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Evidence for spin diffusion in a H,H‐NOESY study of imidazolium tetrafluoroborate ionic liquids
Author(s) -
Heimer Norman E.,
Del Sesto Rico E.,
Carper W. Robert
Publication year - 2004
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1318
Subject(s) - chemistry , tetrafluoroborate , ionic liquid , hydrogen , relaxation (psychology) , ab initio quantum chemistry methods , hydrogen bond , mixing (physics) , two dimensional nuclear magnetic resonance spectroscopy , basis set , ab initio , ionic bonding , proton nmr , spin diffusion , computational chemistry , density functional theory , diffusion , analytical chemistry (journal) , molecule , ion , organic chemistry , thermodynamics , stereochemistry , catalysis , physics , psychology , social psychology , quantum mechanics
The ionic liquids 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([EMIM][BF4]) and 1‐methyl‐3‐propylimidazolium tetrafluoroborate ([PMIM][BF4]) were studied by H,H‐NOESY NMR using a cross‐relaxation matrix analysis. Cross‐peak intensities are seen to increase with increasing mixing time. Experimental and theoretical hydrogen–hydrogen distances are in agreement at short mixing times (50 ms). Mixing times longer than 50 ms result in an increasing contribution of spin diffusion that produces unrealistically short hydrogen–hydrogen distances. Gas‐phase ab initio molecular structures are obtained using Hartree–Fock (HF) and density functional theory (B3LYP) methods at the 6311 + G(2d,p) basis set level. The hydrogen–hydrogen distances obtained from the theoretical structures are in reasonable agreement with those calculated from the cross‐relaxation matrices. Published in 2003 by John Wiley & Sons, Ltd.