Synthesis, Structure Elucidation and Antimicrobial Evaluation of some Novel Triazolo[3,4-b]thiadiazole and Triazolo[3,4-b]thiadiazine Derivatives

Fused triazoles derivatives have been prepared from the reaction of the starting material 4 with some electrophilicreagents. The structures of all new compounds have beenestablished on the basis of elemental analysis and spectroscopicdata. All the synthesized compounds have been screened for their antibacterial activity. 1,2,4-Triazole derivatives 4, 14 and 15 exhibited a good antibacterial activity compared with the standard antibiotic Gentamycin. The tautomeric equilibria of the compounds 4 and 15 thione and thiol form were studied by quantum chemical calculations semi-empirical (AM1, MNDO and PM3) and ab initio level (RHF/3-21G* and RHF/6-31G*) in the gas phase.

Synthesis, characterization and density functional theory study of low cost hydrazone sensitizers

The 2-{4-[2-benzylidenehydrazino]phenyl}ethylene-1,1,2-tricarbonitrile (System 1), 2-{4-[2-(1-naphthylmethylene)hydrazino]phenyl}ethylene-1,1,2-tricarbonitrile (System 2) and 2-{4-[2-(9-anthrylmethylene)- hydrazino]phenyl}ethylene-1,1,2-tricarbonitrile (System 3) were synthesized by direct tricyanovinylation of hydrazones. The bathochromic shift in absorption spectra has been observed by increasing the solvent polarity. The FTIR spectra of these new dyes exhibited three important absorption bands. The first band centered near 3260 cm-1 in System 1 while 3208 cm-1 and 3211 cm-1 in System 2 and System 3 for the nNH absorption, respectively. The second band is a sharp absorption band in the region of 2212-2209 cm-1, which was attributed to the cyano group absorption. The third is an absorption band in the region of 1611-1603 cm-1 ascribed for the C=N. Density functional theory (DFT) calculation of relative energies, relative enthalpies and free energies shows that E isomers are the most stable except System 3 in which the most stable is Z isomers. The conformational energy profile shows two maxima near (-90 and 90o) while three local minima observed at (-180, 0 and 180) for N1-N2-C1-C2 torsional angle. The highest occupied molecular orbitals (HOMOs) are localized on the whole molecules while lowest unoccupied molecular orbitals (LUMOs) are distributed on the tricarbonitrile. KEY WORDS: Dye-sensitized solar cells, HOMO, LUMO, Absorption, FTIR spectra Bull. Chem. Soc. Ethiop. 2015, 29(1), 137-148DOI: http://dx.doi.org/10.4314/bcse.v29i1.1

Effect of stabilizer on optical band gap of ZnO and their performance in dye-sensitized solar cells

ABSTRACT. In dye-sensitized solar cells, transparent metal oxide working electrodes play a vital role in defining the power conversion efficiency. It was found that the size of nanoparticles influences the electrical, optical properties of these electrodes. Herein, we describe the synthesis of ZnO with zinc acetate dihydrate and different stabilizers (diethylamine and triethylamine) by using a modified solvothermal process. The obtained materials were characterized by XRD, SEM, EDX, TEM, HRTEM, UV-visible, FTIR, and Raman methods. The crystallite sizes for ZnO-1 and ZnO-2 samples were indexed as 39.0 and 40.5 nm for the highest peak intensity with diethylamine and triethylamine stabilizer, respectively. We examine the effect of stabilizers on the morphology, optical band gap, and photovoltaic performance of the prepared ZnO. We found that ZnO prepared using diethylamine stabilizer exhibiting significant efficiency of 1.45%, open-circuit voltage 0.454 V, short-circuit current density 2.128 mA/cm2, and 0.66 fill factor were achieved under 44 mW/cm2 illumination powers with dye-3.                 KEY WORDS: Dye-sensitized solar cells, ZnO, Band gap, Photovoltaic performance   Bull. Chem. Soc. Ethiop. 2022, 36(1), 209-222.                                                        DOI: https://dx.doi.org/10.4314/bcse.v36i1.17                                                     &nbsp

Antibacterial activities, DFT and QSAR studies of quinazolinone compounds

The quinazolinone compounds (1 and 2) in this work were examined for their in vitro antibacterial activities against gram-positive (Staphylococcus aureus) and gram-negative bacteria (Klebsiella pneumonia, Proteus bacilli and Shigella flexneri). Compared to the reference antibiotic chloramphenicol, these compounds showed high antibacterial activities against studied strains with inhibition zones observation. The ground state geometries have been optimized by using density functional theory (DFT) at B3LYP/6-31G* level of theory. The absorption spectra have been calculated by using time dependent density functional theory (TDDFT) with and without solvent. The effect of different functionals (B3LYP, MPW1PW91, and PBE1PBE) on the absorption wavelengths has been studied. The ionization potential (IP), electron affinity (EA), energy gap (Egap), electronegativity (χ), hardness (η), electrophilicity (ω), softness (S) and electrophilicity index (ωi) were computed and discussed. The nonlinear optical (NLO) properties vary by changing the theory (DFT to HF) or functional (B3LYP to CAM-B3LYP). The physicochemical parameters have been studied by quantitative structure–activity relationship (QSAR). The computed properties of investigated compounds have been compared with the Chloramphenicol as well as available experimental data.                                                                                              KEY WORDS: Antibacterial activity, Density Functional Theory, Time Dependent Density Functional Theory, Charge transfer, Quantitative structure–activity relationship Bull. Chem. Soc. Ethiop. 2016, 30(2), 307-316.DOI: http://dx.doi.org/10.4314/bcse.v30i2.15 

Radical scavenging activity of some natural tropolones by density functional theory

The ground state neutral geometries of some natural tropolones, i.e. stipitatonic acid (AF1), stipitalide (AF2), stipitaldehydic acid (AF3) and methyl stipitate (AF4) have been optimized by using Density Functional Theory (DFT) at B3LYP/6-31G*, B3LYP/6-31G**, B3LYP/6-31+G* and B3LYP/6-31+G** levels of theory. The excited state geometries of AF1-AF4 were optimized by adopting the Time Dependent Density Functional Theory (TDDFT) at the same levels of theory. The frequencies and cation species of AF1-AF4 were also computed at all the above mentioned levels of theory. We shed light on the electro-optical and molecular properties, e.g. energy gaps, highest occupied molecular orbitals, lowest unoccupied molecular orbitals, absorption wavelengths, electronegativity (χ), hardness (η), electrophilicity (ω), softness (S), electrophilicity index (ωi) and the radical scavenging activity (RSA). Hydrogen atom transfer (HAT) and one-electron transfer mechanisms have been discussed to shed light on the RSA. The smallest ionization potential and bond dissociation energy of AF4 are revealing that this compound would have more RSA than those of other counterparts

Design and fabrication of dioxyphenylcoumarin substituted cyclotriphosphazene compounds photodiodes

The present study introduces cyclotriphosphazene compounds substituted by dioxyphenylcoumarin as a photodiode application. Firstly, 7,8-dihydroxy-3-(3-methylphenyl)coumarin (1b) has been obtained by conventional as well as microwave assisted methods. Novel optoelectronic device characteristics for both mono and disubstituted dioxyphenylcoumarin bearing cyclotriphosphazene compounds (HCP-2 and HCP-4) have been synthesized from the reactions of cyclotriphosphazene containing dioxybiphenyl (HCP-1 and HCP-3) with compound 1b, respectively. The structures of compounds HCP 1–4 were identified by using elemental analysis, 1H, 13C-APT, 31P NMR and 2D HETCOR NMR and FT-IR spectroscopy methods. The Al/HCP-2/p-Si/Al and Al/HCP-4/-p-Si/Al photodiodes properties have been investigated from current-voltage (I−V) and capacitance-voltage (C−V) measurements. The electrical parameters of the prepared diodes such as ideality factor n and series resistance Rs were investigated in dark and at room temperature from (I−V) curve and Nord's method. As can be seen, the Al/HCP-2/p-Si/Al diode of high rectification ratio RR and with ideality factor greater than unity. The influence of light illuminations on the diode shows that the device can be used as photodiode with good efficiency. The barrier height ϕb and series resistance Rs have been calculated from the capacitance-voltage (C−V)and conductance-voltage (G−V) measurements under various applied frequencies from 10 kHz to 1 MHz. the high difference in the results of barrier height obtained from I-V and C-V calculations confirm the influence of series resistance and localized states on transport of charge carriers and the photodiode performance.TUBITAK-110T652 Fırat University, FÜBAP-FF.161

Computational Study on the Inhibitory Effect of Natural Compounds against the SARS-CoV-2 Proteins

COVID-19 is more virulent and challenging to human life. In India, the Ministry of AYUSH recommended some strategies through Siddha, homeopathy, and other methods to effectively manage COVID-19 (Guidelines for AYUSH Clinical Studies in COVID-19, 2020). Kabasura Kudineer and homeopathy medicines are in use for the prevention and treatment of COVID-19 infection; however, the mechanism of action is less explored. This study aims to understand the antagonist activity of natural compounds found in Kabasura Kudineer and homeopathy medicines against the SARS-CoV-2 using computational methods. Potential compounds were screened against NSP-12, NSP-13, NSP-14, NSP-15, main protease, and spike proteins. Structure-based virtual screening results shows that, out of 14,682 Kabasura Kudineer compounds, the 250395, 129677029, 44259583, 44259584, and 88583189 compounds and, out of 3,112 homeopathy compounds, the 3802778, 320361, 5315832, 14590080, and 74029795 compounds have good scoring function against the SARS-CoV-2 structural and nonstructural proteins. As a result of docking, homeopathy compounds have a docking score ranging from −5.636 to 13.631 kcal/mol, while Kabasura Kudineer compounds have a docking score varying from −8.290 to −13.759 kcal/mol. It has been found that the selected compounds bind well to the active site of SARS-CoV-2 proteins and form hydrogen bonds. The molecular dynamics simulation study shows that the selected compounds have maintained stable conformation in the simulation period and interact with the target. This study supports the antagonist activity of natural compounds from Kabasura Kudineer and homeopathy against SARS-CoV-2’s structural and nonstructural proteins.</p