Laboratory of Material Chemistry, Institute of Chemical Materials, China Academy of Engineering Physics (CAEP), P.O. Box 919-327, Mianyang, Sichuan 621900, People's Republic of China.
J Comput Chem. 2011 Jan 15;32(1):152-60. doi: 10.1002/jcc.21612.
The shape and size effects in π–π interactions of face-to-face dimers are discussed, by taking three typical groups of π-systems with different shapes (wave-linear, WL; ladder-shaped, LS; and regular-hexagonal, RH) and sizes (2 to 216 π-electrons) as samples, and carrying out a series of static scanning forcefield calculations. These effects are: (1) for differently shaped π-systems with a same quantity of π-electrons, the denser π-electrons lead to the stronger π–π interactions; (2) the interaction orientation, such as the interplanar distance, is controlled by not only van der Waals (vdW) but also electrostatic potential, even though the former is much stronger and has more contributions to total interaction energy than the latter. Furthermore, these interplanar distances are in a range determined by only monomer shapes, i.e., 3.6–4.1 Å for WL, 3.5–3.7 Å for LS, and 3.4–3.7 Å for RH; (3) a centroid-centroid distance corresponding to the global lowest vdW potential point of a dimer with two identical monomers is only determined by the monomer shape, i.e., 3.6, 3.5, and 3.4 Å, for WL, LS, and RH, respectively; (4) rotation will change the interaction energy when both two monomers with big sizes and low symmetries, and vice versa.
讨论了面对面二聚体中π-π相互作用的形状和大小效应，选择了三个具有不同形状（波状-线性，WL；梯状，LS；和规则六边形，RH）和大小（2 到 216π电子）的典型π-体系作为样品，并进行了一系列静态扫描力场计算。这些效应是：（1）对于具有相同数量π电子的不同形状的π体系，密度较大的π电子会导致更强的π-π相互作用；（2）相互作用方向，如层间距，不仅受范德华（vdW）的控制，也受静电势的控制，尽管前者更强，对总相互作用能的贡献比后者大得多。此外，这些层间距处于仅由单体形状决定的范围内，即 WL 为 3.6-4.1 Å，LS 为 3.5-3.7 Å，RH 为 3.4-3.7 Å；（3）具有两个相同单体的二聚体的全局最低 vdW 势能点的质心-质心距离仅由单体形状决定，即 WL、LS 和 RH 分别为 3.6、3.5 和 3.4 Å；（4）当两个大尺寸和低对称性的单体或反之发生旋转时，会改变相互作用能。
