Coordination polymers of a bis-isophthalate bridging ligand with single molecule magnet behaviour of the CoII analogue
A linear diamine-bisisophthalate bridging linker N,N’-bis(1,3-dicarboxyphenyl-5-methylene)-1,3-dimethylpropanediamine, designed to incorporate amine/ammonium functionalities in the core of the ligand, has been isolated as the pentahydrate of its dihydrochloride salt (H6L)Cl2∙5H2O. Using this compound, four new coordination polymers have been formed, namely poly-[M(H2L)]∙4.5H2O (1M, where M = Co, Zn, Cd) and poly-[Cd(H2L)(OH2)]∙DMF·7H2O (2). Compounds 1M are isostructural 2D coordination polymers that contain 1D channels occupied by water molecules. In the case of 1Co these form a well ordered hydrogen-bonding network as determined by single crystal X-ray studies. Compound 2, synthesised under similar conditions, is a 1D coordination polymer in which the metal is partially solvated. DC and AC magnetic studies of 1Co, which posseses a mononuclear cobalt(II) node, revealed single molecule magnet behaviour (SMM) with an effective barrier height Ueff of 37.7 K and 0 = 1.02 x 10-9 s, among the highest reported for CoII coordination polymers.