Ag2O versus Cu2O in the Catalytic Isomerization of Coordinated Diaminocarbenes to Formamidines: A Theoretical Study.
Ontology highlight
ABSTRACT:
SUBMITTER: Van der Maelen JF
PROVIDER: S-EPMC8778719 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Balancing global energy needs against increasing greenhouse gas emissions requires new methods for efficient CO2 reduction. While photoreduction of CO2 is promising, the rational design of photocatalysts hinges on precise characterization of the surface catalytic reactions. Cu2O is a promising next-generation photocatalyst, but the atomic-scale description of the interaction between CO2 and the Cu2O surface is largely unknown, and detailed experimental measures are lacking. In this study, density-functional theory (DFT) calculations have been performed to identify the Cu2O (110) surface stoichiometry that favors CO2 reduction. To facilitate interpretation of scanning tunneling microscopy (STM) and X-ray absorption near-edge structures (XANES) measurements, which are useful for characterizing catalytic reactions, we present simulations based on DFT-derived surface morphologies with various adsorbate types. STM and XANES simulations were performed using the Tersoff-Hamann approximation and Bethe-Salpeter equation (BSE) approach, respectively. The results provide guidance for observation of CO2 reduction reaction on, and rational surface engineering of, Cu2O (110). They also demonstrate the effectiveness of computational image and spectroscopy modeling as a predictive tool for surface catalysis characterization.
| S-EPMC6508644 | biostudies-literature
Project description:Catalytic amounts of Co(Sal(tBu,tBu))Cl and organosilane irreversibly isomerize terminal alkenes by one position. The same catalysts effect cycloisomerization of dienes and retrocycloisomerization of strained rings. Strong Lewis bases like amines and imidazoles, and labile functionalities like epoxides, are tolerated.
| S-EPMC4277770 | biostudies-literature
Project description:Density functional theory calculations with a Hubbard U correction were used to investigate the selective oxidation of propylene on Cu2O(111) and Cu2O(110) surfaces, and the mechanism for the selective oxidation of propylene was discussed. On both surfaces, acrolein can be generated by two H-stripping reactions in the allylic hydrogen stripping path, while propylene oxide (PO), propanal, and acetone can be created through the propylene oxametallacycle intermediates in the epoxidation path. Our calculation results indicated that Cu2O has a high crystal plane-controlled phenomenon for the selective oxidation of propylene. It was found that the formations of propanal and acetone are unfavorable kinetically and acrolein is the main product on the (111) surface. On the (110) surface, the activation barrier of acrolein formation is too high to produce and PO becomes the favored product, which is different from the case of the (111) surface. Moreover, energetic span model analysis was carried out to discuss the selective oxidation of propylene on these two surfaces and confirm the above calculations. The present study can help people to design the proper crystal plane catalyst to get the target product of PO with high selectivity and activity in the selective oxidation of propylene.
| S-EPMC7114144 | biostudies-literature
Project description:Water oxidation is a linchpin in solar fuels formation, and catalysis by single-site ruthenium complexes has generated significant interest in this area. Combining several theoretical tools, we have studied the entire catalytic cycle of water oxidation for a single-site catalyst starting with [Ru(II)(tpy)(bpm)(OH(2))](2+) (i.e., [Ru(II)-OH(2)](2+); tpy is 2,2':6',2''-terpyridine and bpm is 2,2'-bypyrimidine) as a representative example of a new class of single-site catalysts. The redox potentials and pK(a) calculations for the first two proton-coupled electron transfers (PCETs) from [Ru(II)-OH(2)](2+) to [Ru(IV) = O](2+) and the following electron-transfer process to [Ru(V) = O](3+) suggest that these processes can proceed readily in acidic or weakly basic conditions. The subsequent water splitting process involves two water molecules, [Ru(V) = O](3+) to generate [Ru(III)-OOH](2+), and H(3)O(+) with a low activation barrier (~10 kcal/mol). After the key O-O bond forming step in the single-site Ru catalysis, another PECT process oxidizes [Ru(III)-OOH](2+) to [Ru(IV)-OO](2+) when the pH is lower than 3.7. Two possible forms of [Ru(IV)-OO](2+), open and closed, can exist and interconvert with a low activation barrier (< 7 kcal/mol) due to strong spin-orbital coupling effects. In Pathway 1 at pH = 1.0, oxygen release is rate-limiting with an activation barrier ~12 kcal/mol while the electron-transfer step from [Ru(IV)-OO](2+) to [Ru(V)-OO](3+) becomes rate-determining at pH = 0 (Pathway 2) with Ce(IV) as oxidant. The results of these theoretical studies with atomistic details have revealed subtle details of reaction mechanisms at several stages during the catalytic cycle. This understanding is helpful in the design of new catalysts for water oxidation.
| S-EPMC3465425 | biostudies-literature
Project description:Microbiological reductive sulfidation (RS) has rarely been documented, although it represents an efficient strategy for thiol formation. In this work, we reported on the sulfate-respiring bacterium Desulfovibrio sp.86 that has previously demonstrated RS activity toward the pesticide chlordecone. The purpose of this study was to assess its substrate versatility using a set of 28 carbonyls, to compare with chemical RS and to rationalize the observed trends using a dual experimental and theoretical approach. The chemical RS generally proceeds in two steps (S/O exchange using a sulfur donor like P4S10, reduction of the thione intermediate). Intriguingly, chlordecone was found to be converted into chlordecthiol following the first step. Hence, we designed a protocol and applied it to the 28 substrates to assess their propensity to be directly converted into thiols with the P4S10 treatment alone. Finally, we performed density functional theory calculations on these carbonyls and their thiocarbonyl derivatives to build a set of structural, electronic, and thermodynamic parameters. The results showed that chemical and microbiological RS probably involved two distinct mechanisms. Chemically, we observed that several carbonyls, possessing electron-withdrawing groups and/or aromatic rings, were directly transformed into thiols in the presence of P4S10. The correlation obtained with the electron affinity of the thiones led us to conclude that a probable single-electron reductive transfer occurred during the first step. We also found that Desulfovibrio sp.86 transformed a variety of aldehydes and ketones, without ever detecting thiones. No significant correlation was observed with the calculated parameters, but a relationship between aldehyde RS biotransformation and bacterial growth was observed. Differences in selectivity with chemical RS open the way for further applications in organic synthesis.
| S-EPMC7992082 | biostudies-literature
Project description:A new approach toward the asymmetric synthesis of optically active trifluoromethylated amines was enabled by an unprecedented, highly enantioselective catalytic isomerization of trifluoromethyl imines with a new chiral organic catalyst. Not only aryl but also alkyl trifluoromethylated amines could be obtained in high enantioselectivities.
| S-EPMC3475161 | biostudies-literature
Project description:The conversion of gaseous N2 to ammonia under mild conditions by artificial methods has become one of the hot topics and challenges in the field of energy research today. Accordingly, based on density function theory calculations, we comprehensively explored the d-block of metal atoms (Ti, V, Cr, Mn, Fe, Co, Ni, Nb, Mo, Ru, Rh, W, and Pt) embedded in arsenene (Ars) for different transition systems of phosphorus (P) coordination as potential electrocatalysts for N2 reduction reaction (NRR). By adopting a "two-step" strategy with stringent NRR catalyst screening criteria, we eventually selected Nb@P3-Ars as a research object for a further in-depth NRR mechanism study. Our results show that Nb@P3-Ars not only maintains the thermodynamic stability at mild temperatures but also dominates the competition with the hydrogen evolution reaction when used as the electrochemical NRR (e-NRR) catalyst. In particular, while the NRR process occurs by the distal mechanism, Nb@P3-Ars has a low overpotential (0.36 V), which facilitates the efficient reduction of N2. Therefore, this work predicts the possibility of Nb@P3-Ars as an e-NRR catalyst for reducing N2 from a theoretical perspective and provides significant insights and theoretical guidance for future experimental research.
| S-EPMC8015104 | biostudies-literature
Project description:The human telomerase reverse transcriptase (hTERT) utilizes a template within the integral RNA subunit (hTR) to direct extension of telomeres. Telomerase exhibits repeat addition processivity (RAP) and must therefore translocate the nascent DNA product into a new RNA:DNA hybrid register to prime each round of telomere repeat synthesis. Here, we use single-molecule FRET and nuclease protection assays to monitor telomere DNA structure and dynamics during the telomerase catalytic cycle. DNA translocation during RAP proceeds through a previously uncharacterized kinetic substep during which the 3'-end of the DNA substrate base pairs downstream within the hTR template. The rate constant for DNA primer realignment reveals this step is not rate limiting for RAP, suggesting a second slow conformational change repositions the RNA:DNA hybrid into the telomerase active site and drives the extrusion of the 5'-end of the DNA primer out of the enzyme complex.
| S-EPMC4107311 | biostudies-literature
Project description:Conformational isomerization can be guided by weak interactions such as chalcogen bonding (ChB) interactions. Here we report a catalytic strategy for asymmetric access to chiral sulfoxides by employing conformational isomerization and chalcogen bonding interactions. The reaction involves a sulfoxide bearing two aldehyde moieties as the substrate that, according to structural analysis and DFT calculations, exists as a racemic mixture due to the presence of an intramolecular chalcogen bond. This chalcogen bond formed between aldehyde (oxygen atom) and sulfoxide (sulfur atom), induces a conformational locking effect, thus making the symmetric sulfoxide as a racemate. In the presence of N-heterocyclic carbene (NHC) as catalyst, the aldehyde moiety activated by the chalcogen bond selectively reacts with an alcohol to afford the corresponding chiral sulfoxide products with excellent optical purities. This reaction involves a dynamic kinetic resolution (DKR) process enabled by conformational locking and facile isomerization by chalcogen bonding interactions.
| S-EPMC9378665 | biostudies-literature
Project description:This research was based on the quantum chemical calculations of a set of valid photoswitches of azobenzene compounds, with the aim of describing their thermal isomerization. The influences of familiar fluorine substitution and additional electron-donating groups (EDGs) and electron-withdrawing groups (EWGs) on the para-position were also systematically studied. The results show that the presence of fluorine in different ortho-positions has a distinct effect on the molecular orbital distribution of the E isomer, which realizes the purpose of splitting the n → π* transition between the E and Z isomers. On this basis, further para-substitution can allow tunability on the order of the energy level to the molecular orbitals through their influence on the conjugation pattern of the compound. It is the modification of the substituent on these positions that allows the photoisomerization to proceed under visible wavelength light surroundings. The thermal Z → E isomerization mechanism has also been analyzed, and a detailed comparison of these compounds has been made with respect to the thermal half-life τ 1/2, and the rate constants k Z-E . The results reveal that isomerization is thought to be a process of globally structural change, during which the effect of the substituents is determined by the extent of their influence on the conjugated system.
| S-EPMC9079044 | biostudies-literature