Authors: Prof. Peter A. Beckmann, Dr. Jamie Ford, Prof. William P. Malachowski, Dr. Andrew R. McGhie, Dr. Curtis E. Moore, Prof. Arnold L. Rheingold, Dr. Gilbert J. Sloan, Dr. Steven T. Szewczyk
Publication Type: Journal Article
Source: ChemPhysChem Volume19, Issue18, September 18, 2018, Pages 2423-2436
Details: We report solidstate nuclear magnetic resonance 1H spinlattice relaxation, singlecrystal Xray diffraction, powder Xray diffraction, field emission scanning electron microscopy, and differential scanning calorimetry in solid samples of 2ethylanthracene (EA) and 2ethylanthraquinone (EAQ) that have been physically purified in different ways from the same commercial starting compounds.
The solidstate 1H spinlattice relaxation is always nonexponential at high temperatures as expected when CH3 rotation is responsible for the relaxation. The 1H spinlattice relaxation experiments are very sensitive to the severalmolecule (clusters) structure of these van der Waals molecular solids. In the three differently prepared samples of EAQ, the relaxation also becomes very nonexponential at low temperatures. This is very unusual and the decay of the nuclear magnetization can be fitted with both a stretched exponential and a double exponential. This unusual result correlates with the powder Xray diffractometry results and suggests that the anomalous relaxation is due to crystallites of two (or more) different polymorphs (concomitant polymorphism).