Ｃ－Ｈ....πやπ-π相互作用の存在は様々な分野で確立されたようである。たとえば鉛筆で紙に文字を書く、そして消しゴムで消すなども、これらの相互作用という。さあて次はエネルギー移動か？
d.hatena.ne.jp/greatstone/?of=5
ja.wikipedia.org
ペンタセンは1,2,4-トリクロロベンゼン溶媒中で単体硫黄と反応し、ヘキサチアペンタセンを与える。X線結晶構造解析によるとすべての炭素−硫黄間の結合距離がほぼ等しいことから (170pm)、共鳴限界式 A よりも、完全に電荷が分極した B と C の寄与のほうが大きいとされている。
結晶中においては芳香環どうしのπ-π相互作用によってスタッキングしている。隣接する分子上の硫黄原子間の距離は337pmであり、ファンデルワールス半径 (180pm) の和よりも小さい。
london-nano.com/research-and-facilities/highlight/neutron-scattering-unravels-the-structure-of-aromatic-pi-pi-intera
Aromatic interactions arise from delocalised π-electrons, and they play a key role in a very wide range of natural and industrial processes.
For example protein folding, DNA and RNA base stacking, protein-nucleic acid recognition, drug design and oil recovery.
However, detailed knowledge of the structures adopted by simple model aromatic molecules is currently lacking, and is essential to our fundamental understanding of π-π interactions.
Researchers from the London Centre for Nanotechnology and the ISIS Neutron Scattering Facility (STFC Rutherford Appleton Laboratory) have now obtained definitive structural data for two archetypical aromatic liquids: benzene and toluene. By judiciously labelling these molecules with different isotopes of hydrogen, they were able to use neutron scattering to unravel the spatial and orientational packing of these molecules.
The results identify a configuration that is now termed “Y-shaped” as a dominant motif in aromatic liquids. The near absence of the “T-shaped” geometry, previously proposed as the most favourable, is likely to lead to a significant re-evaluation of aromatic interactions in liquids.
The experiments were conducted on the SANDALS instrument at ISIS, and the work was sponsored in part by the Natural Environment Research Council UK (NERC).
The work was featured on the cover of the Journal of the American Chemical Society (T. F. Headen, C. A. Howard, N. T. Skipper, M. A. Wilkinson, D. T. Bowron, A. K. Soper, J. Am. Chem Soc. (2010), 132, 5735–5742. DOI: 10.1021/ja909084e). Contact author Neal Skipper: n.skipper@ucl.ac.uk.