Synthesis of New Hydrazone Derivatives, Characterization, Single Crystal X‐Ray, Antimicrobial, <scp>SEM</scp> , and <scp>DFT</scp> Studies

Fifteen new hydrazine derivatives were synthesized and structurally characterized using NMR (¹H NMR and ¹³C NMR) spectroscopy techniques. Furthermore, the crystal structure of compound 1647 was figured out by the single crystal X-ray analysis. The in vitro antimicrobial activity was reviewed against five species of pathogenic bacteria (Escherichia coli [ATCC 25922], Serratia marcescens, Klebsiella pneumoniae [ATCC 13883], Staphylococcus aureus [ATCC 29213], Enterococcus faecalis [ATCC 2942]) and three fungal species (Candida albicans [ATCC 24433], Candida krusei [ATCC 6258], and Candida parapsilopsis [ATCC 22019]). Compounds 1646 and 1647 with MIC of 1.95 μg/mL was found to be most active against E. coli (ATCC 25922). The presence of bromine or tert-butyl groups in the para position of the phenyl ring increased the antibacterial activity. It has been shown by SEM study that these compounds cause deterioration in the morphology of E. coli. Using DFT, the X-ray geometry and model geometry of compound 1647 were optimized and compared in terms of both energy and geometry, and it was determined that they were conformers of each other with a difference of 0.11 kcal/mol.