Synthesis, characterization and complexation properties of a heteroditopic cryptand L towards Cu-II and Zn-II: crystal structures of L center dot 3H(2)O and [ZnL][ClO4](2)center dot 2H(2)O

A new heteroditopic cryptand (L) has been synthesized in high yields, at 5 degrees C and in absence of any templating metal ion, by tripod-tripod Schiff-base condensation of tris(3-aminopropyl)amine and 2,2',2 ''-nitrilotris(ethyleneoxy)tris(benzaldehyde) followed by reduction in situ with NaBH4. The molecule has an endo-endo conformation with a distance of 5.291 Angstrom between the two bridgehead nitrogens. The cryptand forms mononuclear cryptates of the general formula [ML][ClO4](2) with copper(II) and zinc(II) perchlorates. The crystal structure of [ZnL][ClO4](2) . 2H(2)O was determined. The Zn-II occupies the N-4 end of the cavity in an almost ideal tetrahedral geometry. The blue copper(II) cryptate exhibits ligand-field bands at 875 and 745 nm and a ligand-to-metal charge transfer at 275 nm in acetonitrile solution at 298 K indicative of pseudo-tetrahedral CuN4 co-ordination. However, its EPR spectral characteristics in the solid state or in solution are typical of a magnetically concentrated complex.