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Exploring new Xe-129 chemical shift ranges in HXeY compounds: hydrogen more relativistic than xenon

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    0380857 - ÚOCHB 2013 RIV GB eng J - Článek v odborném periodiku
    Lantto, P. - Standara, Stanislav - Riedel, S. - Vaara, J. - Straka, Michal
    Exploring new Xe-129 chemical shift ranges in HXeY compounds: hydrogen more relativistic than xenon.
    Physical Chemistry Chemical Physics. Roč. 14, č. 31 (2012), s. 10944-10952. ISSN 1463-9076. E-ISSN 1463-9084
    Grant CEP: GA ČR GA203/09/2037
    Grant ostatní: GA MŠk(CZ) LM2010005; 7th European Framework Program(XE) 230955; CEITEC(XE) CZ.1.05/1.1.00/02.0068
    Výzkumný záměr: CEZ:AV0Z40550506
    Klíčová slova: 129Xe NMR * novel Xe compounds * relativistic effects * rare-gas * ab-initio * NMR properties
    Kód oboru RIV: CF - Fyzikální chemie a teoretická chemie
    Impakt faktor: 3.829, rok: 2012

    In this work we show that Xe-129 NMR chemical shifts in the recently prepared, matrix-isolated xenon compounds appear in new, so far unexplored Xe-129 chemical shift ranges. State-of-the-art theoretical predictions of NMR chemical shifts in compounds of general formula HXeY (Y = H, F, Cl, Br, I, -CN, -NC, -CCH, -CCCCH, -CCCN, -CCXeH, -OXeH, -OH, -SH) as well as in the recently prepared ClXeCN and ClXeNC species are reported. The bonding situation of Xe in the studied compounds is rather different from the previously characterized cases as Xe appears in the electronic state corresponding to a situation with a low formal oxidation state, between I and II in these compounds. Accordingly, the predicted Xe-129 chemical shifts occur in new NMR ranges for this nucleus: ca. 500 1000 ppm (wrt Xe gas) for HXeY species and ca. 1100-1600 ppm for ClXeCN and ClXeNC. These new ranges fall between those corresponding to the weakly-bonded Xe-0 atom in guest-host systems (delta < 300 ppm) and in the hitherto characterized Xe molecules (delta > 2000 ppm). The importance of relativistic effects is discussed. Relativistic effects only slightly modulate the Xe-129 chemical shift that is obtained already at the nonrelativistic CCSD(T) level. In contrast, spin-orbit-induced shielding effects on the H-1 chemical shifts of the H1 atom directly bonded to the Xe center largely overwhelm the nonrelativistic deshielding effects. This leads to an overall negative H-1 chemical shift in the range between -5 and -25 ppm (wrt CH4). Thus, the relativistic effects induced by the heavy Xe atom appear considerably more important for the chemical shift of the neighbouring, light hydrogen atom than that of the Xe nucleus itself.
    Trvalý link: http://hdl.handle.net/11104/0211465

     
     
Počet záznamů: 1  

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