Designing Novel Calix [4] Pyrrole Derivative for Treatment of Herbicides: Thermodynamics of Host-Guest Interactions

摘要

Calix[4]pyrrole and modified calix[4]pyrrole derivatives have been synthesized and characterized, namely calix [4] pyrrole [meso-octamethyl-calix [4] pyrrole], 1, meso-tetramethyl-tetrakis-(4-hydroxyphenyl) calix[4] pyrrole, 2, meso-tetramethyl-tetrakis (3-hydroxyphenyl) calix[4] pyrrole, 3, mesotetramethyl-tetrakis-[(4-N, N diethylacetamide) phenoxymethyl]calix[4] pyrrole, 4 and new mesotetramethyl-bis (diethylamino) ethoxy-bis-(4-hydroxyphenyl) calix[4] pyrrole, 5. Several analytical techniques (~1H NMR, conductance measurements, and titration calorimetry) have been used to assess the interaction of calix[4]pyrrole derivatives and acid herbicides in acetonitrile. Chlorophenoxy acids have been selected out of groups of herbicides to carry out this investigation. *H NMR investigations seem to indicate that the receptor 5 interacts with acid herbicides. Complexation studies in CD3CN show that NH and OH functionalities of the receptor 5 are the active sites of its interaction with herbicides. The composition of the anion complexes was established through conductance measurements. In all cases, 1:2 (ligand: herbicides) complexes are formed between the receptor 5 with chlorophenoxy acids. The thermodynamics of anion complexation in acetonitrile is discussed. Excellent agreement was found between the data derived from nano-isothermal titration calorimetry and those derived by 'H NMR investigations and conductance measurements. For all the systems investigated, the complexation process between these acid herbicides and the receptor 5 was enthalpieally controlled. The enthalpic and entropic contributions to the Gibbs energy associated with these processes are analysed.