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

A binuclear Cu(II) complex of [(Cu-2(HAP)(2)IPA)(OH)(H2O)](ClO4)(2). H2O (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 H-1 NMR studies. The binuclear copper(II) complex crystallizes in the orthorhombic system, space group Pbcn, a = 27.9972(9) Angstrom, b = 8.8713(3) Angstrom, c = 19.5939(6) Angstrom, 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 H-1 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 (tau(c)) is dominated probably by a combination of electronic relaxation time tau(s) and rotational correlation time (tau(r)) due to an exchange-modulated dipolar mechanism for this moderately antiferromagnetically coupled binuclear copper(II) system.