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 2,2′-bipyridines, as co-ligands: [Co(H 2 O)(cdc)(phen)] n ( 1 ); {[Co(H 2 O)(cdc)(4dmb)]·2H 2 O} n ( 2 ); {[Co(H 2 O)(cdc)(5dmb)]·3H 2 O} n ( 3 ), where cdc =  e,a-cis -1,4-ciclohexanedicarboxylato, phen = 1,10-phenantroline, 4dmb = 4,4′-dimethyl-2,2′-bipyridine, and 5dmb = 5,5′-dimethyl-2,2′-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 θ (C-W)  = −9.6, −5.8 and −7.5 K, and E 2  = 0.51, 0.16 and 0.28 cm −1 , accordingly to Curie-Weiss model and Rueff phenomenological approach, respectively.