Novel Zn(ii)-thiazolone-based solid fluorescent chemosensors: naked-eye detection for acid/base and toluene

Abstract

A series of novel thiazolone-based zinc complexes, [Zn(Am4DHotaz)Cl₂]·H₂O (1), [Zn(Am4Motaz)Cl₂] (2), and [Zn(Am4Eotaz)Cl₂] (3) (Am4DHotaz = N-(4-oxothiazolidin-2-ylidene)picolinohydrazonamide, Am4Motaz = N-(3-methyl-4-oxothiazolidin-2-ylidene)picolinohydrazonamide, Am4Eotaz = N-(3-ethyl-4-oxothiazolidin-2-ylidene)picolinohydrazonamide), with intense fluorescence emission and large Stokes shifts in the solid state, have been synthesized and characterized by X-ray crystallography and various spectroscopic methods. Complexes 1–3 exhibit a similar Zn²⁺-coordinated pattern, but different molecular packings arising from substituent variation in the organic ligands, which finally result in individual fluorescent behaviors. All the complexes showed interesting ON/OFF/ON fluorescence switching properties induced by acid/base vapor. More interestingly, for 1, the introduction of toluene brought about a large blue shift, an obvious color change suitable for naked-eye detection, and a distinct increase of fluorescent quantum yield, which could contribute to environmental monitoring and other applications in the field of luminescent materials.