Synthesis, structure and magnetic characterization of dinuclear copper(II) complexes bridged by bicompartmental phenolate

The reaction of Cu(II) salts with the bicompartmental 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-chlorophenol (LCl-OH) ligand afforded four new dinuclear bridged phenoxido Cu(II) complexes. Three doubly bridged complexes namely [Cu2(μ-LCl-O)(μ-X)](ClO4)2 (1: X = OH-, 3: X = O2P(OPh)2-) and 2: [Cu2(μ-LCl-O)(μ-pz)(ClO4)]ClO4 (2) where pz = pyrazolyl anion, and one singly bridged-phenoxido, [Cu2(μ-LCl-O)(dca)2]PF6·2CH3CN (4·2CH3CN) (dca = dicyanamide anion). A complex similar to 4 was also obtained with 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-methylphenol (LMe-OH), [Cu2(μ-LMe-O)(dca)2]PF6·2CH3CN (5·2CH3CN) where in both cases dca are acting as terminal monodentate ligands. The complexes were structurally characterized by various spectroscopic techniques (IR, UV-visible and ESI-MS) and by single crystal crystallog. Magnetic susceptibility measurements at variable temp. revealed strong to very strong antiferromagnetic coupling (AF) in the doubly bridged complexes 1-3 and very weak AF interaction in the dicyanamido compds. 4 and 5. The DFT calcns. for the coupling consts., J were in agreement with the exptl. obsd. behavior. The trend in magnetic properties was attributed to the strength of overlap between the orbitals (dx2-y2/dx2-y2vs. dz2/dx2-y2vs. dz2/dz2) resulting from trigonal bipyramidal (TBP) or square pyramidal (SP) geometries. [on SciFinder(R)]