The relationship between crystal structure and methyl and t-butyl group dynamics in van der Waals organic solids

• Published in: The Journal of chemical physics 2004-03, Vol.120 (11), p.5309-5314
• Main Authors: Beckmann, Peter A, Paty, Carol, Allocco, Elizabeth, Herd, Maria, Kuranz, Carolyn, Rheingold, Arnold L
• Format: Article
• Language: English
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.1642581

We report x-ray diffractometry in a single crystal of 2-t-butyl-4-methylphenol (TMP) and low-frequency solid state nuclear magnetic resonance (NMR) proton relaxometry in a polycrystalline sample of TMP. The x-ray data show TMP to have a monoclinic, P2(1)/c, structure with eight molecules per unit cell and two crystallographically inequivalent t-butyl group (C(CH(3))(3)) sites. The proton spin-lattice relaxation rates were measured between 90 and 310 K at NMR frequencies of 8.50, 22.5, and 53.0 MHz. The relaxometry data is fitted with two models characterizing the dynamics of the t-butyl groups and their constituent methyl groups, both of which are consistent with the determined x-ray structure. In addition to presenting results for TMP, we review previously reported x-ray diffractometry and low-frequency NMR relaxometry in two other van der Waals solids which have a simpler structure. In both cases, a unique model for the reorientational dynamics was found. Finally, we review a similar previously reported analysis in a van der Waals solid with a very complex structure in which case fitting the NMR relaxometry requires very many parameters and serves mainly as a flag for a careful x-ray diffraction study.