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Structural changes in the complexation of benzo-crown ethers—NOESY and variable-temperature 13C NMR study

✍ Scribed by S. V. Santhana Mariappan; L. Gomathi; S. Subramanian

Publisher
John Wiley and Sons
Year
1991
Tongue
English
Weight
817 KB
Volume
29
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

The structural changes during the complexation of benzo‐crown ethers with Cs^+^, K^+^ and Na^+^ were studied by NOESY and variable‐temperature ^13^C NMR spectroscopy. It was found that, on complexation, the distance between the CH‐α and 1‐CH~2~ is reduced in dibenzo‐24‐crown‐8 (DB24C8), dibenzo‐18‐crown‐6 and benzo‐15‐crown‐5. Two mechanisms have been proposed for the distance reduction, the fluttering motion of the benzo group and the elongation of the crown moiety. However, it is concluded that both of these mechanisms seem to play a role in the distance reduction. In the complexed state of DB24C8 with Cs^+^, Cs^+^ is predicted to be slightly above the plane of the crown oxygens with respect to DB24C8.

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