The ωB97XD/6-311+G(2df,2p)//B3LYP/6-31+G(d,p) level of theory can calculate the adiabatic ionization potential as accurate as the high level composite methods such as G4 and G3B3 with root mean square error. Substitution effect on the physiochemical properties was also studied and discussed. The results revealed that electron withdrawing groups increase the values of the physiochemical properties such as adiabatic and vertical ionization potential, electrophilicity, and nucleophilicity, while the reverse is true in case of electron donating groups.

Abstract

In the current paper, the adiabatic ionization potentials (AIP) for 29 hydantoin derivatives and hydantoin-based drugs such as allantoin, phenytoin, mephenytoin, nilutamide, iprodione, nitrofurantoin, and ethotoin were calculated using the double hybrid ωB97XD density functional theory (DFT) in coupling with 6-311+G(2df,2p) basis set at the B3LYP/6-31+G(d,p) optimized geometry. The neutral and cationic radicals of the examined species were firstly optimized using the B3LYP/6-31+G(d,p) level. Final energies were improved by single point calculation using 16 different DFT methods such as B3LYP, ωB97, B97D, TPSSTPSS, M06-2X, …, and so forth, with 6-311+G(2df,2p) basis. Statistical tools such as root mean square error (RMSE) was used to examine the accuracy of the DFT method with respect to the standard reference AIP values. These standard references were calculated, for 12 hydantoin derivatives with less than nine non-hydrogen atoms, by taking the average values of the AIP computed using the G4, G3B3, and CBS-QBS methods. The vertical ionization potentials (VIPs), the vertical electron affinity (VEA), and global quantum parameters such as electrophilicity and nucleophilicity of the 29 molecules were also calculated. Substitution effect on the AIP, VIP, VEA, fundamental gap, electrophilicity, and nucleophilicity of the species under probe was studied and discussed. The results reveal that substitution of electron withdrawing group (EWG) raises the AIP and VIP, electrophilicity, and the fundamental gap, while substitution of electron donating group (EDG) raises the VEA and the nucleophilicity. Furthermore, the condensed Fukui functions were used to identify the active centers for nucleophilic, electrophilic, and free radical attacks.

The Diels–Alder cycloaddition of cyclopentadiene and nitroethene, the intramolecular cycloaddition between a diene and triene, and the Diels–Alder cycloaddition of 2-hydroxyacrolein with 1,3-butadiene involving post-transition-state bifurcation (PTSB) were investigated using the quasi-classical trajectory (QCT), classical molecular dynamics (MD), ring-polymer MD (RPMD) from the ambimodal transition state (TS), and machine-learning analysis. The PTSB dynamics are significantly influenced by the initial coordinates and momenta at the ambimodal TS.

Abstract

The Diels–Alder cycloaddition of cyclopentadiene and nitroethene, the intramolecular cycloaddition between a diene and triene, and the Diels–Alder cycloaddition of 2-hydroxyacrolein with 1,3-butadiene involving post-transition-state bifurcation (PTSB) were studied. These cycloaddition reactions were investigated using quasi-classical trajectory (QCT), classical molecular dynamics (MD), ring-polymer molecular dynamics (RPMD) simulations, and supervised machine-learning binary classification techniques. Room-temperature dynamics simulations started from the ambimodal transition state (TS) using the QCT, classical MD, and RPMD methods presented similar dynamics. Binary classification revealed that the initial geometry displacement from the ambimodal TS for the Diels–Alder cycloaddition of cyclopentadiene and nitroethene contributed to the branching dynamics and that the initial momenta for the intramolecular cycloaddition between a diene and triene and the Diels–Alder cycloaddition of 2-hydroxyacrolein with 1,3-butadiene played a significant role in the bifurcation dynamics.

The studied transition states of proton hopping transfer and bimolecular substitution are the main energy release processes of TNT to 2,4,6-trinitrobenzoic acid catalyzed by THICA.

Abstract

As an organic molecule catalyst, N,N′,N″-trihydroxyisocyanuric acid can selectively catalyze the oxidation of the methyl group of waste 2,4,6-trinitrotoluene to generate 2,4,6-trinitrobenzoic acid. This reaction can avoid environmental pollution by inorganic heavy metal catalysts. In this study, four reaction stages of this catalytic reaction were designed and validated computationally at the M06-2X-D3ZERO/6-311G(d,p) level using the acetic acid solvent model. These validations include transition state searches, intrinsic reaction coordinate calculations, reactant and product optimizations, and frequency calculations. The final reaction network of 23 transition states shows that after N,N′,N″-trihydroxyisocyanuric acid activation and common reaction, the network bifurcates into two stages: alcohol to carboxylic acid and aldehyde to carboxylic acid. Although the former stage releases about 155 kcal/mol of Gibbs free energy, less than the 177 kcal/mol from the latter stage, the overall reaction equation shows that the pathway including former stage does not consume the catalytically active substance IM_T2, which saves the energy required for reactivation and is thus more favorable. Furthermore, the key transition states in the reaction network include bimolecular substitution reactions and proton-hopping transfer reactions. Analyses of their interaction region indicators and intrinsic reaction coordinate results demonstrate strong selectivity. Additionally, the energy barriers and heat releases of the latter are twice and 1.3 times greater than those of the former, respectively. In summary, this study elucidated two competitive reaction pathways and identified the more energetically favorable and selective pathway, and it provides useful insights for further optimization of industrial utilization of 2,4,6-trinitrotoluene.

Bis(dioxaborines) radical anions change from charge-delocalized to charge-localized just by changing the solvent, which is a very rare behavior in mixed valence chemistry.

Abstract

The mixed valence (MV) radical anions of several bis(dioxaborines) with aromatic bridges of different length were studied by Vis/NIR spectroscopy, cyclic voltammetry, and theoretical calculations. The phenyl-bridged (1), the biphenyl-bridged (2), and bithiophene-bridged (5) radical anions show intense low-energy intervalence bands with vibrational structure typical of charge delocalized mixed valence species in the range of solvents studied. However, by subtracting from the experimental spectra of 2 ⁻ in MeCN the fraction corresponding to the delocalized part (taken as the spectrum in tetrahydrofuran [THF]), we get a localized charge-transfer bands that show a significant cutoff effect at the low-energy side, as predicted by classical Marcus–Hush theory. In the radical anions with three aromatic rings on the bridge, the localization of the charge changes with solvent. These radicals are predominantly charge-localized in the high λ _S solvent MeCN, charge-delocalized in the low λ _S solvent THF, and show both type of intervalence bands in DMF. Experimental results and theoretical calculations show that the electronic coupling between dioxaborine units in these three-ring bridged radical anions increases with the number of thiophene rings on the bridge.

The microwave-assisted extraction of the main phenolic components of green coffee beans, such as chlorogenic acid, was carried with deep eutectic solvents, where the best performance was reached by choline chloride/ethylene glycol and choline chloride/urea. Computational calculations were also carried out, and a variety of hydrogen bond types were found in every structure, as well as the thermochemistry of the formation of the corresponding complexes, where the formation of urea-based structures was slightly more effective by approx. 3 kcal/mol.

Abstract

The microwave-assisted extraction of the main phenolic component of green coffee beans, chlorogenic acid (CGA), was carried out employing deep eutectic solvents based on choline chloride and five different hydrogen bond donors (HBD) in a 1:2 ratio. The best performance for the extraction process of CGA was reached by the mixtures of choline chloride/ethylene glycol and choline chloride/urea. To understand the various interactions between the phenolic compound and the two most efficient deep eutectic solvents, computational calculations were carried out at the density functional theory (DFT) level, as well as Atoms in Molecules (AIM) and Non-Covalent Interactions (NCIs) analyses. In that way, a variety of hydrogen bond types were found in every structure. Nevertheless, the CGA does not disrupt the hydrogen bond network established between ChCl and the HBD. Among the strongest interactions are those hydrogen bonds between the quinic acid moiety and the ethylene glycol or the urea. In addition, the thermochemistry of the formation of the two main deep eutectic solvents and their corresponding complexes with CGA was calculated, where the formation of urea-based structures was slightly more effective by ~3 kcal/mol.

We observed all the three flavonoids used in this work form 1:2 complex with CB[7]. Isothermal titration calorimetry study indicates that the complex formation process at room temperature is endothermic in nature. From our result, we observed a comparative binding feature form fluorescence and isothermal titration calorimetry measurement.

Abstract

Due to intrinsic fluorescence behavior, and the environment-dependent excited-state intramolecular proton transfer (ESIPT) process, makes special attention towards flavonoids for conducting photophysical study. The binding of fisetin, morin hydrate, and quercetin with macrocyclic molecule Cucurbit[7]urils (CB[7]) has been studied using different spectroscopic methods. The changes in the thermodynamic parameters during complex formation between the flavonoids with CB[7] are estimated by an isothermal titration calorimetry study. From the spectroscopic measurement, we have seen that in the presence of CB[7], flavonoids show the ESIPT process and the prototropic equilibrium is present between different forms of flavonoids. The isothermal titration calorimetry study shows that the complex formation between these flavonoids with CB[7] spontaneously takes place at room temperature, which is an endothermic process.

In the present study, five new acceptor molecules were designed by end group modification of previously synthesized reference molecule to obtain better in silico efficiency of solar cell devices. All newly fabricated molecules (D1-D5) displayed smaller energy gap, reasonable electron reorganizational energy values, and open circuit voltage (V _oc). D3 being an acceptor when blended with donor polymer portrayed highest charge transfer capability. D5 molecule exhibits higher V _oc, greater light harvesting efficiency, and superior fill factor illustrating superior behavior than other molecules.

Abstract

Organic solar cells (OSCs) have grabbed the attention of researchers due to good power conversion efficiency, low cost, and ability to compensate for light deficit. The aim of the present research work is to increase the efficiency of previously synthesized reference (R) molecule 2,2′-((2Z,2′Z)-(((4,4′-dimethyl-[2,2′-bithiazole]-5,5′-diyl)bis(4-(2-butyloctyl)thiophene-5,2-diyl))bis (methaneylylidene))bis(5,6-dichloro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile by improving its photovoltaic properties via end cap engineering. Five new acceptors, namely, E1, E2, E3, E4, and E5, are used to substitute the end group of reference molecule. Several parameters have been analyzed using density functional theory including the absorption maxima, charge transfer analysis, frontier molecular orbital (FMO), open circuit voltage (V _oc), density of states (DOS), photochemical characteristics, transition density matrix (TDM), and the electron-hole reorganization energies to evaluate the efficiency of specially engineered molecules. All the engineered molecules (D1-D5) had smaller energy gap (4.50–4.71 eV) compared with reference (4.75 eV) and absorption maxima in the range of 443.37–482.67 nm in solvent phase due to end-cap acceptor modification. Fabricated molecules (D1-D5) showed smaller electron reorganizational energy values (0.18–0.27 eV) and V _oc ranging from 1.94 to 2.40 eV. Designed molecule D3 being an acceptor when blended with donor polymer (PTB7-Th) portrayed highest charge transfer capability owing to its smallest energy gap (4.50 eV) among all the engineered molecules. D5 molecule exhibits higher V _oc (2.40 eV), greater LHE (0.9988), and superior result of fill factor (94.15%) as compared with R, which leads to improve the efficiency of OSCs. Theoretical findings illustrated the superior behavior of all the designed molecules making them suitable aspirants to construct efficient OSC devices.

The reaction of ozone with dimethyl sulfide (DMS) was studied by quantum chemistry methods. The addition–elimination mechanism is dominant with DMSO and ¹O₂ formed, and H-abstraction mechanism is subdominant. The total rate constant is 1.13 × 10⁻²⁰ cm³·molecule⁻¹·s⁻¹ at 298 K and 1 atm, in good agreement with previous experimental data. The overall rate constants are positive temperature dependent in the whole temperature range.

Abstract

The potential energy surface (PES) for the reaction of ozone with dimethyl sulfide (DMS) was calculated at the CCSD(T)/6-311++G(3df,2pd)//M06-2X/6-311++G(d,p) levels of theory. Result shows that on the singlet PES the addition–elimination mechanism is dominant, and H-abstraction mechanism is less competitive. The major channel starts from the addition of ozone and DMS leading to a weak intermediate IM1, which decomposes subsequently to DMSO and ¹O₂ via a barrier around 38.8 kJ/mol. With a barrier of 64.0 kJ/mol, the formation of HO₃ + CH₃SCH₂ via H-abstraction mechanism is subdominant. Besides, DMSO + ¹O₂ can take place further reactions to produce several products. The substitution mechanism was located on the triplet PES, however, with a rather high barrier it is negligible. Furthermore, the rate constants for the two channels leading to DMSO + ¹O₂ and HO₃ + CH₃SCH₂ were calculated from 200 to 1000 K. The total rate constant is 1.13 × 10^-20 cm³·molecule^-1·s^-1 at 298 K and 1 atm, in good agreement with previous experimental data. The overall rate constants are positive temperature dependent in the whole temperature range.

Abstract

Gill, W. A., Khan, M. U., Shafiq, Z., Janjua, M. R. S. A., “Exploring the Intermolecular Interactions in Carbon Disulfide Dimer: An Ab Initio Study Using an Improved Lennard–Jones Potential Energy Surface for Physical Insights,” J Phys Org Chem 2023, https://doi.org/10.1002/poc.4548. The above article, published online on 05 June 2023 on Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the journal's Editor in Chief, Professor Rik Tykwinski and John Wiley and Sons LLC. The journal's Editor-in-Chief was contacted by a third party who raised concerns about the article. An independent scientific expert evaluated the article and confirmed that significant problems exist with the data and conclusions of the work, and that it contains inadequate and/or inaccurate citations. As a result, the editors consider the article's conclusions to be unreliable.

DFT and related techniques help to unravel the dependence of proton transfer on solvent polarity in ion pairs of carbamates and thiocarbamates with amidinium- and imidazolium-based counterions.

Abstract

Small, but important, differences in the structure–property relationships between ionomers composed of amidinium or imidazolinium groups with alkylcarbamate or alkyldithiocarbamate counterions have been examined experimentally by us previously. To unravel the sources of these differences, DFT calculations are conducted here for ion-pair complexes (IPs) of these systems and their corresponding uncharged base and acid components (NPs). Calculations include IPs and NPs in which the amidine/amidinium and imidazoline/imidazolinium groups are anchored to a dimethylsiloxane pentamer. A surprising dependence of proton transfer on the dielectric constant (ε) of the medium is found for the systems: Whereas interconversion between the NPs and IPs is strongly dependent on medium dielectric in systems with an alkylcarbamate, none of the initial IP forms with an alkyldithiocarbamate transforms to an NP. Although the calculations do not include individual solvent–solute molecular interactions, they do probe how the components sense their bulk environments. The lack of detectable reversible proton transfer from the amidinium or imidazolinium cations to the dithiocarbamates is consistent with the “principle of proton affinity/pK_a equivalence”: Because the acidity of dithiocarbamates is higher than that of carbamates, the gap between their proton affinities (ΔPA) is decreased, favoring stronger electrostatic-based H-bonds in the ion-pair complexes of the dithiocarbamates. The differences can also be estimated from the Deuri–Phukan nucleophilicity index scale, which is based on DFT calculations and suggests a strong dependence of proton transfer on the nucleophilicity of the base and the dielectric constant of the solvent. Predictions from these calculations on some important experimental systems are mentioned.