Recognition Ability of Cyclodextrin for Alkyl Groups in Nitroxides As Studied by Electron Spin Resonance

Article abstract of DOI:10.1021/ja00196a018

The ability of γ-cyclodextrin to recognize various alkyl groups in a substate to form host-guest inclusion complexes is examined.Electron spin resonance spectra of two kinds of complexes are observed when α-substituted 2,4,6-trimethoxybenzyl tert-butyl nitroxides (1) are mixed with γ-cyclodextrin.The structures of these complexes are assigned to tert-butyl-in and alkyl-in since it is assumed that the 2,4,6-trimethoxyphenyl group is too large to be included in the γ-cyclodextrin cavity.The association constants as well as the hyperfine splitting constants forthe complexes with different alkyl substituents are determined.The ability to recognize various alkyl groups is discussed on the basis of the association constants of each complex.The data suggests that the association constant is dependent only on the characteristics of the included group not on the structure of the whole guest molecule and that the association constant is dependent on the size and hydrophobicity of the included group.