Structure of the Molecular Complexes of 18Crown6 with 1,2,5-Oxadiazole Derivatives (original) (raw)

A number of N-alkyl(nitrobenzo)aza-18-crowns-6 in which the nitrogen atom in the macroring is conjugated with the benzene ring were synthesized, and their complexing power was compared with that of model nitro derivatives of benzo-18-crown-6 and N-phenylaza-18-crown-6 using 1H NMR spectroscopy and DFT/PBE quantum-chemical calculations. The stability constants of the complexes formed by crown ethers with NH4/+, EtNH3/+, Li+, Na+, and K+ in CD3CN were determined by 1H NMR titration. The complexing power of N-alkyl(nitrobenzo)aza-18-crowns-6 toward metal and ammonium cation was considerably higher than that of N-(4-nitrophenyl)aza-18-crown-6 and N-alkyl(nitrobenzo)aza-15-crown-5 and was comparable or higher than that of nitrobenzo-18-crown-6.