Nitro derivatives of N-alkylbenzoaza-15-crown-5: synthesis, structures, and complexation with metal and ammonium cationsстатья

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[1] Nitro derivatives of n-alkylbenzoaza-15-crown-5: synthesis, structures, and complexation with metal and ammonium cations / S. N. Dmitrieva, M. V. Churakova, N. A. Kurchavov et al. // Russian Chemical Bulletin. — 2010. — Vol. 59, no. 6. — P. 1192–1206. A number of N-alkylnitrobenzoaza-15-crown-5 with the macrocycle N atom conjugated with the benzene ring were obtained. The structural and complexing properties of these compounds were compared with those of model nitrobenzo- and N-(4-nitrophenyl)aza-15-crown-5 using X-ray diffraction, (1)H NMR spectroscopy, and DFT calculations. The macrocyclic N atom of benzoazacrown ethers are characterized by a considerable contribution of the sp3-hybridized state and a pronounced pyramidal geometry; the crownlike conformation of the macrocycle is preorganized for cation binding, which facilitates complexation. The stability constants of the complexes of crown ethers with the NH(4) (+), EtNH(3) (+), Na(+), K(+), Ca(2+), and Ba(2+) ions were determined by 1H NMR titration in MeCN-d(3). The most stable complexes were obtained with alkaline-earth metal cations, which is due to the higher charge density at these cations. The characteristics of the complexing ability of N-alkylnitrobenzoaza-15-crown-5 toward alkaline earth metal cations are comparable with analogous characteristics of nitrobenzo-15-crown-5 and are much better than those of N-(4-nitrophenyl)aza-15-crown-5. [ DOI ]

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