Solvent-induced structural transformations of two-dimensional coordination polymers based on trinuclear cobalt unit.

Three two-dimension Co(II) coordination polymers constructed by trinuclear unit of [Co 3 O 12 ] with kgd topology, The different size of solvent molecular can affect the structure of the compounds. The exchange of coordinated solvent molecules on the unsaturated coordination cobalt sites have also been explored. Three new Co(II) coordination polymers based on a flexible ligand 5-(3-carboxybenzyloxy)-isophthalic acid (H 3 L) namely [Co 3 (L) 2 (H 2 O) 4 ] n ·2nDMF (1) (DMF = N,N-dimethylformamide), [Co 3 (L) 2 (DMA) 2 (H 2 O) 2 ] n ·2nDMA (2) (DMA = N,N-dimethylacetamide) and [Co 3 (L) 2 (py) 2 (NMP)(H 2 O)] n ·nNMP·nH 2 O (3) (NMP = N-methyl-2-pyrrolidone) have been assembled using different solvent. The different size of solvent molecular can affect the structure of the compounds. Interestingly, three compounds all constructed by the same trinuclear unit of [Co 3 O 12 ] to exhibit two-dimension architecture with kgd topology. In this building block, there are coordinated water and molecules having the carbonyl group as terminal ligands coordinated with cobalt ions, providing a good example for studying the coordinated solvent exchange. When coordinated solvent molecules were replaced by pyridine molecules, which made two Co ions in asymmetric coordination. This symmetry breaking might the reason for compound 3 crystallizes in the noncentrosymmetric space group. Also, magnetic investigation on compound 1 indicates antiferromagnetic coupling exchange interactions between Co(II) ions in the trinuclear cluster unit. [ABSTRACT FROM AUTHOR]