Salicylaldehyde salicyloyl hydrazone and its copper(II) complex: synthesis, characterization, DFT, optical band gap, antibacterial activity, and molecular docking analysis

Abstract

A complex of Cu(II) with a bidentate Schiff base, salicylaldehyde salicyloyl hydrazone (SSH), was synthesized by refluxing copper(II) chloride with this ligand. The formation of the complex, the nature of bonding, and the geometry of the complex were established via physicochemical and spectroscopic techniques. The composition of the complex was found to be a 1:2 metal-ligand ratio as Cu(SSH)₂. Electronic absorption spectral studies revealed that the copper adopts a distorted tetrahedral geometry upon complexation with SSH. The optical band energy for the complex was determined from absorption spectroscopy. The obtained band gap of 2.66 eV characterizes the complex as a semiconductor. The most stable conformations of the Schiff base (SSH) and Cu(SSH)₂ complex have been computed, shedding light on their structural and electronic properties, and highlighting their potential reactivity and stability. The ligand exhibits a higher reactivity towards electrophiles, while the complex displays a greater affinity for nucleophiles. The in vitro antibacterial analysis with agar cup well method and in silico molecular docking analysis indicate that both the ligand and its complex with copper have potency to inhibit bacterial infections. Based on their growth inhibition, minimum inhibitory concentration (MIC) values, and robust interaction with studied proteins of the pathogens, these compounds hold a prospective avenue for the advancement of antibiotics.

Keywords:

• Hydrazone
• copper(II) complex
• spectral studies
• DFT
• antibacterial
• molecular docking

Acknowledgments

The authors would like to acknowledge the Central Department of Chemistry, Tribhuvan University, Kirtipur Nepal; Nepal Academy of Science and Technology (NAST); and Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China for providing the characterization and analysis facilities.

Author statement

The authors claim that none of the material in the article has been published or is under consideration for publication elsewhere.

Disclosure statement

The authors declare no competing financial interest.

Additional information

Funding

No funding has been received for the research.