction study shows that the complex contains a nearly planar tetranuclear core containing four copper atoms, which occupy four equivalent five-coordinate sites with a square pyramidal environment. Magnetic measurements have been carried out over the temperature range 2–300 K and with 100 Oe field strengths. Analysis of magnetic susceptibility data indicates a strong antiferromagnetic (J₁ = −638 cm⁻¹) exchange interaction between diphenoxo-bridged Cu (II) centers and a moderate antiferromagnetic (J₂ = −34 cm⁻¹) interaction between N–C–N bridged Cu (II) centers. Magnetic exchange interactions (J’s) are also discussed on the basis of a computational study using DFT methodology. The spin density distribution (singlet ground state) is calculated to visualize the effect of delocalization of spin density through bridging groups.