Synthesis of 2,1,3-Benzoxadiazole Derivatives as New Fluorophores-Combined Experimental, Optical, Electro, and Theoretical Study

Recent Advances on the Antimicrobial Activities of Schiff Bases and their Metal Complexes: An Updated Overview

Schiff bases represent a valuable class of organic compounds, synthesized via condensation of primary amines with ketones or aldehydes. They are renowned for possessing innumerable applications in agricultural chemistry, organic synthesis, chemical and biological sensing, coating, polymer and resin industries, catalysis, coordination chemistry, and drug designing. Schiff bases contain imine or azomethine (-C=N-) functional groups which are important pharmacophores for the design and synthesis of lead bioactive compounds. In medicinal chemistry, Schiff bases have attracted immense attention due to their diverse biological activities. This review aims to encompass the recent developments on the antimicrobial activities of Schiff bases. The article summarizes the antibacterial, antifungal, antiviral, antimalarial, and antileishmanial activities of Schiff bases reported since 2011.

Synthetic approaches and applications of an underprivileged 1,2,5-oxadiazole moiety: A review

1,2,5-oxadiazole belongs to five-membered heterocyclic compounds with two nitrogen and one oxygen atom. In comparison with other heterocyclic moieties, 1,2,5-oxadiazoles moiety is considered as underprivileged as it attracted little attention of the researchers although lot of scopes and possible applications in medicinal, material and agriculture science. 1,2,5-oxadiazole and its derivatives have been reported as good pharmacophores as carbonic anhydrase inhibitors, antibacterial, vasodilating agents, antimalarial, anticancer, etc. In the presented manuscript, we reviewed granted patents and different synthetic strategies which have been reported for the synthesis of 1,2,5-oxadiazoles such as cycloaddition, dimerization, cyclodehydration, condensation, thermolysis, nitration, oxidation and ring-conversion. These synthetic methods have also been analysed for their merits and demerits. The manuscript also highlighted various applications of 1,2,5-oxadiazole and its derivatives. We hope that researchers across the scientific streams will be benefitted from the presented review articles for designing their work related to 1,2,5-oxadiazoles.

Enlightening the Path to Protein Engineering: Chemoselective Turn-On Probes for High-Throughput Screening of Enzymatic Activity

Many successful stories in enzyme engineering are based on the creation of randomized diversity in large mutant libraries, containing millions to billions of enzyme variants. Methods that enabled their evaluation with high throughput are dominated by spectroscopic techniques due to their high speed and sensitivity. A large proportion of studies relies on fluorogenic substrates that mimic the chemical properties of the target or coupled enzymatic assays with an optical read-out that assesses the desired catalytic efficiency indirectly. The most reliable hits, however, are achieved by screening for conversions of the starting material to the desired product. For this purpose, functional group assays offer a general approach to achieve a fast, optical read-out. They use the chemoselectivity, differences in electronic and steric properties of various functional groups, to reduce the number of false-positive results and the analytical noise stemming from enzymatic background activities. This review summarizes the developments and use of functional group probes for chemoselective derivatizations, with a clear focus on screening for enzymatic activity in protein engineering.

Antimicrobial and Antibiofilm Activities of 4,5-Dihydro-1H-pyrazole-1-carboximidamide Hydrochloride against Salmonella spp

In the present study, the antimicrobial and antibiofilm activities of two 4,5-dihydro-1H-pyrazole-1-carboximidamide hydrochloride, (trifluoromethyl) phenyl-substituted (compound 1) and bromophenyl-substituted (compound 2), were evaluated against four Salmonella spp. serotypes through broth microdilution and biofilm-forming activity. Further, the cytotoxicity of the compounds was evaluated by cell viability assays using cultures of HeLa and Vero cell lines, and the mutagenic potential was assessed by the Ames test. In the broth microdilution test, compound 1 inhibited 90% of the strains tested at the minimum inhibitory concentration of 62.5 μg mL−1. Furthermore, both compounds prevented biofilm formation, with a reduction of up to 5.2 log10. HeLa and Vero cells exhibited 100% viability in the presence of compound 1. In contrast, low cell viability was observed in the presence of 15 µg mL−1 of compound 2. Furthermore, no mutagenic potential was detected at any of the tested concentrations of compound 1.

Simple 3,6-disubstituted Carbazoles as Potential Hole Transport Materials: Photophysical, Electrochemical and Theoretical Studies

Developing effective and low-cost organic hole-transporting materials (HTMs) is crucial for the construction of high-performance perovskite solar cells (PSCs) and to promote their production in commercial ventures. In this context, we herein report the molecular design, synthesis and characterization of two novel D-A-D-A-D architectured 9-(2-ethylhexyl)-9H-carbazoles, connecting the mono/dimethoxyphenyl substituted cyanovinylene sidearms symmetrically at 3^rd and 6^th positions of the carbazole heterocycle (CZ_1-2 ), as potential hole-transporting materials (HTMs). The current work highlights their structural, photophysical, thermal, electrochemical and theoretical investigations, including their structure-property correlation studies. Evidently, the optical studies showcased their excellent fluorescence ability due to their push-pull natured structure with extended π-conjugation. Further, in-depth solvatochromic studies demonstrated their intramolecular charge-transfer (ICT)-dominated optoelectronic behavior, supported by various correlation studies. Also, the optical results revealed that CZ₁  and CZ₂ display λ_abs  and λ_emi  in the order of 410-430 nm and 530-560 nm, respectively, with a bandgap in the range of 2.5-2.6 eV. Finally, their quantum chemical simulations have provided an insight into the predictions of their structural, molecular, electronic and optical parameters. Conclusively, the study furnishes a deeper understanding of the intricacies involved in the structural modification of carbazole-based HTMs for achieving better performance.

Borophosphate glass as an active media for CuO nanoparticle growth: an efficient catalyst for selenylation of oxadiazoles and application in redox reactions

Herein, we report the preparation of CuO@ borophosphate nanoparticles (CuOnano@glass) and their wide catalytic applications. The glass annealing, under a controlled atmosphere, enables the growth of copper nanoparticles on the glass surface (not within) by an uncommon bottom-up process. Following the thermal annealing of metallic nanoparticles under air atmosphere, supported copper oxide nanoparticles CuONPs on the glass surface can be obtained. The approach enables the glass matrix to be explored as a precursor and a route for the synthesis of supported copper-based nanoparticles in a solvent-free process without immobilization steps or stabilizing agents. In order to demonstrate the wide synthetic utility of this CuONPs glass-based catalyst, one-pot three-component domino reactions were performed under an air atmosphere, affording the desired selenylated oxadiazoles in good to excellent yields. We also extended the application of these new materials as a glass-based catalyst in the phenol hydroxylation and the reduction of 4-nitrophenol.

Selenylated-oxadiazoles as promising DNA intercalators: Synthesis, electronic structure, DNA interaction and cleavage

A series of selenylated-oxadiazoles were prepared and their interaction with DNA was investigated. The photophysical studies showed that all the selenylated compounds presented absorption between 270 and 329 nm, assigned to combined n→π* and π→π* transitions, and an intense blue emission (325-380 nm) with quantum yield in the range of Φ _F = 0.1-0.4. DFT and TD-DFT calculations were also performed to study the likely geometry and the excited state of these compounds. Electrochemical studies revealed the ionization potential energies (-5.13 to -6.01 eV) and electron affinity energies (-2.25 to -2.83 eV), depending directly on the electronic effect (electron-donating or electron-withdrawing) of the substituent attached to the product. Finally, the UV-Vis DNA interaction experiments indicated that the compounds can interact with the DNA molecule due to intercalation, except for 3g (which interacted via electrostatic interaction). Plasmid cleavage assay presented positive results only for 3f that presented the strongest interaction results. These results made the tested selenylated-oxadiazoles as suitable structures for the development of drugs and the design of structurally-related therapeutics.