Padula Daniele, Di Pietro Sebastiano, Capozzi Maria Annunziata M, Cardellicchio Cosimo, Pescitelli Gennaro
Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Pisa, Pisa, Italy; Institute of Organic Chemistry and Biochemistry, Academy of Sciences, Prague, Czech Republic.
Chirality. 2014 Sep;26(9):462-70. doi: 10.1002/chir.22270. Epub 2013 Dec 11.
A series of 13 enantiopure aryl benzyl sulfoxides () with different substituents on the two aromatic rings has been previously analyzed by means of electronic circular dichroism (CD) spectroscopy. Most of these compounds are crystalline and their X-ray structure is established. For almost one-half of the series, CD spectra measured in the solid state were quite different from those in acetonitrile solution. We demonstrate that the difference is due to strong exciton couplings between molecules packed closely together in the crystal. The computational approach consists of time-dependent density functional theory (TDDFT) calculations run on "dimers" composed of nearest neighbors found in the lattice. Solid-state CD spectra are well reproduced by the average of all possible pairwise terms. The relation between the crystal space group and conformation, and the appearance of solid-state CD spectra, is also discussed.
此前通过电子圆二色光谱（CD）对一系列13种在两个芳环上具有不同取代基的对映体纯芳基苄基亚砜进行了分析。这些化合物大多为晶体且其X射线结构已确定。对于该系列中近一半的化合物，固态下测得的CD光谱与乙腈溶液中的光谱有很大不同。我们证明这种差异是由于晶体中紧密堆积的分子之间存在强激子耦合。计算方法包括对晶格中最近邻组成的“二聚体”进行含时密度泛函理论（TDDFT）计算。固态CD光谱通过所有可能的成对项的平均值得到了很好的再现。还讨论了晶体空间群与构象之间的关系以及固态CD光谱的出现情况。
