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Structural changes in the complexation of benzo‐crown ethers—NOESY and variable‐temperature 13 C NMR study
Author(s) -
Mariappan S. V. Santhana,
Gomathi L.,
Subramanian S.
Publication year - 1991
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260290704
Subject(s) - chemistry , moiety , two dimensional nuclear magnetic resonance spectroscopy , nuclear magnetic resonance spectroscopy , stereochemistry , crown (dentistry) , 15 crown 5 , crystallography , crown ether , organic chemistry , ion , medicine , dentistry
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.