Metal-organic frameworks derived from bis-pyridyl-bis-amide ligands : Effect of positional isomerism of the ligands, hydrogen bonding backbone, counter anions on the supramolecular structures and selective crystallization of the sulfate anion

Three new metal-organic frameworks, namely [Co(mu-L1)(2)(Cl)(2)](n) 1, [Cd(mu-L1)(2)(NO3)(2)](n) 2 and [{Co(mu-L1')(H2O)(4)}center dot SO4 center dot 3(H2O)](n) 3 (L1 = N,N'-bis-(4-pyridyl)isophthalamide, L1' = N,N'-bis-(3-pyridyl)isophthalamide) have been synthesized and characterized. The single crystal structures of 1-3 and the free ligand L1 are discussed in the context of the effect of positional isomerism of the ligands, hydrogen bonding backbone and counter anions on the supramolecular structural diversities observed in these MOFs. Selective crystallization of the sulfate anion from a mixture of L1', CoSO4, Co(NO3)(2), CO(ClO4)(2), Co(OAc)(2), Co(BF4)(2) was evident from the isolation of 3 which was confirmed by powder X-ray diffraction, elemental analysis and IR data.