Recent Developments in the Plant‐Mediated Green Synthesis of Ag‐Based Nanoparticles for Environmental and Catalytic Applications

Among different metallic nanoparticles, sliver nanoparticles (Ag NPs) are one of the most essential and fascinating nanomaterials. Importantly, among the metal based nanoparticles, Ag NPs play a key role in various fields such as biomedicine, biosensors, catalysis, pharmaceuticals, nanoscience and nanotechnology, particularly in nanomedicine. A main concern about the chemical synthesis of Ag NPs is the production of hazardous chemicals and toxic wastes. To overcome this problem, many research studies have been carried out on the green synthesis of Ag NPs using green sources such as plant extracts, microorganisms and some biopolymers without formation of hazardous wastes. Among green sources, plants could be remarkably valuable to exploring the biosynthesis of Ag NPs. In this review, the green synthesis of Ag‐based nanocatalysts such as Ag NPs, AgPd NPs, Au?Ag NPs, Ag/AgPd NPs, Ag/Cu NPs, Ag@AgCl NPs, Au?Ag@AgCl nanocomposite, Ag?Cr‐AC nanocomposite and Ag NPs immobilized on various supports such as Natrolite zeolite, bone, ZnO, seashell, hazelnut shell, almond shell, SnO₂, perlite, ZrO₂, TiO₂, α‐Al₂O₃, CeO₂, reduced graphene oxide (rGO), h‐Fe₂O₃@SiO₂, and Fe₃O₄ using numerous plant extracts as reducing and stabilizing agents in the absence of hazardous surfactant and capping agents has been focused. This work describes the state of the art and future challenges in the biosynthesis of Ag‐based nanocatalysts. The fact about the application of living plants in metal nanoparticle (MNPs) industry is that it is a more economical and efficient biosynthesis biosynthetic procedure. In addition, the catalytic activities of the synthesized, Ag‐based recyclable nanocatalysts using various plant extracts in several chemical reactions such as oxidation, reduction, coupling, cycloaddition, cyanation, epoxidation, hydration, degradation and hydrogenation reactions have bben extensively discussed.     

Determination of Rutin in Plant Extracts and Emulsions by HPLC-MS

A method for the determination of rutin was developed from in an O/W emulsion with decyl oleate and Ceteareth-20 containing Ginkgo biloba L., Hedera helix L., and Thymus vulgaris L. extracts. Total quantification of rutin was performed by determination in the aqueous and oily phase. Rutin was extracted from the oily phase by ultrasonication for 30 min at 37°C in methanol and resolved by liquid chromatography on a column containing a Gemini 3 µ C18 110A stationary phase.

Chromatography was carried out using gradient elution with the mobile phase composed of water:formic acid and water:acetonitrile:formic acid, which was varied from 100:0.1 to 50:50:0.1 (v/v/v) over 80 min and delivered at a flow rate of 0.3 ml/min. The analytes were quantified using a UV-VIS absorption spectrometer at a wavelength of 254 nm and a single quadrupole mass spectrometer employing an ESI interface operated in the positive ion mode with single ion monitoring at m/z = 609.14.

Finally, a simple and rapid method for the extraction and determination of rutin in hydrophilic and lipophilic phases of an O/W emulsion with good precision and acceptable recovery was developed. This method might be of special importance for the analysis of rutin and other flavonoids in O/W or W/O emulsion matrices.     

Pd@sPS-NMe_2/AC纳米催化剂制备及在偶联反应中的应用

用胺基功能化间规聚苯乙烯(sPS-NMe_2)与活性炭(AC)分别利用混合沉降法(MP)、混合挥发法(MV)及直接聚合法(DP)制备了sPS-NMe_2/AC复合载体.sPS-NMe_2/AC吸附还原PdCl_2后获得Pd@sPS-NMe_2/AC催化剂.采用扫描电镜和透射电镜对sPS-NMe_2/AC和Pd@sPS-NMe_2/AC形貌进行了分析,考察了sPS-NMe_2/AC复合方法、用量对其形貌、负载Pd金属的影响,发现MV法获得的sPS-NMe_2/AC在其质量比大于1/3时sPS-NMe_2可均匀覆盖AC, Pd纳米粒子为3 nm左右,均匀稳定分散.该催化剂在"借氢"、 Suzuki-Miyaura、 Heck和Sonogashira偶联反应中表现出了优异的催化性能.     

Speciation analysis of orthophosphate and myo‐inositol hexakisphosphate in soil‐ and plant‐related samples by high‐performance ion chromatography combined with inductively coupled plasma mass spectrometry

A novel method based on high‐performance ion chromatography inductively coupled plasma mass spectrometry employing strong anion exchange chromatography with HNO₃ gradient elution for simultaneous analysis of orthophosphate and myo‐inositol hexakisphosphate (IP₆) in soil solution and plant extracts is presented. As inductively coupled plasma mass spectrometry analysis of phosphorus at m/z 31 is hampered by N‐based interferences, ³¹P was measured as ³¹P¹⁶O⁺ at m/z 47 employing dynamic reaction cell technique with O₂ as reaction gas. Orthophosphate and IP₆ were separated within a total chromatographic run‐time of 12 min revealing a limit of detection of 0.3 μmol/L. The coefficients of determination obtained in a working range of 1–100 and 1–30 μmol/L were 0.9991 for orthophosphate and 0.9968 for IP₆, respectively. The method was successfully applied to extracts from three different soils as well as root and shoot extracts of Brassica napus L. The precision of three independently prepared soil extracts was in the range of 4–10% relative standard deviation for PO₄^3? and 3–8% relative standard deviation for IP₆. Soil adsorption/desorption kinetics for IP₆/orthophosphate were performed for investigating the sorption behavior of the two P species in the experimental soils.     

Recent Developments in the Synthesis of Five‐ and Six‐Membered Heterocycles Using Molecular Iodine

Heterocyclic scaffolds represent the key structural subunits of many biologically active compounds. Over the last few years iodine‐mediated reactions have been extensively studied due to their low cost and eco‐friendliness. This Review covers advances in the field of iodine‐mediated synthesis of heterocyclic compounds since 2006, especially with an emphasis on mechanisms of ring formation. In this article, syntheses of different heterocycles are classified based on the manipulation of functional groups.     

Syntheses,Structures, and Catalytic Activities of Copper(I) Complexes with the Ligand 2(4,5‐Diphenyl‐1H‐imidazol‐2‐yl)­pyridine

Two copper(I) complexes of compositions [Cu(HL)I]₂ · EtOH ( 1 ) and [Cu(HL)₃]I · MeOH ( 2 ) were synthesized via the reactions of HL [HL = 2(4,5‐diphenyl‐1H‐imidazol‐2‐yl)pyridine] and CuI in EtOH and MeOH, respectively, under solvothermal conditions. The complexes were characterized by X‐ray single crystal diffraction, IR spectroscopy, and elemental analysis. Compounds 1 and 2 are catalytically active towards ketalization reaction, giving various ketals under mild conditions.     

N-溴代丁二酰亚胺在有机反应中的应用进展

N-溴代丁二酰亚胺(NBS)是有机反应中常用的试剂, 近几年来在多种有机反应中的应用都有了新的研究进展. 综述了其作为反应过程中的催化剂、氧化剂、选择性溴代试剂以及聚合反应引发剂等方面最新的研究成果.     

Synthesis of a Novel C2‐Symmetric Bis‐oxazoline (=Bis[4,5‐dihydrooxazole]) and Its Application as Chiral Ligand in Asymmetric Transition Metal Catalysis

The new C₂‐symmetric bis‐oxazoline (=bis[4,5‐dihydrooxazole]) 2 with a chiral trans‐(2R,3R)‐2,3‐bis(3,5‐diphenylphenyl)cyclopropylidene (=trans‐(2R,3R)‐2,3‐bis([1,1′: 3′,1″‐terphenyl]‐5′‐yl)cyclopropylidene) backbone was efficiently synthesized (Scheme). All synthetic steps were easy to perform and led to the desired product in good overall yields. Compound 2 was tested and compared as ligand in several enantioselective catalytic reactions such as palladium(0)‐catalyzed enantioselective allylic alkylations and copper(I)‐catalyzed enantioselective cyclopropanations and aziridinations.     

A New Compound in the Cu‐In System – the Synthesis and Structure of Cu10In7

A new binary phase, Cu₁₀In₇, was found during the investigation of the η‐phase field in the Cu‐In system. Single crystals of Cu₁₀In₇ were grown from a melt under an inert atmosphere. The compound crystallizes in the monoclinic space group C2/m with cell parameters a = 13.8453(2) Å, b = 11.8462(1) Å, c = 6.7388(1) Å and β = 91.063(1). The structure is based on a unit of face‐sharing octahedra consisting of five Cu₄In₂ octahedra terminated by Cu₅In octahedra at both ends. The crystal structure is closely related to the Cu₁₁In₉ structure type.     

Sensitive and Green Method for Determination of Chemical Oxygen Demand Using a Nano‐copper Based Electrochemical Sensor

Copper nanoparticles (nano‐Cu) were electrodeposited on the surface of glassy carbon electrode (GCE) potentiostatically at −0.6 V vs. Ag/AgCl for 60 s. The developed nano‐copper modified glassy carbon electrode (nano‐Cu/GCE) was optimized and utilized for electrochemical assay of chemical oxygen demand (COD) using glycine as a standard. The surface morphology and chemical composition of nano‐Cu/GCE were investigated using scanning electron microscope (SEM) and energy dispersive X‐ray spectrometer (EDX), respectively. The electrochemical behavior was investigated using linear sweep voltammetry (LSV) which is characterized by a remarkable anodic peak at ∼0.6 V, compared to bare GCE. This indicates that nano‐Cu enhances significantly the electrochemical oxidation of glycine. The effect of different deposition parameters, such as Cu²⁺ concentration, deposition potential, deposition time, pH, and scan rate on the response of the developed sensor were investigated. The optimized nano‐Cu/GCE based COD sensor exhibited a linear range of 15 to 629.3 ppm, and a lower limit of detection (LOD) of 1.7 ppm (S/N=3). This developed method exhibited high tolerance level to chloride ion (0.35 M chloride ion has minimal influence). The analytical utility of the prepared COD sensor was demonstrated by investigating the COD recovery (99.8±4.3) and the assay of COD in different water samples. The results obtained were verified using the standard dichromate method.     

Nanobiocomposite Modified Carbon‐Ceramic Electrode Based on Nano‐TiO2‐Plant Tissue and Its Application for Electrocatalytic Oxidation of Dopamine

A new modified carbon‐ceramic electrode was prepared by incorporating TiO₂ nanoparticle into sol‐gel network by accompanying apple tissue. A mixture of fine graphite powder with 15 wt% of TiO₂ nanoparticle was used for the preparation of the carbon matrix and finally modification with a known amount weighted of apple tissue. The apple tissue containing polyphenol oxidase enzyme acts as molecular recognition element. The electrocatalytic oxidation of dopamine was investigated on the surface of the nanobiocomposite modified carbon‐ceramic electrode using cyclic voltammetry, chronoamperometry and amperometry techniques. Effect of pH, scan rate, TiO₂ percentage on the response of modified electrode was studied. The prepared modified electrode presented a linear range for dopamine from 5.0×10^?6 to 1.2×10^?3 M in buffered solutions with pH 7.4 by amperometry. The detection limit was 3.41×10^?6 M dopamine. The response of the modified carbon‐ceramic electrode and unmodified carbon‐ceramic electrode was compared.     

Recent Advances in the Preparation and Applications of Organo‐functionalized Porous Materials

Organo‐functionalized materials with porous structure offer unique adsorption, catalytic and sensing properties. These unique properties make them available for various applications, including catalysis, CO₂ capture and utilization, and drug delivery. The properties and the performance of these unique materials can be altered with suitable modifications on their surface. In this review, we summarize the recent advances in the preparation and applications of organo‐functionalized porous materials with different structures. Initially, a brief historical overview of functionalized porous materials is presented, and the subsequent sections discuss the recent developments and applications of various functional porous materials. In particular, the focus is given on the various methods used for the preparation of organo‐functionalized materials and their important roles in the heterogenization of homogeneous catalysts. A special emphasis is also given on the applications of these functionalized porous materials for catalysis, CO₂ capture and drug delivery.     

Recent Developments in the MCRs Synthesis of Pyridopyrimidines and Spiro‐Pyridopyrimidines

Because of biological and medicinal properties of pyridopyrimidines, synthesis of these heterocycles has attracted the interest of organic and medicinal chemists. This review focuses on the recent development in the multi‐component synthesis of pyridopyrimidine and spiro‐conjugated pyridopyrimidine systems. The present review describes the literature reports for the period 2000–2015, particularly those that involve the reactions of activated methylene, aldehyde or ketone, and amine in classical and nonclassical conditions.     

Hydroxylation of 4‐Amino‐5‐hydroxynaphthalene‐2,7‐disulfonic Acid Monosodium Salt Catalysed by Horseradish Peroxidase and Hydrogen Peroxide: Computation of Kinetic Parameters Including Its Application to Crude Plant Extracts

The new spectrophotometric assay method for the quantification of peroxidase activity uses 4‐amino‐5‐hydroxynaphthalene‐2,7‐disulfonicacid monosodium salt (AHNDSA) as chromogenic co‐substrate. The method is based on hydroxylation of AHNDSA in presence of H₂O₂/peroxidase forming quinone, having λ_max = 460 nm in the acetate buffer (pH = 4.0) at 30 °C. The linearity of H₂O₂ by kinetic method was 10–332 µM and for peroxidase by kinetic and fixed time methods were 1.18–18.92 and 1.18–9.46 nM, respectively. Catalytic efficiency and catalytic power for peroxidase assay were 7.965 × 10⁴ M^?1min^?1 and 3.76 × 10^?4 min^?1, respectively. From the plot of d(1/A_o) vs d(1/V_o) and d(1/H_o) vs d(1/V_o), the apparent Michaelis‐Menten constants for H₂O₂ and AHNDSA were K = 68 and K = 275 µM, respectively. The method was tested with some plant extracts and also compared with guaiacol/peroxidase system. Except Boerhavia diffusa, all other tested plant samples showed highest peroxidase activity. The proposed method is a rapid and convenient method to determine peroxidase activity by spectrophotometer. This method for the first time reports peroxidase activity in Lantana camara and Oplismenus compositus plants. Kinetic results showed that AHNDSA/peroxidase system can be better hydrogen donor for peroxidase assay than guaiacol system.     

Iron(II) Complexes of Chiral Tridentate Nitrogen Donors and their Application in Catalytic Hydrosilylation Reactions

Enantiomerically pure, C₂-symmetric 2,6-bis(pyrazol-3-yl) pyridine ligands were obtained by treatment of diethyl-2,6-pyridinedicarbonate with (1R,4R)-(+)-camphor in the presence of NaH followed by ring closure with hydrazine. After twofold N-alkylation at the pyrazole rings, the addition of iron(II) chloride led to the according pentacoordinate dichloridoiron(II) complexes. All intermediates of the ligand synthesis, the ligands bearing NCH₃ and NCH₂C₆H₅ groups and the derived iron(II) complexes were structurally characterized by means of X-ray structure analysis. In-situ reaction with iron(II) carboxylates resulted in the formation of iron(II) carboxylate complexes, which turned out to be highly active in the hydrosilylation of acetophenone. However, even at room temperature, the enantiomeric excess of the product 1-phenylethanol is poor. ⁵⁷Fe Mössbauer spectroscopy gave an insight into the species formed during catalysis.     

Synthesis of Silver Nanoparticles Using Ionic‐Liquid‐Based Microwave‐Assisted Extraction from Polygonum minus and Photodegradation of Methylene Blue

A green biogenic, nontoxic, high‐yielding synthetic method is introduced for the synthesis of silver nanoparticles (AgNPs) using ionic‐liquid‐based, microwave‐assisted extraction (ILMAE) from Polygonum minus . The aqueous ionic liquid (1‐butyl‐3‐methylimidazolium chloride [BMIM]Cl)‐based plant extract was used as reducing agent to reduce silver ions to AgNPs. The synthesis of AgNPs was confirmed by UV–visible spectrophotometry. Fourier transforms infrared (FTIR) spectra showed that the plant bioactive compounds capped the AgNPs. The particle size and morphology of Ag NPs were characterized by dynamic light scattering (DLS) and field emission scanning electron microscopy (FESEM), respectively. Elemental analysis was carried out by energy‐dispersive X‐ray (EDX) spectroscopy. Photodegradation studies showed that the AgNPs degraded 98% of methylene blue in 12 min.     

Synthesis of New Diphosphine Ligands and their Application in Pd‐Catalyzed Alkoxycarbonylation Reactions

Carbocyclic and N‐heterocyclic analogues of the industrially applied ligand bis(di‐tert‐butylphosphinomethyl)benzene ( 1 ) have been synthesized in moderate to very good yields. The new ligands are based on benzene, tetralin, lutidine, pyrazine, quinoxaline, and maleimide backbones. Electronic and steric variations of the phosphorous donor sites were performed. As a benchmark reaction, the palladium‐catalyzed methoxycarbonylation of 1‐octene has been tested. Ester yields up to 64 % and high linear selectivities up to 92 % were achieved.     

Recent Mechanistic and Synthetic Developments in the Chemistry of Transition‐Metal Vinylidene Complexes

Transition‐metal vinylidene complexes are intermediates in a number of synthetically important transformations of alkynes. Underpinning these applications is the ability of various electron‐rich transition‐metal complexes to effectively facilitate the conversion of alkynes into their vinylidene tautomers. Recent experimental and theoretical studies have provided considerable insight into the mechanisms by which this process occurs and they are detailed herein. In particular, it has been demonstrated that different substituents on both the metal and the alkyne may have profound effects on both the kinetic and thermodynamic profiles of the alkyne/vinylidene tautomerisation. An important finding is that internal alkynes may be employed to prepare disubstituted vinylidene complexes under easily accessible conditions. This discovery brings to light a new facet of the potential synthetic applications of transition metal vinylidene complexes.     

Selective Determination of Total Capsaicinoids in Plant Material Using Poly(Gallic Acid)‐modified Electrode

Novel voltammetric approach for the selective determination of total capsaicinoids has been developed using glassy carbon electrode modified with multi‐walled carbon nanotubes and poly(gallic acid) (PGA/MWNT/GCE). The modified electrode provides significant improvements in the capsaicinoids voltammetric characteristics in comparison to GCE and MWNT/GCE. The electrooxidation of capsaicinoids is irreversible adsorption‐controlled process with the anodic transfer coefficient of 0.49–0.53 and heterogeneous electron transfer rate constant of 1300–2400 s^?1. The analytical ranges of 0.010–1.0 and 1.0–50 μM for capsaicin, 0.025–0.75 and 0.75–75 μM for dihydrocapsaicin and 0.025–5.0 and 5.0–75 μM for nonivamide with the detection limits of 2.9, 5.9 and 6.1 nM, respectively, have been obtained using differential pulse voltammetry (DPV). The selectivity of the capsaicinoids quantification in the presence of ascorbic acid, α‐tocopherol and carotenoids is shown. The method has been tested on the samples of red hot pepper spices and Capsicum annuum L. tinctures. The results correspond to the chromatographic data.