Controlled synthesis of isomorphous coordination polymers via in situ ligand transformation reaction: crystal structure, thermal and magnetic properties

Abstract

A series of isomorphous [M2(ip)2(L)2]n (M = Co, Ni; ip = isophthalate; L = 4,4′-dipyridyl and pyrazine) coordination polymers was synthesized via in situ ligand transformation reactions, in which 1,2,3-benzene tricarboxylic acid (1,2,3-btcH3) undergoes decarboxylation to isophthalate (ip), which was found to be highly dependent on the reaction temperature. The polymers crystallize in the same crystal triclinic system P. The magnetic properties were investigated by a Quantum Design physical property measurement system (PPMS); all four compounds feature almost isostructural M(II) dimers having ferromagnetic (FM) interactions. The interdimer interactions mediated by two different carboxylate groups of ip are weak, while there is no significant magnetic exchange via the 4,4′-dipyridyl ligands along the chain direction. However, substitution with pyrazine leads to antiferromagnetic exchange of nearest neighbor dimers. © 2010, American Chemical Society