Polymorph‐Dependent Solid‐State Fluorescence and Selective Metal‐Ion‐Sensor Properties of 2‐(2‐Hydroxyphenyl)‐4(3H)‐quinazolinone

Abstract

2-(2-Hydroxy-phenyl)-4(3H)-quinazolinone (HPQ), an organic fluorescent material that exhibits fluorescence by the excited-state intramolecular proton-transfer (ESIPT) mechanism, forms two different polymorphs in tetrahydrofuran. The conformational twist between the phenyl and quinazolinone rings ofHPQleads to different molecular packing in the solid state, giving structures that show solid-state fluorescence at 497 and 511 nm.HPQalso shows intense fluorescence in dimethyl formamide (DMF) solution and selectively detects Zn²⁺ and Cd²⁺ ions at micromolar concentrations in DMF. Importantly,HPQnot only detects Zn²⁺ and Cd²⁺ ions selectively, but it also distinguishes between the metal ions with a fluorescence λ_max that is blue-shifted from 497 to 420 and 426 nm for Zn²⁺ and Cd²⁺ ions, respectively. Hence, tunable solid-state fluorescence and selective metal-ion-sensor properties were demonstrated in a single organic material.