Iron complexes are commonly used in catalysis, but the identity of the active catalyst is often unknown, which prevents a detailed understanding of structure–reactivity relationships for catalyst ...design. Here we report the isolation and electronic structure determination of a well-defined, low-valent iron complex that is an active catalyst in the synthesis of cis,cis-1,5-cyclooctadiene (COD) from 1,3-butadiene. Spectroscopic and magnetic characterization establishes a high-spin Fe(I) center, which is supported by DFT studies, where partial metal–ligand antibonding orbital population is proposed to allow for facile ligand exchange during catalysis.
A single-site, iron catecholate-containing porous organic polymer was prepared and utilized as a stable and remarkably active catalyst for the hydrosilylation of ketones and aldehydes. In some ...instances, catalyst loadings of 0.043–2.1 mol % Fe were sufficient for complete hydrosilylation of aldehydes and ketones within 15 min at room temperature. The catalyst can be recycled at least three times without a drop in catalytic activity. This system is an example of an immobilized homogeneous catalyst with no homogeneous analogue.
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Microalgae have emerged as renewable and sustainable candidates for biorefineries since they can generate bioproducts and bioenergy through the removal of contaminants contained in ...wastewater. In the present study, a native microalgae consortium (NMC) is isolated from a wastewater treatment plant, and used to remove 100 mgL−1 Cr(III). The native microalgae consortium is enriched in a photobioreactor with the following conditions: Bold’s Basal Medium (BBM), pH 8, room temperature and 20 µmolm−2s−1 light intensity. The molecular characterization reveals the presence of the following species: Tetradesmus sp., Scenedesmus sp and Ascomycota sp. The development of microalgae is evaluated through the production of biomass, pH, protein, lipid and carbohydrate, while the consortium presents the potential to obtain biofuels. The ability of the consortium to absorb two different sources of Cr (III) was determined using real tannery wastewater and synthetic water prepared with Cr2(SO4)3. The adsorption efficiency of the microalgae is analyzed using adsorption isotherms of Langmuir model, indicating 99% adsorption efficiency of 100 mgL−1 Cr(III). FT-IR and SEM analyses enable to identify the presence of Cr(III) in the native microalgae consortium. The promising features of this NMC underpin the idea of establishing a sustainable biorefinery to generate different bioproducts, in order to achieve a resource-efficient biomass use for a circular bioeconomy.
The catalytic activity and electrochemical stability of Pd‐CeO2‐NR/C (CeO2‐NR: cerium oxide nanorods) for the Oxygen Reduction Reaction (ORR) and the Ethanol Oxidation Reaction (EOR) is shown in ...alkaline media and compared to Pd/C. Evaluation of catalytic activity for the ORR in a Rotating Ring Disc Electrode (RRDE) set‐up, shows that Pd‐CeO2‐NR/C promotes the reaction with a percentage of hydrogen peroxide production (%H2O2) around 2–4 %, and an electron transfer number (n) close to 4. Tafel plots demonstrates higher mass and specific activities of Pd‐CeO2‐NR/C than Pd/C. Moreover, from cyclic voltammetry tests, Pd‐CeO2‐NR/C shows a higher mass catalytic activity (jm= 697 mA mg−1Pd) for the EOR at a more negative onset potential (Eonset= 0.29 V/RHE) than Pd/C. After Accelerated Degradation Tests (ADT), Pd‐CeO2‐NR/C retains ∼98 % of its Electrochemically Active Surface Area (ECSA), higher than ∼51 % of Pd/C. After ADT, the performance of Pd‐CeO2‐NR/C remains similar for the ORR, while it is significantly higher for the EOR, compared to Pd/C. Thus, the addition of CeO2‐NR enhances the electrocatalytic behavior and stability of Pd towards the ORR and the EOR.
Pd‐CeO2‐NR/C (CeO2‐NR=cerium oxide nanorods) is a novel bifunctional nanocatalyst with application as anode for the Ethanol Oxidation Reaction (EOR) and as cathode for the Oxygen Reduction Reaction (ORR). It shows a high mass and specific catalytic activity for the ORR and excellent performance for the EOR (63 % increase in jm after ADT), along with remarkable electrochemical stability (98 % of ECSA retention) after ADT.
The analysis of Corporate Social Responsibility (CSR) practices in Ecuadorian companies is a relevant topic due to the indeterminacies existing in their implementation. The general objective of this ...analysis is to evaluate CSR practices in companies, considering aspects such as environmental sustainability, responsibility to employees, business ethics, and financial performance. To achieve this, the criteria and comprehensive solutions were evaluated through the modeling of the neutrosophic ELECTRE method. The results of the analysis indicate that the implementation of CSR practices can have multiple benefits, and comprehensive solutions with higher scores were identified, such as the implementation of ethics and transparency policies and the implementation of training and professional development programs. To enhance these comprehensive solutions, it is significant to establish clear and transparent policies, train the personnel, and communicate effectively with the community, and other relevant stakeholders. This ensures that CSR practices in Ecuadorian companies have a positive impact on the community. Keywords: Environmental sustainability, business ethics, corporate social responsibility.
This study explores a new mode of contortion in perylene diimides where the molecule is bent, like a bow, along its long axis. These bowed PDIs were synthesized through a facile fourfold Suzuki ...macrocyclization with aromatic linkers and a tetraborylated perylene diimide that introduces strain and results in a bowed structure. By altering the strings of the bow, the degree of bending can be controlled from flat to highly bent. Through spectroscopy and quantum chemical calculations, it is demonstrated that the energy of the lowest unoccupied orbital can be controlled by the degree of bending in the structures and that the energy of the highest occupied orbital can be controlled to a large extent by the constitution of the aromatic linkers. The important finding is that the bowing results not only in red‐shifted absorptions but also more facile reductions.
Bow to demands: A new mode of contortion in perylene diimides has been investigated, where the molecule is bent along its long axis like a bow. By adjusting the tension in the strings of the bow, the degree of bending can be controlled from flat to highly bowed. The important finding is that the bowing results not only in red‐shifted absorptions but also in more facile reductions.
The redox-active pincer ligand derived from bis(3,5-di-tert-butyl-2-phenol)amine, ONO super(cat)H sub(3), enables reductive elimination of di-tert-butyldisulfide from a putative iron(iii) dithiolate ...complex. The quinonate synthon of the ligand, ONO super(q)K, was used to prepare ONO super(q)FeX sub(2) complexes (1, X = Cl; 2, X = N(SiMe sub(3)) sub(2)), which were characterized by single-crystal X-ray diffraction, EPR and Mossbauer spectroscopies and identified to be high-spin iron(iii) complexes. The protonolysis of 2 with tetrachlorocatechol afforded either monomeric ONO super(q)Fe(ortho-C sub(6)O sub(2)Cl sub(4) )(py) (3) or dimeric {ONO super(q)Fe(ortho-C sub(6)O sub(2)Cl sub(4))} sub(2) (4). In contrast, the protonolysis of 2 with tert-butylthiol resulted in the extrusion of di-tert-butyldisulfide and the formation of a ONO super(cat)Fe fragment trapped with pyridine as monomeric ONO super(cat)Fe(py) sub(3) (5) or dimeric {ONO super(cat)Fe(py)} sub(2) (6). These results indicate that the ONOFe platform can promote reductive elimination of disulfide without incurring changes to the metal oxidation state.
We evaluated the effects of solvents with different polarities—methylene chloride (MC), methanol (MT), and hexane (HE) on the extraction of compounds from Mexican red pitaya seed oil. The fatty acid ...composition and the structural, rheological, and thermal properties of the different extracts were characterized. The results indicated that the highest yield of extraction was generated for MC (26.96%), as well as the greatest amount of Mono and Polyunsaturated fatty acids, while the lowest yield was for MT (16.86%). The antioxidant activity was greater in the MT treatment due to extractable compounds from high polarity. The generated extracts contained unsaturated fatty acids, mostly oleic and linoleic acids, and saturated fatty acids such as palmitic acid. The lowest solidification temperature was −6.35 ℃ for MC due to its fatty acid composition, and the degradation temperature was around 240 ℃. The viscosity is a quality parameter; the highest level was generated for the MC treatment, which was significantly different from HE and MT. The composition of the extracts was analyzed using the FT-IR spectroscopy and showed the typical characteristic of absorption bands for triglycerides with high frequency in bands 2852 cm −1 and 2924 cm −1 , which indicated that the samples were rich in unsaturated and polyunsaturated acids. These results suggested that pitaya seed oil is an excellent alternative source of essential fatty acids with potential physiological benefits.
Template‐assisted synthesis of well‐defined polynuclear clusters remains a challenge for M4 square planar topologies. Herein, we present a tetraamine scaffold RL(NH2)4, where L is a rigidified ...resorcin4arene, to direct the formation of C4‐symmetric RL(NH)4Cu4 clusters with Cu−Cu distances around 2.7 Å, suggesting metal‐metal direct interactions are operative since the sum of copper's van der Waals radii is 2.8 Å. DFT calculations display HOMO to HOMO‐3 residing all within a 0.1 eV gap. These four orbitals display significant electron density contribution from the Cu centers suggesting a delocalized electronic structure. The one‐electron oxidized Cu4+ species was probed by variable temperature X‐band continuous wave‐electron paramagnetic resonance (CW‐EPR), which displays a multiline spectrum at room temperature. This work presents a novel synthetic strategy for M4 clusters and a new platform to investigate activation of small molecules.
Polynuclear reaction sites catalyze some of the most challenging transformations in chemistry. Programmatic assembly of atomically‐precise cluster compounds is challenging. Here we describe the synthesis of supramolecular ligands designed to nucleate well‐defined square planar tetranuclear copper clusters, establishing metal‐metal interactions capable of delocalizing oxidation stress across the cluster.
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