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 solid鈥恠tate nuclear magnetic resonance 1H spin鈥恖attice relaxation, single鈥恈rystal X鈥恟ay diffraction, powder X鈥恟ay diffraction, field emission scanning electron microscopy, and differential scanning calorimetry in solid samples of 2鈥恊thylanthracene (EA) and 2鈥恊thylanthraquinone (EAQ) that have been physically purified in different ways from the same commercial starting compounds.
The solid鈥恠tate 1H spin鈥恖attice relaxation is always non鈥恊xponential at high temperatures as expected when CH3 rotation is responsible for the relaxation. The 1H spin鈥恖attice relaxation experiments are very sensitive to the 鈥渟everal鈥恗olecule鈥 (clusters) structure of these van der Waals molecular solids. In the three differently prepared samples of EAQ, the relaxation also becomes very non鈥恊xponential 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 X鈥恟ay diffractometry results and suggests that the anomalous relaxation is due to crystallites of two (or more) different polymorphs (concomitant polymorphism).