Coordination polymers derived from pyridyl carboxylate ligands having an amide backbone: an attempt towards the selective separation of CuII cation following in situ crystallization under competitive conditions

Abstract

A series of coordination polymers (CPs) derived from pyridyl carboxylate ligands equipped with a hydrogen bonding backbone (amide), namely L1 [sodium 4-(nicotinamido) benzoate] and L2 [sodium 3-(nicotinamido) benzoate], has been synthesized and characterized by single crystal X-ray diffraction. The effect of the ligating topology of these two positional isomers (L1 and L2) on the resultant supramolecular architecture of the corresponding CPs was investigated. The results indicate that most of the CPs display a 1D looped chain topology. Following in situ crystallization technique, attempts were made to separate environmentally toxic metal cation Cu^II in the form of the corresponding Cu^II CPs from a complex mixture of cations (Cu^II, Zn^II and Co^II) using both the ligands, while L1 was unsuccessful, L2 could indeed separate the Cu^II cation. The coordinating ability of the pyridyl and carboxylate moieties on the selective separation of cations was investigated. The results indicate that the selective separation of Cu^II followed the Irving–Williams series. Atomic absorption spectroscopy revealed that ~97% of Cu^II could be separated by this technique.