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    188宝金博页面版: Hydrogen Bonds Involving Sulfur： New Insights from ab Initio Calculations and Gas Phase Laser Spectroscopy

    下载积分： 9950

    内容提示： Chapter 2Hydrogen Bonds Involving Sulfur: New Insightsfrom ab Initio Calculations and Gas PhaseLaser SpectroscopyHimansu S. BiswalAbstract The hydrogen bonds involving sulfur (sulfur center hydrogen bonds;SCHBs) are generally regarded as weak H-bonds in comparison with the conven-tional N–H···O, O–H···O, N–H···N and O–H···N H-bonds. One of the reasonsbeing considered for this is the smaller electronegativity of S than O or N. However,recent high resolution laser spectroscopy in combination ...

    文档格式：PDF | 页数：31 | 浏览次数：21 | 上传日期：2018-04-04 18:35:33 | 文档星级：
    Chapter 2Hydrogen Bonds Involving Sulfur: New Insightsfrom ab Initio Calculations and Gas PhaseLaser SpectroscopyHimansu S. BiswalAbstract The hydrogen bonds involving sulfur (sulfur center hydrogen bonds;SCHBs) are generally regarded as weak H-bonds in comparison with the conven-tional N–H···O, O–H···O, N–H···N and O–H···N H-bonds. One of the reasonsbeing considered for this is the smaller electronegativity of S than O or N. However,recent high resolution laser spectroscopy in combination with quantum chemicalcalculations reveals that SCHBs can be as strong as conventional H-bonds. Surpris-ingly, in the case of methionine containing dipeptides the amide-N–H···S H-bondsare even stronger than amide-N–H···O=C H-bonds. Sulfur is not only a potentialH-bond acceptor, but the S–H group is also a very good H-bond donor and capableof forming a variety of H-bonds. For example, the S–H···π H-bond between H 2 Sandindole/benzeneisfoundtobethestrongestH-bondamongO–H···π, O–H···π,and C–H···π H-bonds. In general the SCHBs are dispersive in nature. This chapterdetails about few SCHB systems, many more systems need to be studied extensivelyandcarefullytounravelmanyfactsandfacetsaboutSCHBs.Themajorchallengeforthe experimentalists is to accurately determine the intra- and intermolecular H-bondenergies and for the theoreticians to propose a universal H-bond descriptor.2.1 IntroductionThe IUPAC’s new def i nition of hydrogen bonding (H-bonding) [1] is stated as “ThehydrogenbondisanattractiveinteractionbetweenahydrogenatomfromamoleculeoramolecularfragmentX–HinwhichXismoreelectronegativethanH,andanatomor a group of atoms in the same or a different molecule, in which there is evidenceof bond formation.” As is mentioned in the def i nition electro negativities of X andY in X–H···Y regulates the H-bond strength, i.e. the H-bond strength increaseswith increasing the electronegativity values of donor and acceptor atoms [2, 3]. Thisis exactly followed by the H-bonds involving second row elements in general andH. S. Biswal ( ? )School of Chemical Sciences, National Institute of Science Education and Research, Institute ofPhysics Campus, PO: Sainik School, 751 005 Bhubaneswar, Odisha, Indiae-mail: himansu@niser.ac.in© Springer International Publishing Switzerland 2015 15S. Scheiner (ed.), Noncovalent Forces, Challenges andAdvances inComputational Chemistry and Physics 19, DOI 10.1007/978-3-319-14163-3_2

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