R. Vrcelj, E. Shepherd, C. Yoon
Sep 7, 2002
Citations
1
Influential Citations
21
Citations
Journal
Crystal Growth & Design
Abstract
Crystals of α−[(4-methoxyphenyl)methylene]-4-nitrobenzeneacetonitrile (C16H12O3N2) are shown by X-ray crystallography to exist in three polymorphic trans forms (I−III) and one cis configuration (IV). Calorimetric studies show that at low temperature form I is thermodynamically the most stable phase, followed by form III and form II. On heating, form III undergoes a phase transformation to form II. There is no direct thermal transformation between forms II and I. Form I melts at 164.5 °C. Mechanical damage of form II initiates a phase transformation into form III, and structural studies confirm that forms II and III, both of which show attractive second-order nonlinear optical behavior, are closely related. Though clearly conformational polymorphs, they also exhibit the essence of orientational polymorphism. Although form I is the most stable of the three trans isomers, nevertheless forms II and III are indefinitely stable and may be useful for development for NLO purposes. Crystal growth studies show that...