Metal Acetates Research Articles

The Fluorometric Detection of Explosives: An Application of Photoluminiscent Coordination Polymers

Two-dimensional coordination polymers (COPs), a class of metal–organic hybrid polymeric systems are catching the attention of both technologists and researchers due to their ability to exhibit remarkable properties ranging from electrical conductivity to fluorescence arising due to their unique molecular structure and composition. Herein, we report on the synthesis and molecular structural characterization of four different two-dimensional coordination polymers obtained by reacting different metal acetates with 1,2,4,5-benzenetetramine. Their structural characterization was carried out using various spectroscopic and microscopic techniques such as FTIR, UV–vis, Raman, XPS, FESEM, HRTEM, etc., to confirm the two-dimensional layered structure unequivocally. Photophysical studies confirm the exhibition of fluorescence by these COPs with reasonably high quantum yields. All four COPs formed showed the capability to sense different nitroaromatic and non-nitro aromatic systems in the solution phase. Among all the explosives used, trinitrophenol and trinitrotoluene showed very high sensitivity as well as selectivity. The sensitivity was found to be as low as 0.2 μM. The quenching mechanism was probed with various methods, and it was found to follow static quenching as the predominating quenching process. This selective and sensitive quenching was used to devise a prototype device capable of detecting TNP at very low concentrations visually.

Intrinsic Josephson effect in biaxially-textured Bi-2212 thin films

Bi2Sr2CaCu2O8+x (Bi-2212) thin film with a thickness of micrometers was prepared by a sol-gel method using metal acetate as starting material. The crystal orientation and the superconducting properties of the thin film were studied. Besides, a pattern with a diameter of 300 µm and a thickness of 1.05 µm was prepared. The I-V curve indicates that the biaxially-textured Bi-2212 thin film has a zero-voltage overcurrent and shows a voltage jump under the zero-voltage current. These characteristics are similar to those of a single crystal and exhibit the unique Josephson effect of a intrinsic junction. In the superconducting state, the zero-voltage current increases linearly with the temperature decresing and the hysteresis area of the curve increases gradually. Further analysis indicates that its I-V characteristics are similar to those of a terahertz source device made from Bi-2212 single crystal. Based on these findings, it is predicted that it may generate THz waves with a frequency range of 0.144 THz-1.29 THz. The radiation frequency can be further regulated by controlling the thickness and bias voltage of the biaxially textured film as well as the envirmental temperature.

Electrochemical reduction of CO2 to CO on bimetallic CoCu–N–C catalyst

Electrochemical reduction of CO2 to valuable chemicals using electricity from renewable sources is a promising approach to realize the carbon cycle. Here, a novel bimetallic nitrogen-doped carbon catalyst (M-N-C, where M denotes the metal) CoCu–N–C electrocatalyst has been synthesized by pyrolyzing a copper-doped cobalt(II) acetate–phenanthroline complex formed from the metal acetates and 1,10-phenanthroline dissolved in ethanol. The optimal CoCu–N–C catalyst with molar ratio of Cu/(Co + Cu) = 0.15 displayed superior performance, enabling a faradaic efficiency of CO production of 76.5% at an overpotential of 0.57 V as well as an increased CO current density of 8.48 mA cm−2 at −0.98 V versus reversible hydrogen electrode (far superior than the Co–N–C of 4.20 mA cm−2 and Cu–N–C of 0.07 mA cm−2) and a decreased charge-transfer resistance compared with Co–N–C and Cu–N–C catalysts. The addition of Cu, which serves as a structure promoter to improve the dispersion of Co, thereby providing sufficient Co-Nx active sites for the electrochemical CO2 reduction reaction (CRR). Moreover, doping Cu changes the electronic environment around Co slightly and promotes the charge transfer capability so that reduces the energy barrier of potential-limiting energy, thereby improving the CRR performance of catalyst.

Effect of Bimetallic-Activated Carbon Impregnation on Adsorption–Desorption Performance for Hydrogen Sulfide (H2S) Capture

This study reports on the impregnation of bi-metallic adsorbents based on commercial coconut activated carbon (CAC), surface-modified with metal acetate (ZnAc2), metal oxide (ZnO and TiO2), and the basic compound potassium hydroxide (KOH). The morphology of the adsorbents was then characterized with SEM-EDX, the microporosity was determined using Brunauer–Emmett–Teller (BET) analysis, the thermal stability was investigated via thermogravity analysis (TGA), and functional group analysis was undertaken with Fourier-transform infrared (FTIR) spectroscopy. These modified adsorbents were subjected to a real adsorption test for H2S capture using a 1 L adsorber with 5000 ppm H2S balanced for N2, with temperature and pressure maintained at an ambient condition. Adsorption–desorption was carried out in three cycles with the blower temperature varied from 50 °C to 150 °C as the desorption condition. Characterization results revealed that the impregnated solution homogeneously covered the adsorbent surface, effecting the morphology and properties. Based on this study, it was found that ZnAc2/TiO2/CAC_DCM showed a significant increase in adsorption capacity with the different temperatures applied for the desorption in the second cycle: 1.67 mg H2S/g at 50 °C, 1.84 mg H2S/g at 100 °C, and 1.96 mg H2S/g at 150 °C. ZnAc2/ZnO/CAC_DCM seemed to produce the lowest percentage of degradation in the three cycles for all the temperatures used in the adsorption–desorption process. Therefore, ZnAc2/ZnO/CAC_DCM has the potential to be used and commercialized for biogas purification for H2S removal.

Transition Metal and Nitrogen-Doped Mesoporous Carbons As Cathode Catalysts for Anion-Exchange Membrane Fuel Cells

Energy is an essential part of our lives and causes significant impact on the environment. As hydrogen is clean, cost-efficient and easily producible, then it is believed to become an essential player in the energy field.1 The proton exchange membrane fuel cells fueled by hydrogen are already used in the transport sector, but their further commercialization is limited by the excess usage of precious metals. To ease the search for replacements, the harsh acidic environment can be changed to alkaline, thus giving opportunity to use non-precious metal catalysts.2 Especially for the cathodic oxygen reduction reaction (ORR), different transition metal-containing nitrogen-doped carbon-based materials have shown great promise.3 This gives an opportunity for the rise of anion exchange membrane fuel cells (AEMFCs) as future hydrogen-based energy devices.2,3 In this work, a novel catalyst support based on mesoporous carbon (MPC, from Pajarito Powder, LLC) is used to produce M−N−C type catalyst materials. Such mesoporous structure is useful for better mass transport in the catalyst layer during AEMFC operation. This MPC support is mixed with 1,10-phenanthroline as nitrogen source and transition metal acetates, followed by high-temperature pyrolysis at 800 °C in an inert atmosphere. Five M-N-C materials are prepared with the following transition metal combinations: Co, Fe, CoFe, CoMn, and FeMn.Several physico-chemical characterization methods (SEM-EDX, STEM, XPS, MP-AES, Raman spectroscopy, and N2 physisorption) are employed to study the materials. These indeed proved that all five catalyst materials have feasible mesoporous structure (pore diameters predominantly 7-8 and 25-35 nm) and the doping with transition metals (content ca. 1 wt%) and nitrogen (ca. 2.3 at%) has been a success. The electrochemical testing to study the ORR pathway and activity of these materials in alkaline media was done using the RRDE method. CoFe-N-MPC, Fe-N-MPC and FeMn-N-MPC catalysts showed similar and excellent electrocatalytic performance by obtaining half-wave potential of 0.9 V vs RHE. The lowest peroxide yield was obtained with Fe-N-MPC and FeMn-N-MPC. The latter two catalyst materials also showed very good performance as cathode catalysts in an H2/O2 AEMFC together with an HMT-PMBI4 membrane, obtaining peak power density of >470 mW cm–2. This indicates that the M-N-MPC materials are promising cathode catalysts for the AEMFC application.References Nazir, H.; Louis, C.; Jose, S.; Prakash, J.; Muthuswamy, N.; Buan, M.E.M.; Flox, C.; Chavan, S.; Shi, X.; Kauranen, P.; Kallio, T.; Maia, G.: Tammeveski, K.; Lymperopoulos, N.; Carcadea, E.; Veziroglu, E.; Iranzo, A.; Kannan, A.M. Is the H2 economy realizable in the foreseeable future? Part I: H2 production methods. J. Hydrogen Energy 2020, 45, 13777-13788, DOI: 10.1016/j.ijhydene.2020.03.092Gottesfeld, S.; Dekel, D. R.; Page, M.; Bae, C.; Yan, Y. S.; Zelenay, P.; Kim, Y. S. Anion exchange membrane fuel cells: current status and remaining challenges. Power Sources 2018, 375, 170-184, DOI: 10.1016/j.jpowsour.2017.08.010Sarapuu, A.; Kibena-Põldsepp, E.; Borghei, M.; Tammeveski, K. Electrocatalysis of oxygen reduction on heteroatom-doped nanocarbons and transition metal–nitrogen–carbon catalysts for alkaline membrane fuel cells. J. Mater. Chem. A 2018, 6, 776-804, DOI: 10.1039/C7TA08690C.Wright, A.G.; Fan, J.T.; Britton, B.; Weissbach, T.; Lee, H.F.; Kitching, E.A.; Peckham, T.J.; Holdcroft, S. Hexamethyl-p-terphenyl poly(benzimidazolium): a universal hydroxide-conducting polymer for energy conversion devices. Energy Environ. Sci., 2016, 9, 2130-2142, DOI: 10.1039/C6EE00656F.

Recent Advances in Base-assisted Michael Addition Reactions

Abstract: The Michael addition is an important, highly efficient, and atom-economical method for the diastereoselective and enantioselective C-C bond formation. MA used in the synthesis of natural products and drugs is tandem sequenced reactions. An important tandem sequence of Michael and Aldol additions is the Robinson annulation. MA is a versatile reaction employed for efficient bond formation between electron-poor olefins as Michael acceptors with varied nucleophiles as Michael donors. Apart from being involved in C-C bond formation, MA is also employed in the formation of C-X bond (X=O, N, S, P etc.) giving rise oxa-, aza-, thia-, phospha-Michael addition products. In recent years many articles have been published on MA. The mechanism of MA gives an insight into the reaction is initiated by the base. The present review provides comprehensive information on recent advancements in base-assisted Michael addition reactions including varied organic and inorganic bases, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,4-Diazabicyclo[2.2.2]octane (DABCO), 4-dimethylaminopyridine (DMAP), triethylamine (Et3N), tributylamine (Bu3N), N,N-diisopropylethylamine (DIEPA), diethylamine (NHEt2), guanidine derivatives, and bifunctional thiourea. A variety of inorganic bases including metal alkoxides, metal acetates, metal hydroxides, metal hydrides, metal carbonates, metal halides, and triphenylphosphine (TPP) can also be successfully used in Michael reactions.

Facile synthesis of the encapsulation of Co-based multimetallic alloys/oxide nanoparticles nirtogen-doped carbon nanotubes as electrocatalysts for the HER/OER

The pivotal challenge of electrocatalysis remains the development of highly effective electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). In this work, a universal strategy of preparing the encapsulation of Co-based multimetallic alloys/oxide nanoparticles in nitrogen-doped carbon nanotubes (named CoM@CNTs, M = Ni/Mn/Fe) was induced by annealing mixtures of the as-synthesized precursor, ethanol and different metallic acetates, including binary CoNi@CNTs, ternary CoNi/MnO@CNTs and quaternary CoNiFe/MnO@CNTs. By virtue of its unique structure with a high electrical conductive network based on CNT substrates, abundant catalytic active sites supplied by multimetallic nanoparticles and protection against nanoparticle corrosion by N-doped carbon layers, the as-synthesized CoNiFe/MnO@CNTs electrocatalyst has remarkable HER properties with a low overpotential of 122 mV and OER activity with a low overpotential of 275 mV at 10 mA cm−2 and excellent stability and durability under long-term testing in alkaline solutions. Therefore, this strategy will provide a new route for fabricating multimetallic-based CNTs as HER/OER electrocatalysts with excellent stability and high catalytic activity.

Band-Gap Tuning Induced by Germanium Introduction in Solution-Processed Kesterite Thin Films.

In the last few decades, the attention of scientific community has been driven toward the research on renewable energies. In particular, the photovoltaic (PV) thin-film technology has been widely explored to provide suitable candidates as top cells for tandem architectures, with the purpose of enhancing current PV efficiencies. One of the most studied absorbers, made of earth-abundant elements, is kesterite Cu2ZnSnS4 (CZTS), showing a high absorption coefficient and a band gap around 1.4–1.5 eV. In particular, thanks to the ease of band-gap tuning by partial/total substitution of one or more of its elements, the high-band-gap kesterite derivatives have drawn a lot of attention aiming to find the perfect partner as a top absorber to couple with silicon in tandem solar cells (especially in a four-terminal architecture). In this work, we report the effects of the substitution of tin with different amounts of germanium in CZTS-based solar cells produced with an extremely simple sol–gel process, demonstrating how it is possible to fine-tune the band gap of the absorber and change its chemical–physical properties in this way. The precursor solution was directly drop-cast onto the substrate and spread with the aid of a film applicator, followed by a few minutes of gelation and annealing in an inert atmosphere. The desired crystalline phase was obtained without the aid of external sulfur sources as the precursor solution contained thiourea as well as metal acetates responsible for the in situ coordination and thus the correct networking of the metal centers. The addition of KCl in dopant amounts to the precursor solution allowed the formation of well-grown compact grains and enhanced the material quality. The materials obtained with the optimized procedure were characterized in depth through different techniques, and they showed very good properties in terms of purity, compactness, and grain size. Moreover, solar-cell prototypes were produced and measured, exhibiting poor charge extraction due to heavy back-contact sulfurization as studied in depth and experimentally demonstrated through Kelvin probe force microscopy.

Facile microwave-assisted hydrothermal synthesis and improved electrochemical performance of micro rhombus ZnMn2O4 anodes for Li-ion batteries

• Rhombus ZnMn 2 O 4 micro sheets are synthesized by microwave-assisted hydrothermal route. • The micro sheet composed of primary nanoparticles can inhibit the volume change. • The synthesis conditions of ZnMn2O4 were optimized by orthogonal experiment. Spinel structure ZnMn 2 O 4 anode materials were synthesized via an inexpensive microwave-assisted hydrothermally route from metal acetate raw material in an aqueous solution. The effects of reaction temperature and time, compactness, and pH on the synthesis conditions were systematically studied by designing four-factor and three-level orthogonal test method. The reaction temperature has the most significant influence on the experiment. X-ray diffraction structure study shows that all nine groups of ZnMn 2 O 4 contain different contents of ZnO impurities. Rhombus-type ZnMn 2 O 4 micro sheets were identified by scanning electron microscopy. Among them, the Li/ZnMn 2 O 4 cells delivered an initial discharge capacity of 1057.3 mAh·g −1 and the capacity of 337.3 mAh·g −1 remains after 40 cycles for the as-synthesized sample under the optimized conditions of the reaction temperature at 200 ℃, the compactness of 60 vol%, the reaction time of 35 min and the pH value of 10. It is surprising to note that ZnMn 2 O 4 prepared under this condition exhibits more stable and superior cyclic performance than other samples, which is due to its unique morphology. Finally, the reaction mechanism of ZnMn 2 O 4 electrode material was studied by electrochemical test combined with the capacity differential curve. This research makes a step forward to the zinc manganese spinel oxide and shows that ZnMn 2 O 4 is a promising anode material for lithium-ion batteries.

Alkali Metal Di-tert-butyl Phosphates: Single-Source Precursors for Homo- and Heterometallic Inorganic Phosphate Materials.

The reaction of alkali metal acetates, M(OAc)·nH2O (M = Li, Na, K), with thermally and hydrolytically unstable di-tert-butylphosphate ((tBuO)2PO2H, dtbp-H) in a 1:1 molar ratio in MeOH at room temperature leads to clean formation of group 1 metal phosphates [Li(μ-dtbp)]n (1), [Na(μ-dtbp)]n (2), and [K4(μ-dtbp)4(μ-H2O)3]n (3). All three compounds are essentially M/L 1:1 complexes. Owing to the presence of larger potassium ions, additional coordinated water molecules are found in 3, which has been further employed as a precursor for the synthesis of a mixed-metal phosphate polymer [CaK(μ-H2O)3(μ-dtbp)3]n (4) by reacting 3 with Ca(OAc)2. Compounds 1-4 have been characterized by various analytical and spectroscopic techniques. Molecular structures of 1-4 have been established in the solid state by single-crystal X-ray diffraction studies, which reveal them to be one-dimensional polymers, where the adjacent metal centers are connected through -O-P-O- bridges formed by the dtbp ligand. These complexes are rare examples of analytically pure alkali metal alkyl phosphates bearing no additional N-donor ligands (other than dtbp ligands, only water molecules are coordinated to the metal centers). Therefore, these compounds can be employed as single-source precursors (SSPs) for nano-sized ceramic phosphates. The thermogravimetric analysis of 1-4 reveals the loss of thermally labile tert-butyl substituents of the organophosphate ligands to form organic-free phosphate materials in the temperature range 300-500 °C. Solvothermal decomposition of 1-3 in boiling toluene leads to the formation of corresponding dihydrogen phosphates M(H2PO4) (M = Li, Na, and K). The thermal decomposition of heterometallic 4 in the temperature range 400-800 °C leads to the formation of phase-pure mixed-metal calcium potassium metaphosphate CaK(PO3)3.

Ozonation of 4-aminotoluene as a new method of synthesis of 4-aminobenzaldehyde – an intermediate for the production of anti-tuberculosis drugs

Solutizon is an original anti-TB drug that is effective in resisting mycobacteria to other anti-TB drugs, which is obtained by the interaction of thiosemicarbazone 4-aminobenzaldehyde and sodium oxymethylene sulfonate. 4-Aminobenzaldehyde is synthesized by redox conversion of 4-nitrotoluene in the presence of sodium polysulfide. The reaction is carried out in boiling alcohol, and 4-aminobenzaldehyde is separated after steam distillation with a yield of 40–50 %. However, today this method loses its practical, environmental and economic attractiveness, as it has significant disadvantages – low product yield, high reaction temperature (80–120 °C), the formation of sulfur-containing wastewater. Therefore, the development of low-temperature, environmentally friendly methods for obtaining 4-aminobenzaldehyde is an urgent task. The aim of the work is to study the kinetic features and mechanism of the liquid-phase reaction of ozone with 4-aminotoluene to create a new low-temperature, environmentally friendly method for the synthesis of 4-aminobenzaldehyde. Materials and methods. Sigma acetic anhydride of сh.р. qualification was used for the experiments. 4-Aminotoluene company “Sinbias” qualification “сh.р.”; 4-Acetamidotoluene and its derivatives were used chromatographically pure. Acetates of metals of qualification “сh.р.”, potassium bromide of qualification “pharmacopoeial” were used without additional purification. Continuous control of the current ozone concentration and recording the results in the form of a kinetic curve was carried out when passing ozone-containing gas through the container of the spectrophotometer “SF-46 LOMO” at a certain wavelength of a monochromatic light source. The results of the analysis were recorded using the KSP-4 potentiometer included in the spectrophotometer optical density reference circuit. This device automatically compensated the photocurrent by recording its value. The scale KSP-4 was calibrated in units of optical density, and the conversion into absolute ozone concentration was carried out according to the Lambert-Ber equation using molar extinction coefficients. Relative analysis error ≤5 %. At the optical stroke length of the container 10 ÷ 100 mm, the sensitivity of the device was ~10-7mol·l-1 ozone. Results. The kinetic features and mechanism of the liquid-phase reaction of ozone with 4-aminotoluene have been studied. It is shown that the developed catalytic system Mn(II)-KBr-H2SO4-Ac2O significantly increases the depth, rate, and selectivity of oxidation of 4-aminotoluene and the main reaction product is 4-aminobenzaldehyde in the form of the corresponding benzylidenediacetate with a yield of 69.5 %. The active particle responsible for the inclusion of the substrate in the oxidation of the methyl group in the presence of manganese (II) acetate and potassium bromide is manganese bromide ion radical (Mn(II)Br•), which is more active than Mn (III) and therefore more high-speed initiates oxidation by the methyl group. Conclusions. Catalytic systems have been developed that allow the oxidation of ozone to be directed mainly to the methyl group of 4-aminotoluene and to stop the reaction at different oxidation depths. It was found that manganese (II) acetate, which has a relatively low redox potential, in the system Ac2O-ArCH3-H2SO4-O3 at a temperature of 20 °C has a high substrate selectivity in the reactions of formation of 4-aminobenzyl alcohol. Manganese (II) acetate in the presence of potassium bromide forms a manganese bromide complex with increased catalytic activity, which under the same conditions contributes to the predominant production of 4-aminobenzaldehyde.

Synthesis, structural elucidation, in vitro antibacterial activity, DFT calculations, and molecular docking aspects of mixed-ligand complexes of a novel oxime and phenylalanine

An oxime ligand (HL) was synthesized by the condensation of 4-biphenylhydroxymoyl chloride with 2-amino-5-bromopyridine. The oxime ligand was reacted with l-phenylalanine and metal(II) acetate salts (Co(II), Ni(II), and Cu(II)) to synthesize mixed-ligand complexes. Structural elucidation of the newly synthesized ligand and complexes was performed by elemental analysis, 13C NMR, 1H NMR, FT-IR, ICP-OES, the measurements of molar conductivity and magnetic susceptibility. The thermal properties of the compounds were characterized by TG/DTA analyses. The antibacterial activities of the compounds were evaluated in vitro by the resazurin-aided broth microdilution method. Optimized molecular geometries of the HL and its metal complexes were calculated using the density functional theory (DFT) of the B3LYP method with 6-311G (d, p) and LANL2DZ basis sets. The NMR chemical shift values, vibrational frequencies, and HOMO-(LUMO or SOMO) energies were also computed using the mentioned level. A molecular docking study was performed to demonstrate the interactions of the synthesized compound with beta-ketoacyl-ACP synthase III (KAS III), an enzyme that has a key role in bacterial survival. Based on the MIC values and binding energy scores, both in vitro and in silico studies showed that the antibacterial activity of the Cu(II) complex was better than the other studied molecules.

Synthesis, Characterization, and Evaluation of Electrochemical and Thermal Properties of New Cobalt Phthalocyanine(Copc) using Phthalamide as Precursor

Cobalt phthalocyanine was synthesized from 3-nitrophthalonitrile using phthalamide as a precursor. Nitration in position 3 of the phthalamide led to the formation of 3-nitrophthalamide; then dehydration bythionyl chloride in N, N-dimethylformamide led to the formation of 3- nitrophthalonitrile. Phthalonitrile derivative was prepared by a nucleophilic substitution reaction of 3 nitrophthalonitrile in the presence of K2CO3 as a base in a non aqueous organic solvent. Cyclotetramerization of phthalonitrilein in the presence of metal acetate, (Co(Ac)2.4H2O) gave peripherally substituted metal phthalocyanine complexes. The structure of the synthesized compounds was characterized by different analytical tools such as UV-Vis, FT-IR spectrophotometry and cyclic voltammetry The disappearance of the C≡N stretching vibration from the IR spectra of phthalonitrile wasobserved at 2230 cm−1. The FT-IR vibration results for cobalt phthalocyanine was found to be 1709cm-1, 1611 cm-1 and 1275 cm-1 for C=O, C=C and C-O respectively. Solubility of metal phthalocyanine complexes was found to be very low in common laboratory solvents such as tetrahydrofuran (THF) and dimethylformamide (DMF). The electronic spectrum of CoPc in dimethylformamide (DMF) showed intense Q absorption at 677 nm. UV-Vis spectra of phthalocyanines showed electronic spectra with two strong absorption bands, Q and B bands. The Q band was found in 600–750 nm and B at 300 400 nm for both. The thermal stability of the phthalocyanine derivative was checked by T.G.A and the degradation was observed to start at 300oC, which showed that the complex could withstand fairly high temperature. It could therefore be concluded that the metal phthalocyanine prepared in this study showed fairly high thermal stability and can be used for various applications such as dye.

2,2′-Bipyridine based biologically active mixed ligand metal(II) complexes: Synthesis, characterization, DFT and antioxidant studies

Mixed ligand [CoL(bpy)], [NiL(bpy)], [CuL(bpy)] and [ZnL(bpy)] complexes were synthesized from Schiff base ligand L, metal(II) acetates of Co, Ni, Cu and Zn with 2,2′-bipyridine (bpy). The synthesized compounds were characterized using molar conductance, elemental analyses, 1H-NMR, FTIR and mass spectral studies. The geometry of metal complexes has been assigned by magnetic moment analysis and UV-vis spectral techniques. The X-band ESR spectra of [CuL(bpy)] complex in DMSO were recorded at room temperature and liquid nitrogen temperature. Grain size of metal complexes was predicted using Powder XRD. Computational DFT studies were performed using Gaussian 6.0 program package. HOMO-LUMO of L, optimized geometry, bond angle and bond length calculations were preceded at B3LYP/GENECP level with 6-31G (d,p) basis sets. Antimicrobial and antioxidant activities of complexes were evaluated.

Investigation of initiator metal efficiency in the ring‐opening polymerization of lactones: an experimental and computational study

AbstractPoly(δ‐valerolactone) (PVL) was synthesized by ring‐opening polymerization (ROP), employing tin(II) acetate (SnAcet2), lead(II) acetate trihydrate (PbAcet2·3H2O) and cadmium(II) acetate dihydrate (CdAcet2·2H2O) complexes as initiators without any co‐initiator. The highest molecular weight PVL (45 438 g mol−1, 91% yield) was obtained with CdAcet2·2H2O. Characterization of the synthesized products was performed by FTIR, 1H NMR, 13C NMR, gel permeation chromatography (GPC), matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF/TOF MS), TGA and DSC. Electrostatic data (natural bond orbital and Hirshfeld) and lowest unoccupied molecular orbital (LUMO) of the initiators were obtained by using several density functional theory methods (B3LYP, ωB97X‐D, PBEPBE, BPV86, HSEH1PBE, MPW1PW91, M06 and M062X). In addition, the initiation stage of the ROP mechanism of δ‐valerolactone with these metal acetate complexes was investigated at the ωB97X‐D level with a mixed basis set. It was computationally determined that the most effective initiator was also CdAcet2. The molecular weight variation of PVLs synthesized with these initiators can be associated with the combined evaluation of atomic charge, LUMO and orbital overlap analyses. The computationally obtained reaction barriers for the initiators support this idea, also. In addition, toxicity tests carried out for PVLs synthesized with acetate complexes containing Sn, Cd and Pb revealed that the Sn and Cd complexes do not have a toxic effect on cell viability at some dilution rates. © 2021 Society of Industrial Chemistry.

Transition metal and nitrogen-doped mesoporous carbons as cathode catalysts for anion-exchange membrane fuel cells

Transition metal- and nitrogen-doped mesoporous carbons are prepared, characterised, and used as oxygen reduction reaction (ORR) electrocatalysts in an anion exchange membrane fuel cell (AEMFC). Novel mesoporous carbon (MPC) based engineered catalyst support is doped using high-temperature pyrolysis in the presence of metal acetate(s) and 1,10-phenanthroline (nitrogen source). Three transition metals are used to prepare materials with the following metal compositions: Fe, Co, CoFe, FeMn, and CoMn. Physico-chemical characterisation shows the success of doping with similar morphology and textural properties of all materials. The rotating ring-disc electrode experiments in alkaline solution show that all five catalysts exhibit good electrocatalytic activity towards the ORR, with Fe-N-MPC, CoFe-N-MPC and FeMn-N-MPC being best-performing materials with excellent stability. The HO2– yield depends on the metal composition with Fe-N-MPC and FeMn-N-MPC giving the lowest percentage. The latter two are employed in the AEMFC and reach power densities of 473 and 474 mW cm–2, respectively.

XPS as a probe for the bonding nature in metal acetates

XPS appears to be an excellent probe for exploring the coordination chemistry in metal acetates.

Synthesis, Characterization and Bioactivity Studies of S-Allyl-β-N-(1-(4-methoxyphenyl)- ethylidene)dithiocarbazate and its Bis-chelated Cu(II), Ni(II) and Zn(II) Complexes

The general formula M(mAp-sadtc)2 type of metal complexes (where M = Cu2+, Ni2+, Zn2+) were synthesized by reaction of S-allyl-β-N-(1-(4-methoxyphenyl)ethylidene)dithiocarbazate ligand [H-(mAp-sadtc)] with metal(II) acetate salts (M = Ni2+, Cu2+ or Zn2+). The bis-chelated metal complexes were synthesized by subsequent reaction of metal(II) acetate salts and dithiocarbazate ligand in 1:2 proportion, respectively. The metal complexes and dithiocarbazate Schiff base were characterized by available methods like elemental analysis, 1H NMR, UV-Vis spectroscopy, 13C NMR, FT-IR spectroscopy, molar conductance and magnetic moments. Both nitrogen atoms of azomethine moiety (C=N) and deprotonated thiolate sulfur of dithiocarbazate ligand coordinated to the central metal ion formed five-membered rings on chelation. The synthesized dithiocarbazate ligand [H-(mAp-sadtc)] (1) and its bis-chelated M(mAp-sadtc)2 complexes (2-4) were screened for bioactivity against bacterial strains. The antibacterial results show that the metal(II) complexes exhibited significantly prominent antibacterial activity than dithiocarbazate ligand. Among the synthesized bis-chelated metal complexes, Ni-complex exhibited prominent antibacterial and antifungal activity as compared to other metal(II) complexes and ligand.

Changes in glucose concentration in the blood serum of carp due to exposure to heavy metals

The article deals with one of the most urgent problems of aquatic toxicology - the impact of heavy metals on the body of fish. The aim of the study was to analyze glucose indicators in carp after exposure to various concentrations of lead acetate, cadmium, zinc and copper. The experiment included 4 series of experiments, each of which was dedicated to a specific metal (lead, cadmium, zinc, copper). During the research, 1 control group (10 fish) was formed, and in each series of experiments, 3 experimental groups (10 fish) were formed. Experimental groups of fish were contained in a solution of heavy metal acetate with concentrations exceeding the MPC of heavy metals for fishery reservoirs by 10, 100 and 1000 times, respectively. The concentration of serum glucose was studied. An increase in glucose concentration due to heavy metal poisoning was found. However, exposure to 10 and 1000 MPC of zinc leads to a decrease in the concentration of glucose in the blood.

Electrochemical performance of spherical Li-rich LMNCO cathode materials prepared using a two-step spray-drying method

In this study we synthesized Li-rich Li1.2Ni0.13Mn0.54Co0.13O2 (LMNCO) as a composite cathode material through a two-step spray-drying method, using transition metal (TM) acetates and citric acid (CA, as a chelating agent) at various molar ratios and then calcining at various temperatures for various periods of time. This two-step spray-drying method created hierarchical nano/micro-sphere structures of the LMNCO cathode material. The LMNCO cathode exhibited the best electrochemical performance when synthesized with a TM:CA ratio of 3:2, a calcination temperature of 900 °C, and a calcination time of 5 h. This as-prepared LMNCO composite was then modified with polyimide (PI) at various weight ratios (PI/LMNCO = 0.5, 1.0, and 1.5 wt%) to improve its electrochemical properties. Among the various structures, the LMNCO cathode material coated with 1.0 wt% of PI at a layer thickness of approximately 1.88 nm achieved the best initial discharge capacities. This modified electrode also displayed enhanced cycle stability, with over 93.3 and 87.9% of the capacity retained after 30 cycles at 0.1C and 100 cycles at 1C, respectively. In comparison, the capacity retention of the unmodified LMNCO electrode measured under the same conditions was no more than 91.3% at 0.1C and 70.1% at 1C. Thus, surface modification with PI was an effective method for improving the coulombic efficiency, discharge capacity, and long-term cycling performance of the LMNCO cathode. Such PI-coated LMNCO composite cathode materials appear to be potential candidates for use in next-generation high-performance lithium-ion batteries.