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.

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.

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.

Two-Dimensional WSe2/Organic Acceptor Hybrid Nonvolatile Memory Devices Based on Interface Charge Trapping

Two-dimensional (2D) materials, with atomic thickness and unique electronic structure, hold great potentials in electronic device applications. Charge transfer at the interface of 2D materials further provides a versatile platform for applications in electronics. Here, we report nonvolatile memory devices based on interface charge trapping between 2D WSe₂ and organic electron acceptors. The 2D WSe₂-organic acceptor hybrid structure exhibits a high storage performance, such as large gate memory windows, high on/off ratios (>10³), and long retention time (>1000 s). Further analysis revealed that organic acceptors with a stronger electron affinity (i.e., higher redox potential) have a larger electron-trapping ability and hence a better memory performance.

Spectrophotometric and photocatalytic studies of H-bonded charge transfer complex of oxalic acid with imidazole: single crystal XRD, experimental and DFT/TD-DFT studies

The photocatalytic activity of a new CT complex was tested. Spectrophotometric studies were performed to understand its formation through N⁺–H⋯O⁻ hydrogen bonding, and the structure was confirmed by single crystal XRD.

Synthesis, structure, spectral properties and DFT quantum chemical calculations of 4-aminoazobenzene dyes. Effect of intramolecular hydrogen bonding on photoisomerization

In this paper three different "push-pull" 4-aminoazobenzene dyes have been synthesized in order to characterize their photochromic behavior in different solvents. The molecular geometry was optimized by DFT/B3LYP functional combined with the standard 6-31+G(d,p) basis set for trans (E) and cis (Z) isomers and the energy levels of HOMO and LUMO frontier orbitals were computed using IEFPCM solvation in CHCl₃ and DMF. The calculated results were compared to the experimental optical band gap and HOMO values of cyclic voltammetry. The intramolecular six-membered hydrogen bond was formed in both isomers of the synthesized dyes. The thermodynamic parameters such as total electronic energy E (RB3LYP), enthalpy H₂₉₈ (sum of electronic and thermal enthalpies), free Gibbs energy G₂₉₈ (sum of electronic and thermal free Gibbs energies) and dipole moment μ were computed for trans (E) and cis (Z) isomers in order to estimate the ΔE_trans→cis, Δμ_trans→cis, ΔH_trans→cis, ΔG_trans→cis and ΔS_trans→cis values. The NBO analysis was performed in order to understand the intramolecular charge transfer and energy of resonance stabilization. The solvatochromic shift was evaluated by UV-VIS spectroscopy in CHCl₃ (nonpolar), EtOH (polar protic) and DMF (polar aprotic) solvents to determine the electron withdrawing and donating properties of the substituents on electron transitions energy. Through the increasing solvent polarity a strong bathochromic shift is observed. The photoisomerization experiments have been performed in two solvents CHCl₃ (nonpolar) and DMF (polar aprotic) by UV light irradiation with λ=365nm at equal concentrations and time of illuminations. The electronic spectra were computed by TD-DFT after geometry optimization using IEFPCM solvation in CHCl₃ and DMF. The degree of photoisomerization was calculated for the three azo chromophores in both solvents. By using first derivative of the UV-VIS spectra it was possible to resolve the overlapped electron transitions absorption bands. The existing intramolecular hydrogen bond in the azo chromophores was discussed in relation to the isomerization mechanisms and relative stability of the cis (Z) isomers.