title: Squarato-metal(II) complexes. 2. unusual bonding mode for a squarato-bridged trinuclear copper(II) complex.
abstract: Herein, we report the structural characterization and magnetic properties of the unique squarato-bridged-tricopper(II) complex, [Cu3(pmap)3(micro1,2,3-C4O4)](ClO4)(4).2H 2O (1), based on the tripod tripyridylamine ligand bis[2-(2-pyridyl)ethyl]-(2-pyridyl)methylamine (pmap). Each of the three copper centers is penta-coordinated by four N atoms of a pmap ligand and one bridging O atom of the central squarato dianion. This complex is the first example of a non-polymeric X-ray structurally characterized trimeric transition metal complex with the three metal cations being bridged by a single squarato ligand in a micro1,2,3 coordination mode. The magnetic properties of the complex were measured over the temperature range 2-300 K. The complex exhibits moderate bulk antiferromagnetic interaction. The three magnetic exchange pathways have J values of -27.8, -20.8, and -31.9 cm(-1). The DFT calculations corroborate the relatively strong antiferromagnetic couplings obtained from the fitting of the experimental magnetic susceptibility data and allow an assignment of the fitted J values. Several geometrical parameters have been analyzed using theoretical calculations to establish magnetostructural correlations for complex 1.
authors.affiliation: Departament de Química Inorgànica, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain. ramon.vicente@qi.ub.es
authors.forename: Ramon
authors.initials: R
authors.lastname: Vicente
authors.forename: Joan
authors.initials: J
authors.lastname: Cano
authors.forename: Eliseo
authors.initials: E
authors.lastname: Ruiz
authors.forename: Salah S
authors.initials: SS
authors.lastname: Massoud
authors.forename: Franz A
authors.initials: FA
authors.lastname: Mautner