Multicolor Amplified Spontaneous Emissions Based on Organic Polymorphs That Undergo Excited‐State Intramolecular Proton Transfer

Abstract

Two polymorphs emitting near-infrared (1 R form: α phase, λem =702 nm, Φf =0.41) and orange-red fluorescence (1 O form: β phase, λem =618 nm, Φf =0.05) were synthesized by finely controlling the crystallization conditions of compound 1, a structurally simple excited-state intramolecular proton transfer (ESIPT)-active molecule. Multicolor amplified spontaneous emissions (ASEs) were realized, for the first time, based on these polymorphs. Notably, the 1 O crystal underwent heating-induced phase transformation from the β phase to the α form in a single-crystal to single-crystal (SCSC) manner accompanied with an unprecedented ASE changing. The ASE behavior of polymorphs 1 R, 1 O as well as the ASE changing during SCSC was investigated. The feasibility of multicolor lasing based on the present organic polymorphs was confirmed, which may provide a new development strategy for organic laser science and technology.