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

Abstract

The dihydroxo-bridged dinuclear copper(II) compound [Cu 2(dpyam) 2(μ-OH) 2]I 2 ( 1) and the triply bridged dinuclear copper(II) compounds with a formato bridge [Cu 2(dpyam) 2(μ-O 2CH)(μ-OH)(μ-OMe)](ClO 4) ( 2) and [Cu 2(dpyam) 2(μ-O 2CH)(μ-OH)(μ-Cl)](ClO 4) · 0.5H 2O ( 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(μ-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 Å 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 CuN 2O 3 chromophore. In the dinuclear unit of compound 3, the triply bridged copper(II) ions show a distorted trigonal-bipyramidal coordination of the CuN 2O 2Cl chromophore. The Cu–Cu distances are 2.933(2), 3.023(1) and 3.036(1) Å for compounds 1, 2 and 3, respectively. The magnetic susceptibility measurements, measured from 5 to 280 K, revealed a weak antiferromagnetic 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.