Synthesis, spectral studies and DFT computational analysis of hydrogen bonded-charge transfer complex between chloranilic acid with 2,4-diamino-quinoline-3-carbonitrile in different polar solvents

Charge-transfer chemistry of two corticosteroids used adjunctively to treat COVID-19. Part II: The CT reaction of hydrocortisone and dexamethasone donors with TCNQ and fluoranil acceptors in five organic solvents

Hydrocortisone (termed as D1) and dexamethasone (termed as D2) are corticosteroids currently used to treat COVID-19. COVID-19 is a disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Exploring additional chemical properties of drugs used in the treatment protocols for COVID-19 could help scientists alike improve these treatment protocols and potentially even the vaccines (i.e., Janssen, Moderna, AstraZeneca, Pfizer-BioNTech). In this work, the charge-transfer (CT) properties of these two corticosteroids (D1 and D2) with two universal acceptors: 7,8,8-tetracyanoquinodimethane (termed as TCNQ) and fluoranil (termed as TFQ) in five different solvents were investigated. The examined solvents were MeOH, EtOH, MeCN, CH₂Cl₂, and CHCl₃. The CT interactions formed stable corticosteroid CT complexes in all examined solvents. Several spectroscopic parameters were derived, and the oscillator strength (f) and transition dipole moment (μ_e.g.) values revealed that the interaction between the investigated corticosteroids with TCNQ acceptor is much stronger than their interaction with TFQ acceptor. The CT interactions were proposed to process via n → π* transition.

Charge-transfer chemistry of two corticosteroids used adjunctively to treat COVID-19. Part I: Complexation of hydrocortisone and dexamethasone donors with DDQ acceptor in five organic solvents

COVID-19 is the disease caused by a novel coronavirus (CoV) named the severe acute respiratory syndrome coronavirus 2 (termed SARS coronavirus 2 or SARS-CoV-2). Since the first case reported in December 2019, infections caused by this novel virus have led to a continuous global pandemic that has placed an unprecedented burden on health, economic, and social systems worldwide. In response, multiple therapeutic options have been developed to stop this pandemic. One of these options is based on traditional corticosteroids, however, chemical modifications to enhance their efficacy remain largely unexplored. Obtaining additional insight into the chemical and physical properties of pharmacologically effective drugs used to combat COVID-19 will help physicians and researchers alike to improve current treatments and vaccines (i.e., Pfizer-BioNTech, AstraZeneca, Moderna, Janssen). Herein, we examined the charge-transfer properties of two corticosteroids used as adjunctive therapies in the treatment of COVID-19, hydrocortisone and dexamethasone, as donors with 2,3-dichloro-5,6-dicyano-p-benzoquinone as an acceptor in various solvents. We found that the examined donors reacted strongly with the acceptor in CH₂Cl₂ and CHCl₃ solvents to create stable compounds with novel clinical potential.

Charge Transfer Complex between O-Phenylenediamine and 2, 3-Dichloro-5, 6-Dicyano-1, 4-Benzoquinone: Synthesis, Spectrophotometric, Characterization, Computational Analysis, and its Biological Applications

UV-vis electronic absorption spectroscopy was used to investigate the new molecular charge transfer complex (CTC) interaction between electron donor O-phenylenediamine (OPD) and electron acceptor 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ). The CTC solution state analysis was carried out by two different polarities. The stoichiometry of the prepared CTC was determined by using Job's, photometric, and conductometric titration methods and was detemined to be 1:1 in both solvents (at 298 K). The formation constant and molar extinction coefficient were determined by applying the modified (1:1) Benesi-Hildebrand equation. The thermodynamic parameter ΔG° result indicated that the charge transfer reaction was spontaneous.The stability of the synthesized CTC was evaluated by using different spectroscopic parameters like the energy, ionization potential, oscillator strength, resonance energy, dissociation energy, and transition dipole moment. The synthesized solid CTC was characterized by using different analytical methods, including elemental analysis, Fourier transform infrared, nuclear magnetic resonance, TGA-DTA, and powder X-ray diffraction. The biological evolution of the charge transfer (CT) complex was studied by using DNA binding and antibacterial analysis. The CT complex binding with calf thymus DNA through an intercalative mode was observed from UV-vis spectral study. The CT complex produced a good binding constant value (6.0 × 10⁵ L.mol^-1). The antibacterial activity of the CT complex shows notable activity compared to the standard drug, tetracycline. These results reveal that the CT complex may in future be used as a bioactive drug. The hypothetical DFT estimations of the CT complex supported the experimental studies.

Molecular docking, theoretical calculations, synthesis of Ru(III), Pd(II) and VO(II) complexes and activity determination as antibacterial and antioxidant

Molecular modeling calculations were used to validate 3D structures of new complexes of Ru(III), Pd(II) and VO(II) ions chelated with (E)-2-(phenylamino)-N-(pyridine-2-yl)methylene)acetohydrazide ligand. Furthermore, the calculations were used to estimate selected electronic chemical descriptors which are responsible for the biological activity. The first insight of the compound activity as antibacterial was evaluated by molecular docking analysis. The titled models showed stable binding towards lanosterol 14 alpha-demethylase (CYP51) enzyme of E. coli, indicating their inhibition effect toward bacterial growth. Structural study of the ligand and Ru(III), Pd(II) and VO(II) chelates was done using elemental analysis, FT-IR, 1H-NMR techniques. Furthermore, complexes were physically investigated based on magnetic moment, molar conductance, electronic spectroscopic and thermal analysis techniques. The antibacterial study of the synthesized compounds screened against both Gram-positive and Gram-negative bacteria revealed that these compounds display remarkable antibacterial activity and can be used as therapeutic drugs for pathogenic bacterial diseases. All complexes and ligand showed good scavenging activities which indicate a promising result for their applications as antioxidants.

Charge-transfer chemistry of azithromycin, the antibiotic used worldwide to treat the coronavirus disease (COVID-19). Part II: Complexation with several π-acceptors (PA, CLA, CHL)

Finding a vaccine or cure for the coronavirus disease (COVID-19) responsible for the worldwide pandemic and its economic, medical, and psychological burdens is one of the most pressing issues presently facing the global community. One of the current treatment protocols involves the antibiotic azithromycin (AZM) alone or in combination with other compounds. Obtaining additional insight into the charge-transfer (CT) chemistry of this antibiotic could help researchers and clinicians to improve such treatment protocols. Toward this aim, we investigated the CT interactions between AZM and three π-acceptors: picric acid (PA), chloranilic acid (CLA), and chloranil (CHL) in MeOH solvent. AZM formed colored products at a 1:1 stoichiometry with the acceptors through intermolecular hydrogen bonding. An n → π* interaction was also proposed for the AZM-CHL CT product. The synthesized CT products had markedly different morphologies from the free reactants, exhibiting a semi-crystalline structure composed of spherical particles with diameters ranging from 50 to 90 nm.

Charge-transfer chemistry of azithromycin, the antibiotic used worldwide to treat the coronavirus disease (COVID-19). Part I: Complexation with iodine in different solvents

Around the world, the antibiotic azithromycin (AZM) is currently being used to treat the coronavirus disease (COVID-19) in conjunction with hydroxychloroquine or chloroquine. Investigating the chemical and physical properties of compounds used alone or in combination to combat the COVID-19 pandemic is of vital and pressing importance. The purpose of this study was to characterize the charge transfer (CT) complexation of AZM with iodine in four different solvents: CH2Cl2, CHCl3, CCl4, and C6H5Cl. AZM reacted with iodine at a 1:1 M ratio (AZM to I2) in the CHCl3 solvent and a 1:2 M ratio in the other three solvents, as evidenced by data obtained from an elemental analysis of the solid CT products and spectrophotometric titration and Job's continuous variation method for the soluble CT products. Data obtained from UV-visible and Raman spectroscopies indicated that AZM strongly interacted with iodine in the CH2Cl2, CCl4, and C6H5Cl solvents by a physically potent n→σ* interaction to produce a tri-iodide complex formulated as [AZM·I+]I3 -. XRD and TEM analyses revealed that, in all solvents, the AZM-I2 complex possessed an amorphous structure composed of spherical particles ranging from 80 to 110 nm that tended to aggregate into clusters. The findings described in the present study will hopefully contribute to optimizing the treatment protocols for COVID-19.

Charge Transfer Complex of Neostigmine with 2,3-Dichloro-5,6-Dicyano-1,4-Benzoquinone: Synthesis, Spectroscopic Characterization, Antimicrobial Activity, and Theoretical Study

BACKGROUND

Electron donor-acceptor interactions are important molecular reactions for the activity of pharmacological compounds. The aim of the study is to develop a charge transfer (CT) complex: synthesis, characterization, antimicrobial activity, and theoretical study.

METHOD AND RESULTS

A solid CT complex of neostigmine (NSG) with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was synthesized and characterized by infrared spectra, NMR, and UV-visible spectroscopy. The results confirm the formation of a CT complex. The stability of the CT complex between NSG and DDQ in acetonitrile was determined in solution via spectrophotometric measurement, ie, by calculating the formation constant, molar extinction coefficient, and different spectroscopic parameters. The stoichiometry of the formed NSG-DDQ complex was determined using Job's method. The absorption band of the NSG-DDQ complex can be used for the quantification of NSG.

CONCLUSION

The DFT geometry optimization of NSG, DDQ, and the CT complex and the UV comparative study of both theoretical and experimental structures are presented. The experimental results confirm the charge transfer structure. The bacterial study shows that the NSG-DDQ complex has good antibacterial activity against both Gram-positive and Gram-negative bacteria as well as antifungal activity against Candida albicans.

π-Orbital Yin–Yang Kagome bands in anilato-based metal–organic frameworks

π-Orbital Yin–Yang Kagome bands consisting of two flat bands with opposite Chern numbers have been disclosed in anilato-based metal–organic frameworks.

Molecular structure, spectroscopic, dielectric and thermal study, nonlinear optical properties, natural bond orbital, HOMO-LUMO and molecular docking analysis of (C6Cl2O4) (C10H14N2F)2·2H2O

A new chloranilate compound with 1-(2-fluorophenyl)piperazine has been synthesized and characterized using spectroscopic methods and X-ray diffraction. The atomic arrangement can be described by an H-bonded 3D network, formed by anionic entities, organic cations and H₂O molecules linked together via NH…O, OH…Cl, CH…Cl and CH…O hydrogen bonds. The vibrational absorption bands of the various characteristic groups of this compound have been identified by infrared spectroscopy. Moreover, the thermal and dielectric analyses have shown that the title compound has a phase transition at 393 K. The surface mapped over the d_norm property, highlights the A⋯H (AO, C, Cl and F) as the main intermolecular contacts. On the other hand, the geometry, intermolecular bonds and harmonic vibrational frequencies of the title molecule have been investigated using the B3LYP/6-31G (d, p) method. The stability of the structure obtained, as well as the charge transfer within the molecule, have been confirmed by determining the energies of the HOMO and LUMO levels and the theoretical gap energy. Molecular docking studies of the title compound have also been conducted as part of this study.

Melatonin charge transfer complex with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone: Molecular structure, DFT studies, thermal analyses, evaluation of biological activity and utility for determination of melatonin in pure and dosage forms

A simple, accurate and fast spectrophotometric method for the quantitative determination of melatonin (ML) drug in its pure and pharmaceutical forms was developed based on the formation of its charge transfer complex with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as an electron acceptor. The different conditions for this method were optimized accurately. The Lambert-Beer's law was found to be valid over the concentration range of 4-100μgmL^-1 ML. The solid form of the CT complex was structurally characterized by means of different spectral methods. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations were carried out. The different quantum chemical parameters of the CT complex were calculated. Thermal properties of the CT complex and its kinetic thermodynamic parameters were studied, as well as its antimicrobial and antifungal activities were investigated. Molecular docking studies were performed to predict the binding modes of the CT complex components towards E. coli bacterial RNA and the receptor of breast cancer mutant oxidoreductase.