Synthesis of a novel hydrazone-based compound applied as a fluorescence turn-on chemosensor for iron(<scp>iii</scp>) and a colorimetric sensor for copper(<scp>ii</scp>) with antimicrobial, DFT and molecular docking studies

Abstract

Hydrazone-hydrazide-based linkers perform a crucial role in environmental as well as biological fields. Such linkers are employed to detect exact metal ions at a minute level; hence, numerous probes are available. Even though thiophene-based molecules have a unique position in the medicinal arena, only very few chemosensors are reported based on such a moiety. In this current work, a novel hydrazide-hydrazone-based fluorogenic molecule 5-bromo-2-hydroxy-<i>N</i>'-[(1<i>E</i>)-1-(thiophen-2-yl)ethylidene]benzohydrazide (L) has been successfully designed and synthesized. The sensing studies of L demonstrated a ratio metric as well as turn-on-enhanced fluorescence and colorimetric response toward Fe³⁺ and Cu²⁺ ions, respectively and it was observed to be insensitive toward various metal ions. The Job plots revealed that the binding stoichiometry of L and metal ions is 2 : 1. In addition, density functional theory (DFT) results strongly suggested that L can be used as a powerful colorimetric sensor for the detection of Cu²⁺ ions. <i>In vitro</i> antimicrobial activities of L were evaluated by disk diffusion and results revealed good antibacterial activities against <i>E. coli</i>. Further, molecular docking was executed with DNA gyrase (PDB ID: 1KZN) of <i>E. coli</i> and the calculated interaction energy value was found to be -7.7 kcal mol^-1. Finally, molecular docking, fluorescence, colorimetry and the HOMO-LUMO energy gap of the compound can provide new insights into developing drugs and detecting metals in biomolecules.