Browse
Submit Data
Databases
API
Help

Dataset Information

10 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Increasing the Alkaline Stability of N,N-Diaryl Carbazolium Salts Using Substituent Electronic Effects.

ABSTRACT: Anion-exchange membrane fuel cells (AEMFCs) have attracted the attention of the scientific community during the past years, mostly because of the potential for eliminating the need for using costly platinum catalysts in the cells. However, the broad commercialization of AEMFCs is hampered by the low chemical stability of the cationic functional groups in the anion-conducting membranes required for the transportation of hydroxide ions in the cell. Improving the stability of these groups is directly connected with the ability to recognize the different mechanisms of the OH^- attack. In this work, we have synthesized eight different carbazolium cationic model molecules and investigated their alkaline stability as a function of their electronic substituent properties. Given that N,N-diaryl carbazolium salts decompose through a single-electron-transfer mechanism, the change in carbazolium electron density leads to a very significant impact on their chemical stability. Substituents with very negative Hammett parameters demonstrate unparalleled stability toward dry hydroxide. This study provides guidelines for a different approach to develop stable quaternary ammonium salts for AEMFCs, making use of the unique parameters of this decomposition mechanism.

SUBMITTER: Gjineci N

PROVIDER: S-EPMC8014904 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Substituent effects on the stability and antioxidant activity of spirodiazaselenuranes.

Project description:Spirodiazaselenuranes are structurally interesting compounds and the stability of these compounds depends highly on the nature of the substituents attached to the nitrogen atoms. Aromatic substituents are known to play important roles in stabilizing the Se-N bonds in spiro compounds. In this study, several spirodiazaselenuranes are synthesized by introducing benzylic and aliphatic substituents to understand their effect on the stability of the Se-N bonds and the antioxidant activity. Replacement of phenyl substituent by benzyl/alkyl groups significantly reduces the stability of the spirodiazaselenuranes and slows down the oxidative cyclization process. The selenium centre in the spiro compounds undergoes further oxidation to produce the corresponding selenurane oxides, which are stable at room temperature. Comparison of the glutathione peroxidase (GPx) mimetic activity of the compounds showed that the diaryl selenides having heterocyclic rings are significantly more active due to the facile oxidation of the selenium centre. However, the activity is reduced significantly for compounds having aliphatic substituents. In addition to GPx activity, the compounds also inhibit peroxynitrite-mediated nitration and oxidation reaction of protein and small molecules, respectively. The experimental observations suggest that the antioxidant activity is increased considerably upon substitution of the aromatic group with the benzylic/aliphatic substituents on the nitrogen atoms.

| S-EPMC6332218 | biostudies-literature

Revealing substituent effects on the electronic structure and planarity of Ni-porphyrins.

Project description:Using density functional theory, we have studied the effects on structural and electronic consequences (including HOMO-LUMO energy gaps, vertical ionization potentials (IPv), and vertical electron affinities (EAv)) of the following two factors: (a) meso- and ?-substituents acting as inductive donors (CH3), inductive acceptors that are electron-donating through resonance (Br), inductive electron acceptors (CF3), and resonance enabled acceptors (NO2); and (b) complete replacement of pyrrole nitrogens with P-atoms. The principal results of the study are: (1) For the bare Ni-porphyrin, the solvents were found not to affect the HOMO-LUMO gaps but to change the IPv and EAv noticeably. (2) In the series CH3 ? Br ? CF3 ? NO2 the HOMO-LUMO energy gaps, IPv, and EAv increase for both meso- and ?-substituents. The ruffling distortion of the porphyrin core is retained, and becomes stronger for the two acceptor groups. In general, effects of meso-substituents on the ruffling distortion of the porphyrin core is more pronounced. (3) Most significantly, complete replacement of pyrrole nitrogens in the NiP with phosphorus atoms produces the species, NiP(P)4, with the structural and electronic features drastically different from the original NiP. This implies that NiP(P)4 can possess interesting and unusual novel properties, including aromaticity and reactivity, leading to its various beneficial potential applications. Furthermore, NiP(P)4 high stability both in the gas phase and different solvents was shown, implying the feasibility of its synthesis.

| S-EPMC3613567 | biostudies-literature

Tuning hydrogel properties and function using substituent effects.

Project description:The physical properties and function of hydrogels are shown to depend on the substituents present in three novel 1,3,5-tri-azaadamantane (TAA) cross-linkers. Gel stiffness and degradation rate at varied pHs could be predictably tuned with the cross-linker substituents used to form the gel. Subsequently, protein release from the hydrogel were controlled with chemical structure of the cross-linker.

| S-EPMC2915463 | biostudies-literature

Modulation of water exchange in europium(III) DOTA-tetraamide complexes via electronic substituent effects.

Project description:The chemical exchange saturation transfer (CEST) efficiency for a series Eu3+-based tetraamide complexes bearing p-substituents on a single coordinating pendant arm is highly sensitive to water exchange rates. The CEST effect increases in the order Me < MeO < F approximately CO2tBu < CN < H. These results show that CEST contrast can be modulated by changes in electron density at a single ligating atom, and this forms the basis of creating imaging agents that respond to chemical oxidation and reduction.

| S-EPMC2716115 | biostudies-literature

Modeling the Alkaline Hydrolysis of Diaryl Sulfate Diesters: A Mechanistic Study.

Project description:Phosphate and sulfate esters have important roles in regulating cellular processes. However, while there has been substantial experimental and computational investigation of the mechanisms and the transition states involved in phosphate ester hydrolysis, there is far less work on sulfate ester hydrolysis. Here, we report a detailed computational study of the alkaline hydrolysis of diaryl sulfate diesters, using different DFT functionals as well as mixed implicit/explicit solvation with varying numbers of explicit water molecules. We consider the impact of the computational model on computed linear free-energy relationships (LFER) and the nature of the transition states (TS) involved. We obtain good qualitative agreement with experimental LFER data when using a pure implicit solvent model and excellent agreement with experimental kinetic isotope effects for all models used. Our calculations suggest that sulfate diester hydrolysis proceeds through loose transition states, with minimal bond formation to the nucleophile and bond cleavage to the leaving group already initiated. Comparison to prior work indicates that these TS are similar in nature to those for the alkaline hydrolysis of neutral arylsulfonate monoesters or charged phosphate diesters and fluorophosphates. Obtaining more detailed insights into the transition states involved assists in understanding the selectivity of enzymes that hydrolyze these reactions.

| S-EPMC7304899 | biostudies-literature

The Alkaline Stability of Anion Exchange Membrane for Fuel Cell Applications: The Effects of Alkaline Media.

Project description:Alkaline alcohols (methanol, ethanol, propanol, and ethylene glycol) have been applied as fuels for alkaline anion exchange membrane fuel cells. However, the effects of alkaline media on the stability of anion exchange membranes (AEMs) are still elusive. Here, a series of organic cations including quaternary ammonium, imidazolium, benzimidazolium, pyridinium, phosphonium, pyrrolidinium cations, and their corresponding cationic polymers are synthesized and systematically investigated with respect to their chemical stability in various alkaline media (water, methanol, ethanol, and dimethyl sulfoxide) by quantitative 1H nuclear magnetic resonance spectroscopy and density functional theory calculations. In the case of protic solvents (water, methanol, and ethanol), the lower dielectric constant of the alkaline media, the lower is the lowest unoccupied molecular orbital (LUMO) energy of the organic cation, which leads to the lower alkaline stability of cations. However, the hydrogen bonds between the anions and protic solvents weaken the effects of low dielectric constant of the alkaline media. The aprotic solvent accelerated the SN2 degradation reaction of "naked" organic cations. The results of this study suggest that both the chemical structure of organic cations and alkaline media (fuels) applied affect the alkaline stability of AEMs.

| S-EPMC6097010 | biostudies-literature

Effect of Alkaline Salts on Calcium Sulfoaluminate Cement Hydration.

Project description:This work analyzes the effect of the presence of 5 wt.% of solid sodium salts (Na2SO4, Na2CO3, and Na2SiO3) on calcium sulfoaluminate cement (CSA) hydration, addresses hydration kinetics; 2-, 28-, and 90-d mechanical strength, and reaction product microstructure (with X-ray diffraction (XRD), and Fourier transform infrared spectroscopy, (FTIR). The findings show that the anions affect primarily the reactions involved. Ettringite and AH3, are the majority hydration products, while monosulfates are absent in all of the samples. All three salts hasten CSA hydration and raise the amount of ettringite formed. Na2SO4 induces cracking in the ≥28-d pastes due to post-hardening gypsum and ettringite formation from the excess SO42- present. Anhydrite dissolves more rapidly in the presence of Na2CO3, prompting carbonation. Na2SiO3 raises compressive strength and exhibits strätlingite as one of its reaction products.

| S-EPMC8037319 | biostudies-literature

Substituent Effects on the Electrochemistry and Electronic Coupling of Terphenyl-Bridged Cyclometalated Ruthenium-Amine Conjugated Complexes.

Project description:Six terphenyl-bridged cyclometalated ruthenium-amine conjugated complexes 4(PF6)-9(PF6) were synthesized and studied. Three different substituents, methoxy, methyl, and chloro, were used to vary the electronic nature of the amine unit, and two terminal ligands 2,2':6',2?-terpyridine (tpy) and trimethyl-4,4',4?-tricarboxylate-2,2':6',2?-terpyridine (Me3tctpy) were used to tune the electronic nature of the ruthenium component. All complexes, except 7(PF6) with the methoxy substituent and Me3tctpy ligand, display two well-separated redox waves in the potential range of +0.5 to +1.1 V versus Ag/AgCl. The regular electrochemical changes of these complexes help to establish the oxidation order of ruthenium and amine and hence of the direction of the electron transfer in odd-electron state. The degree of electronic coupling was estimated by analyzing the donor-to-acceptor charge transfer band in the near-infrared region obtained by oxidative spectroelectrochemical measurements. Electron paramagnetic resonance analyses and density functional theory calculations were performed on the one-electron oxidized forms to obtain information on the spin distribution of these complexes.

| S-EPMC6643824 | biostudies-literature

Increasing storage stability of freeze-dried plasma using trehalose.

Project description:Preservation of blood plasma in the dried state would facilitate long-term storage and transport at ambient temperatures, without the need of to use liquid nitrogen tanks or freezers. The aim of this study was to investigate the feasibility of dry preservation of human plasma, using sugars as lyoprotectants, and evaluate macromolecular stability of plasma components during storage. Blood plasma from healthy donors was freeze dried using 0-10% glucose, sucrose, or trehalose, and stored at various temperatures. Differential scanning calorimetry was used to measure the glass transition temperatures of freeze-dried samples. Protein aggregation, the overall protein secondary structure, and oxidative damage were studied under different storage conditions. Differential scanning calorimetry measurements showed that plasma freeze-dried with glucose, sucrose and trehalose have glass transition temperatures of respectively 72±3.4°C, 46±11°C, 15±2.4°C. It was found that sugars diminish freeze-drying induced protein aggregation in a dose-dependent manner, and that a 10% (w/v) sugar concentration almost entirely prevents protein aggregation. Protein aggregation after rehydration coincided with relatively high contents of ?-sheet structures in the dried state. Trehalose reduced the rate of protein aggregation during storage at elevated temperatures, and plasma that is freeze- dried plasma with trehalose showed a reduced accumulation of reactive oxygen species and protein oxidation products during storage. In conclusion, freeze-drying plasma with trehalose provides an attractive alternative to traditional cryogenic preservation.

| S-EPMC7289390 | biostudies-literature

Disilane Cleavage with Selected Alkali and Alkaline Earth Metal Salts.

Project description:The industry-scale production of methylchloromonosilanes in the Müller-Rochow Direct Process is accompanied by the formation of a residue, the direct process residue (DPR), comprised of disilanes Men Si2 Cl6-n (n=1-6). Great research efforts have been devoted to the recycling of these disilanes into monosilanes to allow reintroduction into the siloxane production chain. In this work, disilane cleavage by using alkali and alkaline earth metal salts is reported. The reaction with metal hydrides, in particular lithium hydride (LiH), leads to efficient reduction of chlorine containing disilanes but also induces disproportionation into mono- and oligosilanes. Alkali and alkaline earth chlorides, formed in the course of the reduction, specifically induce disproportionation of highly chlorinated disilanes, whereas highly methylated disilanes (n>3) remain unreacted. Nearly quantitative DPR conversion into monosilanes was achieved by using concentrated HCl/ether solutions in the presence of lithium chloride.

| S-EPMC6856802 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data