"Through-Space" Relativistic Effects on NMR Chemical Shifts of Pyridinium Halide Ionic Liquids

被引:6
作者
Ariai, Jama [2 ,3 ]
Saielli, Giacomo [1 ]
机构
[1] CNR Inst Membrane Technol, Padova Unit, Via Marzolo 1, I-35131 Padua, Italy
[2] Univ Padua, Dept Chem Sci, Via Marzolo 1, I-35131 Padua, Italy
[3] Justus Liebig Univ, Inst Organ Chem, Heinrich Buff Ring 17, D-35392 Giessen, Germany
关键词
chemical shifts; density functional theory; ionic liquids; nuclear magnetic resonance; relativistic effects; DENSITY-FUNCTIONAL THEORY; ORDER REGULAR APPROXIMATION; SPIN-ORBIT; HEAVY-ATOM; SHIELDING CONSTANTS; DFT CALCULATIONS; SCREENING MODEL; GRADIENT APPROXIMATION; CORRELATION-ENERGY; HYDROGEN-BONDS;
D O I
10.1002/cphc.201800955
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
We have investigated, using two-component relativistic density functional theory (DFT) at ZORA-SO-BP86 and ZORA-SO-PBE0 level, the occurrence of relativistic effects on the H-1, C-13, and N-15 NMR chemical shifts of 1-methylpyridinium halides [MP][X] and 1-butyl-3-methylpyridinium trihalides [BMP][X-3] ionic liquids (ILs) (X=Cl, Br, I) as a result of a non-covalent interaction with the heavy anions. Our results indicate a sizeable deshielding effect in ion pairs when the anion is I- and I-3(-). A smaller, though nonzero, effect is observed also with bromine while chlorine based anions do not produce an appreciable relativistic shift. The chemical shift of the carbon atoms of the aromatic ring shows an inverse halogen dependence that has been rationalized based on the little C-2s orbital contribution to the sigma-type interaction between the cation and anion. This is the first detailed account and systematic theoretical investigation of a relativistic heavy atom effect on the NMR chemical shifts of light atoms in the absence of covalent bonds. Our work paves the way and suggests the direction for an experimental investigation of such elusive signatures of ion pairing in ILs.
引用
收藏
页码:108 / 115
页数:8
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