Three new metastable polymorphs of 1-(9-anthryl)-2-(1-naphthyl)ethylene and the polymorph-dependent phase transition and fluorescence change properties

Abstract

Here three new metastable polymorphs of (E)-1-(9-anthryl)-2-(1-naphthyl)ethylene (ANE) are successfully obtained via solvent–antisolvent rapid precipitation (ANE-d), contact line crystallization from diethyl ether solution (ANE-e), and melt crystallization (ANE-f), respectively. They exhibit different fluorescence properties and metastable-to-stable phase transition under organic vapour or thermal treatment. For ANE-d and ANE-e, two crystal-to-crystal phase transition pathways occur simultaneously upon organic vapour treatment, which could result in the formation of concomitant polymorphism. Interestingly, crystallinity is found to affect the polymorphic transition pathway of ANE-e, and its polymorphic transition outcome could be changed by grinding. The reason is studied through the comparison of crystal structures. Different from ANE-d and ANE-e, ANE-f only transforms to one stable polymorph under the action of organic vapour. Annealing can also induce the phase transition of the three metastable polymorphs, while the outcomes are different from vapour treatment. Accompanied with the phase transition, the luminescence colour changes accordingly. Among the three metastable polymorphs, ANE-f displays the largest spectral shift in response to external stimuli.