5-Hydroxydibenzo[a,i]phenazine-8,13-dione: A selective and sensitive colorimetric and fluorescent ‘turn-off’ sensor for iodide ion

Abstract

The present manuscript reports 5-hydroxydibenzo[a,i]phenazine-8,13-dione (HDP) as a novel colorimetric and fluorescent chemosensor for the selective and sensitive detection of iodide ion. The probe was synthesized by a condensation reaction of 2,3-diaminonaphthoquinone with 2-hydroxynaphthoquinone and characterized using FT-IR and NMR. The ground state geometry has been optimized using DFT based methods and utilized for the prediction of various electrostatic properties such as HOMO, LUMO, NBOs and Fukui. The vertical excitation spectra have been evaluated in different solvents and compared with experimentally determined absorption spectra. HDP exhibits solvatochromic behavior showing hypsochromic shift with change in polarity of solvent from chloroform to DMSO. The sensing application was investigated with different metal ions and anions. Addition of iodide ion to HDP solution exhibits a new absorption band at 517 nm along with disappearance of band at 405 nm. Similarly, the fluorescence intensity at 565 nm showed a reduction upon addition of I−. The developed probe exhibited high selectivity and sensitivity towards iodide ion over other tested analytes with a detection limit of 21 nM. Additionally, the probe responded within 5 sec for the sensitive detection of iodide ion. Job's plot experiment,1H NMR titration and DFT studies were performed further to evaluate the binding stoichiometry and mechanism, respectively.