Controlled access to mixed-metal pyridazine-linked cryptates

The pyridazine-linked cryptand L [formed by the 3+2 condensation of 3,6-diformylpyridazine with tris(2-aminoethyl)amine (tren)] has been used to generate a series of heterodinuclear cryptates by a one-pot two-step method. The cryptates [(MnCuL)-Cu-II-L-I](ClO4)(2)(BF4), [(FeCuL)-Cu-II-L-I](BF4)(3)(CH3CN)-C-. and [(NiCuL)-Cu-II-L-I](BF4)(3)(H2O)-H-. have been structurally characterized, with elemental analyses and mass spectroscopic data providing further evidence of their heterodinuclear nature. The synthesis, structures and characterisation of the corresponding mononuclear cryptates [(ML)-L-II](X)(2) (M = Mn, Fe, Ni, X = BF4- or ClO4) are also reported, along with the synthesis and characterisation of the homodinuclear dizinc(II) and disodium(I) cryptates, [Zn2L](ClO4)(4) and [Na2L](CF3SO3)(2). Electrochemical studies on the heterodinuclear cryptates in CH3CN indicate that the presence of the divalent cation influences the electrochemical potential and reversibility of the Cu-I --> Cu-II oxidation with the redox potential of the Cu-I/Cu-II couple being inversely correlated with the distance between the two metal ions in the solid state as determined by X-ray crystallography. The previously synthesised [(CoCuL)-Cu-II-L-I](BF4)(3) is an exception to this trend, probably due to oxidation of the Co-II ion prior to that of the Cu-I ion. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.