Copper(II) Schiff base complex derived from salen ligand: structural investigation, Hirshfeld surface analysis, anticancer and anti-SARS-CoV-2

Abstract

This work deals with the synthesis and characterization of copper(II) complex [Cu(salen)(H₂O)](1) of salen-type Schiff base ligand derived from the condensation of 5-bromo-2-hydroxy-3-methoxybenzaldehyde and ethylenediamine in EtOH. This complex was characterized by different spectroscopic and physicochemical methods. Single crystal X-ray crystallography study revealed that Cu(II) in complex (1) is five-coordinate and adopts a distorted square pyramidal geometry. A DFT calculation was employed to evaluate the optimized electronic structure, HOMO-LUMO, energy gap, and global parameters. A detailed structural and non-covalent interaction on the complex is investigated by single crystal structure analysis and computational approaches. The strength of the interaction and 3D topology of the crystal packing are visualized through an energy framework. Hirshfeld surface and 2D fingerprint plots have been explored in the crystal structure of the complex. The anticancer properties of copper(II) complex was studied against the selected cancerous cell lines of breast cancer, cervical cancer, colon cancer and hepatocellular carcinoma. Additionally, molecular docking and MD simulations was performed on the complex to predict the binding mode and interactions between the ligand and the main protease of the SARS-CoV-2 (PDB ID: 7CBT and 7D1M). The molecular docking calculations of the complex (1) with SARS-CoV-2 virus revealed the binding energy of –8.1 kcal/mol and –7.5 kcal/mol with an inhibition constant of 3.245 µM and 2.318 µM at inhibition binding site of receptor towards 7CBT and 7D1M main protease (M^pro), respectively. Besides this, molecular docking results (–7.6 kcal/mol, 3.196 µM) towards Escherichia coli PBP2 targets (PDB ID: 6G9S) was also studied.

Communicated by Ramaswamy H. Sarma

Graphical Abstract

Keywords:

• Copper
• X-ray crystallography
• Hirshfeld surface analysis
• SARS-CoV-2
• penicillin binding protein

Acknowledgements

The authors are thankful to the Sophisticated Analytical Instrument Facility (SAIF), IIT Madras, India for single crystal data collection of salen-type copper (II) complex [Cu(salen)(H₂O)](1). The authors are also thankful to the Head, Department of Chemistry, NIT Patna, India for providing the necessary facilities (computational facility & spectral analysis) required to carry out this work.

Disclosure statement

The authors declare no conflict of interest.

Scheme 1. Synthetic route for salen-type Schiff base ligand and its copper (II) complex (1).

Additional information

Funding

S. Kumar thankful to NIT Patna, India for research fellowship under TEQIP.