Browse
Submit Data
Databases
API
Help

Dataset Information

27 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Tuning the π-Accepting Properties of Mesoionic Carbenes: A Combined Computational and Experimental Study.

ABSTRACT: Mesoionic imidazolylidenes are recognized as excellent electron-donating ligands in organometallic and main group chemistry. However, these carbene ligands typically show poor π-accepting properties. A computational analysis of 71 mesoionic imidazolylidenes that bear different aryl or heteroaryl substituents in C2 position was performed. The study has revealed that a diphenyltriazinyl (Dpt) substituent renders the corresponding carbene particularly π-acidic. The computational results could be corroborated experimentally. A mesoionic imidazolylidene with a Dpt substituent was found to be a better σ-donor and a better π-acceptor compared to an Arduengo-type N-heterocyclic carbene. To demonstrate the utility of the new carbene, the ligand was used to stabilize a low-valent paramagnetic tin compound.

SUBMITTER: Dong Z

PROVIDER: S-EPMC8456875 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Combined Experimental and Computational Study of Ruthenium <i>N</i>-Hydroxyphthalimidoyl Carbenes in Alkene Cyclopropanation Reactions.

Project description:A combined experimental-computational approach has been used to study the cyclopropanation reaction of N-hydroxyphthalimide diazoacetate (NHPI-DA) with various olefins, catalyzed by a ruthenium-phenyloxazoline (Ru-Pheox) complex. Kinetic studies show that the better selectivity of the employed redox-active NHPI diazoacetate is a result of a much slower dimerization reaction compared to aliphatic diazoacetates. Density functional theory calculations reveal that several reactions can take place with similar energy barriers, namely, dimerization of the NHPI diazoacetate, cyclopropanation (inner-sphere and outer-sphere), and a previously unrecognized migratory insertion of the carbene into the phenyloxazoline ligand. The calculations show that the migratory insertion reaction yields an unconsidered ruthenium complex that is catalytically competent for both the dimerization and cyclopropanation, and its relevance is assessed experimentally. The stereoselectivity of the reaction is argued to stem from an intricate balance between the various mechanistic scenarios.

| S-EPMC8419840 | biostudies-literature

The role of the donor group and electron-accepting substitutions inserted in π-linkers in tuning the optoelectronic properties of D-π-A dye-sensitized solar cells: a DFT/TDDFT study.

Project description:The design of low-cost and high-efficiency sensitizers is one of the most important factors in the expansion of dye-sensitized solar cells (DSSCs). To obtain effective sensitizer dyes for applications in dye-sensitized solar cells, a series of metal-free organic dyes with the D-π-A-A arrangement and with different donor and acceptor groups have been designed by using computational methodologies based on density functional theory (DFT) and time-dependent density functional theory (TD-DFT). We have designed JK-POZ(1-3) and JK-PTZ(1-3) D-π-A-A organic dyes by modifying the donor and π-linker units of the JK-201 reference dye. Computational calculations of the structural, photochemical properties and electrochemical properties, as well as the key parameters related to the short-circuit current density and open-circuit voltage, including light-harvesting efficiency (LHE), singlet excited state lifetime (τ), reorganization energies (λ total), electronic injection-free energy (ΔG inject) and regeneration driving forces (ΔG reg) of dyes were calculated and analyzed. Moreover, charge transfer parameters, such as the amount of charge transfer (q CT), the charge transfer distance (D CT), and dipole moment changes (μ CT), were investigated. The results show that ΔG reg, λ max, λ total and τ of JK-POZ-3 and JK-PTZ-3 dyes are superior to those of JK-201, indicating that novel JK-POZ-3 and JK-PTZ-3 dyes could be promising candidates for improving the efficiency of the DSSCs devices.

| S-EPMC9006569 | biostudies-literature

Stabilization of Boron-Boron Triple Bonds by Mesoionic Carbenes.

Project description:Density functional theory-based computations are carried out to analyze the electronic structure and stability of B2(MIC)2 complexes, where MIC is a mesoionic carbene, viz., imidazolin-4-ylidenes, pyrazolin-4-ylidene, 1,2,3-triazol-5-ylidene, tetrazol-5-ylidene, and isoxazol-4-ylidene. The structure, stability, and the nature of bonding of these complexes are further compared to those of the previously reported B2(NHC)2 and B2(cAAC)2. A thorough bonding analysis via natural bond order, molecular orbital, and energy decomposition analyses (EDA) in combination with natural orbital for chemical valence (NOCV) reveals that MICs are suitable ligands to stabilize B2 species in its (3)1∑g + excited state, resulting in an effective B-B bond order of 3. Their high dissociation energy and endergonicity at 298 K for the dissociations L-BB-L → 2 B-L and L-BB-L → BB + 2 L (L = Ligand) indicate their viability at ambient condition. The donor property of MICs is comparable to that of NHCMe. The orbital interaction plays a greater role than the coulombic interaction in forming the B-L bonds. The EDA-NOCV results show that the sum of the orbital energies associated with the (+, +) and (+, -) L→[B2]←L σ-donations is far larger than that of L←[B2]→L π-back donation. It also reveals that cAACMe possesses the largest σ-donation and π-back donation abilities among the studied ligands, and the σ-donation and π-back donation abilities of MICs are comparable to those of NHCMe. Therefore, the present study shows that MICs would also be an excellent choice as ligands to experimentally realize new compounds having a strong B-B triple bond.

| S-EPMC6644692 | biostudies-literature

Mesoionic Carbenes in Low- to High-Valent Vanadium Chemistry.

Project description:We report the synthesis of vanadium(V) oxo complex 1 with a pincer-type dianionic mesoionic carbene (MIC) ligand L1 and the general formula [VOCl(L1)]. A comparison of the structural (SC-XRD), electronic (UV-vis), and electrochemical (cyclic voltammetry) properties of 1 with the benzimidazolinylidene congener 2 (general formula [VOCl(L2)]) shows that the MIC is a stronger donor also for early transition metals with low d-electron population. Since electrochemical studies revealed both complexes to be reversibly reduced, the stronger donor character of MICs was not only demonstrated for the vanadium(V) but also for the vanadium(IV) oxidation state by isolating the reduced vanadium(IV) complexes [Co(Cp*)2][1] and [Co(Cp*)2][2] ([Co(Cp*)2] = decamethylcobaltocenium). The electronic structures of the compounds were investigated by computational methods. Complex 1 was found to be a moderate precursor for salt metathesis reactions, showing selective reactivity toward phenolates or secondary amides, but not toward primary amides and phosphides, thiophenols, or aryls/alkyls donors. Deoxygenation with electron-rich phosphines failed to give the desired vanadium(III) complex. However, treatment of the deprotonated ligand precursor with vanadium(III) trichloride resulted in the clean formation of the corresponding MIC vanadium(III) complex 6, which undergoes a clean two-electron oxidation with organic azides yielding the corresponding imido complexes. The reaction with TMS-N3 did not afford a nitrido complex, but instead the imido complex 10. This study reveals that, contrary to popular belief, MICs are capable of supporting early transition-metal complexes in a variety of oxidation states, thus making them promising candidates for the activation of small molecules and redox catalysis.

| S-EPMC8527456 | biostudies-literature

Structural and Photophysical Properties of Various Polypyridyl Ligands: A Combined Experimental and Computational Study.

Project description:Covalent triazine frameworks (CTFs) with polypyridyl ligands are very promising supports to anchor photocatalytic complexes. Herein, we investigate the photophysical properties of a series of ligands which vary by the extent of the aromatic system, the nitrogen content and their topologies to aid in selecting interesting building blocks for CTFs. Interestingly, some linkers have a rotational degree of freedom, allowing both a trans and cis structure, where only the latter allows anchoring. Therefore, the influence of the dihedral angle on the UV-Vis spectrum is studied. The photophysical properties are investigated by a combined computational and experimental study. Theoretically, both static and molecular dynamics simulations are performed to deduce ground- and excited state properties based on density functional theory (DFT) and time-dependent DFT. The position of the main absorption peak shifts towards higher wavelengths for an increased size of the π-system and a higher π-electron deficiency. We found that the position of the main absorption peak among the different ligands studied in this work can amount to 271 nm; which has a significant impact on the photophysical properties of the ligands. This broad range of shifts allows modulation of the electronic structure by varying the ligands and may help in a rational design of efficient photocatalysts.

| S-EPMC7756581 | biostudies-literature

Dissecting C-H∙∙∙π and N-H∙∙∙π Interactions in Two Proteins Using a Combined Experimental and Computational Approach.

Project description:C-H∙∙∙π and N-H∙∙∙π interactions can have an important contribution for protein stability. However, direct measurements of these interactions in proteins are rarely reported. In this work, we combined the mutant cycle experiments and molecular dynamics (MD) simulations to characterize C-H∙∙∙π and N-H∙∙∙π interactions and their cooperativity in two model proteins. It is shown that the average C-H∙∙∙π interaction per residue pair is ~ -0.5 kcal/mol while the N-H∙∙∙π interaction is slightly stronger. The triple mutant box measurement indicates that N-H∙∙∙π∙∙∙C-H∙∙∙π and C-H∙∙∙π∙∙∙C-H∙∙∙π can have a positive or negative cooperativity. MD simulations suggest that the cooperativity, depending on the local environment of the interactions, mainly arises from the geometric rearrangement when the nearby interaction is perturbed.

| S-EPMC6934659 | biostudies-literature

Nickel-Catalyzed Intramolecular 1,2-Aryl Migration of Mesoionic Carbenes (iMICs).

Project description:Intramolecular 1,2-Dipp migration of seven mesoionic carbenes (iMICAr ) 2 a-g (iMICAr =ArC{N(Dipp)}2 CHC; Ar=aryl; Dipp=2,6-iPr2 C6 H3 ) under nickel catalysis to give 1,3-imidazoles (IMDAr ) 3 a-g (IMDAr =ArC{N(Dipp)CHC(Dipp)N}) has been reported. The formation of 3 indicates the cleavage of an N-CDipp bond and the subsequent formation of a C-CDipp bond in 2, which is unprecedented in NHC chemistry. The use of 3 in accessing super-iMICs (5) (S-iMIC=ArC{N(Dipp)N(Me)C(Dipp)}C) has been shown with selenium (6), gold (7), and palladium (8) compounds. The quantification of the stereoelectronic properties reveals the superior σ-donor strength of 5 compared to that of classical NHCs. Remarkably, the percentage buried volume of 5 (%Vbur =45) is the largest known amongst thus far reported iMICs. Catalytic studies show a remarkable activity of 5, which is consistent with their auspicious stereoelectronic features.

| S-EPMC7898293 | biostudies-literature

Crystalline 1H-1,2,3-triazol-5-ylidenes: new stable mesoionic carbenes (MICs).

Project description: Not available

| S-EPMC3131155 | biostudies-literature

Combined experimental and computational study of high-pressure behavior of triphenylene.

Project description:We have performed measurements of Raman scattering, synchrotron x-ray diffraction, and visible transmission spectroscopy combined with density functional theory calculations to study the pressure effect on solid triphenylene. The spectroscopic results demonstrate substantial change of the molecular configuration at 1.4 GPa from the abrupt change of splitting, disappearance, and appearance of some modes. The structure of triphenylene is found be to stable at high pressures without any evidence of structural transition from the x-ray diffraction patterns. The obtained lattice parameters show a good agreement between experiments and calculations. The obtained band gap systematically decreases with increasing pressure. With the application of pressure, the molecular planes become more and more parallel relative to each other. The theoretical calculations indicate that this organic compound becomes metallic at 180 GPa, fueling the hope for the possible realization of superconductivity at high pressure.

| S-EPMC4861917 | biostudies-other

Rationalization of the Color Properties of Fluorescein in the Solid State: A Combined Computational and Experimental Study.

Project description:Fluorescein is known to exist in three tautomeric forms defined as quinoid, zwitterionic, and lactoid. In the solid state, the quinoid and zwitterionic forms give rise to red and yellow materials, respectively. The lactoid form has not been crystallized pure, although its cocrystal and solvate forms exhibit colors ranging from yellow to green. An explanation for the observed colors of the crystals is found using a combination of UV/Vis spectroscopy and plane-wave DFT calculations. The role of cocrystal coformers in modifying crystal color is also established. Several new crystal structures are determined using a combination of X-ray and electron diffraction, solid-state NMR spectroscopy, and crystal structure prediction (CSP). The protocol presented herein may be used to predict color properties of materials prior to their synthesis.

| S-EPMC4982065 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

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