Structural Properties and Nonlinear Optical Responses of Halogenated Compounds: A DFT Investigation on Molecular Modelling

Computational chemistry is used to evaluate structures of different compounds by using principles of theoretical and quantum chemistry integrated into useful computer programs. It is used to determine energies, dipole moments and thermodynamic properties of different compounds. The present work reports the computational study of six donor-acceptor dyes. The computational method CAM-B3LYP with 6-31G(d,p) was used in this research to determine the effect of halogens on non-linear optical compounds. HOMO-LUMO energy gaps, dipole polarizabilities, first hyperpolarizabilities, and absorption spectra of six studied compounds (dye 1: 4-(2-(4-fluorophenyl)ethynyl)benzenamine; dye 2: 4-(2-(4-chlorophenyl)ethynyl)benzenamine; dye 3: 4-(2-(4-bromophenyl)ethynyl)benzenamine; dye 4: 5-(2-(4-fluorophenyl)ethynyl)benzene-1,2,3-triamine; dye 5: 5-(2-(4-chlorophenyl)ethynyl)benzene-1,2,3-triamine; dye 6: 5-(2-(4-bromophenyl)ethynyl)benzene-1,2,3-triamine) with aniline and halo phenyl segments were computed by using density functional theory (DFT) and time-dependent density functional theory (TDDFT). Results indicate that all dyes showed wavelengths of maximum absorbance in the visible region. Small HOMO-LUMO energy gaps were observed in all investigated dyes. The present calculations on these dyes (1-6) offer an understanding of the direction of charge transfer (CT) and how NLO behavior can be explained. The aniline-to-halo phenyl CT, caused by the combination of the donor amino group and the acceptor halo group, could be a reason for NLO behavior of these sorts of compounds. These compounds exhibit significant molecular second-order NLO responses, especially dyes (6) and (5), with second-order polarizability determined to be approximately 4600 a.u

Computational Study on Non-linear Optical and Absorption Properties of Benzothiazole based Dyes: Tunable Electron-Withdrawing Strength and Reverse Polarity

Various organic dyes possessing characteristic D-π-A-A configuration have been designed in this article. The analysis of the relation between polarity of charge transfer and the unsymmetrical nature of the benzothiazole group has been studied. The absorption spectra, electronic characteristic properties and non-linear optical responses were simulated using a quantum chemical approach. The results have indicated that the systems show higher polarizability (α) and hyperpolarizability (β) with commonly used polarity in comparison to the reverse polarity. A red-shifted absorption spectra were observed with systems having common polarities. This study illustrates the rule to design non-linear optical material with low energy charge transfer excited states and high value of oscillation

Green synthesis of silver nanoparticles through reduction with Solanum xanthocarpum L. berry extract: characterization, antimicrobial and urease inhibitory activities against Helicobacter pylori

A green synthesis route for the production of silver nanoparticles using methanol extract from Solanum xanthocarpum berry (SXE) is reported in the present investigation. Silver nanoparticles (AgNps), having a surface plasmon resonance (SPR) band centered at 406 nm, were synthesized by reacting SXE (as capping as well as reducing agent) with AgNO3 during a 25 min process at 45 °C. The synthesized AgNps were characterized using UV–Visible spectrophotometry, powdered X-ray diffraction, and transmission electron microscopy (TEM). The results showed that the time of reaction, temperature and volume ratio of SXE to AgNO3 could accelerate the reduction rate of Ag+ and affect the AgNps size and shape. The nanoparticles were found to be about 10 nm in size, mono-dispersed in nature, and spherical in shape. In vitro anti-Helicobacter pylori activity of synthesized AgNps was tested against 34 clinical isolates and two reference strains of Helicobacter pylori by the agar dilution method and compared with AgNO3 and four standard drugs, namely amoxicillin (AMX), clarithromycin (CLA), metronidazole (MNZ) and tetracycline (TET), being used in anti-H. pylori therapy. Typical AgNps sample (S1) effectively inhibited the growth of H. pylori, indicating a stronger anti-H. pylori activity than that of AgNO3 or MNZ, being almost equally potent to TET and less potent than AMX and CLA. AgNps under study were found to be equally efficient against the antibiotic-resistant and antibiotic-susceptible strains of H. pylori. Besides, in the H. pylori urease inhibitory assay, S1 also exhibited a significant inhibition. Lineweaver-Burk plots revealed that the mechanism of inhibition was noncompetitive

First Theoretical Framework of Triphenylamine–Dicyanovinylene-Based Nonlinear Optical Dyes: Structural Modification of π‑Linkers

This work was inspired by a previous report [Janjua, M.R.S.A. Inorg. Chem. 2012, 51, 11306−11314] in which the nonlinear optical (NLO) response strikingly improved with double heteroaromatic rings. Herein, series of triphenylamine–dicyanovinylene based donor−π–acceptor dyes had been designed by structural tailoring of π-conjugated linkers and theoretical descriptions of their molecular NLO properties were reported. Density functional theory and time-dependent density functional theory calculations were performed on optimized geometries to elucidate the electronic structures, absorption spectra, and NLO properties and also to shed light on how structural modification influences the NLO properties. The simulated absorption spectra results indicate that all of the dyes showed the maximum absorbance wavelength in the visible region. The lowest unoccupied molecular orbital–highest occupied molecular orbital energy gaps of all of the dyes have been found smaller, which results in large NLO response. Calculation of natural bond orbital analysis reveals that electrons successfully migrated from donor to acceptor via π-conjugated linkers and a charge separation state was formed. High NLO response revealed that this class of metal free organic dyes possess eye-catching and remarkably large first hyperpolarizability values, especially D8 with highest ⟨α⟩ and β_tot computed to be 771.80 and 139 075.05 au, respectively. Our research presented a vital confirmation for controlling the kinds of π-conjugated linker that was a significant approach for the design of new appealing NLO compounds. This theoretical framework also highlighted the NLO properties of organic dyes that can be valuable for their uses in modern hi-tech applications

Compositional difference in antioxidant and antibacterial activity of all parts of the Carica papaya using different solvents

Background: Carica papaya is a well known medicinal plant used in the West and Asian countries to cope several diseases. Patients were advised to eat papaya fruit frequently during dengue fever epidemic in Pakistan by physicians. This study was conducted to establish Polyphenols, flavonoids and antioxidant potential profile of extracts of all major parts of the C. papaya with seven major solvents i.e. water, ethanol, methanol, n-butanol, dichloromethane, ethyl acetate, and n-hexane. Results: TPC, TFC, antioxidant and antibacterial potential were determined using different aqueous and organic solvents in addition to the determination of trace element in leaves, pulp and peel of C. papaya. Total soluble phenolics and flavonoids were found in promising quantity (≈66 mg GAE/g) especially in case of methanol and ethanol extracts. Antioxidant activity using DPPH free radical scavenging assay indicated leaves, bark, roots and pulp extracts showed >75.0 % scavenging potential while leaves and pulp showed 84.9 and 80.9 % inhibition of peroxidation, respectively. Reducing power assay showed leaves, pulp and roots extracts active to reduce Fe3+ to Fe2+ ions. The antibacterial study showed pulp extract is the best to cope infectious action of bacteria. Conclusion: This study was conducted to test the medicinal profile of all parts of C. papaya by extracting secondary metabolites with organic and aqueous solvents. Ethanol and methanol both were found to be the best solvents of choice to extract natural products to get maximum medicinal benefits and could be used to medicinal formulation against different infectious diseases