Design, synthesis, characterizing and DFT calculations of a binary CT complex co-crystal of bioactive moieties in different polar solvents to investigate its pharmacological activity

Abstract

Imidazole (IM) and salicylic acid (SA) have a significant class among the medical compound. These are widely used as topical drugs like antifungal, antibacterial, anticancer, immunosuppressive agent, etc. These two bioactive organic moieties are combined by a weak hydrogen bond formed by hydrogen transfer. The charge transfer (CT) complex of acceptor (SA) and donor (IM), has been synthesized at room temperature in methanol and confirmed by signal-crystal XRD, conductance and UV–visible spectroscopy. The X-ray crystallography provides the original structural information of CT complex and displays the existence of N⁺—H––O^– bond between IM and SA. The physical properties such as (E_CT), (R_N), (I_D), (f), (D) and ($\Delta$ G⁰) along with molar extinction coefficient (ε_CT) and formation constant (K_CT) were estimated through UV–visible spectroscopy. Job’s method and Benesi-Hildebrand equation suggested 1:1 stoichiometry of ([IM]⁺[SA]⁻). The results indicate a complete transfer of hydrogen atom and CT complex formation with 1:1 molar ratio of IM and SA. Antimicrobial activity was veiled against different bacteria like Escherichia coli, Bacillus subtilis and Staphylococcus aureus; and different fungi as Fusarium oxysporum, Candida albicans and Aspergillus niger by disc diffusion method. CT complex was also tested for cytotoxic activity against lung cancer cell lines in comparison to breast cancer cell lines. Molecular docking provides the information of binding of [(IM)⁺(SA)⁻] with the cancer marker (1M17), which has substantial application for drug designing. The investigational studies were supplemented through time-dependent density functional theory (TD-DFT) using basis set B3LYP/6-311G**. Through DFT calculations, HOMO→LUMO electronic energy gap ($\Delta E)$ was obtained.

A new organic charge transfer complex co-crystal has been prepared, characterized and explored for, Antioxident, Anticancer, antibacterial and antifungal activities. The experimental results are supported by theoretical analysis.

Communicated by Ramaswamy H. Sarma

Keywords:

• Single crystal X-Ray diffrection
• anticancer
• antioxidant
• antimicrobial
• molecular docking
• DFT/TD-DFT

Acknowledgment

Special thanks to Chairman, Department of Chemistry, AMU, Aligarh for providing research facilities at Physical Chemistry lab. Also, thank for financial assistance in the form of the UGC-BSR Start Up Grant No. F.-3-46/2014(BSR).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by UGC-BSR Start Up grant No. F.-3-46/2014(BSR).