Cyano-bridged extended heteronuclear supramolecular architectures with hexacyanoferrates(II) as building blocks

Two cyano-bridged heteronuclear coordination polymers [{Cu(bipn)}3Fe(CN)6]n(ClO4)2n·4nH2O (bipn=bis(3-aminopropyl)amine) (1) and [{Cd(tet)}2Fe(CN)6]n·3nH2O (tet=triethylenetetramine) (2) were synthesized and their structures determined. Both complexes were obtained from the assembly reactions of [MLn]2+ (M=Cu, Cd; n=1, 2) and [Fe(CN)6]4− in aqueous solutions. Complex 1 exhibits a honeycomb structure with twisty rings formed by Cu(II), Fe(II), and cyanides. The anions ClO4− weakly coordinate to Cu(II) and form hydrogen bonds with amino groups of bipn, while water molecules link to the 2D network via hydrogen bonds. In complex 2, the neutral polymer [{Cd(tet)}2Fe(CN)6]n forms zigzag chains. The water molecules insert between chains and pull them together to form a layered structure via a series of interchain hydrogen bonds. Thermal analyses over the temperature range 30–700°C show both complexes decompose completely above 460°C.