Nitro derivatives of <Emphasis Type="Italic">N</Emphasis>-alkylbenzoaza-15-crown-5: synthesis,structures, and complexation with metal and ammonium cations |
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Authors: | 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 |
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Institution: | 1.Photochemistry Center,Russian Academy of Sciences,Moscow,Russian Federation;2.N. S. Kurnakov Institute of General and Inorganic Chemistry,Russian Academy of Sciences,Moscow,Russian Federation;3.N. D. Zelinsky Institute of Organic Chemistry,Russian Academy of Sciences,Moscow,Russian Federation;4.Department of Chemistry,University of Durham,Durham,UK |
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Abstract: | 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. |
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