Synthesis, structures and magnetic properties of dimeric copper and trimeric cobalt complexes supported by bridging cinnamate and chelating phenanthroline

Two polynuclear transition-metal complexes, [Co-3(II)(cinna)(6)(phen)(2)] (1), [Cu-2(II)(cinna)(2) (phen)(2)(NO3)(H2O)]NO3 center dot CH3OH (2), where cinna = trans-cinnamate, PhCH = CHCO2- and phen = 1,10-phenanthroline, have been synthesized and characterized by elemental analyses, infrared spectroscopy, single-crystal X-ray diffraction (XRD) and magnetic measurements. 1 contains two independent geometrical isomers of [Co-3(cinna)(6)(phen)(2)], where the cobalt atoms form a linear spine bridged by carboxylate from cinnamate radiating perpendicular to it, the 1,10-phenanthroline chelating the ends. Weak C-H center dot center dot center dot O hydrogen bonds in two directions generate a bidimensional network. 1 behaves as a paramagnet due to the absence of magnetic exchange between the trimers in the absence of chemical bonds between trimers. 2 contains a positively charged dimer of copper ions bridged to two cinnamate in syn-syn mode with two almost parallel phenanthroline molecules chelating the two copper ions, while a water molecule and one NO3- coordinate their axial positions. The dimer is described as a pincer molecule. Weak O-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds and pi-pi stacking interactions are consistent with a description of a supramolecular assembly of dimers. The exchange coupling within the doubly-bridged copper atoms is antiferromagnetic (J=-153(1) K). (C) 2014 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.