Search

This article provides a comprehensive overview of the Nobel Prizes in Chemistry related to computational chemistry. It explores the history and development of the field, highlighting the contributions of notable scientists and their groundbreaking work in areas such as chemical dynamics, molecular structure, and electronic structure calculations. The article also discusses the Nobel Prizes awarded in specific years, recognizing the achievements of laureates and their significant research contributions. It acknowledges the underrepresentation of women in Nobel Prizes and reflects on the author's personal experiences and hopes for the future of computational chemistry. [Extracted from the article]

This article presents an educational overview of the latest mathematical developments in coupled cluster (CC) theory, beginning with Schneider's seminal work from 2009 that introduced the first local analysis of CC theory. We provide a tutorial review of second quantization and the CC ansatz, laying the groundwork for understanding the mathematical basis of the theory. This is followed by a detailed exploration of the most recent mathematical advancements in CC theory. Our review starts with an in‐depth look at the local analysis pioneered by Schneider which has since been applied to various CC methods. We subsequently discuss the graph‐based framework for CC methods developed by Csirik and Laestadius. This framework provides a comprehensive platform for comparing different CC methods, including multireference approaches. Next, we delve into the latest numerical analysis results analyzing the single reference CC method developed by Hassan, Maday, and Wang. This very general approach is based on the invertibility of the CC function's Fréchet derivative. We conclude the article with a discussion on the recent incorporation of algebraic geometry into CC theory, highlighting how this novel and fundamentally different mathematical perspective has furthered our understanding and provides exciting pathways to new computational approaches. [ABSTRACT FROM AUTHOR]

Starting compound 1 was synthesized according to reference.1 Benzylidene thiazole pyrimidin-3(5H)-ones were synthesized reactions of 1 with bromoacetic acid and various aryl-aldehydes in the same vessel via one-step, unlike studies in the literature. Quantum chemical parameters and full geometry optimizations for all compounds were computed using DFT based on B3LYP. Cytotoxic action potential of synthesized compounds was evaluated using trypan blue dye exclusion and MTT assays in different cell lines including adenocarcinoma alveolar basal epithelial-like adherent A549 cells, the colon adenocarcinoma HT-29 cells, prostate adenocarcinoma DU-145 cells, and diploid ARPE-19 retinal pigment epithelial cells. Embryotoxicity and genotoxicity assessments were performed on pluripotent human embryonal carcinoma NT2 and human lymphocyte cells, respectively. Compound A1 exhibited good anticancer activity on A549 and DU-145 cell lines, and the compounds including A3, 4, 6, and 9 induced cytotoxicity on A549 cells. The compounds A1-10 also showed a good biosafety profile at relatively lower concentrations. [ABSTRACT FROM AUTHOR]

The catalytic activity of Vanadium, Scandium, Titanium and Ferrum (Sc, V, Ti and Fe) doped Carbon, Silicon, Germanium, Aluminum Nitride and Boron Phosphide (C60, Si46, Al30N30, Ge72 and B41P41) nanocages for reduction reaction of carbon dioxide are investigated. The ∆Ebinding of V2-C58, Sc2-Si44, V2-Al29N29, Ti2-Ge70 and Fe2-B40P40 nanocages are -5.90, -6.23, -6.13, -7.28 and -6.97 eV, respectively. The ∆Eformation of V2-C58, Sc2-Si44, V2-Al29N29, Ti2-Ge70 and Fe2-B40P40 nanocages are -4.54, -4.84, -4.76, -5.66 and -5.42 eV, respectively. The ∆Ebinding and ∆Eformation of double metal atoms doped nanocages are demonstrated that they are stable nano-structures. The rate-determining step for CH4 and CH3OH production is the catalyst-*CO → catalyst-*CHO on double metal atoms doped nanocages. The overpotential of CH3OH and CH4 production on Ti2-Ge70, Fe2-B40P40, V2-C58, V2-Al29N29 and Sc2-Si44 nanocages are 0.19 to 0.26 V and 0.18 to 0.24 V, respectively. The Sc2-Si44, V2-Al29N29, Ti2-Ge70 and Fe2-B40P40 can catalyze the CO2-RR with high efficiency. The double metal atoms doped nanocages (Ti2-Ge70, Fe2-B40P40, V2-C58, V2-Al29N29 and Sc2-Si44) can be considered as electro-catalysts for CH4 and CO3OH creation from CO2 reduction reaction. [ABSTRACT FROM AUTHOR]

Furfural is an industrially relevant biobased chemical platform. Unlike classical furan, or C‐alkylated furans, which have been previously described in the current literature, the =C5H bond of furfural is unreactive. As a result, on a large scale, C=C and C=O bond hydrogenation/hydrogenolysis is mainly performed, with furfuryl alcohol and methyl tetrahydrofuran being the two main downstream chemicals. Here, we show that the derivatization of the ‐CHO group of furfural restores the reactivity of its =C5H bond, thus permitting its double condensation on various alkyl aldehydes. Overcoming the recalcitrance of the =C5H bond of furfural has opened an access to a biobased monomer, whose potential have been investigated in the fabrication of renewably‐sourced poly(silylether). By means of a combined theoretical‐experimental study, a reactivity scale for furfural and its protected derivatives against carbonylated compounds has been established using an electrophilicity descriptor, a means to predict the molecular diversity and complexity this pathway may support, and also to de‐risk any project related to this topic. Finally, by using performance criteria for industrial operations in the field of fuels and commodities, we discussed the industrial potential of this work in terms of cost, E‐factor, reactor productivity and catalyst consumption. [ABSTRACT FROM AUTHOR]

The critical role of global electron density transfer (GEDT) in increasing the reaction rate of polar organic reactions has been studied within the framework of Molecular Electron Density Theory (MEDT). To this end, the series of the polar Diels–Alder (P-DA) reactions of cyclopentadiene with cyanoethylene derivatives, for which experimental kinetic data are available, have been chosen. A complete linear correlation between the computed activation Gibbs free energies and the GEDT taking place at the polar transition state structures (TSs) is found; the higher the GEDT at the TS, the lower the activation Gibbs free energy. An interacting quantum atoms energy partitioning analysis allows for establishing a complete linear correlation between the electronic stabilization of the electrophilic ethylene frameworks and the GEDT taking place at the polar TSs. This finding supports Parr's proposal for the definition of the electrophilicity ω index. The present MEDT study establishes the critical role of the GEDT in the acceleration of polar reactions, since the electronic stabilization of the electrophilic framework with the electron density gain is greater than the destabilization of the nucleophilic one, making a net favorable electronic contribution to the decrease in the activation energy. [ABSTRACT FROM AUTHOR]

To satisfy the need for catalyst materials with high activity, selectivity, and stability for energy conversion, material design and discovery guided by theoretical insights are a necessity. In the past decades, the rise in theoretical investigations into the properties of catalyst materials, reaction mechanisms, and catalyst design principles has shed light on the catalysis field. Quantitative structure–activity relationships have been developed through incorporating spectroscopic simulations, electronic structure calculations, and reaction mechanistic studies. In this review, we report the state-of-the-art computational approaches to catalyst materials characterization for supported single-atom and cluster catalysts utilizing spectroscopic simulations, i.e., XANES simulation, and material properties investigation via electronic-structure calculations. Furthermore, approaches regarding reaction mechanisms, focusing on active site heterogeneity, are also discussed. [ABSTRACT FROM AUTHOR]

Context: The abilities of Co-Al18P18, Ni-Al21N21, Fe-B24N24, Mn-B27P27, Ti-C60 and Cu-Si72 as catalysts for N2-RR to create the NH3 are investigated by theoretical levels. The ∆Eadoption and ∆Eformation of Co-Al18P18, Ni-Al21N21, Fe-B24N24, Mn-B27P27, Ti-C60 and Cu-Si72 are investigated. The ∆Eadsorption of N2-RR intermediates and ΔGreaction of reaction steps of N2-RR on Co-Al18P18, Ni-Al21N21, Fe-B24N24, Mn-B27P27, Ti-C60 and Cu-Si72 are examined. In acceptable mechanisms, the *NN → *NNH step is potential limiting step and *NN → *NNH step in enzymatic mechanism is endothermic reaction. The ∆Greaction of *NHNH2 → *NH2NH2 step on Co-Al18P18, Ni-Al21N21, Fe-B24N24, Mn-B27P27, Ti-C60 and Cu-Si72 are -0.904, -0.928, -0.860, -0.882, -0.817 and -0.838 eV, respectively. The Co-Al18P18 and Ni-Al21N21 have the highest ∆Greaction values for reaction steps of N2-RR. Finally, it can be concluded that the Co-Al18P18, Ni-Al21N21, Fe-B24N24 and Mn-B27P2 have acceptable potential for N2-RR by acceptable pathways. Methods: The structures of Co-Al18P18, Ni-Al21N21, Fe-B24N24, Mn-B27P27, Ti-C60 and Cu-Si72 and N2-RR intermediates are optimized by PW91PW91/6-311+G (2d, 2p) and M06-2X/cc-pVQZ as theoretical levels in GAMESS software. The convergence for force set displacement of Co-Al18P18, Ni-Al21N21, Fe-B24N24, Mn-B27P27, Ti-C60 and Cu-Si72 and N2-RR intermediates are 1.5 × 105 Hartree/Bohr and 6.0 × 10-5 Angstrom. The Opt = Tight and MaxStep = 30 are considered to optimize Co-Al18P18, Ni-Al21N21, Fe-B24N24, Mn-B27P27, Ti-C60 and Cu-Si72 and N2-RR intermediates. The frequencies of Co-Al18P18, Ni-Al21N21, Fe-B24N24, Mn-B27P27, Ti-C60 and Cu-Si72 and N2-RR intermediates are calculated. [ABSTRACT FROM AUTHOR]

Here, the catalytic activity of Mn-C48, Mn-Si48, Cu-C38, Cu-B19N19, Ni-C44, Ni-B22P22, Fe-C80, Fe-Al40P40 nanocages for N2-RR are investigated. The possible mechanisms of N2-RR on metal adsorbed nanocages are examined. The limiting step in distal, enzymatic and alternating pathways for N2-RR on metal adsorbed nanocages is metal-*NN → Metal-*NNH. The metal-*NN → Metal-*NNH is limiting step for N2-RR on metal adsorbed nanocages by mixed pathway. In distal and enzymatic pathways, the Metal-*NN → Metal-*NNH and Metal-*NNH2 → Metal-*N + NH3 are endothermic steps. In alternating and mixed pathways, the Metal-*NN → Metal-*NNH and Metal-*NH2NH2 → Metal-*NH2NH3 are endothermic steps. The Mn-Si48, Cu-B19N19, Ni-B22P22 and Fe-Al40P40 nanocages have higher catalytic activity than carbon nanocages for N2-RR. The over-potential for N2-RR on Fe-Al40P40 by studied pathways are 0.220, 0.230, 0.223 and 0.238 V. The Mn-Si48, Cu-B19N19, Ni-B22P22 and Fe-Al40P40 nanocages can be proposed as new catalysts for N2-RR to create the NH3 molecule. [ABSTRACT FROM AUTHOR]

Here, the potential of Zn doped carbon nanostructures and Zn doped silicon nanostructures to catalyze the OER and ORR processes is investigated by theoretical methods. The O*, H*, *OH, *OOH, O2 and H2O species are adsorbed on Zn-CNT(5, 0) and Zn-SiNT(5, 0). The potential-determining steps on catalysts are *OH removal and *OOH formation. The overpotential of ORR are 1.01, 0.96, 1.13 and 1.10 V, respectively. The H2O is adsorbed on Zn-C70, Zn-Si70, Zn-CNT(5, 0) and Zn-SiNT(5, 0) catalysts physically. The H2O can desorb on on Zn-C70, Zn-Si70 and Zn-CNT(5, 0) catalysts, easily. The overpotential for OER are 1.15, 1.09, 1.25 and 1.20 V, respectively. The Zn-SiNT(5, 0) catalyst has lower overpotential values than Zn-C70, Zn-Si70 and Zn-CNT(5, 0) catalysts. The Zn-SiNT(5, 0) with acceptable catalytic activity is proposed to catalyze the ORR and OER processes. [ABSTRACT FROM AUTHOR]

Protein secondary structure discrimination is crucial for understanding their biological function. It is not generally possible to invert spectroscopic data to yield the structure. We present a machine learning protocol which uses two-dimensional UV (2DUV) spectra as pattern recognition descriptors, aiming at automated protein secondary structure determination from spectroscopic features. Accurate secondary structure recognition is obtained for homologous (97%) and nonhomologous (91%) protein segments, randomly selected from simulated model datasets. The advantage of 2DUV descriptors over one-dimensional linear absorption and circular dichroism spectra lies in the cross-peak information that reflects interactions between local regions of the protein. Thanks to their ultrafast (∼200 fs) nature, 2DUV measurements can be used in the future to probe conformational variations in the course of protein dynamics.

The ability and capacity of silicon and carbon nanocages (C38, F-C38, Cl-C38, Si38, F-Si38, Cl-Si38) as anodes of batteries are investigated to suggest the new nano-compounds as basic material of electrodes of batteries with suitable performance. The electrochemical parameters of C and Si nanocages as anodes of batteries are examined and compared by using of the computational models. The halogen (F and Cl) atoms are linked to Si38 and C38 as anodes in batteries to improve their capacity by theoretical models. The interaction energies of nanostructures with F and Cl atoms, interaction energies of nanostructures with Li and Mg and interaction energies of F-nanostructures and Cl-nanostructures with Li+ and Mg+2 ions are calculated by theoretical models. Finally, the F-Si38 and Cl-Si38 nanocages are suggested as suitable effective nano structures to utilize as electrodes in batteries. [ABSTRACT FROM AUTHOR]

Abstract In this study, phenyl (1,4,6-triphenyl-2-thioxo-1,2,3,4-tetrahydropyrimidin-5-yl)methanone was obtained by using the Biginelli reaction method. The structure of this compound was analyzed using elemental analysis, IR, 1H, and 13C NMR. The quantum chemical calculations (QCC) of this compound were performed density functional theory (DFT) method, 6–31 G (d, p) base set, and B3LYP functions with the Gaussian09W software package. Literature shows that pyrimidine-derived compounds have very active biological properties. For this reason, the biologically active properties of the synthesized compound were also examined. To determine embryotoxic, genotoxic, and cytotoxic effects of compound, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT), lactate dehydrogenase (LDH) release, micronucleus (MN) and 8-OH-dG assays were carried out. On the other hand, pharmacokinetic and toxicity properties (ADMET) were predicted in silico via SwissADME and Protox-II web tools. In silico estimates of this compound used in the study showed that the compound has the covetable physicochemical properties for bioavailability. In conclusion, the obtained results of our study clearly showed that this compound exerted strong toxicity potential. [ABSTRACT FROM AUTHOR]

In this study, a series of electron donor (–NH2, –NMe2 and –tBu) and electron-withdrawing substituents (–F, –CN and –NO2) were used to tune the nucleophilicity or electrophilicity of a series of square planar Ni2+, Pd2+ and Pt2+ malonate coordination complexes towards a pentafluoroiodobenzene and a pyridine molecule. In addition, Bader's theory of atoms in molecules (AIM), noncovalent interaction plot (NCIplot), molecular electrostatic potential (MEP) surface and natural bond orbital (NBO) analyses at the PBE0-D3/def2-TZVP level of theory were carried out to characterize and discriminate the role of the metal atom in the noncovalent complexes studied herein. We hope that the results reported herein may serve to expand the current knowledge regarding these metals in the fields of crystal engineering and supramolecular chemistry. [ABSTRACT FROM AUTHOR]

Per- and polyfluorinated alkyl substances (PFAS), known for their widespread environmental presence and slow degradation, pose significant concerns. Of the approximately 10,000 known PFAS, only a few have undergone comprehensive testing, resulting in limited experimental data. In this study, we employed a combination of physics-based methods and data-driven models to address gaps in PFAS bioaccumulation potential. Using the COnductor-like Screening MOdel for Realistic Solvents (COSMO-RS) method, we predicted n-octanol/water partition coefficients (logKOW), crucial for PFAS bioaccumulation. Our developed Quantitative Structure-Property Relationship (QSPR) model exhibited high accuracy (R2 = 0.95, RMSEC = 0.75) and strong predictive ability (Q2LOO = 0.93, RMSECV = 0.83). Leveraging the extensive NORMAN, we predicted logKOW for over 4,000 compounds, identifying 244 outliers out of 4519. Further categorizing the database into eight Organisation for Economic Co-operation and Development (OECD) categories, we confirmed fluorine atoms role in enhanced bioaccumulation. Utilizing predicted logKOW, water solubility logSW, and vapor pressure logVP values, we calculated additional physicochemical properties that are responsible for the transport and dispersion of PFAS in the environment. Parameters such as Henry’s Law (kH), air–water partition coefficient (KAW), octanol–air coefficient (KOA), and soil adsorption coefficient (KOC) exhibited favorable correlations with literature data (R2 > 0.66). Our study successfully filled data gaps, contributing to the understanding of ubiquitous PFAS in the environment and estimating missing physicochemical data for these compounds.

The critical role of global electron density transfer (GEDT) in increasing the reaction rate of polar organic reactions has been studied within the framework of Molecular Electron Density Theory (MEDT). To this end, the series of the polar Diels–Alder (P-DA) reactions of cyclopentadiene with cyanoethylene derivatives, for which experimental kinetic data are available, have been chosen. A complete linear correlation between the computed activation Gibbs free energies and the GEDT taking place at the polar transition state structures (TSs) is found; the higher the GEDT at the TS, the lower the activation Gibbs free energy. An interacting quantum atoms energy partitioning analysis allows for establishing a complete linear correlation between the electronic stabilization of the electrophilic ethylene frameworks and the GEDT taking place at the polar TSs. This finding supports Parr’s proposal for the definition of the electrophilicity ω index. The present MEDT study establishes the critical role of the GEDT in the acceleration of polar reactions, since the electronic stabilization of the electrophilic framework with the electron density gain is greater than the destabilization of the nucleophilic one, making a net favorable electronic contribution to the decrease in the activation energy.

In this study, we characterize the structure and some topological indices of a class of random spider trees (RSTs) such as degree-based Gini index, degree-based Hoover index, generalized Zagreb index, and other indices associated with these. We obtain the exact and asymptotic distributions of the number of leaves via probabilistic methods. Moreover, we relate this model to the class of RSTs that evolves in a preferential attachment manner.

To satisfy the need for catalyst materials with high activity, selectivity, and stability for energy conversion, material design and discovery guided by theoretical insights are a necessity. In the past decades, the rise in theoretical investigations into the properties of catalyst materials, reaction mechanisms, and catalyst design principles has shed light on the catalysis field. Quantitative structure–activity relationships have been developed through incorporating spectroscopic simulations, electronic structure calculations, and reaction mechanistic studies. In this review, we report the state-of-the-art computational approaches to catalyst materials characterization for supported single-atom and cluster catalysts utilizing spectroscopic simulations, i.e., XANES simulation, and material properties investigation via electronic-structure calculations. Furthermore, approaches regarding reaction mechanisms, focusing on active site heterogeneity, are also discussed.

Summary: We establish a general kinetic scheme for energy transfer and trapping in the photosystem I (PSI) of cyanobacteria grown under white light (WL) or far-red light (FRL) conditions. With the help of simultaneous target analysis of all emission and transient absorption datasets measured in five cyanobacterial strains, we resolved the spectral and kinetic properties of the different species present in PSI. WL-PSI can be described by Bulk Chl a, two Red Chl a, and a reaction center compartment (WL-RC). The FRL-PSI contains two additional Chl f compartments. The lowest excited state of the FRL-RC is downshifted by ≈ 29 nm. The rate of charge separation drops from ≈900 ns−1 in WL-RC to ≈300 ns−1 in FRL-RC. The delayed trapping in the FRL-PSI (≈130 ps) is explained by uphill energy transfer from the Chl f compartments with Gibbs free energies of ≈kBT below that of the FRL-RC.

Summary: Current classifications of oxygen evolution catalysts are based on energy levels of the clean catalysts. It is generally asserted that a LOM-catalyst can only follow LOM chemistry in each electron transfer step and that there can be no mixing between AEM and LOM steps without an external trigger. We use ab initio theory to track the charge flow of the water-on-catalyst system and show that the position of water orbitals is pivotal in determining whether an electron transfer step is water dominated oxidation (WDO), lattice-oxygen dominated oxidation (LoDO), or metal dominated oxidation (MDO). Microscopic photo-catalytic pathways of TiO2 (110), a material whose lattice oxygen bands lie above the metal bands, show that viable OER pathways follow either all AEM steps or mixed AEM-LOM steps. The results provide a correct description of redox chemistries at the atomic level and advance our understanding of how water-splitting catalysts produce desorbed oxygen.

For the first time, an extensive theoretical comparative study of the electronic structure and spectra of the η5-cyclopentadienyl half-sandwich [(Cp)(EPh3)], E = Se, Te) organochalcogenides was carried out using direct space electronic structure calculations within hybrid, meta, and meta-hybrid DFT GGA functionals coupled with double-ζ polarized 6-31G* and correlation-consistent triple-zeta cc-pVTZ-pp basis sets. The absence of covalent bonding between the cyclopentadienyl (Cp) ligands and Te/Se coordination centers was revealed. It was found that the chalcogens are partially positively charged and Cp ligands are partially negatively charged, which directly indicates a visible ionic contribution to Te/Se-Cp chemical bonding. Simulated UV–Vis absorption spectra show that all complexes have a UV-active nature, with a considerable shift in their visible light absorption due to the addition of methyl groups. The highest occupied molecular orbitals exhibit π-bonding between the Te/Se centers and Cp rings, although the majority of the orbital density is localized inside the Cp π-system. The presence of the chalcogen atoms and the extension of π-bonds across the chalcogen-ligand interface make the species promising for advanced photovoltaic and light-emitting applications. [ABSTRACT FROM AUTHOR]

Azo dyes represent the most important class of textile dyes. Biotransformation of azo dyes can release aromatic amines. It is well known that some aromatic amines have genotoxic and/or carcinogenic properties. In this study, it was aimed to investigate the effects of azo dyes, which are composed of aromatic amines, and are widely used in the textile industry, on the environment using acute water toxicity test. The acute water toxicity test using Daphnia Magna was investigated experimentally and theoretically. The OECD QSAR Toolbox program, which has recently attracted attention in theoretical studies and is also used in international regulations, has been preferred. As a result of the studies, it was seen that the experimental and theoretical results gave parallel results. This study showed that theoretical studies can be substituted for experimental studies in order to reduce cost, time, and animal mortality in acute toxicity tests on Daphnia Magna. In addition, according to the results of this study, it was found by experimental and theoretical methods that Basic Yellow 28, Disperse Blue 291, and Disperse Brown 27-1 azo dye are ecotoxicologically toxic. [ABSTRACT FROM AUTHOR]

Comets are likely to contain various carbon oxide molecules potentially including C(O)OC and c-C 2 O 2 on their surfaces and comae, as well as their silicon-substituted analogues possibly playing a role in the formation of interstellar dust grains. In this work, high-level quantum chemical data are provided to support such potential future astrophysical detection through the generation of predicted rovibrational data. Laboratory-based chemistry would also benefit from such aforementioned computational benchmarking considering these molecules' historic computational and experimental elusiveness. Coupled-cluster singles, doubles, and perturbative triples, the F12b formalism, and the cc-pCVTZ-F12 basis set garner the rapid, yet highly trusted F12-TcCR level of theory leveraged presently. This current work points to all four molecules' strong IR activity, coupled with large intensities, thus suggesting the potential for JWST detection. Although Si(O)OSi possesses a permanent dipole moment significantly larger than those of the other molecules of present interest, the significant abundance of the potential precursor carbon monoxide suggests that the dicarbon dioxide molecules may yet be observable in the microwave region of the electromagnetic spectrum. Thus, this present work details the likely existence and detectability of these four cyclic molecules, providing updated implications compared to previous work performed both experimentally and computationally. [ABSTRACT FROM AUTHOR]

Abilities of SiNT and CNT for anodes of batteries are studied. Effects of titanium and copper oxides (TiO and CuO) and ruthenium and manganese oxides (RuO2 and MnO2) on abilities of SiNT and CNT as anodes of M-IBs are calculated by M06-2X/6–311 + G (2d, 2p) and PW91PW91/cc-pVQZ models. The cell voltage of SiNT-RuO2 for anode of M-IB is greater than SiNT-TiO and SiNT in various environments. The Vcell of CNT-MnO2 and CNT-CuO for anodes of sodium batteries are greater than in potassium batteries. The calculated cell voltage in this study are in agreement with Vcell of various C and Si nanostructures as anodes in batteries which are reported in previous published works by experimental and theoretical models and methods. The CuO, RuO2, TiO and MnO2 are improved the abilities of nanotubes for anodes of M-IBs, remarkably. [ABSTRACT FROM AUTHOR]

The accurate and high-throughput generation of kinetic data for combustion detailed chemical kinetic models remains a challenge given the large size of these models. For large organic molecules, the majority of kinetic data of the kinetic models are estimated using quantitative structure activity relationships within reaction classes and reaction rate rules approaches. In this work, we question the limits of the rate rule approach for the isomerization reaction classes, using electronic structure calculations and reaction rate theories. Systematic calculations were performed to investigate the effect of the size and the degree of branching of alkyl radicals on the rate coefficients and their consequences on the rate rule approach. Our computed kinetic data show that when the size of alkyl group is increased, the rate coefficients remains close to each other. This allows the use of methyl as representative models of larger alkyl groups to investigate the influence of increasing the degree of branching. The computed rate coefficients for 1,3- and 1,4-H-atom shifts show that the increase of the branching level, with spectator methyl groups in the transition state cyclic structure can strongly increase the rate coefficients, up to several orders of magnitude. Consequently, a single rate rule is not feasible for any degree of branching of a reaction belonging to the same isomerization reaction class. As variation in rate coefficients are important, this would lead to an explosion of the number rate rules as a function of branching in 5-, 6-, and 7-membered cyclic transition states. A new approach is demonstrated and proposed where model transition states are tabulated, and methyl groups are assumed as alkyl groups and all combinations of substitutions in the model TSs, for a given reaction class, are included in a table with associated ab initio rate coefficients. The automation of the construction of such tables is possible and could be an interesting high-throughput / high-accuracy alternative to on-the-fly ab initio calculations of kinetic parameters. [ABSTRACT FROM AUTHOR]

Summary: A prominent role of water in aqueous-phase heterogeneous catalysis is to modify free energies; however, intuition about how is based largely on pure metal surfaces or even homogeneous solutions. Using multiscale modeling with explicit liquid water molecules, we show that the influence of water on the free energies of adsorbates at metal/support interfaces is different than that on pure metal surfaces. We specifically compute free energies of solvation for methanol and its constituents on a Pt/Al2O3 catalyst and compare the results to analogous values calculated on a pure Pt catalyst. We find that the more hydrophilic Pt/Al2O3 interface leads to smaller (more positive) free energies of solvation due to an increased entropy penalty resulting from the additional work necessary to disrupt the interfacial water structure and accommodate the interfacial species. The results will be of interest in other fields, including adsorption and proteins.

In this paper, we introduce specific approximations to simplify the vibronic treatment in modeling absorption and emission spectra, allowing us to include a huge number of vibronic transitions in the calculations. Implementation of such a simplified vibronic treatment within our general approach for modelling vibronic spectra, based on molecular dynamics simulations and the perturbed matrix method, provided a quantitative reproduction of the absorption and emission spectra of aqueous indole with higher accuracy than the one obtained when using the existing vibronic treatment. Such results, showing the reliability of the approximations employed, indicate that the proposed method can be a very efficient and accurate tool for computational spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: Why was it that Roald Hoffmann was the perfect collaborator for R. B. Woodward for proposing the Principle of Conservation of Orbital Symmetry as the solution to the no‐mechanism puzzle? This publication presents 17 "tools" that Hoffmann used extensively and effectively prior to the Woodward‐Hoffmann collaboration that would he call upon reveal the mechanism of pericyclic reactions. In a sense, this is a biography of Hoffmann with a focus on his personal and professional skills as of May 5, 1964. [ABSTRACT FROM AUTHOR]

In 1965, R. B. Woodward and Roald Hoffmann published five communications that formed the basis of the Principle of Conservation of Orbital Symmetry which explained mechanisms of all pericyclic reactions and predicted the allowedness and forbiddeness of such reactions, whether thermal or photochemical. A brief biographical discussion of Hoffmann up to May 1964 is explains why Hoffmann was the ideal individual to participate in the collaboration with Woodward. Why May 1964? Because it was then that the Woodward‐Hoffmann collaboration began. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three conformations, labeled A, B, and C were obtained from the interaction of XCN with CH 3 NH 2. • Conformation A is stabilized by cyclic TB-HB, while conformations B and C are stabilized by linear TB and XB interactions. • The halogen ligand belonging to the XCN played a key role in the interaction energy. • Conformation C is significantly more stable compared to the other two conformations. • MEP, EDA, QTAIM, NBO, and NCI were used to analyze the complexes. In this study, quantum calculations were conducted to investigate the nature, formation mechanism, and properties of complexes resulting from the interaction between methylamine (MA) and halogen cyanide molecules (XCN, X = F, Cl, Br, and I). Three types of complexes were formed from the interaction of MA with XCN, characterized as Tetrel bond-hydrogen bond (TB-HB), Tetrel bond (TB), and Halogen bond (XB), denoted by symbols A, B, and C, respectively. The data obtained from the interaction energy indicated that complexes with structure C are significantly more stable compared to the other two structures. Molecular electrostatic potential map (MEP) analysis revealed that the size of the σ-hole of the halogen atom ligand plays a crucial role in the stability of structure C complexes. To further evaluate the properties of the resulting complexes, various analyses were conducted, including Molecular electrostatic potential map (MEP), Geometry optimization, Spectroscopy, Interaction energy (SE), Natural bond orbital (NBO), Atoms in molecules (AIM), Non-covalent interaction index (NCI), and Energy decomposition analysis (EDA). [ABSTRACT FROM AUTHOR]

[Display omitted] • The substitution of more fluorine atoms increases the electrostatic surface potential. • The improvement of electron/hole transfer in m2/N3 -based devices facilitates charge separation. • The structure-performance relationship of all-small-molecule with different number of fluorine based organic solar cells were theoretically investigated. Side-chain engineering plays a crucial role in advancing the performance of organic solar cells (OSCs). Here, the symmetrical difluorophenyl molecule 1 (m1), the small molecule 2 (m2) and N3 were selected to systematically study the influences of fluorination on the photophysical properties. It was found that the planarity of the backbones of m1 and m2 facilitates charge transfer. Also, the investigated m1 or m2 and N3 show strong and broad light absorption in the visible region, demonstrating good short-circuit current density. Moreover, Compared to the m1 / N3 system, the change in the number of fluorine atoms provides the m2 / N3 system more favorable interfacial charge transfer mechanisms. In addition, the calculated electron separation rate and hole separation rate of the m2 / N3 system are higher than those of the m1 / N3 system, facilitating charge separation. We hope this work could provide theoretical guidance for further experimental work in molecular design, especially for fluorination. [ABSTRACT FROM AUTHOR]

The energies of CH2=CH−CH=N+R2+HNR*2→CH2=CH−CH=N+R*2+HNR2 reactions (exchange of propenal between two secondary amines) and of similar equilibria with cinnamaldehyde have been calculated and compared. Iminium ions from pyrrolidines with substituents that can help stabilize the positive charge are especially stable in the gas phase, as expected, whereas in very polar solvents the predicted order of stability (of their iminium ions) is: O‐tert‐butyldiphenylsilylprolinol>pyrrolidine>O‐methylprolinol>2‐tert‐butylpyrrolidine>Jørgensen‐Hayashi catalyst>2‐tritylpyrrolidine>N,N‐dimethylprolinamide>trimethylsilyl prolinate>3‐triflamidopyrrolidine>methyl prolinate≫MacMillan‐1 catalyst>MacMillan‐2 catalyst. When ion pairs such as iminium tetrafluoroborates, in CHCl3, are compared, the order is similar. These data can be used to predict which iminium salts may predominate when two or more secondary amines and appropriate acids are added to conjugated carbonyl compounds. [ABSTRACT FROM AUTHOR]

Machine learning and artificial intelligence are increasingly gaining in prominence through image analysis, language processing, and automation, to name a few applications. Machine learning is also making profound changes in chemistry. From revisiting decades-old analytical techniques for the purpose of creating better calibration curves, to assisting and accelerating traditional in silico simulations, to automating entire scientific workflows, to being used as an approach to deduce underlying physics of unexplained chemical phenomena, machine learning and artificial intelligence are reshaping chemistry, accelerating scientific discovery, and yielding new insights. This review provides an overview of machine learning and artificial intelligence from a chemist's perspective and focuses on a number of examples of the use of these approaches in computational chemistry and in the laboratory. [ABSTRACT FROM AUTHOR]