Nitro derivatives of N-alkylbenzoaza-15-crown-5: synthesis, structures, and complexation with metal and ammonium cations
作者:S. N. Dmitrieva、M. V. Churakova、N. A. Kurchavov、A. I. Vedernikov、L. G. Kuz’mina、A. Ya. Freidzon、A. A. Bagatur’yants、Yu. A. Strelenko、J. A. K. Howard、S. P. Gromov
DOI:10.1007/s11172-010-0222-0
日期:2010.6
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, 1H 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 NH4 +, EtNH3 +, Na+, K+, Ca2+, and Ba2+ ions were determined by 1H NMR titration in MeCN-d3. 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.
研究人员获得了一些 N-烷基硝基苯并氮杂-15-冠醚-5,其大环 N 原子与苯环共轭。利用 X 射线衍射、1H NMR 光谱和 DFT 计算将这些化合物的结构和络合性质与模型硝基苯并氮杂环-15-冠-5 和 N-(4-硝基苯基)氮杂环-15-冠-5 的结构和络合性质进行了比较。苯并氮冠醚的大环 N 原子具有相当大的 sp3 杂化态贡献和明显的金字塔几何特征;大环的冠状构象为阳离子结合预组织,这有利于络合。冠醚与 NH4+、EtNH3+、Na+、K+、Ca2+ 和 Ba2+ 离子的络合物的稳定常数是在 MeCN-d3 中通过 1H NMR 滴定法测定的。碱土金属阳离子得到的络合物最稳定,这是因为这些阳离子的电荷密度较高。N- 烷基硝基苯并-15-冠醚-5 对碱土金属阳离子的络合能力与硝基苯并-15-冠醚-5 的类似特性相当,而且远优于 N-(4-硝基苯基)氮杂-15-冠醚-5。