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

The dihydroxo-bridged dinuclear copper(II) compound [Cu2(dpyam)2(μ-OH)2]I2 (1) and the triply bridged dinuclear copper(II) compounds with a formato bridge [Cu2(dpyam)2(μ-O2CH)(μ-OH)(μ-OMe)](ClO4) (2) and [Cu2(dpyam)2(μ-O2CH)(μ-OH)(μ-Cl)](ClO4) · 0.5H2O (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 [Cu2(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 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) Å for compounds 1, 2 and 3, respectively.