【作者】 李勇； 王琪； 吴国是；

【Author】 Yong LI Qi WANG Guo-Shi WU Department of Chemistry,Tsinghua University,Beijing 100084

【机构】 清华大学化学系；

【摘要】 <正>杯芳烃是一类环状低聚物,因其可与许多离子型和非离子型客体均能形成稳定的配合物或包合物,在众多研究领域得到了广泛应用,被誉为是继环糊精和冠醚之后的第三类新型主体化合物。但有关自旋标记杯芳烃的研究却很少。本工作合成了一种新型杯芳烃双基自由基Ⅰ(图1),并研究了其低温 ERS 谱。更多还原

【Abstract】 A new calixarene biradical （Ⅰ） was synthesized and studied using ESR at low temperatures.A triplet ESR spectrum （Fig.2） was observed at 77K.Based on the spectrum,zero-field splitting parameters D and E were obtained.|D|=172.3 G=0.0184 cm^-1,|E|=1.9G= 0.0002 cm^-1.|E|（?）|D|/3,which means that E_X≈E_Y and the biradical takes somewhat symmetry.According to the D value and the approximation of point charge,the distance between two intramolecular radicals was estimated as 0.544nm,which is close to one estimated based on the conformational optimization of I using MNDO method.The increase in the half-field transition intensity was also observed when the temperature was reduced （Fig.3）.Using the modified Bleany—Bowers’ equation to fit the relation between the half-field peak intensities and temperatures,the spin exchange parameter J was calculated.Because J ≈137cm^-1＞0,one can say that the ground state of I is triplet at low temperature and the energy of triplet is about 274cm^-1 （0.034eV） lower than that of singlet.更多还原