ROY confined in hydrogen-bonded frameworks: coercing conformation of a chromophore

Abstract

5-Methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile is a crystalline compound rich in conformational polymorphs largely owing to the flexible torsion angle that leads to distinct colors, earning it the moniker ROY (Red-Orange-Yellow). Guanidinium organosulfonate hydrogen-bonded frameworks form six crystalline inclusion compounds with ROY, described here, in which the framework limits conformational twisting out of plane. Three of the six inclusion compounds enforce greater planarity and π-conjugation than any of nine ROY polymorphs that have been characterized by single crystal X-ray diffraction.