Cobalt(II) coordination polymers containing trans-1,2-Bis(4-pyridyl)ethene and their magnetic properties

Abstract

Reaction of the CoII ion and the bpe [trans-1,2-bis(4-pyridyl)- ethene] ligand in the presence of the CH3CO2 -, CF3CO2 -, C6H5CO 2 - and NO3 - anions affords six coordination polymers, namely [Co2(μ-bpe)2(μ-O 2CCH3)2(O2CCH3) 2].H2O (1), [Co2(μ-bpe)2(μ- O2CCF3)2(O2CCH3) 2] (2), [Co(μ-bpe)2-(O2CCF3) 2] (3), [Co(μ-bpe)(O2CC6H5) 2(HO{O}CC6H5)2] (4), [Co(μ-bpe)(O2CC6H5)2(CH 3OH)2] (5)and[Co2(μ-bpe)3(NO 3)3- (CH3OH)](NO3) (6). All the compounds have been characterized by X-ray crystallography, IR spectroscopy and thermogravimetry. Variable-temperature magnetic measurements were also performed on 3 and 6. Compounds 1 and 2 form 1D molecular ladder coordination polymers bridged by acetate ligands. Replacing the acetate ligands completely by trifluoroacetate ligands produced interpenetrated squaregrid sheets in 3. Replacing acetate and trifluoroacetate ligands by benzoate ligands resulted in two 1D coordination polymers, 4 and 5, having zigzag and linear structures, respectively. When the nitrate anion was used, a 3D network, 6, was afforded with inclined interpenetration of a 1D molecular ladder structure with threefold polycatenation. The variation of anions, reaction conditions and the ratio of reactants profoundly affect the final topological structure of the coordination polymers synthesized. The trifluoroacetate and nitrate anions influence the topology and the degree of interpenetration in the coordination polymers 3 and 6, respectively. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.