Structural, Electronic and NLO Properties of 6-aminoquinoline: A DFT/TD-DFT Study

Synthesis, Structural Elucidation, In Silico and In Vitro Studies of New Class of Methylenedioxyphenyl-Based Amide Derivatives as Potential Myeloperoxidase Inhibitors for Cardiovascular Protection

Novel methylenedioxyphenyl-based amides, especially N-(4-methoxybenzyl)-6-nitrobenzo-[1,3]-dioxole-5-carboxamide (MDC) and N-(3-acetylphenyl)-6-nitrobenzo-[1,3]-dioxole-5-carboxamide (ADC), potential cardiovascular preventive agents, are successfully synthesized, and their chemical structures are verified by 1H and 13C NMR, Fourier transform infrared (FT-IR), high-resolution mass spectrometry (HRMS), and single-crystal X-ray diffraction (SC-XRD) analyses. Data obtained from SC-XRD reveal that MDC and ADC are both monoclinic molecules with Z = 2 and 4, respectively. From density functional theory (DFT) calculations, 3.54 and 3.96 eV are the energy gaps of the optimized MDC and ADC structures, respectively. MDC and ADC exhibit an electrophilicity index value of more than 1.5 eV, suggesting that they can act as an electrophile, facilitating bond formation with biomolecules. Hirshfeld surface analysis demonstrates that more than 25% of atomic interactions in both MDC and ADC are from H···H interactions. Based on pharmacokinetic predictions, MDC and ADC exhibit drug-like properties, and molecular docking simulations revealed favorable interactions with active site pockets. Both MDC and ADC achieved higher docking scores of -7.74 and -7.79 kcal/mol, respectively, with myeloperoxidase (MPO) protein. From docking results, MPO was found to be most favorable followed by dipeptidyl peptidase-4 (DPP-4) and α-glucosidase (α-GD). Antioxidant, anti-inflammatory, and in vitro enzymatic studies of MDC and ADC indicate that MDC is more selective toward MPO and more potent than ADC. The application of MDC to inhibit myeloperoxidase could be ascertained to reduce the cardiovascular risk factor. This can be supported from the results of computational docking (based on hydrogen bonding and docking score), in vitro antioxidant and anti-inflammatory properties, and MPO enzymatic inhibition (based on the percentage of inhibition and IC50 values).

Possible NLO response and electrical/charge transfer capabilities of natural anthraquinones as p-type organic semiconductors: a DFT approach

CONTEXT

Organic semiconductors (OSCs) have attracted a great deal of interest in recent days. There are various types of OSCs, among which small molecules have various inherent benefits. Further research is needed to advance this new kind of material because the field is still developing, and the current focus is on creating small molecules that exist naturally for OSCs. OSCs with nonlinear optical (NLO) characteristics offer a significant advantage over others. Thus, this study theoretically investigates naturally occurring anthraquinones such as chrysophanol and rhein as potential OSCs, as well as their NLO properties. The calculated properties include the ionization potential (IP), electron affinity (EA), and bandgap (Eg). The FMO energy levels together with the Eg, IP (8.17-8.53 eV), and EA (1.87-2.44 eV) suggest the semiconductor nature of the studied compounds. The calculated values of reorganization energy (λ) and transfer integrals (V) suggest the p-type character of both molecules. Rhein has the lowest λh (0.19 eV) and Eg (3.28 eV) and the highest Vh, predominantly because of its better p-type character. The polarizability increases due to the presence of an electron-withdrawing substituent, leading to better NLO performance for Rhein, which is supported by its lower LUMO and Eg values.

METHODS

The studied molecules were optimized with the DFT/B3LYP-GD3/6-31+G(d,p) method using Gaussian 16 software. The crystal structure was simulated with Materials Studio 7.0, and the V values were calculated with the ADF package. The CDD and DOS plots were obtained with the Multiwfn 3.8 program.

Theoretical investigation of novel electron donors for bulk heterojunction solar cells with potential photovoltaic characteristics

Engineering electronic organic donor materials are one of the most critical steps in producing bulk-heterojunction solar cells (BHJ) with good photovoltaic properties. Compared to standard donor materials, electron donors derived from thiophene have made significant progress as they can be better suited for optoelectronics and are cheaper and more stable. Therefore, the use of new thiophene derivatives (M1-M4) as donor molecules in BHJs has been the subject of this extensive theoretical analysis. Density functional theory (DFT) and time-dependent DFT (TD-DFT) computations have been used to investigate the boundary molecular orbital (FMO) analysis, the density of states analysis, electron and hole reorganization energy, molecular electrostatic potential, global reactivity parameters, and photovoltaic properties. The effects of end-donor modifications on the photovoltaic and electronic characteristics of the new molecules (M1-M4) are investigated. According to the results, the molecules have good optical properties, a small band gap, a perfect open-circuit voltage, and a good alignment energy level between the designated donor molecules and the acceptor phenyl-C61-butyric acid methyl ester (PCBM). These results suggest that further research in this area could enhance the efficacy of organic solar cells.

Effect of Zn2+ on emodin molecules studied by time-resolved fluorescence spectroscopy and quantum chemical calculations

Emodin is a natural drug for treating neurodegenerative diseases and plays a vital role in the mitigation of nerve damage. Metal ions can modify the drug properties of emodin, where Zn²⁺ can synergize with the emodin molecule and enhance the drug effect of emodin. Besides, complex changes can be observed in the fluorescence intensity and fluorescence lifetime of the emodin molecule as the concentration of Zn²⁺ increases. Herein, the synergistic effects of ligand structural in Zn(II)-Emodin complexes and the electronic effects of metal elements on the antioxidant properties of the complexes are discussed in detail based on UV-vis absorption spectroscopy, fluorescence spectroscopy, time-correlated single photon counting (TCSPC) technique and quantum chemical calculations at the B3LYP/6-31G(d) level. The experimental results confirm that Zn²⁺ can coordinate with the hydroxyl groups on the emodin to make the molecule structure more rigid, thus inhibiting the non-radiative processes such as high-frequency vibrations of the emodin molecule in solution. The suppression of non-radiative processes leads to an increase in the average fluorescence lifetime of the emodin molecule, and finally results in the enhanced fluorescence intensity. The chemical softness of Zn(II)-Emodin is then confirmed to be higher than that of emodin by Gaussian calculations, indicating its higher chemical reactivity and lower stability. The stronger electron donating ability of Zn(II)-Emodin compared to emodin may explain the higher antioxidant activity of Zn(II)-Emodin, which gives it a stronger pharmacological activity. The results of this study show that emodin can well complex with Zn²⁺ to remove excess Zn²⁺ in human body and the resulting complex has better antioxidant properties, which helps to understand the role of Zn²⁺ in drug-metal coordination and provides guidance for the design of new drugs.

DFT study of alkali and alkaline earth metal-doped benzocryptand with remarkable NLO properties

Strategies for designing remarkable nonlinear optical materials using excess electron compounds are well recognized in literature to enhance the applications of these compounds in nonlinear optics. In this study, density functional theory simulations are performed to study alkali and alkaline earth metal-doped benzocryptand using the B3LYP/6-31G+(d, p) level of theory. Vertical ionization energies (VIEs), reactivity parameters, interaction energies, and binding energies exposed the thermodynamic stability of these complexes. FMO analysis revealed that HOMO is located on alkali metals having polarized electrons, which are easy to excite. The doping strategy enhanced the charge transfer with low bandgap energy in the range of 0.68–2.23 eV, which is lower than that of the surface BC (5.50 eV). Also, the lower transition energies and higher oscillator strength indicate that these complexes exhibit excellent electronic and optical properties. Non-covalent interaction analysis suggested the presence of van der Waals interactions between dopants and surface. IR analysis provided information about the frequencies of stretching vibrations present in the complexes due to different bonds. UV-vis analysis revealed that all the newly designed excess electron complexes are transparent in the UV region and possessed maximum absorption in the visible and NIR region, ranging from 753.6 to 2150 nm, which is higher than the surface (244 nm). Thus, these complexes have a potential for high-performance NLO materials in the applications of optics. Natural bond orbital analysis (NBO), transition density matrix (TDM), electron density difference map (EDDM), and density of state (DOS) analyses were also performed to study the charge transfer properties. Moreover, these complexes possessed remarkable optoelectronic properties due to a significant increase in the isotropic linear polarizability (α_iso) in the range of 629.59–1423.23 au. Further, these systems demonstrated an extraordinary large total first hyperpolarizability (β_tl) in the range of 3695.55–910 706.43 au. The rationalization of hyperpolarizability by the two-level model reflected a noteworthy increase in β_tl because of low transition energies (ΔE) and high transition dipole moment (Δμ). Thus, our results showed that alkali and alkaline earth metal-doped BC might be a competitor for efficient nonlinear optical properties with practical applications in the area of optoelectronics.

Strategies for designing remarkable nonlinear optical materials using excess electron compounds are well recognized in literature to enhance the applications of these compounds in nonlinear optics.

Solvatochromism and estimation of ground and excited state dipole moments of 6-aminoquinoline

The spectral behaviour of 6AQ was investigated using fluorescence spectroscopy in several polar and non-polar solvents. Both the absorption and fluorescence spectra displayed solvatochromism. The Stokes shift increased significantly with increasing solvent polarity and signifies a more polar excited state with possible change in the excited state (ES) geometry. The involvement of π→π^∗ transition was observed. The ground state (GS) and excited state (ES) dipole moments were determined by the solvatochromic shift method using Bilot-Kawaski, Lippert-Mataga, Kawski-Chamma-Viallet, and Reichardt equations. The experimental value of GS dipole moment matches closely with the theoretical value computed using DFT/B3LYP/6-311G(d,p). The ES dipole moment is higher than the GS dipole moment. Besides, the solvatochromic study reveals that the ES of 6AQ is more polarized than the GS due to intramolecular charge transfer (ICT), possibly aided by a change in the geometry of the molecule in the ES. The influence of the non-specific and specific interactions in the photophysical properties of the titled molecule was analyzed using the Catalan scale. The study shows that 6AQ has reasonable band-gap energy and good CIE chromaticity coordinate in the blue region close to the national television standard committee system (NTSC) for the ideal blue CIE coordinate. Therefore, future research into 6AQ as a source of light-emitting diodes and fluorescent sensors may have potential applications in the field of optoelectronics.