Novel Benzothiazole-Benzonitrile-Based Fluorescent Chromophore: Synthesis, DFT, Antimicrobial Properties

The synthetic strategy for the benzothiazole-benzonitrile chromophore 6 involved three sequences of reactions. It was initiated by condensation of 2-amino-4-nitrothiophenol (2) with 4-(piperidin-1-yl)benzaldehyde (1) to produce the corresponding 5-nitrobenzothiazole compound 3 followed by reduction of compound 3 into the 5-aminobenzothiazole compound 4 and then ended by condensation of 5-aminobenzothiazole compound 4 with 4-formylbenzonitrile (5). The chromophore's absorption and emission spectra have been measured in EtOH and presented good Stokes' shift ( $$  = 8363 cm^-1). The DFT configuration of the frontier molecular orbits in gas and solvated ground state (S_o) were compared with the solvated excited state (S₁). The synthesized chromophore 6 was assessed for its antimicrobic properties against a group of bacterial and fungal strains. The minimum inhibitory concentration (MIC) values were determined using standard broth microdilution assay. Notably, chromophore 6 exhibited remarkable MIC values against Staphylococcus aureus and Escherichia coli (< 48 and < 118 μg/mL). Regarding the antibacterial effectiveness against both S. aureus and E. coli, molecular docking was performed to simulate their binding interactions with two protein structures, PDB:2eg7 and PDB:3u2k. The SwissADME study has been applied to explore the pharmacokinetic and pharmacodynamic characteristics of chromophore 6.