Showing papers in "Journal of Chemical Sciences in 2021"

Designing, spectroscopic characterization, biological screening and antioxidant activity of mononuclear transition metal complexes of bidentate Schiff base hydrazones

Abstract: In this article, a series of coordination complexes of Co(II), Ni(II), Cu(II) and Zn(II) metals were prepared by four novel Schiff base ligands (E)-N’-(4-(prop-2-yn-1-yloxy)benzylidene)benzohydrazide (HL1), (E)-4-chloro-N’-(4-(prop-2-yn-1-yloxy)benzylidene)benzohydrazide (HL2), (E)-N’-((2-(benzyloxy)naphthalen-1-yl)methylene)benzohydrazide (HL3), (E)-N’-((2-(benzyloxy)naphthalen-1-yl)methylene)-4-chlorobenzohydrazide (HL4) obtained by the condensation reaction of benzoic acid hydrazide/4-chloro benzoic acid hydrazide with oxy derivatives of 2-hydroxy-1-napthaldehyde/4-hydroxy benzaldehyde. The proposed structure of the complexes have been established by spectroscopic and analytical techniques like C, H, N and metal analysis, FT-IR, 1H and 13C NMR, mass, UV-Vis, EPR, fluorescence, molar conductance, magnetic susceptibility and TGA which concluded that Schiff bases act as bidentate NO donor ligands coordinating through nitrogen atom of azomethine linkage and uninegative oxygen atom of carbonyl group in enolic form and resulting in complexes of the type [M(L1–4)·(CH3COO)·3H2O] in 1:1 molar ratio. The synthesized compounds were screened for their in vitro antimicrobial activities against two gram +ve bacteria i.e. S. aureus and S. gordonii; two gram -ve bacteria i.e. E. coli and P. aeruginosa and two fungal strains i.e. A. niger and C. albicans and found that metal chelates were more noxious than their parent Schiff bases. The copper(II) complex 19 was found to be the highest noxious antimicrobial active compound. The compounds were also assessed for their antioxidant activity and found that the complexes are more potent and show excellent efficiency in decolorizing the DPPH purple colored solution than their free ligands. The complexes 6, 7, 10, 11, 14, 15, 18, 19 were found to be excellent antioxidants and copper(II) complexes were the most potent antioxidant compounds with lowest IC50 values (2.04–2.56 µM)) among all the tested compounds. Total 20 compounds of Schiff bases transition metal complexes were synthesized and characterized. The copper complex (19) was found to be highest antimicrobial against Streptococcus gordonii, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger, Candida albicans. The copper(II) complex (11) exhibits outstanding and highest antioxidant activity (IC50 = 2.04 µM).

Greener route for intensified synthesis of Tricaprylin using Amberlyst-15

Abstract: Tricaprylin is a triglyceride of caprylic acid. Tricaprylin is a medium-chain triglyceride. Medium-chain triglycerides are considered as a nutraceutical and have a wide range of application in health foods and nutraceutical industry. In the present study, the synthesis of tricaprylin is investigated using environment-friendly approach i.e., with the application of microwave and heterogeneous catalyst dry acidic Amberlyst-15. The result of various reaction conditions like the molar ratio of reactant, reaction temperature, and catalyst amberlyst loading on the conversion of caprylic acid into tricaprylin is studied. The microwave synthesis is compared with traditional or normal synthesis of tricaprylin. In the present study, it is found that microwave synthesis resulted in a high degree of conversion in less time as compared to conventional synthesis. Conversion of 99.5% is observed in 16 min of reaction between medium-chain fatty acid (C8) and glycerol under optimized reaction parameters of the molar ratio of caprylic acid:glycerol as 3:5 with reaction temperature 800 °C and catalyst loading of 4% (by weight of fatty acid).

Modification of UiO-66 for removal of uranyl ion from aqueous solution by immobilization of tributyl phosphate

Abstract: Two modified metal–organic frameworks (MOFs), were synthesized by immobilization of tributyl phosphate (TBP) on the UiO-66 and vacated UiO-66 (UiO-66-vac), and investigated for the removal of uranyl ion from aqueous solution Characterization of MOFs was carried out by various techniques such as X-ray diffraction (XRD), Fourier Transform Infra-Red Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), and BET surface area FTIR confirmed efficient immobilizing of the TBP on the MOFs Sorption results show that modification of MOFs enhances uranyl sorption capacity Kinetics of sorption was investigated by pseudo-first-order and pseudo-second-order models It is shown that at pH 5, sorption equilibrium for all MOFs, reaches a little more than 8 h Equilibrium studies were done by Langmuir and Freundlich models and the sorption capacity of UiO-66, UiO-66-vac, UiO-66-TBP and UiO-66-vac-TBP obtained 1771, 1938, 2019 and 2035 mg g−1, respectively Moreover, TBP immobilized MOFs, show more selectivity than UiO-66 and UiO-66-vac towards uranyl in wastewater containing cationic and anionic interferences The effect of the contact time and pH for maximum removal of uranyl was studied Two modified metal–organic frameworks (MOFs), were synthesized by immobilization of tributyl phosphate (TBP) on the UiO-66 and vacated UiO-66 (UiO-66-vac), and investigated for the removal of uranyl ion from aqueous solution

Synergistic degradation of tetracycline by BiOBr microspheres combined with peroxydisulfate under visible LED light irradiation

Abstract: A solvothermal method was employed to prepare BiOBr microspheres, which firstly combined with peroxydisulfate (PDS, S2O82−) to synergistically remove tetracycline (TC) from water under visible LED (Vis-LED) light illumination. About 80.3% of TC (20 mg·L−1) was degraded by BiOBr/PDS/Vis-LED system within 90 min, whereas 28.0%, 28.8% and 65.1% of TC was removed by PDS/Vis-LED, BiOBr/PDS and BiOBr/Vis-LED system, respectively. The degradation of TC in BiOBr/PDS/Vis-LED system obeyed the pseudo-second-order kinetic with a reaction rate constant at 3.6 × 10−3 L·mg−1·min−1. The influence of some key parameters (PDS dose, initial solution pH, reaction temperature and inorganic anions) on TC removal in BiOBr/PDS/Vis-LED system was studied. PDS was activated by photo-induced e− to produce SO4·−, and PDS also assisted O2 and e− to generate O2·−. The trapping experiments and ESR analysis indicated that SO4·−, ·OH, h+ and O2·− contributed to TC degradation. According to the detected intermediates, the possible degradation pathways of TC were established. Furthermore, the catalytic performance of BiOBr/PDS/Vis-LED system for TC degradation in the actual water matrix was studied. The visible LED (Vis-LED) light-driven photocatalytic performance of BiOBr microspheres for tetracycline (TC) degradation can be enhanced in the presence of peroxydisulfate (PDS) because adding PDS into BiOBr/Vis-LED system inhibits the recombination of photo-induced electrons and holes, with SO4·− generated at the same time. The degradation of TC in BiOBr/PDS/Vis-LED system obeyed the pseudo-second-order kinetic, and SO4·−, ·OH, h+ and O2·− all contributed to TC degradation. The possible degradation pathways of TC were proposed and the catalytic performance of BiOBr/PDS/Vis-LED system for TC removal in actual water matrix was also investigated.

Heteroatom-bridged pillar[4]quinone: evolutionary active cathode material for lithium-ion battery using density functional theory

Abstract: Quinone-based macrocyclic compounds have been proposed as promising electrode materials for rechargeable lithium-ion batteries (LIBs). To improve the electrochemical performance, in this paper, two heteroatom-bridged pillar[4]quinones (namely, oxa- and thia-pillar[4]quinones) are presented as active cathode materials for LIBs. The geometry structures, electronic structural properties, and electrochemical properties of these new species are calculated by Density Functional Theory (DFT) at the M06-2X/6-31G(d,p) level of theory. Two heteroatom-bridged pillar[4]quinones possess higher theoretical specific capacity (659 mA h g−1 and 582 mA h g−1 for oxa- and thia- pillar[4]quinones, respectively) than that of parental pillar[4]quinone (446 mA h g−1). The electrochemical performances of oxa- and thia-pillar[4]quinones are predicted theoretically to be superior to those of pillar[4]quinone as cathode material for LIBs. Compared with oxa-pillar[4]quinone, thia-pillar[4]quinone is predicted to be slightly more suitable as cathode electrode material. These results may provide fresh ideas and guidelines for enhancing the performance of quinones organic electrode materials for LIBs. Two heteroatom-bridged pillar[4]quinones, Oxapillar[4]quinone and Thiapillar[4]quinone, are proposed as the electrode active molecules. The lithium storage mechanisms and electrochemical properties are investigated by using DFT calculations. The results show that the heteroatom-bridged pillar[4]quinones are predicted theoretically to exihibit a better electrode material performance than the parent pillar[4]quinone.

Synthesis of some novel piperidine fused 5-thioxo-1H-1,2,4-triazoles as potential antimicrobial and antitubercular agents

Abstract: A novel series of analogues based on 5-(1-(4-chloro-3-methoxyphenyl)piperidin-4-yl)-4-phenyl-2H-1,2,4-triazole-3(4H)-thione core have been synthesized and their potential as antibacterial, antifungal and antitubercular agents was examined. The structure-activity relationship (SAR) studies of these derivatives 5 (a–k) clearly indicate the vital role of lipophilicity as a major factor in enhancing the biological activity of these compounds. Among the compounds screened, 5a, 5c, 5d, 5j and 5k displayed significant activity against Mycobacterium tuberculosis H37Rv strain.

Visible light-induced catalytic abatement of 4-nitrophenol and Rhodamine B using ZnO/g-C3N4 catalyst

Abstract: In this study, pure ZnO and g-C3N4 were synthesized using coprecipitation and simple calcination methods, respectively. Further, ZnO is impregnated on a g-C3N4 surface with 10, 20 & 30 weight percentages, respectively. Besides, these materials are characterized by various physicochemical techniques such as PXRD, UV-Vis-DRS, TEM, PL, and FT-IR, etc. Vitally, as-prepared materials, catalytic activity was tested for removal of Rhodamine B and 4-nitrophenol from the wastewater under visible light irradiation. Among all these catalysts, 20 wt% ZnO/g-C3N4 showed better activity and showed 67% and 75% mineralization. The graphical abstract simply represents the proposed mechanism for photocatalytic removal of 4-nitrophenol and Rhodamine B with ZnO/g-C3N4 composite. ZnO was a hexagonal plate type structure and g-C3N4 shows a sheet-type structure.

A perspective on the nature of cation-π interactions

Abstract: Recent years have witnessed a remarkable surge in the study of noncovalent interactions and their role in diverse areas of chemistry, biology, material science and allied fields. Among all, hydrogen bonding is quite extensively studied. Several other noncovalent interactions continue to attract wide attention. Notably, cation-π interactions play a crucial role in the function of several binding sites, reaction mechanisms, self-assemblies, catalytic mechanisms, adhesion and cohesion properties in many biological and chemical systems. The current review focuses on the character of cation-π interactions, its range and its occurrence from a conceptual point of view. The range and nature of cation-π interactions depend on the type of π-system and cation involved, besides solvent and environment. The size and polarizability of the π-systems and the effective nuclear charge on cation and its multiplicity and spin dictate the structural and energetic aspects of cation-π interaction. Further, factors affecting the modulation of strength and nature are brought out in the review. The interplay between the cation-π interaction and the other noncovalent interactions, solvent and counter-ion effects are analysed, and the cooperativity of these forces in organizing supramolecular architectures are discussed. How strong is cation-π interaction depends on various factors: It may be weak, medium or strong depending on the nature of cation, π system and environment. The strength of the interaction was shown to alternate a few orders of magnitude depending on the environment.

Highly active zinc oxide-supported lithium oxide catalyst for solvent-free Knoevenagel condensation

Abstract: Li2O/ZnO catalyst was prepared by wet impregnation method and characterized by XRD, SEM, EDX, FTIR, BET surface area and UV-Vis diffuse reflectance spectroscopy. This study revealed a decrease in average particle size and change in the shape of the particles when Li2O was supported on ZnO. The activity of ZnO-supported lithium oxide catalyst was tested for Knoevenagel condensation of a variety of aromatic aldehydes with malononitrile and ethyl cyanoacetate at room temperature under solvent-free condition. The reaction was completed in a very short time with yields above 90% and the catalyst presented excellent reusability without any loss in the activity. Novel lithium oxide supported on zinc oxide catalyst was synthesized and analysed using several techniques. Lithium doping decreases the particle size, and band gap energy and increases the surface area and basic properties of the catalyst. The olefin derivatives were obtained in a very short reaction time under the solvent free condition at room temperature in a green protocol.

Temperature and Ph-sensıtıve Super absorbent Polymers based on Modıfıed Maleıc Anhydrıde

Abstract: Maleic anhydride was modified with 1-decanol at two different ratios to obtain derivatives named MD-75 (75% modified) and MD-100 (100% modified). By using these derivatives and acrylamide (AAm), many hydrogels with different AAm/MD ratios were synthesized. Ammonium persulphate (APS), N,N,N′,N′-tetramethyl ethylenediamine (TMEDA) and N,N′-methylene bisacrylamide (MBAAm) were used as initiator, catalyts and crosslinker agent respectively in the synthesis reaction. The modification reactions were clarified by FTIR and 1H-NMR methods. Swelling behaviours, swelling capacities and effect of temperature, pH of the swelling medium and hydrogel composition on these parameters were studied. The swelling capacity of the hydrogels increased up to 82700% with decreasing the AAm/MD ratio. Temperature and pH of the swelling medium and the composition of the hydrogels were found to have a strong effect on the swelling behaviour and the swelling capacity of the hydrogels. The gels showed low swelling capacity with single-step swelling behaviour at low temperatures (T≤50 °C) and high swelling capacity with two-step swelling behaviour at higher temperatures. The swelling and diffusion kinetics of the hydrogels were also determined. All of the synthesized hydrogels showed uniform diffusion type at low temperatures while two types of diffusion observed at high temperatures. Hydrogels of modified maleic anhydride were prepared by chemical cross-linking. Hydrogels showed excellent swelling capacity up to 82,700%. Temperature and pH have a strong effect on the swelling capacity of the hydrogels. Hydrogels showed two-step swelling behaviour.

Metal-Organic Framework and Carbon Black supported MOFs as dynamic electrocatalyst for oxygen reduction reaction in an alkaline electrolyte

Abstract: The Pt-based expensive catalysts and sluggish kinetics at cathode in oxygen reduction reaction (ORR) hinder the rapid commercialization of fuel cells. The quest for cheap, non-noble metal catalysts to replace Pt-based catalysts has thus become a critical issue in the field of fuel cells. The carbon black (CB) and CB supported catalyst have been explored with the ultimate goal of finding a substitute for Pt-based catalysts in fuel cells. In the present work, we synthesized Zn-based MOF (1), 1 selectivity gives H2O2 followed by two-electron pathways. However, sample 1 modification might be needed to enhance its selectivity for the generation of H2O. Two composites of MOFs with carbon black and 1 were prepared to increase the H2O yield, called 1⊃CB and 1⊃SCB. The electrochemical generation of H2O2 was analyzed by the rotating ring disk electrode (RRDE) using catalyst 1. Following the addition of CB, H2O2 yields decreased from above 93% (1) to 59% and 75% for 1⊃CB and 1⊃SCB, respectively. CB modified catalysts moved towards four-electron pathways due to the conductive nature of CB. Electrochemical Impedance Spectroscopy (EIS) has also been performed to study in detail the conductivity effect of CB and kinetic behavior of ORR in alkaline electrolyte. This research opens up a new path for ORR to advance non-precious metal catalysts based on MOFs. Synopsis: This paper describes how we synthesized carbon Black (CB) supported MOF: Zn-based MOF (1), 1 selectivity gives H2O2 (two-electron pathways). Two composites of MOFs (1⊃CB and 1⊃SCB) were prepared to increase the H2O yield. After addition of CB, H2O2 yields decreased from above 93% (1) to 75% (1⊃SCB) and 59% (1⊃CB).

Cyclodimerization of norbornadiene (NBD) into high energy-density fuel pentacyclotetradecane (PCTD) over mesoporous silica supported Co–Ni nanocatalyst

Abstract: The present study focuses on the synthesis of high energy-density fuel pentacyclotetradecane (PCTD) through cyclodimerization followed by hydrogenolysis of norbornadiene (NBD) over mesoporous silica-supported Co–Ni-based nanocatalyst. Catalytic materials are synthesized by incipient wetness impregnation method using Al-MCM-41, MCM-48 and γ-alumina as supporting materials for Co–Ni metals. The textural properties of the catalyst have been investigated through XRD, TEM and N2 physisorption, and the parameters concerning the reactivity of the catalyst optimized. The reaction was performed in a single pot (pressure reactor), and the structure of the product was elucidated by using FTIR and NMR techniques. The optimum reaction parameters (catalyst, temperature, and pressure) were developed to produce a yield of ≥ 85%. The physicochemical properties such as calorific value (10754 cal./g), density (1.08 g/cc), etc. were evaluated, and these can be utilized for ramjet application. Dimerization of NBD into a high energy-density pentacyclotetradecane fuel over mesoporous aluminosilicate supported Co–Ni nanocatalyst.

3-Pyrrolyl BODIPY Based Selective Cu2+ Ion “Off-On” Fluorescent Sensor

Abstract: 3-Pyrrolyl BODIPY-Schiff base conjugate was synthesized by treating α-formyl 3-pyrrolyl BODIPY with o-hydroxy aniline in ethanol at reflux followed by recrystallization. The conjugate was thoroughly characterized by HR-MS, 1D & 2D NMR and X-ray crystallography. The X-ray analysis revealed that the BODIPY core was in planar arrangement, with the central boron atom coordinated with two pyrrole nitrogens of dipyrrin moieties and two axial fluoride ions in a tetrahedral geometry. The 3-pyrrolyl BODIPY-Schiff base conjugate exhibited a strong absorption band at 616 nm and broad weak fluorescence band at 660 nm. The absorption and fluorescence titration studies with various metal ions revealed that 3-pyrrolyl BODIPY can act as colorimetric optical sensor and specific “off-on” fluorescent sensor for Cu2+ ion. SYNOPSIS: 3-Pyrrolyl BODIPY-Schiff base conjugate was synthesized starting from α-formyl 3-pyrrolyl BODIPY. The conjugate was thoroughly characterized by HR-MS, NMR and X-ray crystallography. The absorption and fluorescence titration studies with various metal ions revealed that 3-pyrrolyl BODIPY can act as specific “off-on” fluorescent sensor for Cu2+ ion.

Rational design, preparation and characterization of a ternary non-ionic room-temperature deep eutectic solvent derived from urea, acetamide, and sorbitol

Abstract: Deep eutectic solvents (DESs) have emerged as a new kind of solvent and an excellent alternative to ionic liquids, thanks to its simplicity in preparing and availability of a large number of potential constituents to tune the properties. However, most of the reported DESs are ionic, and to the best of our knowledge, only a few non-ionic DESs are available, which are liquid at room temperature.

Nitrogen-rich compounds: s-triazine and tri-s-triazine derivatives as high energy materials

Abstract: This article describes the syntheses, characterization, and energetic properties of 4, 6-diazido-N, N-dimethyl-1, 3, 5-triazin-2-amine and 2, 4, 6-tris (5-(3, 5-dinitrophenyl)-1H-tetrazol-1-yl)-1, 3, 5-triazine. Also, this paper emphasizes the insensitive and thermally stable energetic molecules like melem, melem-ammonium perchlorate mixture, and hydrazinium cyamelurate. All these compounds possess good energetic properties viz., the heat of formation and heat of combustion. Synthesis and characterizations and energetic properties of 4, 6-diazido-N, N-dimethyl-1, 3, 5-triazin-2-amine (3); 2, 4, 6-tris (5-(3, 5-dinitrophenyl)-1H-tetrazol-1-yl)-1, 3, 5-triazine (4) and hydrazinium cyamelurate (10) are described. The thermal stabilities, energetic properties and sensitivity parameters are compared with standard high-energy materials. (i) Syntheses and characterization of 4, 6-diazido-N, N-dimethyl-1, 3, 5-triazin-2-amine (3); 2, 4, 6-tris (5-(3, 5-dinitrophenyl)-1H-tetrazol-1-yl)-1, 3, 5-triazine (4) and hydrazinium cyamelurate (10) are described. (ii) Experimental energetic properties and sensitivity parameters of these compounds were discussed.

Activated Mont K10-Carbon supported Fe2O3: A versatile catalyst for hydration of nitriles to amides and reduction of nitro compounds to amines in aqueous media

Abstract: The iron oxide was successfully supported on activated clay/carbon through an experimentally viable protocol for both hydrations of nitrile to amide and reduction of nitro compounds to amines. The as-prepared catalyst has been extensively characterised by XPS, SEM-EDX, TEM, TGA, BET surface area measurements and powdered X-ray diffraction (PXRD). A wide variety of substrates could be converted to the desired products with good to excellent yields by using water as a green solvent for both the reactions. The catalyst was recyclable and reusable up to six consecutive cycles without compromising its catalytic proficiency. Activated Mont K10 carbon-supported Fe2O3 is a very efficient and versatile heterogeneous catalytic system for hydration of nitriles to amides and reduction of nitro compounds to amines and can be reused up to six consecutive cycles without significant loss in catalytic activity.

Developing a highly potent anthelmintic: study of catalytic application of l-proline derived aminothiourea in rapid synthesis of biscoumarins and their in vitro anthelmintic essay

Abstract: Due to serious side effects of benzimidazoles such as apoptosis and mitotic arrest, development of alternative anthelmintic drugs with comparable efficacy to target the acetylcholine receptors of parasites is considered very important to control this parasitic disease. Here we have developed an excellent method for synthesis of biscoumarins by employing a mild and efficient proline derived bifunctional thiourea catalyst bearing pyrrolidine and thiourea catalytic sites and tested their anthelmintic activity against helminth parasites Raillietina echinobothrida and Syphacia obvelata. The compounds 2a, 2j, 2k and 2o demonstrated much stronger anthelmintic activity against Raillietina echinobothrida in comparison to the standard drug, Praziquantel. Molecular docking simulations of the optimized compounds with β-tubulin showed excellent binding interactions with several amino acid residues of the active site and the docking scores with β-tubulin were found to be comparable to the in vitro anthelmintic activity. A series of biscoumarins were synthesized and they showed excellent anthelmintic properties in comparison to conventional benzimidazoles.

An unsymmetrical Schiff-base derived recyclable Pd-catalyst for Suzuki–Miyaura and Sonogashira reactions in aqueous media

Abstract: A water-soluble palladium (II) complex containing an unsymmetrical Schiff-base ligand was synthesized and applied as catalyst Suzuki–Miyaura and Sonogashira cross-coupling reactions in aqueous media. Notably, moderate to excellent yields of biaryls were obtained in Suzuki reaction with usually less reactive aryl and heteroaryl chlorides under relatively mild condition. Moderate-to-high yields of aryl-alkynes were also obtained in Sonogashira reactions using aryl bromides. Apart from hydrophilic nature, the accomplishment of reactions in water, high recyclability, broad functional group tolerance, etc., are other advantages of the system.

Kinetic investigation of oxidation of alkanolamine by Cerium(IV) in acidic medium: catalytic effect of Mn(II)

Abstract: The decomposition kinetics of ethanolamine in acid medium using Ce(IV) as oxidant and Mn(II) as a catalyst has been reported. Michaelis–Menten type of kinetic pattern is suggested based on the nature of rate dependence on substrate concentration. First-order dependence of rate on oxidant was observed up to more than three half-lives. The rate constant decreased with an increase in acid concentration and the negative slope of Zucker–Hammett plot demonstrates inverse dependence of rate on the acid concentration. Ce(OH)3+ is considered as the most active species of Cerium in the reaction medium based on the kinetic observations. The rate increased with the catalyst concentration although the order is fractional. The products formed have not shown any effect on the progress of the reaction. From the temperature dependence studies, activation parameters for the oxidation reaction are evaluated and the entropy of activation was found to be negative. Based on all kinetic findings and presuming a complex species formation between the substrate, catalyst and the oxidant suitable mechanism has been proposed. The micro-rate constants involved in the proposed reaction mechanism has also been determined.

One-pot three-component condensation for the synthesis of 2,4,6-triarylpyridines and evaluation of their antimicrobial activity

Abstract: A new series of 2,4,6-triarylpyridines are synthesised through one-pot three-component condensation of triazole pyrazolyl aldehydes and acetophenones with ammonium acetate in moderate to good yields The structures of the synthesised compounds are confirmed by spectral methods viz IR, 1H NMR, 13C NMR and mass spectral analysis All these scaffolds are evaluated for their in vitro antimicrobial activity and found to exhibit promising antimicrobial potency Synopsis: A library of new 2,4,6-triarylpyridine derivatives were synthesised through one-pot three-component condensation of triazole pyrazolyl aldehydes and acetophenones with ammonium acetate in good yields The synthesised compounds were screened for their in vitro antimicrobial activity and exhibited moderate to good activity against various bacterial and fungal strains

Copper nanoparticles (CuNPs) catalyzed chemoselective reduction of nitroarenes in aqueous medium

Abstract: A procedure for practical synthesis of CuNPs from CuSO4·5H2O is established, under appropriate reaction conditions, using rice (Oryza sativa) as an economic source of reducing as well as a stabilizing agent. Optical and microscopic techniques are employed for the characterization of the synthesized CuNPs and the sizes of the particles were found to be in the range of 8 ± 2 nm. The nanoparticles are used as a catalyst for chemoselective reduction of aromatic nitro compounds to corresponding amines under ambient conditions and water as a reaction medium. CuNPs are synthesized using hydrolysed rice and used as catalyst for chemoselective reduction of nitroarenes to their corresponding amines in water.

Mixed oxides derived from layered double hydroxides of Ni and Co as photocatalysts for desulfurization of dibenzothiophene

Abstract: The synthesis of cobalt–nickel mixed oxides with different ratios of Ni/Co was carried out by co-precipitation method and used as a photocatalyst in the removal of dibenzothiophene (DBT) from a gasoline model under visible light. The structure of the synthesized samples was analyzed by the XRD, FTIR, BET and EDX spectrum. Also, the morphology of the mixed oxides was investigated with SEM images. It was found that the particle size is in the range of 15–30 nm, and the shape of the particles was almost spherical and distinctly separate. The mixed oxides exhibited promising photocatalytic activity to remove dibenzothiophene under visible light. The process was optimized by the one-factor at a time method. The effects of different factors such as the type of photocatalyst, dibenzothiophene concentration, temperature and time on the dibenzothiophene removal process were investigated and the optimal conditions resulted in the DBT concentration of 150 ppm catalyzed by 0.2 Co–Ni (1:1) photocatalyst at 50 °C for 3 h. The results indicated that DBT was degraded to SO2 gas and Biphenyl during the photocatalytic desulfurization. Mechanism of photo-desulfurization of di-benzothiophene over Ni-Co LDH/oxide.

Electrochemical and spectroscopic studies of the interaction of (+)-epicatechin with bovine serum albumin

Abstract: The mechanism of the electrochemical oxidation of (+)-epicatechin (epiCAT) in a hydro-alcoholic medium, at a glassy carbon electrode, was studied using cyclic and square wave voltammetric techniques and at different pHs. It proceeds in a cascade mechanism related to the two resorcinol hydroxyl groups and the other three hydroxyl groups in epiCAT which present electroactivity and is pH-dependent. The oxidation of the 3′,4′-dihydroxyl moiety, occurs first at a very low positive potential, and it is a two-electron/two proton reversible reaction. The product obtained from the oxidation of the 3′,4′-dihydroxyl moiety then undergoes a chemical reaction followed by an electrochemical process to give an electroinactive product. The proposed mechanism is an ECE type mechanism. After the addition of bovine serum albumin (BSA) to epiCAT solution, the oxidation peak currents decreased with no peak potential shift and no new peaks appeared. The diffusion coefficients of both free and bound epiCAT were estimated from the cyclic voltammetry data (Df = 2.37 × 10−10 cm2s−1 and Db = 6.28 × 10−11 cm2s−1). An epiCAT-BSA complex is formed with binding constant Kapp = 1.8 × 104, calculated from UV-vis spectroscopy data. The oxidation process of (+)-epicatechin (I to I’ and II) in a hydro-alcoholic medium at a glassy carbon electrode follows an ECE type mechanism.

A facile one-pot synthesis of 1 H -pyrano[2,3- d ]pyrimidin-4(5 H )-ones and evaluation of their Ct-DNA interaction, antibacterial and anti-inflammatory activity

Abstract: In this paper, we reported the synthesis of coumarin-pyrimidine derivatives by a four-component reaction involving 4-hydroxycoumarin, aldehyde, thiobarbituric acid and piperidine in ethanol. All the synthesized compounds were well-characterized by IR, NMR and mass spectroscopic techniques. Further, to evaluate the biological potency of the synthesized compounds, initially, DNA cleavage studies were performed. Encouraged by the results obtained from the cleavage studies, the synthesized compounds were screened for in-vitro antibacterial and anti-inflammatory activity. From the biological activity results, it revealed that most of the synthesized compounds were found to exhibit potent antimicrobial and anti-inflammatory activity with least IC50 than compared with standard.

Chitosan-zirconia microballs for proficient removal of chromate and phosphate ions from water bodies

Abstract: Zirconia-chitosan beads (Zr-CTB) were synthesized for detoxification of Chromate and Phosphate ions from water bodies. Zr-CTB was thoroughly characterized using FT-IR, SEM, EDX, TGA and BET studies. The beads were found to have a near-spherical shape with diameter of the order of 1 mm and the batch adsorption parameters such as pH, contact time, initial concentrations, amount of adsorbent, temperature, were optimized. The pH point of zero charge for the adsorbent was found to be 5.97. Maximum removal capacities towards chromate and phosphate ions were found to be 73.81 mg g−1 and 65.51 mg g−1, respectively at pH 5.0. The experimental data fitted well with Langmuir adsorption isotherm model and followed pseudo-second-order kinetics. Thermodynamics parameters confirmed that the process of adsorption was spontaneous, exothermic and leading to a decrease in entropy. The exposed material was regenerated using 5% NaCl solution with negligible change in adsorption efficiency up to 5 cycles. The effect of co-existing ions on adsorption efficiency was determined and the material was also tested by tea-bag model studies for convenient usage. Zirconia-chitosan beads (Zr-CTB) were synthesized, characterized using FT-IR, SEM, EDX, TGA and BET studies and applied for adsorptive removal of chromate and phosphate ions from water bodies. Maximum removal capacities towards chromate and phosphate ions were found to be 73.81 mg g−1 and 65.51 mg g−1 respectively at pH 5.0.

Nickel(II), copper(II) and zinc(II) complexes with an N-pendent dimethyl derivative of an octamethyl macrocyclic ligand: synthesis, characterization and antimicrobial studies

Abstract: Interaction of CH3I with L (3,10-C-meso-Me8[14]diene) in the ratio of 4:1 in ethanolic solution at room temperature yielded N-pendent dimethyl derivative [(L-2H)(–CH3)2] denoted by LZ. Interaction of nickel(II) acetate tetrahydrate with LZ and subsequent addition of NaClO4·6H2O produced square planar orange-yellow product, [NiLZ](ClO4)2. The reaction of copper(II) perchlorate hexahydrate with LZ afforded four coordinated square planar red [CuLZ](ClO4)2. However, on the reaction of zinc(II) nitrate hexahydrate with LZ furnished white six coordinated two distereoisomeric complexes [ZnLZα(NO3)2] and [ZnLZβ(NO3)2]. Axial addition reactions on four coordinated square planar [NiLZ](ClO4)2 with KX (X= SCN, NO3, Cl, Br or I) and NaNO2 resulted in six coordinated octahedral and square pyramidal axial addition products, such as [NiLZ(NCS)2], [NiLZ(NO3)(ClO4)], [NiLZCl(ClO4)], [NiLZBr2], [NiLZI2] and [NiLZ(NO2)](ClO4), respectively. However axial substitution reactions on [ZnLZα(NO3)2] with KY (Y= SCN, Cl or Br) and NaNO2 produced six coordinated octahedral axial substitution products [ZnLZα(NCS)2], [ZnLZαCl2], [ZnLZαBr2] and [ZnLZα(NO2)2]. Similarly, the axial substitution reactions on [ZnLZβ(NO3)2] with KI and NaClO4.6H2O resulted in six coordinated octahedral axial substitution products [ZnLZβI2] and [ZnLZβ(H2O)2](ClO4)2, respectively. The compounds have been characterized by analytical, spectroscopic, magnetochemical and conductivity data. The antimicrobial activities of the new ligand and its complexes have been tested against different micro pathogens. Nickel(II), copper(II) and zinc(II) complexes with an N-pendent dimethyl derivative ligand LZ of an octamethyl tetraazmacrocyclic ligand were prepared. The compounds were characterized by different analytical and spectroscopic methods. Antibacterial and antifungal activities of these compounds against some bacteria and fungi were also investigated.

Catalytic and photocatalytic properties of zinc-nickel ferrites

Abstract: A synthetic procedure combining high energy ball-milling and calcination at 900 °C was applied to obtain mixed metal oxides of the type Zn1−xNixFe2O4 (x = 0.25; 0.5; 0.75). The formation of spinel-like structures and the phase composition were confirmed by XRD in combination with Mossbauer, IR and Raman spectroscopy. The crystallite size was analysed from X-ray diffraction data revealing nanometric crystallites with an average size in the interval 20–60 nm. The IR spectra showed two fundamental absorption bands in the range 650–400 cm−1, which are characteristics of the metal-oxygen vibrations in tetrahedral and octahedral configurations. The mixed metal oxides were tested as catalysts for the decomposition of methanol to syngas and the degradation of the water pollutant malachite green in model solutions under UV light irradiation. Both the catalytic and photocatalytic activities were found to increase with increasing content of Ni(II) in the mixed metal oxides. The reduction behaviour of the samples was characterized by temperature-programmed reduction—thermogravimetric analysis and related to the catalytic conversion of methanol in the presence of the oxides. The most active samples for malachite degradation had the lowest band gap energy of 1.43 and 1.45 eV. The measurements of the reaction liquor by atomic absorption spectroscopy verified the stability of the samples tested as photocatalysts during the photocatalytic test. Zn/Ni ferrites of the type Zn1−xNixFe2O4 (x = 0.25; 0.5; 0.75) active both as catalysts for methanol conversion (a) and malachite green decomposition in model solutions under UV light irradiation (b)

Dielectric relaxations of molten acetamide: dependence on the model interaction potentials and the effects of system size

Abstract: Molecular dynamics simulations of dielectric relaxations (DRs) in neat molten acetamide (CH3CONH2) at ~358 K have been carried out by employing two different versions of the OPLS force field parameters, namely, the OPLS-UA (united-atom) and the OPLS-AA (all-atom) model interactions. Three systems consisting of 250, 500, and 1000 molecules have been studied to examine the impact of system size on the simulated dielectric properties. A comparison between our simulation predictions and the experimental DR data in the MHz-GHz frequency regime reveals that the OPLS-UA interaction parameters better reproduce the experimental static dielectric constant, whereas the OPLS-AA interaction describes well the measured DR time constants. Moreover, a weak system size dependence has been observed. A Cole-Cole plot of the simulated and experimental dielectric spectra reveal non-Debye nature of liquid acetamide and corroborates well with the earlier observation on the collective single-particle reorientational relaxation of liquid acetamide. The simulated single dipole reorientation dynamics also reflects this weak non-Debye nature and reveals its contribution to the collective polarization relaxation. Simulation results obtained here set the right ground for investigating the colossal dielectric constant (~106) of ionic acetamide deep eutectics reported earlier via DR measurements in the KHz-MHz regime.

How to train free radicals for organic synthesis? A modern approach

Abstract: In this review, the journey of free radicals, from being shrewdly untamable until its emergence as a powerful tool in chemistry, has been tracked A modern perspective on the generation of radicals has been offered through the lens of photoredox, metal mediation, redox-active scaffolds, and EDA complexes Spotlight has been on the catalysis of radical reactions harboring unique strategies like smart initiation, electron and hole catalysis, and polarity reversal catalysis