1,4-Cyclohexanedicarboxylato-bridged cobalt coordination polymers: Synthesis, crystal structures and magnetic properties

Abstract

Three coordination polymers have been synthesized, using self-assembly solution reactions at ambient conditions, combining Co(II) ion with 1,4-ciclohexanedicarboxylic acid, in the presence of 1,10-phenantrolione and two different 2,20-bipyridines, as co-ligands: [Co(H2O)(cdc)(phen)]n (1); {[Co(H2O)(cdc)(4dmb)] 2H2O}n (2); {[Co(H2O)(cdc)(5dmb)] 3H2O}n (3), where cdc = e,a-cis-1,4-ciclohexanedicarboxylato, phen = 1,10-phenantroline, 4dmb = 4,40-dimethyl-2,20-bipyridine, and 5dmb = 5,50-dimethyl-2,20-bipyridine. Crystallographic studies show that these compounds have one-dimensional (1D) structures; Co(II) in 1–3 is six-coordinated with a distorted-octahedral coordination sphere. Complexes 2 and 3 exhibit a novel bridging motif of the cdc ligand in its equatorial, axial cis configuration. In addition, the solid-state self-assembly of the polymeric structure of 1 gives rise to a 2D supramolecular framework, mainly through hydrogen bonding. In contrast, complex 2 forms an infinite 1D supramolecular array, made of double Co ion rows bridged by hydrogen bonding interactions. Complex 3 generates an intricate 2D supramolecular framework also throughout hydrogen bonding. The thermal stabilities of the three coordination polymers were investigated. Magnetic properties measurements reveal that complexes 1–3 exhibit weak antiferromagnetic ordering with h(C-W) = 9.6, 5.8 and 7.5 K, and E2 = 0.51, 0.16 and 0.28 cm 1, accordingly to Curie-Weiss model and Rueff phenomenological approach, respectively.