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

Experimental and density functional theory studies on some metal oxides and the derived nanoclusters: a comparative effects on human ferritin

A comprehensive investigation into the green synthesis of metal oxide nanoparticles (NPs) has garnered significant attention due to its commendable reliability, sustainability, and environmentally friendly attributes. Green synthesis methods play a crucial role in mitigating the adverse effects associated with conventional approaches employed for nanostructure preparation. This research endeavors to examine the impact of ginger plant extract-assisted green synthesis of metal oxides NPs on the serum ferritin levels of anemic diabetic patients in vitro, focusing specifically on α-Fe2O3 and ZnO NPs. Sixty diabetic volunteers with anemia (35-50 years) and thirty healthy volunteers were enrolled as controls. The assessment was conducted using the VIDAS Ferritin (FER) assay. Photoluminescence (PL) spectroscopy measurements were performed to elucidate the intrinsic and extrinsic transitions of these NPs, affirming the successful formation of α-structured iron oxide. Density functional theory (DFT) calculations were carried out at the B3LYP/6-311++G(d,2p) level of theory to investigate the geometry optimization and molecular electrostatic potential maps of the NPs. Furthermore, TD-DFT calculations were employed to explore their frontier molecular orbitals and various quantum chemical parameters. The binding affinity and interaction types of ZnO and α-Fe2O3 NPs to the active site of the human H-Chain Ferritin (PDB ID: 2FHA) target were determined with the help of molecular docking. Results unveiled the crystalline structure of ZnO and the α-structure of α-Fe2O3. Analysis of the frontier molecular orbitals and dipole moment values demonstrated that ZnO (total dipole moment (D) = 5.80 µ) exhibited superior chemical reactivity, biological activity, and stronger molecular interactions with diverse force fields compared to α-Fe2O3 (D = 2.65 µ). Molecular docking of the metal oxides NPs with human H-chain ferritin provided evidence of robust hydrogen bond interactions and metal-acceptor bonds between the metal oxides and the target protein. This finding could have a great impact on using metal oxides NPs-ferritin as a therapeutic protein, however, further studies on their toxicity are required.

Synthesis, characterization, biological activity and computation-based efficacy of cobalt(II) complexes of biphenyl-2-ol against SARS-CoV-2 virus

Cobalt(II) complexes of biphenyl-2-ol of composition, CoCl2-n(OC6H4C6H5-2)n(H2O)4 (where n = 1 or 2), were prepared by reacting cobaltous(II) chloride with equi- and bimolar ratios of sodium salt of biphenyl-2-ol. The structural characterization of the synthesized complexes was accomplished by NMR, FTIR, thermogravimetry (TGA), high resolution mass spectroscopy (HRMS), electronic spectroscopic techniques coupled with density functional theory (DFT). The stability of the complexes in different pH media of solvent was studied. Chemical reactivity parameters of the newly synthesized complexes, computed using DFT, indicated greater reactivity of complex 2 over complex 1 and free ligand as indicated by its low HOMO-LUMO energy gap corresponding to 1.71 eV. Molecular docking (MD) studies were carried out in order to study the binding affinities between amino acid residues of DNA duplex (PDB ID: 1BNA) and SARS-CoV-2 (PDB ID: 7T9K) with newly synthesized complexes. Complex 2 has shown promising antivirus behaviour with an inhibition constant value of 0.0423 µmol-1 with amino acid residues of SARS-CoV-2 virus. Toxicity of the complexes was predicted using ProTox-II online server. Antibacterial studies have indicated the complexes to exhibit greater efficacy than the free ligand, while the antioxidant activities have suggested them to display enhanced antioxidant behaviour as compared to reference compounds.Communicated by Ramaswamy H. Sarma.

Antiureolytic activity of new water-soluble thiadiazole derivatives: Spectroscopic, DFT, and molecular docking studies

Two new water-soluble thiadiazole compounds are prepared and characterized with various techniques. These compounds, 5-amino-1,3,4-thiadiazole hydrochloride (1) and 5-amino-3-(N-propane-2-imine)-1,3,4-thiadiazole chloride salt (2) were synthesized via Mannich reaction, and characterized by microelemental analysis, and some spectroscopic means (FTIR, UV-Vis, ¹H NMR, ¹³C NMR and mass), in addition to single-crystal X-ray diffraction for compound 2. DFT calculations were conducted to study their geometry optimization, vibrational spectra, MEP maps, and NBO analysis. In addition, TD-DFT calculations were performed to study their absorption spectra. The prepared compounds were tested against Jack beans urease enzyme (in vitro) to indicate their antiureolytic activity potency. The activity of the enzyme was measured under optimal conditions, before and after mixing with the prepared organic compounds. The results showed that both compounds have potentially inhibited the enzyme activity with respect to their IC₅₀ values: 13.76 µM ± 0.15 for 1, and 18.81 µM ± 0.18 for 2. These values are even lower than that of thiourea (21.40 ± 0.21 µM) as a standard inhibitor. The inhibition activity of urease enzyme was confirmed by a Lineweaver-Burk plot. According to the kinetic parameters obtained from the Lineweaver-Burk plot, the inhibition of urease enzyme by compounds 1 and 2 seems to be non-competitive. Molecular docking studies of the prepared compounds 1 and 2 were performed in order to interpret the obtained biological results and to investigate their interactions with the urease enzyme active site. These studies reveal that compounds 1 and 2 are good candidates as inhibitors for urease enzyme. Moreover, compound 1 exhibits a higher promising inhibition activity.

Charge-transfer complexation of TCNE with azithromycin, the antibiotic used worldwide to treat the coronavirus disease (COVID-19). Part IV: A comparison between solid and liquid interactions

Finding a cure or vaccine for the coronavirus disease (COVID-19) is the most pressing issue facing the world in 2020 and 2021. One of the more promising current treatment protocols is based on the antibiotic azithromycin (AZM) alone or in combination with other drugs (e.g., chloroquine, hydroxychloroquine). We believe gaining new insight into the charge-transfer (CT) chemistry of this antibiotic will help researchers and physicians alike to improve these treatment protocols. Therefore, in this work, we examine the CT interaction between AZM (donor) and tetracyanoethylene (TCNE, acceptor) in either solid or liquid forms. We found that, for both phases of starting materials, AZM reacted strongly with TCNE to produce a colored, stable complex with 1:2 AZM to TCNE stoichiometry via a n → π* transition (AZM → TCNE). Even though both methodologies yielded the same product, we recommend the solid-solid interaction since it is more straightforward, environmentally friendly, and cost- and time-effective.

Development of UV-visible spectrophotometric methods for the quantitative and in silico studies for cilazapril optimized by response surface methodology

For cilazapril (CLZ), analytical methods based on donor-acceptor phenomenon that are simple, rapid with broad linear dynamic range for the quantification of drug are not available in the literature. Considering the requirement for the methods, in this study, two economic, potent analytical methods based on the complexation of CLZ with π-acceptors, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and 2,5-dichloro-3,6-dihydroxy-p-benzoquinone (CA) were developed, validated, and studied spectrophotometrically. Various analytical data were discussed. The effects of experimental variables were optimized from the results of in silico technique, i.e. Box-Behnken design under response surface methodology. Linear dynamic range was significantly good in the range of 6-60 µg mL^-1 and 20-260 µg mL^-1 for DDQ and CA methods. Moreover, molecular docking studies corroborated the experimental results. Further, the methods were supplemented by the pharmaceutical and biological application for the quantitative assay of CLZ. Collectively, the results of the reported method of the analysis suggest that the developed approach is simple, sensitive, accurate and precise.

Charge-transfer chemistry of azithromycin, the antibiotic used worldwide to treat the coronavirus disease (COVID-19). Part III: A green protocol for facile synthesis of complexes with TCNQ, DDQ, and TFQ acceptors

Investigating the chemical properties of molecules used to combat the COVID-19 pandemic is of vital and pressing importance. In continuation of works aimed to explore the charge-transfer chemistry of azithromycin, the antibiotic used worldwide to treat COVID-19, the disease resulting from infection with the novel SARS-CoV-2 virus, in this work, a highly efficient, simple, clean, and eco-friendly protocol was used for the facile synthesis of charge-transfer complexes (CTCs) containing azithromycin and three π-acceptors: 7,7,8,8-tetracyanoquinodimethane (TCNQ), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), and tetrafluoro-1,4-benzoquinone (TFQ). This protocol involves grinding bulk azithromycin as the donor (D) with the investigated acceptors at a 1:1 M ratio at room temperature without any solvent. We found that this protocol is environmentally benign, avoids hazardous organic solvents, and generates the desired CTCs with excellent yield (92–95%) in a straightforward means.

Charge Transfer Complexes of Ketotifen with 2,3-Dichloro-5,6-dicyano-p-benzoquinone and 7,7,8,8-Tetracyanoquodimethane: Spectroscopic Characterization Studies

The reactions of ketotifen fumarate (KT) with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as π acceptors to form charge transfer (CT) complexes were evaluated in this study. Experimental and theoretical approaches, including density function theory (DFT), were used to obtain the comprehensive, reliable, and accurate structure elucidation of the developed CT complexes. The CT complexes (KT-DDQ and KT-TCNQ) were monitored at 485 and 843 nm, respectively, and the calibration curve ranged from 10 to 100 ppm for KT-DDQ and 2.5 to 40 ppm for KT-TCNQ. The spectrophotometric methods were validated for the determination of KT, and the stability of the CT complexes was assessed by studying the corresponding spectroscopic physical parameters. The molar ratio of KT:DDQ and KT:TCNQ was estimated at 1:1 using Job's method, which was compatible with the results obtained using the Benesi-Hildebrand equation. Using these complexes, the quantitative determination of KT in its dosage form was successful.

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 complexes: Emerging and promising colorimetric real-time chemosensors for hazardous materials

After introducing the concept of charge transfer (CT) complex formation by Mulliken and the discovery of crystalline picrate (association of picric acid and aromatic hydrocarbons) by Fritzsches, a large interest has been drawn in this field. CT complexes have been explored and exploited for different applications for several decades. The research has been aimed mostly for discovering and characterizing new CT materials and exploring applications mainly in the field of optoelectronic properties, antimicrobial activities and DNA/protein binding properties for the last six years. However, nowadays, CT complexes are exploited for their photocatalytic activities and designing chemosensors for the colorimetric real-time detection of hazardous materials like nitro explosives, anions and toxic heavy metal ions in an aqueous medium. This review sheds light on updates on CT complexes, their types, synthesis and applications. The brief discussion on the emergence of CT complexes as highly potential chemosensors along with the explanation of sensing mechanism through article summarization is the centerpiece of this review. The final outcomes are discussed and concluded.

Heteroleptic complexes of cocaine/TMEDA with some f block metals: Synthesis, DFT studies, spectral, thermal, cytotoxicity and antimetastatic properties

A series of new three heteroleptic complexes of the general formula [Ln(Cn)(TMEDA)Cl(OH₂)]·2Cl·xH₂O, (where Ln = La(III), Er(III) and Yb(III), Cn = cocaine and TMEDA = N,N,N',N'-tetramethylethylenediamine) were synthesized, structurally characterized by elemental analysis, spectroscopic methods, molar conductivity and mass spectrometry. Thermal properties of the synthesized complexes and their kinetic thermodynamic parameters were studied. Theoretical calculations including geometry optimization, electronic structure and electronic and thermal energies were carried out using DFT and TD-DFT calculations at B3LYP/LANL2DZ level of theory and the different quantum chemical parameters were calculated. The in vitro antiproliferative activity of the newly synthesized complexes was assessed by MTT assay on MCF-7 and HepG-2 cancer cell lines. Yb(III) complex showed promising cytotoxic activity comparable to that of cisplatin on both cell lines with minimum effect on human normal cells. Further molecular mechanistic investigations showed that Yb(III) complex is an apoptotic inducer as it raises the caspase-3 and caspase-9 cellular level in the MCF-7 cell line. Furthermore, it showed an elevating effect on the level of the tumor suppressor nuclear proteins P21 and P27 concentrations in MCF-7 cells. Moreover, Yb(III) complex hindered the cellular scavenger system of the reactive oxygen species through reducing the glutathione peroxidase (GPx) cellular level imperiling MCF-7 cells by unmanageable oxidative stress. In addition to its cytotoxic effect, Yb(III) complex showed antimetastatic properties as it decreased the cellular levels of matrix metalloproteinases MMP-3 and MMP-9. These results showed that the Yb(III) complex is a promising cytotoxic metal-based agent that exerts its action through various molecular mechanisms with minimum effects on normal cells and with additional antimetastatic properties.