Benzothiazole-based Schiff base for sensing Ca2+ ions: Synthesis, DFT studies, toxicity evaluation in zebrafish embryo and in silico analysis of MMP-9 inhibition

Abstract

A new heterocyclic Schiff base, 2-(2-benzo(d)thiazol-2yl)hydrazono)methyl)phenol (BTAZ) synthesized from 2-hydrazinobenzothaizole and salicyclaldehyde was characterized by spectral, mass and single crystal XRD data and subjected to sense Ca²⁺ ions in methanol–water mixture (1:1, v/v) using UV–visible absorption and fluorescence emission spectral studies. The probe BTAZ showed specific detection of Ca²⁺ ions in a solution containing various metal ions with a detection limit as low as 5.1 × 10⁻⁶ M via photo-induced electron transfer (PET) pathway. The binding stoichiometry between BTAZ and Ca²⁺ was determined to be 2:1 by Job’s plot method. The stoichiometry and optical properties of both BTAZ and BTAZ-Ca²⁺ complex showed good correlation with theoretical results based on DFT and TD-DFT calculations. The pharmacological evaluation of the probe BTAZ against bacterial and fungal stains also demonstrated its notable efficacy to control their growth in vitro along with anti-oxidant capabilities. Further, toxicity assay of the probe BTAZ against zebrafish embryo did demonstrate that it is non-toxic to the test model in vivo. Ability of the probe BTAZ to inhibit matrix metalloproteinase-9 (MMP-9) enzyme was analyzed in detail using in silico experiments.