H-2 NMR lineshape analysis using automated fitting procedures based on local and quasi-global optimization techniques

摘要

A new approach is presented for the analysis of wideline H-2 NMR lineshapes, based on automated fitting of simulated spectra to experimental spectra using either 'downhill simplex' or simulated annealing algorithms. This approach provides an objective assessment of the level of agreement between experimental and simulated H-2 NMR spectra, and removes much of the subjectivity that is characteristic of the traditional approach involving trial-and-error variation of the parameters used in the simulation, followed by visual comparison between experimental and simulated H-2 NMR spectra to assess the quality of fit. Applications of our new approach are reported for the analysis of (i) static H-2 NMR powder patterns, (ii) the temperature dependence of H-2 NMR powder patterns in the intermediate motion regime (including the case of fitting experimental spectra with poor signal-to-noise ratio) and (iii) the dependence of quadrupole echo 2H NMR spectra on the echo delay. Quantitative details relating to the dynamic properties of thiourea-d(4) in its pure crystalline phase and in the chlorocyclohexane-thiourea-d(4) inclusion compound are presented, in addition to the motion of the guest molecules iri the benzenetricarbonylchromium-d(6)-thiourea inclusion compound and the pyrazine-d(4)-alpha-zirconium phosphate intercalation material. (C) 1998 John Wiley & Sons, Ltd. [References: 42]