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

0380857 - ÚOCHB 2013 RIV GB eng J - Journal Article
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
R&D Projects: GA ČR GA203/09/2037
Grant - others:GA MŠk(CZ) LM2010005; 7th European Framework Program(XE) 230955; CEITEC(XE) CZ.1.05/1.1.00/02.0068
Institutional research plan: CEZ:AV0Z40550506
Keywords : 129Xe NMR * novel Xe compounds * relativistic effects * rare-gas * ab-initio * NMR properties
Subject RIV: CF - Physical ; Theoretical Chemistry
Impact factor: 3.829, year: 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.
Permanent Link: http://hdl.handle.net/11104/0211465