A Series of Polymorphs with Different Colors in Fluorescent 2,5-Diamino-3,6-dicyanopyrazine Dyes

摘要

We found a series of polymorphs with different colors in 2,5-diamino-3,6-dicyanopyrazine dyes.Their color difference was found to be caused by conformational change in the crystals,not by exciton interactions.Polymorphism is a phenomenon in which a substance exhibits two or more different arrangements of molecules in a crystalline state.The importance of polymorphism has long been recognized,because a single substance can yield solids having entirely different properties as a result of different molecular arrangements.Therefore,much scientific and technological work has been dedicated to the interpretation of polymorphic phenomena as well as to controlling the properties of solids exhibiting it.