title: The relationship between crystal structure and methyl and t-butyl group dynamics in van der Waals organic solids.
abstract: 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.
authors.affiliation: Department of Physics, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010-2899, USA.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Beckmann
authors.forename: Carol
authors.initials: C
authors.lastname: Paty
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Allocco
authors.forename: Maria
authors.initials: M
authors.lastname: Herd
authors.forename: Carolyn
authors.initials: C
authors.lastname: Kuranz
authors.forename: Arnold L
authors.initials: AL
authors.lastname: Rheingold