파라 터셔리 부틸 칼릭스[6]아렌 알킬 에스터 유도체의 착물 형성에 대한 13C NMR 연구

초록

The structure for several free p-tert-butylcalix[6]arene alkyl esters and its complexes with ethylammonium ion and cesium ion were examined by 13C NMR spectroscopy at various temperatures in CDCl3. It was inferred that methyl ester derivative of p-tert-butylcalix[6]arene 1 adopt one of several equivalent 1,2,3-alternate conformations over the observed range of temperatures. Measurements of spin-lattice relaxation time (T1) as well as 13C spectra at various temperatures revealed that complexation of not only p-tert-butylcalix[6]arene methyl ester also ethyl ester 2 produces a cone conformation with ethylammonium ion. Ethyl ester derivative was also found to form cone conformation when complexed with cesium ion, but methyl ester derivatives seemed to have low affinity for cesium ion. Mono ethyl ester 3 adopts cone conformation in free state. Activation energies for complexed p-tert-butylcalix[6]arene alkyl ester derivatives obtained from T1 data and these activation energy data show that cone conformation is more stable than the other conformations.