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

Two polymorphs emitting near-infrared (1R form: phase, (em)=702nm, phi(f)=0.41) and orange-red fluorescence (1O form: phase, (em)=618nm, phi(f)=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 1O crystal underwent heating-induced phase transformation from the phase to the form in a single-crystal to single-crystal (SCSC) manner accompanied with an unprecedented ASE changing. The ASE behavior of polymorphs 1R, 1O 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.