Synthesis, single-crystal, DNA interaction, spectrophotometric and spectroscopic characterization of the hydrogen-bonded charge transfer complex of 2-aminopyrimidine with π-acceptor chloranilic acid at different temperature in acetonitrile

Enhancement of Haloperidol Binding Affinity to Dopamine Receptor Via Forming a Charge-Transfer Complex with Picric Acid and 7,7,8,8-Tetracyanoquinodimethane for Improvement of the Antipsychotic Efficacy

Haloperidol (HPL) is a typical antipsychotic drug used to treat acute psychotic conditions, delirium, and schizophrenia. Solid charge transfer (CT) products of HPL with 7,7,8,8-tetracyanoquinodimethane (TCNQ) and picric acid (PA) have not been reported till date. Therefore, we conducted this study to investigate the donor–acceptor CT interactions between HPL (donor) and TCNQ and PA (π-acceptors) in liquid and solid states. The complete spectroscopic and analytical analyses deduced that the stoichiometry of these synthesized complexes was 1:1 molar ratio. Molecular docking calculations were performed for HPL as a donor and the resulting CT complexes with TCNQ and PA as acceptors with two protein receptors, serotonin and dopamine, to study the comparative interactions among them, as they are important neurotransmitters that play a large role in mental health. A molecular dynamics simulation was ran for 100 ns with the output from AutoDock Vina to refine docking results and better examine the molecular processes of receptor–ligand interactions. When compared to the reactant donor, the CT complex [(HPL)(TCNQ)] interacted with serotonin and dopamine more efficiently than HPL only. CT complex [(HPL)(TCNQ)] with dopamine (CTtD) showed the greatest binding energy value among all. Additionally, CTtD complex established more a stable interaction with dopamine than HPL–dopamine.

Insights on structure and interactions of 2-amino-4-methoxy-6-methylpyrimidinium salts with 4-aminosalicylate and 5-chlorosalicylate: a combined experimental and theoretical charge–density analysis

The proton-transfer complexes 2-amino-4-methoxy-6-methylpyrimidinium (2A4M6MP) 4-aminosalicylate (4AMSA), C6H10N3O+·C7H6NO3 −, I, and 5-chlorosalicylate (5ClSA), C6H10N3O+·C7H4ClO3 −, II, were synthesized by slow evaporation and crystallized. The crystal structures of both I and II were determined by single-crystal X-ray structure analysis. The crystal structures of both salts exhibit O—H...O, N—H...O, N—H...N and C—H...O interactions in their crystals. The 4AMSA and 5ClSA anions in combination with the 2A4M6MP cations form distinct synthons, which are represented by the graph-set notations R 2 2(8), R 4 2(8) and R 2 2(8). Furthermore, the ΔpK a values were calculated and clearly demonstrate that 2A4M6MP is a good salt former when combined with carboxylic acids. Hirshfeld surface analysis was used to quantify the weak and strong interactions in the solid state, and energy framework calculations showed the stability of the hydrogen-bonding interactions. QTAIM (quantum theory of atoms in molecules) analysis revealed the nature of the chemical bonding in I and II, and the charge–density distribution in the intermolecular interactions in the crystal structures.

Exploring the charge transfer dynamics of hydrogen bonded crystals of 2-methyl-8-quinolinol and chloranilic acid: synthesis, spectrophotometric, single-crystal, DFT/PCM analysis, antimicrobial, and DNA binding studies

The new chemistry of the hydrogen-bonded charge and proton transfer complex (HB CT) between electron-donor 2-methyl-8-quinolinol (2 MQ) and electron-acceptor chloranilic acid (CHLA) has been studied using electronic absorption spectroscopy in acetonitrile (ACN), methanol (MeOH), and ethanol (EtOH) polar media at room temperature. The stoichiometric proportion of the HB CT complex was observed to be 1 : 1 from the Job data and photometric titration process. The association constant (K _CT) and molar absorptivity (ε _CT) of the HB CT complex were determined by using the modified Benesi-Hildebrand equation in three polarities. Other spectroscopic physical parameters like the energy of interaction (E _CT), ionization potential (I _D), resonance energy (R _N), standard free energy change (ΔG°), oscillator strength (f), and transition dipole moment (μ) were also evaluated. The HB CT complex structure was confirmed by different characterization techniques, such as FT-IR, NMR, TGA-DTA, and SEM-EDX analysis. Powder XRD and single-crystal XRD were used to determine the nature and structure of the synthesized HB CT complex. DNA binding studies for the HB CT complex produced a good binding constant value of 2.25 × 10⁴ L mol^-1 in UV-visible and 1.17 × 10⁴ L mol^-1 in fluorescence spectroscopy. The biological activity of the HB CT complex was also tested in vitro against the growth of bacteria and fungi, and the results indicated remarkable activity for the HB CT complex compared to the standard drugs, ampicillin and clindamycin. Hence, the abovementioned biological results of the synthesized HB CT complex show it could be used as a pharmaceutical drug in the future. Computational analysis was carried out by DFT studies using the B3LYP function with a basis set of 6-31G(d,p) in the gas phase and PCM analysis. The computational studies further supported the experimental results by confirming the charge and proton transfer complex.

New Charge Transfer Complexes of K+-Channel-Blocker Drug (Amifampridine; AMFP) for Sensitive Detection; Solution Investigations and DFT Studies

UV-Vis spectroscopy was used to investigate two new charge transfer (CT) complexes formed between the K⁺-channel-blocker amifampridine (AMFP) drug and the two π-acceptors 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and tetracyanoethylene (TCNE) in different solvents. The molecular composition of the new CT complexes was estimated using the continuous variations method and found to be 1:1 for both complexes. The formed CT complexes' electronic spectra data were further employed for calculating the formation constants (K_CT), molar extinction coefficients (ε_CT), and physical parameters at various temperatures, and the results demonstrated the high stability of both complexes. In addition, sensitive spectrophotometric methods for quantifying AMFP in its pure form were proposed and statistically validated. Furthermore, DFT calculations were used to predict the molecular structures of AMFP-DDQ and AMFP-TCNE complexes in CHCl₃. TD-DFT calculations were also used to predict the electronic spectra of both complexes. A CT-based transition band (exp. 399 and 417 nm) for the AMFP-TCNE complex was calculated at 411.5 nm (f = 0.105, HOMO-1 → LUMO). The two absorption bands at 459 nm (calc. 426.9 nm, f = 0.054) and 584 nm (calc. 628.1 nm, f = 0.111) of the AMFP-DDQ complex were theoretically assigned to HOMO-1 → LUMO and HOMO → LUMO excitations, respectively.

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.

Synthesis, characterization, antimicrobial and DNA binding properties of an organic charge transfer complex obtained from pyrazole and chloranilic acid

The chemistry of an organic charge transfer complex (CT complex) between pyrazole (donor) and chloranilic acid (acceptor) has been explored in ethanol at room temperature. The synthesized complex has been characterized by various techniques such as FTIR, NMR, Single crystal X-ray diffraction and UV-visible spectroscopy. These techniques indicate that the cation and anion are joined together by the weak hydrogen bonding. This molecular framework is a result of inter N⁺-H⋯O^- bonding between donor and acceptor moieties. The elemental analysis and FTIR spectrum of semi-crystal complex along with Job's plot indicate the formation of 2: 1 HBCT-complex. The bioorganic chemistry of the present CT complex is established well toward antimicrobial screening and DNA binding capabilities. Antimicrobial activity was screened for gram positive and gram negative bacteria and various fungi. Molecular docking shows that the CT complex binds perfectly with the B-DNA and reveals free energy of binding (FEB) value of -198.4 kcal mol^-1. TD-DFT calculations using basis set B3LYP/6-311G^** give theoretical confirmation along with HOMO (-3.9421 eV) → LUMO (-2.4903 eV) electronic energy gap (ΔE) to be 1.4521 eV. Theoretical analysis corroborates well the biological properties.