Synthesis, structure, magnetic properties, and ¹H NMR studies of a moderately antiferromagnetically coupled binuclear copper(II) complex

Abstract

A binuclear Cu(II) complex of [(Cu²(HAP)₂IPA)(OH)(H₂O)](ClO₄)₂·H₂ O (HAP = 3-amino-1-propanol; IPA = 2-hydroxy-5-methylisophthalaldehyde) has been synthesized and characterized by X-ray crystallography, by solid state magnetic susceptibility, and in solution by ¹H NMR studies. The binuclear copper(II) complex crystallizes in the orthorhombic system, space group Pbcn, a = 27.9972(9) Å, b = 8.8713(3) Å, c = 19.5939(6) Å, and Z = 8. The two copper(II) atoms in this binuclear Cu(II) complex are bridged by the oxygen atoms of the phenolate and hydroxy groups. The axial position at one Cu atom is occupied by a water molecule while another Cu has weak interaction with a perchlorate group. The coordination geometries around the two Cu atoms are distorted square pyramid and square planar. The solid state magnetic susceptibility measurement reveals a moderate antiferromagnetic exchange interaction between the two Cu atoms with a -2J value of 113 ± 9 cm^-1. The variable-temperature ¹H NMR studies in CD₃CN solution show that the observed relatively sharp hyperfine shifted signals follow a Curie behavior. The exchange coupling constant (-2J) obtained in solution by using chemical shift as a function of temperature also reveals a moderate antiferromagnetic exchange interaction between two Cu(II) ions. An analysis of the relaxation data shows that the reorientational correlation time (τ_c) is dominated probably by a combination of electronic relaxation time τ_sand rotational correlation time (τ_r) due to an exchange-modulated dipolar mechanism for this moderately antiferromagnetically coupled binuclear copper(II) system.