Synthesis, structure, magnetic properties, and H-1 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 (H AP = 3-amino-1-propanol; IPA = 2-hydroxy-5-methylisophthalaldehyde) has bee n synthesized and characterized by X-ray crystallography, by solid state ma gnetic susceptibility, and in solution by H-1 NMR studies. The binuclear co pper(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 br idged by the oxygen atoms of the phenolate and hydroxy groups. The axial po sition at one Cu atom is occupied by a water molecule while another Cu has weak interaction with a perchlorate group. The coordination geometries arou nd the two Cu atoms are distorted square pyramid and square planar. The sol id state magnetic susceptibility measurement reveals a moderate antiferroma gnetic exchange interaction between the two Cu atoms with a -2J value of 11 3 +/- 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 b y using chemical shift as a function of temperature also reveals a moderate antiferromagnetic exchange interaction between two Cu(II) ions. An analysi s of the relaxation data shows that the reorientational correlation time (t au(c)) is dominated probably by a combination of electronic relaxation time tau(s) and rotational correlation time (tau(r)) due to an exchange-modulat ed dipolar mechanism for this moderately antiferromagnetically coupled binu clear copper(II) system.