A solid-state study of the inclusion of endosulfan in native and derivatised cyclodextrins using X-ray diffraction and thermoanalytical methods

Abstract

Endosulfan is a highly toxic insecticide used in several countries and known to be relatively persistent in the environment. This recently banned agrochemical is capable of forming solid-state inclusion complexes with both native and derivatised cyclodextrins (CDs). Differential scanning calorimetry and powder X-ray diffraction (PXRD) techniques were used to confirm complexation of β-CD, γ-CD and randomly methylated β-CD (RAMEB) with the technical 7α:3β isomeric sample of endosulfan. The PXRD traces obtained for the inclusion complexes of the native CDs (β-CD and γ-CD) with endosulfan match those of other isostructural CD inclusion complexes. The single crystal X-ray structure of the complex formed between heptakis(2,6-di-O-methyl)-β-CD (DIMEB) and the β-endosulfan isomer is presented and shown to have a novel packing arrangement. The implications of the encapsulation of endosulfan in CDs are discussed with reference to the potential for sequestering the insecticide from contaminated areas.