✍ Scribed by Norman E. Heimer; Rico E. Del Sesto; W. Robert Carper
No coin nor oath required. For personal study only.
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.
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