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New bis(crown ether) ligands (1 - 3) of Schiff base type containing recognition sites for sodium and nickel guest cations have been synthesized by the condensation of two equivalents of 4′-formyl-5′-hydroxy(benzo-15-crown-5)with 1,5-diamino-3-azapentane, 1,8-diamino-3,6- diazaoctane or 1,8-diamino-3,6-dioxaoctane. Homonuclear ditopic crystalline 2:1 (Na + :ligand) complexes (1a - 3a) of the ligands with NaClO 4  have been prepared. Heteronuclear tritopic crystalline 2:1:1 (Na ⊕  : Ni 2⊕  : ligand) complexes (2b and 3b) have also been synthesized from the reactions of the ditopic complexes (2a and 3a) with Ni(CH 3 COO) 2  · 6H 2 O. The UV-VIS spectra of 1 - 3, their sodium complexes 1a - 3a and sodium-nickel complexes 2b and 3b have been recorded in polar and non-polar solvents as well as in acidic and basic media. In polar solvents and basic solutions, tautomeric equilibria (phenol-imine and keto-amine forms, O-H···N⇌O···H-N ) are present, depending on the hydrogen bonding. The results indicate that the concentrations of the keto forms of the compounds generally increase as the polarity of the solvent increases

zeitschrift für naturforschung b

Synthesis, Complex Formation and Spectral Investigation of New Tritopic Bis(Crown Ether) Compounds Containing Recognition Sites for Sodium and Nickel Guest Cations*