Two- and Three-Dimensional Divalent Metal Isophthalate Coordination Polymers Incorporating Flexible Bispyridylmethylpiperazine Tethers: Structure Direction through Coordination Geometry Preferences, Carboxylate Binding Mode, and Ligand Conformation

Abstract

Hydrothermal synthesis has afforded a family of divalent metal coordination polymers incorporating both the isophthalate dianion (ip) and the flexible organodiimine N,N′-bis(4-pyridylmethyl)piperazine (bpmp). The compounds of type {[M(ip)(bpmp)]·H2O} (M = Co, 1; M = Cd, 2) are isomorphous, possessing puckered two dimensional (2D) rectangular grid layers built from the linkage of [M2(ip)2] double chains through bpmp tethers. In contrast, the nickel congener {[Ni(ip)(bpmp)(H2O)]·H2O} (3) displays a corrugated, interpenetrated 2D structure. {[Zn(ip)(bpmp)]·H2O} (4) adopts a 5-fold interpenetrated three-dimensional diamondoid topology due to the tetrahedral coordination at Zn. Analysis of the variable temperature magnetic susceptibility of 1 indicated the presence of ferromagnetic coupling and zero-field splitting effects within the dinuclear subunits along with possible long-range ferromagnetic interactions transmitted through the ip ligands. The d10 derivatives 2 and 4 exhibited blue-violet luminescence upon exposure to ultraviolet radiation. The materials also exhibited high thermal stability.