Electronic and magnetic structure of a triacetylphloroglucinol-bridged C-3-symmetric trinuclear copper complex: Magnetic characterization, ESR spectroscopy, and DFT calculations

For the trinuclear copper complex [Cu-3(tapg)(H(2)bhea)(3)](ClO (4))(3) based on the tritopic bridging ligand 2,4,6-triacetylphloroglucinol (H(3)tapg) and the capping ligand 2-[bis-(2-hydroxyethyl) amino] ethylamine (H(2)bhea) a detailed study on the magnetic and electronic properties is presented. The C-3-symmetric structure of the molecular assembly is preserved in the solid state structure of the compound which crystallizes in the space group R3c with a threefold rotation axis passing through the center of the molecule. Susceptibility measurements show weak ferromagnetic interactions with a coupling constant J = 1.10(4) cm(-1) mediated by a spin-polarization mechanism. This is confirmed by DFT calculations according the broken symmetry approach at B3LYP/def2-TZVP level of theory. Extended characterization by ESR spectroscopy both in X- and W-band confirm an exchange-coupled system with axial symmetry with g(perpendicular to) = 2.0633(4), g(parallel to) = 2.2303(4) and an effective axial hyperfine constant A(parallel to,eff) = 64 G. (C) 2010 Elsevier B.V. All rights reserved.