Strong Ferromagnetic Coupling in Linear Mixed μ-Acetato, μ-Hydroxo Trinuclear Copper(II) Complexes withN-sulfonamide derivatives − Synthesis, Structure, EPR and Magnetic Properties

Abstract

Two new trinuclear copper(II) complexes have been synthesised and structurally characterised: [Cu3(L1)2(CH3COO)2(OH)2(DMF)2] (1) [HL1 = N-(pyrid-2-ylmethyl)benzenesulfonylamide] and [Cu3(L2)2(CH3COO)2(OH)2]∞ (2) [HL2 = N-(pyrid-2-ylmethyl)naphthalenesulfonylamide]. In both complexes the central copper ion has a regular square planar geometry. The coordination spheres of the terminal copper atoms are square pyramidal, the apical positions being occupied by a DMF oxygen atom in 1 and by a sulfonamido oxygen of the contiguous trimer in 2, as a consequence the latter can be considered a chain of trinuclear species. For the two compounds the three copper atoms are in a strict linear arrangement and adjacent coppers are connected by a hydroxo bridge and a bidentate syn-syn carboxylato group. The mixed bridging by a hydroxide oxygen atom and a bidentate carboxylato group leads to a noncoplanarity of the adjacent basal coordination planes with a dihedral angle of 54.4(1)° for compound 1 and 58.34(3)° for compound 2. Susceptibility measurements (2−300 K) reveal a strong ferromagnetic coupling, J = 94.0 and 59.1 cm−1, respectively, in the mixed-bridged moiety leading to a quadruplet ground state that is confirmed by the EPR spectra. The ferromagnetic coupling arising from the countercomplementarity of the hydroxo and acetato bridges has been discussed on the basis of DFT calculations on model compounds. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)