The crystal structure of a novel octanuclear copper(II) complex containing the bidentate 1,10-phenanthroline ligand (abbreviated as phen) with cooperative carbonato and hydroxido bridging ligands, [Cu-8(phen)(12)(mu(3)-OH)(2)(p-OH)(2)(mu(3)-CO3)(2)](CF3SO3)(8)(DMF)(2)(H2O)(0.5) (1) (when DMF = N,N-dimethylformamide) is described. Compound 1 consists of two symmetry-related di-p-hydroxido-bis(1,10-phenanthroline)copper(II) groups which held together by long Cu-O(H) bonds, creating a Cu-2(OH)(2) core of a tetranuclear hydroxido-bridged copper(II) unit, further coordinated with trans-axially at Cu(3) and Cu(3)A by [mu(3)-carbonato-tetrakis(phen)dicopper(II)] moieties. The di-mu-hydroxidocopper(II) species play an important role for the apparent ferromagnetic interaction with the Cu-OH-Cu angles (theta) of 95.8(2)degrees and 93.5(1)degrees. The spectroscopic properties (IR, reflectance and EPR spectra) and the magnetic susceptibility data of this compound are investigated and compared with other related polynuclear copper(II) compounds. (C) 2008 Elsevier B.V. All rights reserved.