Showing papers on "Polarizable continuum model published in 2021"
TL;DR: In this article, the adsorption of Rhodamine B (Rh.B) was achieved by Zeolite imidazolate framework-8 (ZIF-8) in the dark condition, and the adaption rate was noticeably increased under visible and UV light irradiations.
68 citations
TL;DR: In this article, the deep neural network FieldSchNet is used to simulate a wide range of molecular spectra, such as infrared, Raman and nuclear magnetic resonance, and to design an external environment capable of lowering the activation barrier of the rearrangement reaction significantly.
Abstract: Fast and accurate simulation of complex chemical systems in environments such as solutions is a long standing challenge in theoretical chemistry. In recent years, machine learning has extended the boundaries of quantum chemistry by providing highly accurate and efficient surrogate models of electronic structure theory, which previously have been out of reach for conventional approaches. Those models have long been restricted to closed molecular systems without accounting for environmental influences, such as external electric and magnetic fields or solvent effects. Here, we introduce the deep neural network FieldSchNet for modeling the interaction of molecules with arbitrary external fields. FieldSchNet offers access to a wealth of molecular response properties, enabling it to simulate a wide range of molecular spectra, such as infrared, Raman and nuclear magnetic resonance. Beyond that, it is able to describe implicit and explicit molecular environments, operating as a polarizable continuum model for solvation or in a quantum mechanics/molecular mechanics setup. We employ FieldSchNet to study the influence of solvent effects on molecular spectra and a Claisen rearrangement reaction. Based on these results, we use FieldSchNet to design an external environment capable of lowering the activation barrier of the rearrangement reaction significantly, demonstrating promising venues for inverse chemical design.
30 citations
TL;DR: In this article, an effective computational protocol (cLR2) was proposed to describe both solvatochromism and fluorosolvatochemism, which couples the polarizable continuum model to time-dependent density functional theory, simultaneously accounts for both linear response and state-specific solvation effects.
Abstract: We present an effective computational protocol (cLR2) to describe both solvatochromism and fluorosolvatochromism. This protocol, which couples the polarizable continuum model to time-dependent density functional theory, simultaneously accounts for both linear-response and state-specific solvation effects. A series of test cases, including solvatochromic and fluorosolvatochromic compounds and excited-state intramolecular proton transfers, are used to highlight that cLR2 is especially beneficial for modeling bright excitations possessing a significant charge-transfer character, as well as cases in which an accurate balance between states of various polarities should be restored.
22 citations
TL;DR: In this article, a fundamental aqueous hydride transfer reaction-carbon dioxide (CO2) reduction by sodium borohydride (NaBH4)-was used as a test case to evaluate how different solvent models perform in aqueously phase charge migrations that would be relevant to renewable energy catalysis mechanisms.
Abstract: Computational quantum chemistry provides fundamental chemical and physical insights into solvated reaction mechanisms across many areas of chemistry, especially in homogeneous and heterogeneous renewable energy catalysis. Such reactions may depend on explicit interactions with ions and solvent molecules that are nontrivial to characterize. Rigorously modeling explicit solvent effects with molecular dynamics usually brings steep computational costs while the performance of continuum solvent models such as polarizable continuum model (PCM), charge-asymmetric nonlocally determined local-electric (CANDLE), conductor-like screening model for real solvents (COSMO-RS), and effective screening medium method with the reference interaction site model (ESM-RISM) are less well understood for reaction mechanisms. Here, we revisit a fundamental aqueous hydride transfer reaction-carbon dioxide (CO2) reduction by sodium borohydride (NaBH4)-as a test case to evaluate how different solvent models perform in aqueous phase charge migrations that would be relevant to renewable energy catalysis mechanisms. For this system, quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations almost exactly reproduced energy profiles from QM simulations, and the Na+ counterion in the QM/MM simulations plays an insignificant role over ensemble averaged trajectories that describe the reaction pathway. However, solvent models used on static calculations gave much more variability in data depending on whether the system was modeled using explicit solvent shells and/or the counterion. We pinpoint this variability due to unphysical descriptions of charge-separated states in the gas phase (i.e., self-interaction errors), and we show that using more accurate hybrid functionals and/or explicit solvent shells lessens these errors. This work closes with recommended procedures for treating solvation in future computational efforts in studying renewable energy catalysis mechanisms.
20 citations
TL;DR: In this article, an all-electron implementation of quasiparticle self-consistent GW for molecular systems is presented, from which a static non-local exchange-correlation potential is calculated via analytical continuation.
Abstract: Low-order scaling GW implementations for molecules are usually restricted to approximations with diagonal self-energy. Here, we present an all-electron implementation of quasiparticle self-consistent GW for molecular systems. We use an efficient algorithm for the evaluation of the self-energy in imaginary time, from which a static non-local exchange-correlation potential is calculated via analytical continuation. By using a direct inversion of iterative subspace method, fast and stable convergence is achieved for almost all molecules in the GW100 database. Exceptions are systems which are associated with a breakdown of the single quasiparticle picture in the valence region. The implementation is proven to be starting point independent and good agreement of QP energies with other codes is observed. We demonstrate the computational efficiency of the new implementation by calculating the quasiparticle spectrum of a DNA oligomer with 1,220 electrons using a basis of 6,300 atomic orbitals in less than 4 days on a single compute node with 16 cores. We use then our implementation to study the dependence of quasiparticle energies of DNA oligomers consisting of adenine-thymine pairs on the oligomer size. The first ionization potential in vacuum decreases by nearly 1 electron volt and the electron affinity increases by 0.4 eV going from the smallest to the largest considered oligomer. This shows that the DNA environment stabilizes the hole/electron resulting from photoexcitation/photoattachment. Upon inclusion of the aqueous environment via a polarizable continuum model, the differences between the ionization potentials reduce to 130 meV, demonstrating that the solvent effectively compensates for the stabilizing effect of the DNA environment. The electron affinities of the different oligomers are almost identical in the aqueous environment.
16 citations
TL;DR: In this paper, density functional theory/Becke three-parameter Lee-Yang-Parr (DFT/B3LYP) methodology was carried out instead of using pharmacological methodologies because of economic benefits and high accuracy.
Abstract: The following review article attempts to compare the antioxidant activity of the compounds. For this purpose, density functional theory/Becke three-parameter Lee–Yang–Parr (DFT/B3LYP) methodology was carried out instead of using pharmacological methodologies because of economic benefits and high accuracy. This methodology filtrates the compounds with the lowest antioxidant activity. At first, the Koopmans’ theorem was carried out to calculate some descriptors to compare antioxidants. The energy of the highest occupied molecular orbitals (HOMO) was accepted as the best indicator, and then some studies confirmed that the highest occupied molecular orbital/lowest unoccupied molecular orbital (HOMO–LUMO) energy gap is the more precise descriptor. Although it would be better to compare spin density distribution (SDD) on the oxygen of the corresponding radical in the polarizable continuum model (PCM) to evaluate their capability to chain reaction inhibition. Next, it was mentioned that in the multi-target directed ligands (MTDLs), the antioxidant is connected to other moieties in para positions to create better antioxidants or novel hybrid compounds. Indeed, SDD was introduced as a descriptor for MTDL antioxidant effectiveness. Then, the relation between antioxidants and aromaticity was investigated. The more the aromaticity of an antioxidant, the more stable the corresponding radical is. Subsequently, in preferred antioxidant activity, it was defined that the hydrogen atom transfer (HAT) mechanism is more favored in metabolism phase I. It has been seen that the solvent model can change the antioxidant mechanism. Therefore, the solvent model is more important than the chemical structure of antioxidants, and an ideal antioxidant should be evaluated in PCM for pharmacological evaluations.
15 citations
TL;DR: In this article, the intermolecular driving forces determining the adsorption of DNA/RNA nucleobases and base-pairs onto graphene and phosphorene are studied with density functional theory (DFT) calculations in the gas phase and solution with a polarizable continuum model.
13 citations
TL;DR: In this paper, the authors report a computational study on vibronic effects in the spectroscopy, photoinduced processes and decay back to the ground state of aza[7]helicene, a helicene with an unusually high fluorescence quantum yield (QY = 0.39).
Abstract: We report a computational study on vibronic effects in the spectroscopy, photoinduced processes and decay back to the ground state of aza[7]helicene, a helicene with an unusually high fluorescence quantum yield (QY = 0.39). In a first step, we compute and assign the absorption and electronic circular dichroism (ECD) spectra in its full frequency range from 2.7 to 5.0 eV, accounting for nonadiabatic effects. Then we compute the quantum dynamics of the cascade of ultrafast internal conversions of the highly-excited singlet states to the lowest-energy one S1. Finally we adopt Fermi golden rule rates to compute the QY of the dye, taking into account the competition between the radiative decay and the nonradiative decays to the ground state and to the energy-accessible triplet states. We use time-dependent density functional theory (TD-DFT), including solvent (dichloromethane) effects within the polarizable continuum model, to parameterize a linear vibronic coupling (LVC) model involving the first lowest 12 singlet states and all the normal coordinates. Nonadiabatic spectra and internal conversions dynamics are then computed through wavepacket propagations with the Multilayer (ML) extension of the Multiconfigurational Time Dependent Hartree method (ML-MCTDH). We highlight the molecular vibrations playing a major role in determining the shape of the spectra and analyse the effect of inter-state couplings. At the same time we report a breakdown of perturbative Herzberg–Teller approach. The computed QY is in perfect agreement with experiment and allows us to ascertain that intersystem crossings are the processes limiting the fluorescence from S1. They involve the three lowest triplet states and are made effective by spin–orbit coupling and vibronic effects.
10 citations
TL;DR: In this paper, a series of nonaggregated zinc phthalocyanine derivatives containing either bulky thiophenol or phenol substituents were synthesized as a novel donor component for bulk heterojunction (BHJ) solar cell applications.
9 citations
TL;DR: In this paper, the azobenzene 1-arylazo-2-naphthol has been synthesized and characterized by elemental analysis, 1H NMR, IR and UV-Vis spectroscopies using both experimental and theoretical methods.
8 citations
TL;DR: In this paper, an adiabatic on-the-fly molecular dynamics simulations have been performed for isolated 3-hydroxyflavon (3-HF) in an aqueous solution using a polarizable continuum model and including explicit water molecules to represent adequately hydrogen bonding.
Abstract: 3-Hydroxyflavon (3-HF) represents an interesting paradigmatic compound to study excited-state intramolecular proton transfer (ESIPT) and intermolecular (ESInterPT) processes to explain the experimentally observed dual fluorescence in solvents containing protic contamination (water) as opposed to single fluorescence in highly purified nonpolar solvents. In this work, adiabatic on-the-fly molecular dynamics simulations have been performed for isolated 3-HF in an aqueous solution using a polarizable continuum model and including explicit water molecules to represent adequately hydrogen bonding. For the calculation of the excited state, time-dependent density functional theory and the Becke-3-Lee-Yang-Parr (B3LYP) functional have been used. For the isolated 3-HF, ultrafast ESIPT from the enol group to the neighboring keto group has been observed. The calculated PT time of 48 fs agrees well with the experimental value of 39 fs. Addition of one water molecule quenches this ESIPT process but shows an intermolecular concerted or stepwise tautomerization process via the bridging water molecule. Adding a second or more water molecules inhibits this ESInterPT process to a large degree. Most of the trajectories do not show any PT, preserving the initial excited-state enol structure, which is the origin of the violet-blue fluorescence appearing in the solvents contaminated with protic components.
TL;DR: In this article, a nearly linear scaling implementation of coupled-cluster with singles and doubles excitations (CCSD) can be achieved by means of the domain-based local pair natural orbital (DLPNO) method.
Abstract: A nearly linear scaling implementation of coupled-cluster with singles and doubles excitations (CCSD) can be achieved by means of the domain-based local pair natural orbital (DLPNO) method. The combination of DLPNO-CCSD with implicit solvation methods allows the calculation of accurate energies and chemical properties of solvated systems at an affordable computational cost. We have efficiently implemented different schemes within the conductor-like polarizable continuum model (C-PCM) for DLPNO-CCSD in the ORCA quantum chemistry suite. In our implementation, the overhead due to the additional solvent terms amounts to less than 5% of the time the equivalent gas phase job takes. Our results for organic neutrals and open-shell ions in water show that for most systems, adding solvation terms to the coupled-cluster amplitudes equations and to the energy leads to small changes in the total energy compared to only considering solvated orbitals and corrections to the reference energy. However, when the solute contains certain functional groups, such as carbonyl or nitrile groups, the changes in the energy are larger and estimated to be around 0.04 and 0.02 kcal/mol for each carbonyl and nitrile group in the solute, respectively. For solutes containing metals, the use of accurate CC/C-PCM schemes is crucial to account for correlation solvation effects. Simultaneously, we have calculated the electrostatic component of the solvation energy for neutrals and ions in water for the different DLPNO-CCSD/C-PCM schemes. We observe negligible changes in the deviation between DLPNO-CCSD and canonical-CCSD data. Here, DLPNO-CCSD results outperform those for Hartree-Fock and density functional theory calculations.
TL;DR: In this article, the dependence of the simulation results on the use of the polarizable continuum approximation and on the importance of the solvent effect in nonpolar solvents was investigated.
Abstract: An implicit account of the solvent effect can be carried out using traditional static quantum chemistry calculations by applying an external electric field to the studied molecular system. This approach allows one to distinguish between the effects of the macroscopic reaction field of the solvent and specific solute–solvent interactions. In this study, we report on the dependence of the simulation results on the use of the polarizable continuum approximation and on the importance of the solvent effect in nonpolar solvents. The latter was demonstrated using experimental data on tautomeric equilibria between the pyridone and hydroxypyridine forms of 2,6-di-tert-butyl-4-hydroxy-pyridine in cyclohexane and chloroform.
TL;DR: In this paper, the authors examined the cyclometalation in the (η3-C5H5)Co(η2-C2H2)(PMe3) and (δ-3-c9H7) Co(δ 2-C 2H2) complexes by using mPW1PW91 functional and the solvent effects were explored on the energy barrier, frontier orbitals energies, and reactivity parameters.
TL;DR: In this paper, the effects of a solvent on the BODIPY dye were described with the polarizable continuum model using the linear response (LR) approach as well as state-specific methods.
Abstract: The radiative emission lifetime and associated S1 excited state properties of a BODIPY dye are investigated with TDDFT and EOM-CCSD calculations. The effects of a solvent are described with the polarizable continuum model using the linear response (LR) approach as well as state-specific methods. The Franck–Condon (FC), Herzberg–Teller (HT) and Duschinsky vibronic effects are evaluated for the absorption and emission spectra, and for the radiative lifetime. The transition energies, spectra shapes and radiative lifetime are assessed with respect to experimental results. It is found that the TDDFT transition energies are overestimated by about 0.4–0.5 eV, whereas EOM-CCSD improves the vertical emission energy by about 0.1 eV in comparison to TDDFT. The solvatochromic and Stokes shifts are better reproduced by the state-specific solvation methods, which show that these methods are more suited than the LR model to describe the solvent effects on the BODIPY dye. The vibronic effects lead to an increase of the radiative lifetime of about 0.4 to 1.0 ns depending on the theoretical approach, which highlights the importance of such effects. Moreover, the HT effects are negligible on both the spectra and lifetime, which demonstrates that the FC approximation is accurate for the BODIPY dye. Finally, the comparison with experimental data shows that the radiative lifetimes predicted by EOM-CCSD and TDDFT have comparable accuracy.
TL;DR: In this paper, the authors present a model that can predict the photoluminescent properties of a given compound from first principles, both within and beyond the Franck-Condon approximation.
Abstract: Here, we present a concise model that can predict the photoluminescent properties of a given compound from first principles, both within and beyond the Franck–Condon approximation. The formalism required to compute fluorescence, Internal Conversion (IC), and Inter-System Crossing (ISC) is discussed. The IC mechanism, in particular, is a difficult pathway to compute due to difficulties associated with the computation of required bosonic configurations and non-adiabatic coupling elements. Here, we offer a discussion and breakdown on how to model these pathways at the Density Functional Theory (DFT) level with respect to its computational implementation, strengths, and current limitations. The model is then used to compute the photoluminescent quantum yield (PLQY) of a number of small but important compounds: anthracene, tetracene, pentacene, diketo-pyrrolo-pyrrole (DPP), and Perylene Diimide (PDI) within a polarizable continuum model. Rate constants for fluorescence, IC, and ISC compare well for the most part with respect to experiment, despite triplet energies being overestimated to a degree. The resulting PLQYs are promising with respect to the level of theory being DFT. While we obtained a positive result for PDI within the Franck–Condon limit, the other systems require a second order correction. Recomputing quantum yields with Herzberg–Teller terms yields PLQYs of 0.19, 0.08, 0.04, 0.70, and 0.99 for anthracene, tetracene, pentacene, DPP, and PDI, respectively. Based on these results, we are confident that the presented methodology is sound with respect to the level of quantum chemistry and presents an important stepping stone in the search for a tool to predict the properties of larger coupled systems.
TL;DR: The description of the high-pressure effects with the GPU-accelerated XP-PCM is feasible for any molecule tractable for gas-phase DFT calculation, and the accuracy of the method is validated on small molecules whose properties under high pressure are known from experiments or previous theoretical studies.
Abstract: Pressure plays essential roles in chemistry by altering structures and controlling chemical reactions. The extreme-pressure polarizable continuum model (XP-PCM) is an emerging method with an efficient quantum mechanical description of small- and medium-sized molecules at high pressure (on the order of GPa). However, its application to large molecular systems was previously hampered by a CPU computation bottleneck: the Pauli repulsion potential unique to XP-PCM requires the evaluation of a large number of electric field integrals, resulting in significant computational overhead compared to the gas-phase or standard-pressure polarizable continuum model calculations. Here, we exploit advances in graphical processing units (GPUs) to accelerate the XP-PCM-integral evaluations. This enables high-pressure quantum chemistry simulation of proteins that used to be computationally intractable. We benchmarked the performance using 18 small proteins in aqueous solutions. Using a single GPU, our method evaluates the XP-PCM free energy of a protein with over 500 atoms and 4000 basis functions within half an hour. The time taken by the XP-PCM-integral evaluation is typically 1% of the time taken for a gas-phase density functional theory (DFT) on the same system. The overall XP-PCM calculations require less computational effort than that for their gas-phase counterpart due to the improved convergence of self-consistent field iterations. Therefore, the description of the high-pressure effects with our GPU-accelerated XP-PCM is feasible for any molecule tractable for gas-phase DFT calculation. We have also validated the accuracy of our method on small molecules whose properties under high pressure are known from experiments or previous theoretical studies.
TL;DR: In this article, the authors considered trans-1,2-diamino cyclohexane as the ligand for the cross-coupling reaction and found that diamine ligated copper (I) acetylide was the active state of the catalyst, which on further reaction with aryl halide undergoes a concerted oxidative addition and reductive elimination process giving the crosscoupled product aryyl acetylene while regenerating the active catalytic species.
TL;DR: In this paper, the behavior of cyclopentadienyl and indenyl ligands in (η5-C5H5) and (3-C9H7) W(CO) compounds was investigated by applying the mPW1PW91 functional.
TL;DR: In this article, the effect of solvent on structure, electronic, reactivity, and 31P NMR chemical shift values of a rhenabenzyne complex was examined using the self-consistent reaction field theory (SCRF) based on the conductor-like polarizable continuum model (CPCM).
TL;DR: In this paper, the synthesis, antioxidant activity, spectroscopic, electronic, and thermodynamic properties of 2-ethoxy-4-[(5-oxo-3-phenyl-1,5-dihydro- 1,2,4-triazol-4-ylimino)-methyl]-phenyl -4-methoxybenzoate (EPM) were examined.
Abstract: In the present study, the synthesis, antioxidant activity, spectroscopic, electronic, and thermodynamic properties of 2-ethoxy-4-[(5-oxo-3-phenyl-1,5-dihydro-1,2,4-triazol-4-ylimino)-methyl]-phenyl-4-methoxybenzoate (EPM) were examined. The novel 2-ethoxy-4-[(5-oxo-3-phenyl-1,5-dihydro-1,2,4-triazol-4-ylimino)-methyl]-phenyl-4-methoxybenzoate (EPM) compound was successfully synthesized with novel derived biologically important 1,2,4-triazole Schiff base. This biologically active 1,2,4-triazole Schiff base was obtained through condensation of 3-phenyl-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-one with 2-ethoxy-4-formylphenyl-4-methoxybenzoate. The characterization of the obtained compound was identified utilizing FT-IR, UV–Vis, 1H-, and 13C-NMR spectroscopies. The antioxidant activities of the newly synthesized Schiff base were evaluated employing the Oyaizu, Dinis, and Blois techniques. The optimized molecular structure, vibrational frequencies, ultraviolet–visible spectrums, and nuclear magnetic resonance values of the newly synthesized Schiff base were assessed through the use of density functional theory (DFT) with standard B3LYP/6–311++G(d,p) level. The harmonic vibration peaks were performed via comparison of the scaled values with the experimental FT-IR spectrum. The nuclear magnetic resonance chemical shift values were determined by the gauge-independent atomic orbital (GIAO) method. The nuclear magnetic resonance chemical shift values of the newly synthesized Schiff base in various solvents were examined at B3LYP/6–311++G(d,p) level utilizing integral equation formalism polarizable continuum model (IEFPCM). The chemical shift values of EPM were computed and compared with experimental findings. The correlational analysis (R2) and RMSD results were evaluated to demonstrate correction and accuracy between calculated and experimental parameters. The HOMO–LUMO orbital forms and their energies were determined. The molecular electrostatic potential (MEP), Mulliken atomic charges, electronic absorption maximum wavelengths, thermodynamic characteristics (i.e., entropy, thermal capacity, and enthalpy), and nonlinear optical (NLO) properties (i.e., the first hyperpolarizability and polarizability) of the newly synthesized Schiff base were investigated. The correlational analysis results indicated a strong relationship between experimental and theoretical findings. The metal chelating activity of the newly synthesized Schiff base and standards was observed to decrease in the order of EDTA > EPM > α-tocopherol according to Dinis method. The newly synthesized Schiff base displayed such a good NLO property that it was 34 times as great as the property of urea. As a result, this chromophore could be a potential building block for nonlinear optical materials.
TL;DR: In this paper, the authors proposed a method to enhance deferasirox (DFX) solubility by employing the co-solvency approach using the density functional theory and polarizable Continuum Model.
TL;DR: In this article, the structure, reactivity, and nonlinear optical response of new metabolites dihydrochalcone (4), 3,4,5-trimethoxychalcone(5), and 2,3, 4,4-4,4’-tetramethoxydihydrochcones (6) obtained by biotransformation of chalcone (1), 3.
TL;DR: In this paper, the effects of donor and acceptor on the first hyperpolarizability of Lindquist-type organo-imido polyoxometalates (POMs) were investigated.
Abstract: Density functional theory and time-dependent density functional theory have been enacted to investigate the effects of donor and acceptor on the first hyperpolarizability of Lindquist-type organo-imido polyoxometalates (POMs). These calculations employ a range-separated hybrid exchange-correlation functional (ωB97X-D), account for solvent effects using the implicit polarizable continuum model, and analyze the first hyperpolarizabilities by using the two-state approximation. They highlight the beneficial role of strong donors as well as of π-conjugated spacers (CH=CH rather than C≡C) on the first hyperpolarizabilities. Analysis based on the unit sphere representation confirms the one-dimensional push-pull π-conjugated character of the POMs substituted by donor groups and the corresponding value of the depolarization ratios close to 5. Furthermore, the use of the two-state approximation is demonstrated to be suitable for explaining the origin of the variations of the first hyperpolarizabilities as a function of the characteristics of a unique low-energy charge-transfer excited state and to attribute most of the first hyperpolarizability changes to the difference of dipole moment between the ground and that charge-transfer excited state.
TL;DR: It was found that the presence of a polar solvent decreased the energy barrier for the bridged proton transfer, however, it did not significantly affect the aromaticity and electronic structure.
Abstract: Intra- and inter-molecular interactions were studied in 2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone and 1,4-dihydroxy-anthraquinone to shed more light on the molecular assembly phenomena. The electronic ground and excited states features of the compounds were investigated to find structure-property dependencies. The theoretical study was carried out on the basis of Density Functional Theory (DFT), its Time-Dependent (TD-DFT) extension, and using Car–Parrinello Molecular Dynamics (CPMD). In order to show how the environmental effects modulate the physico-chemical properties, the simulations were performed in vacuo, with the solvent reaction field (Polarizable Continuum Model (PCM) and water as a solvent) and crystalline phase. The intramolecular hydrogen bonds and the bridged proton dynamics were analyzed in detail. The aromatic rings and electronic structure changes were estimated using the Harmonic Oscillator Model of Aromaticity (HOMA) and Atoms in Molecules (AIM) theory. The Symmetry-Adapted Perturbation Theory (SAPT) was employed for interaction energy decomposition in the studied dimers and trimers. It was found that the presence of a polar solvent decreased the energy barrier for the bridged proton transfer. However, it did not significantly affect the aromaticity and electronic structure. The SAPT results showed that the mutual polarization of the monomers in the dimer was weak and that the dispersion was responsible for most of the intermolecular attraction. The intermolecular hydrogen bonds seem to be much weaker than the intramolecular bridges. The TD-DFT results confirmed that the electronic excitations do not play any significant role in the intramolecular proton transfer. The CPMD results indicated that the protons are very labile in the hydrogen bridges. Short proton transfer and proton-sharing events were observed, and a correlation between them in the twin bridges was noticed, especially for the first investigated compound.
TL;DR: In this paper, the excited-state rotatory strengths of cyclic ketones were reported at a correlated ab initio level with the algebraic diagrammatic construction scheme of the polarization propagator up to the third order.
Abstract: Excited-state rotatory strengths are reported for the first time at a correlated ab initio level, here with the algebraic diagrammatic construction scheme of the polarization propagator up to the third order. To demonstrate the capabilities of this computational approach, the gas phase S1 electronic circular dichroism spectra of the bicyclic ketones (1R)-camphor, (1R)-norcamphor, and (1R)-fenchone have been calculated at the ADC(3) level of theory. Furthermore, the solution excited-state spectra of the energetically lowest conformer of R-(+)-1,1'-bi(2-naphthol) have been computed with inclusion of a polarizable continuum model at the ADC(2) level of theory.
TL;DR: The present study elucidates the reinvestigation of the photophysical behavior of 3-aminobenzoic acid (3ABA) in solvents of different polarities using the steady-state spectroscopic techniques and describes unnoticed sigmoidal behavior in the ground state and synergistic impact in the excited state.
TL;DR: In this paper, the authors show that a parametrized polarizable continuum model (PCM) which represents solvation in a mean field approach by a continuous polarizable media, possesses catastrophic limitations for the modelling of ionic and charged interfaces.
Abstract: First-principles calculations are an important tool to investigate the complex processes occurring at solid/liquid interfaces which are at the heart of modern technologies. Currently, capturing the whole electrochemical environment at an interface, including the applied potential and solvation, still remains challenging as it necessitates to couple different approaches whose interactions are not fully understood. In this work, a grand canonical density functional theory approach is coupled with solvation models to investigate the electrochemical interfaces under applied potential. We show that a parametrized polarizable continuum model (PCM) which represent solvation in a mean field approach by a continuous polarizable media, possesses catastrophic limitations for the modelling of ionic and charged interfaces. We reveal the origin of PCM instabilities under chemical or electrochemical strong oxidation to be the consequence of a phase transition in the surface Li electronic structure. Thus, PCM undergoes an unphysical response to this phase transition by penetrating within the atomic radius of surface Li atoms. To recover a physical response, an explicit first solvation shell has to be included in addition to the PCM in order to properly describe the electrochemistry of the interface. The Fukui functions show that the first solvation shell becomes involved in the redox process as solvent electron doublet is transferred to the acidic Li+. If another explicit solvent layer is added, the interface electrochemical properties become independent of the PCM parameters: in particular capacitance can then be computed from a parameter-free electrochemical approach. This is an important conclusion as the experimental electrochemical capacitance are not easily found and thus the parametrization of the PCM for electrochemical interface can be difficult. This approach can easily be applied to investigate electrochemical properties at the atomic scale and generalized to any electrochemical device for which interfaces play a crucial role.
TL;DR: In this article, the authors investigated the thermal dimerization of 1,3-cyclohexadiene at 1 atm and high pressures up to 6 GPa and showed that the reduction of reaction barrier is more profound in concerted reactions than in stepwise reactions, rationalized on the basis of the volume profiles of different mechanisms.
Abstract: Quantum chemical calculations are reported for the thermal dimerizations of 1,3-cyclohexadiene at 1 atm and high pressures up to 6 GPa. Previous experiments [Klarner et al. Angew. Chem. Int. Ed. 1986, 25, 108], based on measured activation energies and activation volumes, suggested concerted mechanisms for the formation of the endo [4+2] cycloadduct and a [6+4]-ene adduct, and stepwise mechanisms for the formation of the exo [4+2] cycloadduct and two [2+2] cycloadducts. Computed activation enthalpies (ωB97XD, CCSD(T) and SC-NEVPT2) of plausible dimerization pathways at 1 atm agree well with the experiment activation energies and the values from previous calculations [Ess et al. J. Org. Chem. 2008, 73, 7586]. High-pressure reaction profiles, computed by the recently-developed extreme pressure-polarizable continuum model (XP-PCM), show that the reduction of reaction barrier is more profound in concerted reactions than in stepwise reactions, which is rationalized on the basis of the volume profiles of different mechanisms. A clear shift of the transition state towards the reactant by high pressure is revealed for the [6+4]-ene reaction by the calculations. The computed activation volumes by XP-PCM agree excellently with the experimental values, confirming the existence of competing mechanisms in the thermal dimerizations of 1,3-cyclohexadiene.