Synthesis, crystal structure, spectroscopic and magnetic properties of doubly and triply bridged dinuclear copper(II) compounds containing di-2-pyridylamine as a ligand

摘要

The dihydroxo-bridged dinuclear copper(II) compound [Cu-2(dpyam)(2)(mu-OH)(2)]I-2 (1) and the triply bridged dinuclear copper(II) compounds with a formato bridge [Cu-2(dpyam)(2)(mu-O2CH)(mu-OH)(mu-OMe)](ClO4) (2) and [Cu-2(dpyam)(2)(mu-O2CH)(mu-OH)(mu-OH)(mu-Cl)](ClO4).0.5H(2)O (3) (in which dpyam = di-2-pyridylamine) have been synthesized and their crystal structures determined by X-ray crystallographic methods. All three compounds are either centrosymmetric, or have a symmetry plane in the molecule. Compound 1 contains the [Cu-2(dpyam)(2)(mu-OH)(2)](+) unit and iodide anions. Each copper(II) ion is in a slightly tetrahedrally distorted square planar coordination with the square plane consisting of two nitrogen atoms of the dpyam ligand and two bridging hydroxo groups. The Cu-I distances of 3.321 Angstrom are quite long and only involve a weak semi-coordination. Compound 2 contains a triply bridged dinuclear copper(II) species, the coordination environment around each copper(II) ion involves a distorted trigonal-bipyramidal CuN2O3 chromophore. In the dinuclear unit of compound 3, the triply bridged copper(II) ions show a distorted trigonal-bipyramidal coordination of the CuN2O2Cl chromophore. The Cu-Cu distances are 2.933(2), 3.023(1) and 3.036(1) Angstrom for compounds 1, 2 and 3, respectively.The magnetic susceptibility measurements, measured from 5 to 280 K, revealed a weak anti ferromagnetic interaction between the Cu(II) atoms for compound 1 with a singlet-triplet energy gap (J) of -15.3 cm(-1), whereas compounds 2 and 3 are ferromagnetic with J = 62.5 and 79.1 cm(-1), respectively. (C) 2004 Elsevier B.V. All rights reserved.