Robertson Patrick A, Villani Luigi, Dissanayake Uresha L M, Duncan Luke F, Abbott Belinda M, Wilson David J D, Robertson Evan G
Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, 3086, Australia.
Phys Chem Chem Phys. 2018 Mar 28;20(12):8218-8227. doi: 10.1039/c7cp07365h. Epub 2018 Mar 12.
The electronic spectra of 2-bromoethylbenzene and its chloro and fluoro analogues have been recorded by resonant two-photon ionisation (R2PI) spectroscopy. Anti and gauche conformers have been assigned by rotational band contour analysis and IR-UV ion depletion spectroscopy in the CH region. Hydrate clusters of the anti conformers have also been observed, allowing the role of halocarbons as hydrogen bond acceptors to be examined in this context. The donor OH stretch of water bound to chlorine is red-shifted by 36 cm, or 39 cm in the case of bromine. Although classed as weak H-bond acceptors, halocarbons are favourable acceptor sites compared to π systems. Fluorine stands out as the weakest H-bond acceptor amongst the halogens. Chlorine and bromine are also weak H-bond acceptors, but allow for more geometric lability, facilitating complimentary secondary interactions within the host molecule. Ab initio and DFT quantum chemical calculations, both harmonic and anharmonic, aid the structural assignments and analysis.
通过共振双光子电离（R2PI）光谱记录了2-溴乙苯及其氯代和氟代类似物的电子光谱。通过旋转带轮廓分析和CH区域的红外-紫外离子耗尽光谱确定了反式和顺式构象体。还观察到了反式构象体的水合物簇，从而能够在此背景下研究卤代烃作为氢键受体的作用。与氯结合的水的供体OH伸缩振动红移了36 cm，与溴结合时则红移了39 cm。尽管卤代烃被归类为弱氢键受体，但与π体系相比，它们是有利的受体位点。在卤素中，氟是最弱的氢键受体。氯和溴也是弱氢键受体，但具有更大的几何灵活性，有利于主体分子内的互补二级相互作用。从头算和DFT量子化学计算，包括谐波和非谐波计算，有助于结构归属和分析。
