Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, United States.
J Org Chem. 2013 Mar 1;78(5):1768-77. doi: 10.1021/jo3009897. Epub 2012 Jul 23.
We examine the insertion of two dipolar molecular rotors as guests into a host, tris(o-phenylenedioxy)cyclotriphosphazine (TPP, 1), using differential scanning calorimetry, solid-state NMR, powder X-ray diffraction, and dielectric spectroscopy. The rotors are 1-(4'-n-pentylbiphenyl-4-yl)-12-(2,3-dichlorophenyl)-p-dicarba-closo-dodecaborane and 1,12-bis(2,3-dichlorophenyl)-p-dicarba-closo-dodecaborane. Both enter the bulk even though their nominal diameter exceeds the nominal channel diameter and although a closely related rotor, 1-n-hexadecyl-12-(2,3-dichlorophenyl)-p-dicarba-closo-dodecaborane, is known to produce a surface inclusion compound. Rotational barriers of 5.4-9.3 kcal/mol were found for the dichlorophenyl rotator contained within the TPP channel. Clearly, van der Waals diameters in themselves do not suffice to predict TPP channel entry. It is suggested that the efficacy of the p-carborane stopper is reduced by the presence of the two relatively bulky adjacent benzene rings, which help to stretch the channel, and by the axial direction of its axis, which prevents the attached rotator from contributing to the stopping action.
我们使用差示扫描量热法、固态 NMR、粉末 X 射线衍射和介电谱研究了两个偶极分子转子（1-(4'-正戊基联苯-4-基)-12-(2,3-二氯苯基)-p-二碳杂-closo-十二硼烷和 1,12-双(2,3-二氯苯基)-p-二碳杂-closo-十二硼烷）作为客体插入到主体化合物 tris(o-苯二氧基)环三磷腈（TPP，1）中的情况。尽管这两个转子的名义直径超过了通道的名义直径，而且与之密切相关的转子 1-正十六烷基-12-(2,3-二氯苯基)-p-二碳杂-closo-十二硼烷被认为会产生表面包含化合物，但它们都进入了主体中。在 TPP 通道内的二氯苯基转子的旋转势垒为 5.4-9.3 kcal/mol。显然，范德华直径本身不足以预测 TPP 通道的进入。有人提出，由于两个相对较大的相邻苯环的存在，p-卡硼烷止动器的功效降低了，这有助于拉伸通道，并且由于其轴的轴向方向，阻止了连接的转子对止动作用做出贡献。
