Molecular iodine adsorption within Hofmann-type structures M(L)[M′(CN)4] (M = Ni, Co; M′ = Ni, Pd, Pt): impact of their composition

Abstract

A series of thermally stable Hofmann-type clathrate structures with the general formula M(pz)[M′(CN)₄], where M and M′ are bivalent metal ions M^II = Ni^II, Co^II, M^II′ = Ni^II, Pd^II, Pt^II, and pz is the pyrazine bidentate ligand, was synthesized and investigated for the efficient entrapment of iodine (I₂) in solution and in the gas phase. Iodine-containing clathrates thus prepared were analysed to determine the saturation capacity, thermal stability, guest-induced structural changes of the clathrate's lattice and the nature of the confined iodine according to the chemical composition of the host structure. An efficient confinement of about 1 I₂ per unit cell is observed for the series of clathrates with the Ni^II and Pd^II ions in the square planar position whatever the bivalent metal ion in the octahedral position. Specific responses in the lattice adjustment are detected for Co^II in the octahedral and Pd^II in the square planar positions.