Preparation, and Thermal and Electronic Properties of Double Complex Salts and Cyanide-bridged Complexes Containing Cationic Copper(II) Complexes and Hexacyanoferrate(II) Ion

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Abstract
Reaction of copper(II) ion with hexacyanoferrate(II) ion, [Fe(CN)6]4−, in an aqueous solution containing such an amine as en (1,2-ethanediamine), tn (1,3-propanediamine), dien (bis(2-aminoethyl)amine), or dpt (bis(3-aminopropyl)amine), gave two types of complexes: Double complex salts, [Cu(en or tn)2]2[Fe(CN)6]·nH2O(n=5–8), and cyanide-bridged complexes, [(Cu(dien or dpt))2(NC)2Fe(CN)4]·4H2O. The infrared spectra of the complexes in the νCN region revealed that the complexes, [(Cu(dien or dpt))2(NC)2Fe(CN)4]·4H2O, contain cyanide bridges, while in [Cu(en or tn)2]2[Fe(CN)6]·nH2O, no cyanide bridge is present. The thermal reactions of the complexes in the solid state were investigated by means of derivatography under dynamic conditions (D conditions). It was found that dehydration from [Cu(en)2Fe(CN)6]·nH2O resulted in formation of cyanide bridge in the apical position of square planer [Cu(en)2]2+. For [(Cu(dien or dpt))2(NC)2Fe(CN)4]·4H2O, dehydration resulted in the formation of additional cyanide bridges. All the complexes showed metal to metal (iron(II) to copper(II)) charge-transfer transitions (MMCT) in the near ultraviolet or visible region. The complexes, [Cu(en or tn)2]2[Fe(CN)6]·nH2O, exhibited the outer sphere iron(II) to copper(II) charge-transfer bands (OSMMCT) in the near ultra-violet region. [(Cu(dien or dpt))2(NC)2Fe(CN)4]·4H2O and the dehydrated complexes prepared by thermal reaction showed the inner-sphere iron(II) to copper(II) charge transfer bands (ISMMCT) in the visible region. A good correlation was observed between the energies of the MMCT and the d-d band maxima of copper(II) ions

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