H-2 NMR LINESHAPE ANALYSIS USING AUTOMATED FITTING PROCEDURES BASED ON LOCAL AND QUASI-GLOBAL OPTIMIZATION TECHNIQUES

A new approach is presented for the analysis of wideline H-2 NMR lines hapes, based on automated fitting of simulated spectra to experimental spectra using either 'downhill simplex' or simulated annealing algori thms. This approach provides an objective assessment of the level of a greement between experimental and simulated H-2 NMR spectra, and remov es 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 an d 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 N MR powder patterns, (ii) the temperature dependence of H-2 NMR powder patterns in the intermediate motion regime (including the case of fitt ing experimental spectra with poor signal-to-noise ratio) and (iii) th e dependence of quadrupole echo 2H NMR spectra on the echo delay. Quan titative details relating to the dynamic properties of thiourea-d(4) i n its pure crystalline phase and in the chlorocyclohexane-thiourea-d(4 ) inclusion compound are presented, in addition to the motion of the g uest molecules iri the benzenetricarbonylchromium-d(6)-thiourea inclus ion compound and the pyrazine-d(4)-alpha-zirconium phosphate intercala tion material. (C) 1998 John Wiley & Sons, Ltd.