Yano Megumi, Taketsugu Tetsuya, Hori Kayako, Okamoto Hiroaki, Takenaka Shunsuke
Graduate School of Humanities and Sciences, Ochanomizu University, Bunkyo-ku, Tokyo 112-8610, Japan.
Chemistry. 2004 Aug 20;10(16):3991-9. doi: 10.1002/chem.200400123.
The series of alkyl 4-[2-(perfluorooctyl)ethoxy]benzoates (F8-n) shows a systematic change of crystal structures depending on the length of the alkyl chain: separate packing of perfluorooctyl (Rf) and alkyl (Rh) chains from each other for shorter (n=2) and longer (n=11) members, alternate packing of Rf and Rh chains for middle (n=6,7) members, and an intermediate type of packing for n=4. Semiempirical MO calculations show slightly repulsive interactions between the Rf chains, and attractive ones between Rf and Rh chains and between Rh and the core of a molecular pair. It is concluded that fluorination determines the molecular shape of the crystal structures by making the chain rigid. It is confirmed that the interactions between Rf chains are small compared with those between other moieties and that they are forced to aggregate owing to the exclusion from other moieties. Thus, the effect is dependent on the geometries and intermolecular interactions of the other moieties.
一系列4-[2-(全氟辛基)乙氧基]苯甲酸烷基酯（F8-n）的晶体结构呈现出随烷基链长度的系统性变化：对于较短（n = 2）和较长（n = 11）的成员，全氟辛基（Rf）链和烷基（Rh）链彼此分离堆积；对于中间（n = 6,7）的成员，Rf链和Rh链交替堆积；对于n = 4，则为中间类型的堆积。半经验分子轨道计算表明，Rf链之间存在轻微的排斥相互作用，而Rf链与Rh链之间以及Rh链与分子对核心之间存在吸引相互作用。得出的结论是，氟化通过使链刚性化来决定晶体结构的分子形状。证实了Rf链之间的相互作用与其他部分之间的相互作用相比很小，并且由于被其他部分排斥，它们被迫聚集。因此，这种效应取决于其他部分的几何形状和分子间相互作用。
