New Polymorphs of ROY and New Record for Coexisting Polymorphs of Solved Structures

• Published in: Journal of the American Chemical Society Vol. 127; no. 27; pp. 9881 - 9885
• Main Authors: Chen, Shuang, Guzei, Ilia A, Yu, Lian
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 13.07.2005
• Subjects: Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Exact sciences and technology; Physics; Structure of solids and liquids; crystallography; Five membered ring; Directional solidification; Molecular crystals; Polymorphic transformations; XRD; Experimental study; Lattice parameters; Raman spectroscopy; Melt crystallization; Sulfur heterocycle; Thermodynamic parameter; Nitriles; Organic compounds
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja052098t

With six polymorphs coexisting at room temperature, 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile (ROY) is the top system in the current Cambridge Structural Database (Feb. 2005) for the number of polymorphs of solved crystal structures. Here we report two new ROY polymorphs, Y04 and YT04, and the crystal structure of YT04. Y04 is a metastable polymorph that tends to crystallize first from a melt at room temperature, and YT04 is a product of solid-state transformation of Y04. Despite its late discovery, YT04 is the densest among the polymorphs at 25 °C and likely the second most stable at 0 K. The conformation of ROY in YT04 is similar to those in the other two yellow polymorphs (Y and YN) but significantly different from those in the orange and red colored polymorphs (ON, OP, ORP, and R). Having escaped years of solution crystallization in several laboratories, Y04 and YT04 exemplify polymorphs that are likely missed by solvent-based screening and discovered through alternative routes.