Through-space interactions between face-to-face, center-to-edge oriented arenes: importance of polar–π effects
作者:Franco Cozzi、Rita Annunziata、Maurizio Benaglia、Mauro Cinquini、Laura Raimondi、Kim K. Baldridge、Jay S. Siegel
DOI:10.1039/b208871a
日期:——
Two series of conformationally restricted polycyclic compounds (1â3 and 4â7) have been synthesized as model systems for studying the through-space interactions between face-to-face, center-to-edge (parallel-offset) oriented arenes. These compounds feature different X substituents on one of the interacting rings. By monitoring the variation of the ÎGâ for the rotation around the arylâaryl bond in 1â7 as a function of X by 2D [1H,1H] EXSY NMR spectroscopy, it was found that the barriers increase on passing from electron-donating to electron-withdrawing substituted derivatives. Quantum mechanical calculations [MP2/DVZ (2d,p)//B3LYP/DVZ(2d,p)] gave barrier values and variations in agreement with the experimental data. The results are consistent with a repulsive areneâarene interaction dominated by electrostatic effects.
两系列构象受限的多环化合物(1–3 和 4–7)已被合成,作为研究面对面、中心到边(平行错位)取向芳烃之间通过空间相互作用的模型系统。这些化合物在一个相互作用环上具有不同的X取代基。通过监测1–7中芳基–芳基键周围旋转的吉布斯自由能变ΔG与X的关系,采用二维[1H,1H] EXSY NMR光谱,发现从电子给体取代衍生物转变为电子吸引取代衍生物时,势垒增加。量子力学计算[MP2/DVZ (2d,p)//B3LYP/DVZ(2d,p)]给出的势垒值和变化与实验数据一致。结果表明,芳烃之间的排斥性相互作用以静电效应为主导。