[Study on the molecular recognization of fungicide of kresoxim-methyl with beta-cyclodextrin and its derivatives]

The molecular recognition of fungicide of kresoxim-methyl with beta-cyclodextrin (beta-CD), methyl-beta-cyclodextrin (RAMEB)and hydroxypropyl-beta-cyclodextrin (RAMEB) was investigated by using UV-Vis spectroscopy analysis. The effect of temperature and polarity of solvent on the recognition interaction was studied. The driving force and the possible structure of the inclusion complexes were also discussed. The results presented that they formed inclusion complexes with a stoichiometry of 1:1, and the formation constant of inclusion complexes was in the order of Ku(HP-beta-CD)>(beta-CD)Kp(RAMEB) at 298.15 K. Elevation of the temperature triggered a decrease in stability of the inclusion complexes and the value of K(beta-D) was the biggest at > or =303.15 K. The formation constant reduced sharply with the decreasing polarity of the solvent. The standard molar Gibbs energies, enthalpies and entropies were all negative. All the results indicated that the association of the guest molecule with beta-CD was favored by enthalpy changes, and hydrophobicity and hydrogen bond interaction were main driving forces for the inclusion reaction. Our findings provided an important proof for the use of inclusion complexes of kresoxim-methyl with CDs.