Electrostatic and Steric Effects in the Selective Complexation of Cations in Nonactin

Science  06 Jun 1975:
Vol. 188, Issue 4192, pp. 1027-1029
DOI: 10.1126/science.188.4192.1027


The ester carbonyl stretch frequencies of complexes of the macrotetrolide nonactin with Na+, K+, Rb+, Cs+, Tl+, NH4+, NH3OH+, and (NH2)2CNH2+ have been measured. For the larger alkali cations and the polyatomic cations, the ester carbonyl stretch frequency is linearly proportional to the cation-ester carbonyl electrostatic interaction energy. This constitutes direct evidence that the cation-nonactin interaction is primarily electrostatic, rather than mechanical (steric).

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