Fluorescent chemosensor based on sensitive Schiff base for selective detection of Zn2+

•Chemosensor showed very high selectivity to Zn2+ through fluorescence.•The stoichiometric ratio evaluated using both Benesi – Hildebrand relation and Job’s plot gives 1:1 stoichiometry.•Chemosensor was able to distinguish Zn2+ from Cd2+ commonly having similar properties.•Chemosensor exhibits very good fluorescence sensing ability to Zn2+ over a wide range of pH.

A Schiff-base fluorescent compound – N, N′-bis(salicylidene)-1,2 – phenylenediamine (LH2) was synthesized and evaluated as a chemoselective Zn2+ sensor. Addition of Zn2+ to ethanol solution of LH2 resulted in a red shift with a pronounced enhancement in the fluorescence intensity. Moreover, other common alkali, alkaline earth and transition metal ions failed to induce response or minimal spectral changes. Notably, this chemosensor could distinguish clearly Zn2+ from Cd2+. Fluorescence studies on free Schiff base ligand LH2 and LH2 – Zn2+ complex reveal that the quantum yield strongly increases upon coordination. The stoichiometric ratio and association constant were evaluated using Benesi – Hildebrand relation giving 1:1 stoichiometry. This further corroborated 1:1 complex formation based on Job’s plot analyses.

Graphical abstractA Schiff-base fluorescent compound – N, N′-bis(salicylidene)-1,2 – phenylenediamine was synthesized and evaluated as a chemoselective Zn2+ sensor. Upon treatment with Zn2+, the complexation of LH2 with Zn2+ resulted in a red shift with a pronounced enhancement in the fluorescence intensity in ethanol. Notably, this chemosensor could distinguish clearly Zn2+ from Cd2+. The stoichiometric ratio and association constant were evaluated using Benesi – Hildebrand relation giving 1:1 stoichiometry. This further corroborated 1:1 complex formation based on Job’s plot analyses.Figure optionsDownload full-size imageDownload as PowerPoint slide