A crystal engineering rationale in designing a Cd^II coordination polymer based metallogel derived from a C3 symmetric tris-amide-tris-carboxylate ligand

Abstract

A crystal engineering rationale was employed to generate coordination polymer based metallogels derived from a C3-symmetric tris-amide-tris-carboxylate ligand, namely N,N′,N′′-bis-(4-carboxylate) trimesicamide (L1). Reactions of L1 with various metal salts such as Cd(NO₃)₂, Cu(NO₃)₂, Co(NO₃)₂ and Zn(NO₃)₂ in pure water resulted in metallogels G1, G2, G3 and G4, respectively. The gels were thermo-irreversible indicating their coordination polymeric nature. Crystallization of L1 and Cd(NO3)2 from a MeOH–water mixture afforded the coordination polymer CP1, the composition of which was established as [{Cd(μ3-L1)(H₂O)}·13H₂O]₃ from single crystal X-ray diffraction. The crystal structure of CP1 revealed the existence of a 3-fold interpenetrated highly undulating (6,3)-network topology having a large solvent accessible area volume. The results clearly supported the crystal engineering rationale, on which the generation of metallogels was based.