Hybrid Solvation Research Articles

Calculated Aqueous Reduction Potentials of Neutral and Anionic Halogen Diatomic Molecules.

The free energy of hydration, aqueous, and gas phase electron affinity and aqueous reduction potentials of F2, Cl2, Br2, I2, ClF, BrF, IF, BrCl, ICl, IBr, and their corresponding anions were calculated using an electronic structure approach previously developed for these properties for X• and XO•, where X is a halogen which yielded excellent results. The gas phase electron affinities were calculated at the Feller-Peterson-Dixon level based on complete basis set extrapolation of CCSD(T) results with additional corrections. The agreement with the available experimental data is excellent, and the calculations provide a complete set of reliable electron affinities for these diatomic halogens. The hybrid solvation approach uses single point implicit solvation calculations on gas phase optimized clusters with explicit solvent molecules. The gas phase energy calculations were performed using MP2 and CCSD(T)-F12b for tetramer clusters (four explicit waters) and MP2 for octamer clusters (eight explicit waters). The final redox potentials were obtained at the MP2/aug-cc-pVTZ (aT) with a self-consistent reaction field (SMD) level using the octamer clusters. The aqueous reduction potentials of the neutral diatomic halogens are predicted within 0.06 V of the experiment for diatomic neutrals. The same agreement of 0.06 V is predicted for the redox potential resulting from dissociation electron attachment of the diatomic halogen anions. The current work extends reduction potentials for multiple redox couples for which no experimental data is available, for example, those containing iodine and the interhalogen anions. F2•- is predicted to dissociate for its lowest energy structure in both the tetramer and octamer clusters to form solvated F-, HF, and OH•.

Solvation Free Energies from Machine Learning Molecular Dynamics.

The present work proposes an extension to the approach of [Xi, C; et al. J. Chem. Theory Comput. 2022, 18, 6878] to calculate ion solvation free energies from first-principles (FP) molecular dynamics (MD) simulations of a hybrid solvation model. The approach is first re-expressed within the quasi-chemical theory of solvation. Then, to allow for longer simulation times than the original first-principles molecular dynamics approach and thus improve the convergence of statistical averages at a fraction of the original computational cost, a machine-learned (ML) energy function is trained on FP energies and forces and used in the MD simulations. The ML workflow and MD simulation times (≈200 ps) are adjusted to converge the predicted solvation energies within a chemical accuracy of 0.04 eV. The extension is successfully benchmarked on the same set of alkaline and alkaline-earth ions.

Theoretical investigation on potential of zero free charge of (111) and (100) surfaces of Group 10 and 11 metals

The potential of zero free charge (PZFC) value is a crucial parameter in electrochemistry. However, the evaluations of PZFC have traditionally been difficult. To overcome this challenge, we applied a hybrid solvation method that incorporates, both an explicit water layer next to the metal surface and an implicit water layer, combined with density functional theory (DFT) to simplify the PZFC evaluation. Using the (111) and (100) surfaces of Group 10 and 11 metals as model systems, we calculated their PZFC values, which showed excellent agreement with the reported data. This great match validates the accuracy and reliability of our theoretical approach. Notably, we observed that the surface structure and the orientation of water molecules have a significant influence on the PZFC values of the metals. Our study, therefore, paves the way for efficiently and accurately calculating the PZFC values of materials, which can greatly benefit their practical applications.

DFT investigation on the structural and vibrational behaviours of the non-protein amino acids in hybrid explicit/continuum solvent: a case of the zwitterions γ-aminobutyric and α - aminoisobutyric acids.

The influence of hybrid solvation models on the molecular structures and vibrational characteristics of g-aminobutyric acid (GABA) and a-aminoisobutyric acid (AIB) zwitterions was assessed by employing a variety of Density Functional Theory (DFT). The quantum chemical methods included the B3LYP and B3PW91 hybrid functionals and the 6‑311++G(d,p) basis set. The most stable conformation derived from the potential energy surface (PES) scans using the B3LYP/6-311++G(d,p) model chemistry for each studied molecule was predicted within a continuum environment represented by the COSMO and SMD solvation models. The stable structures were subsequently immersed in explicit/COSMO and explicit/SMD hybrid solvation models, where 10 and 8 water molecules were explicitly positioned around the functional groups of the GABA and AIB zwitterions, respectively. The number of water molecules chosen was sufficient to prevent proton transfer among the carboxylate group (COO-) and the ammonium group (NH3+) within each molecule under investigation. After optimizing the geometry of each hydrated complex, the normal vibrational modes were determined. The scaled theoretical frequencies obtained from the various model chemistries were then compared to available experimental data from infrared (IR) and Raman spectroscopy. In the case of GABA and AIB molecules, the comparisons revealed that the B3LYP/6-311++G(d,p) model chemistry yielded wavenumber values that closely matched the experimental IR and Raman data, particularly when the explicit/SMD solvent was employed. The computed results indicate deviations of less than 4% when compared to the experimental data for the two molecules under investigation.

Improved prediction of reaction kinetics for amine absorbent-based carbon capture using reactive site-based transition state conformer search method

There is no doubt that carbon emissions are one of the greatest challenges facing humanity today. Carbon capture, utilization, and storage is an effective way to achieve carbon neutrality. However, the commonly used commercial absorbents for post-combustion captures still have some limitations such as low chemical absorption rate constants. In this paper, a universal reaction kinetic model is developed for amine-based carbon capture based on the transition state theory, density functional theory, and hybrid solvation model. The developed reaction kinetic model is applicable to a wide range of amine-solvent solutions involving primary/secondary/tertiary amines and aqueous/nonaqueous solvents. The key contribution of this work is developing a reactive site-based search method for the GENeration of Conformers for Transition States (GENConf-TS). GENConf-TS has greatly improved the prediction accuracy of the reaction kinetic model from R2 = 0.882 to R2 = 0.950 based on a dataset of 23 various amine-solvent solutions. The results highlight the critical impacts of the transition state conformational isomers on amine-based CO2 chemical absorption rate constants.

First hyperpolarizability of the di-8-ANEPPS and DR1 nonlinear optical chromophores in solution. An experimental and multi-scale theoretical chemistry study

The solvent effects on the linear and second-order nonlinear optical properties of an aminonaphtylethenylpyridinium (ANEP) dye are investigated by combining experimental and theoretical chemistry methods. On the one hand, deep near infrared (NIR) hyper-Rayleigh scattering (HRS) measurements (1840–1950 nm) are performed on solutions of di-8-ANEPPS in deuterated chloroform, dimethylformamide, and dimethylsulfoxide to determine their first hyperpolarizablity (βHRS). For the first time, these HRS experiments are carried out in the picosecond regime in the deep NIR with very moderate (≤3 mW) average input power, providing a good signal-to-noise ratio and avoiding solvent thermal effects. Moreover, the frequency dispersion of βHRS is investigated for Disperse Red 1 (DR1), a dye commonly used as HRS external reference. On the other hand, these are compared with computational chemistry results obtained by using a sequential molecular dynamics (MD) then quantum mechanics (QM) approach. The MD method allows accounting for the dynamical nature of the molecular structures. Then, the QM part is based on TDDFT/M06-2X/6-311+G* calculations using solvation models ranging from continuum to discrete ones. Measurements report a decrease of the βHRS of di-8-ANEPPS in more polar solvents and these effects are reproduced by the different solvation models. For di-8-ANEPPS and DR1, comparisons show that the use of a hybrid solvation model, combining the description of the solvent molecules around the probe by point charges with a continuum model, already achieves quasi quantitative agreement with experiment. These results are further improved by using a polarizable embedding that includes the atomic polarizabilities in the solvent description.

Electrocatalytic Mechanisms for an Oxygen Evolution Reaction at a Rhombohedral Boron Monosulfide Electrode/Alkaline Medium Interface.

Rhombohedral boron monosulfide (r-BS) with a layer stacking structure is a promising electrocatalyst for an oxygen evolution reaction (OER) within an alkaline solution. We investigated the catalytic mechanisms at the r-BS electrode/alkaline medium interface for an OER using hybrid solvation theory based on the first-principles method combined with classical solution theory. In this study, we elucidate the activities of the OER at the outermost r-BS sheet with and without various surface defects. The Gibbs free energies along the OER path indicate that the boron vacancies at the first and second layers of the r-BS surface (VB1 and VB2) can promote the OER. However, we found that the VB1 is easily occupied by the oxygen atom during the OER, degrading its electrocatalytic performance. In contrast, VB2 is suitable for the active site of the OER due to its structure stability. Next, we applied a bias voltage with the OER potential to the r-BS electrode. The bias voltage incorporates the positive excess surface charge into pristine r-BS and VB2, which can be understood by the relationship between the OER potential and potentials of zero charge at the r-BS electrode. Because the OH- ions are the starting point of the OER, the positively charged surface is kinetically favorable for the electrocatalyst owing to the attractive interaction with the OH- ions. Finally, we qualitatively discuss the flat-band potential at a semiconductor/alkaline solution interface. It suggests that p-type carrier doping could promote the catalytic performance of r-BS. These results explain the previous measurement of the OER performance with the r-BS-based electrode and provide valuable insights into developing a semiconductor electrode/water interface.

A Combined Reaction Path Search and Hybrid Solvation Method for the Systematic Exploration of Elementary Reactions at the Solid-Liquid Interface.

We present a combined simulation method of single-component artificial force induced reaction (SC-AFIR) and effective screening medium combined with the reference interaction site model (ESM-RISM), termed SC-AFIR+ESM-RISM. SC-AFIR automatically and systematically explores the chemical reaction pathway, and ESM-RISM directly simulates the precise electronic structure at the solid-liquid interface. Hence, SC-AFIR+ESM-RISM enables us to explore reliable reaction pathways at the solid-liquid interface. We applied it to explore the dissociation pathway of an H2O molecule at the Cu(111)/water interface. The reaction path networks of the whole reaction and the minimum energy paths from H2O to H2 + O depend on the interfacial environment. The qualitative difference in the energy diagrams and the resulting change in the kinematically favored dissociation pathway upon changing the solvation environments are discussed. We believe that SC-AFIR+ESM-RISM will be a powerful tool to reveal the details of chemical reactions in surface catalysis and electrochemistry.

Entropic Penalty Switches Li+ Solvation Site Formation and Transport Mechanisms in Mixed Polarity Copolymer Electrolytes.

Emerging solid polymer electrolyte (SPE) designs for efficient Li-ion (Li+) conduction have relied on polarity and mobility contrast to improve conductivity. To further develop this concept, we employ simulations to examine Li+ solvation and transport in poly(oligo ethylene methacrylate) (POEM) and its copolymers with poly(glycerol carbonate methacrylate) (PGCMA). We find that Li+ is solvated by ether oxygens instead of the highly polar PGCMA, due to lower entropic penalties. The presence of PGCMA promotes single-chain solvation, thereby suppressing interchain Li+ hopping. The conductivity difference between random copolymer PGCMA-r-POEM and block copolymer PGCMA-b-POEM is explained in terms of a hybrid solvation site mechanism. With diffuse microscopic interfaces between domains, PGCMA near the POEM contributes to Li+ transport by forming hybrid solvation sites. The formation of such sites is hindered when PGCMA is locally concentrated. These findings help explain how thermodynamic driving forces govern Li+ solvation and transport in mixed SPEs.

A Buckycatcher in Solution-A Computational Perspective.

In this work, we study the buckycatcher (C60H28) in solution using quantum chemical models. We investigate the conformational equilibria in several media and the effects that molecules of solvent might have in interconversion barriers between the different conformers. These are studied in a hypothetical gas phase, in the dielectric of a solvent, as well as with hybrid solvation. In the latter case, due to a disruption of π-stacking interactions, the transition states are destabilized. We also evaluate the complexation of the buckycatcher with solvent-like molecules. In most cases studied, there should be no adducts formed because the enthalpy driving force cannot overcome entropic penalties.

Carbon-supported CoS4-C single-atom nanozyme for dramatic improvement in CO2 electroreduction to HCOOH: A DFT study combined with hybrid solvation model

Single-atom nanozymes (SANs) have attracted extensive attention due to their characteristics of both single-atom catalysts (SACs) and enzymes. Using spin-polarized density functional theory (DFT) calculations combined with the hybrid solvation model, this work designed a series of carbon-supported Group VIII transition metals TMS4-C SANs, similar to the TMS4 active center of formate dehydrogenase (FADH), aiming to develop highly efficient SANs for CO2 electroreduction. DFT calculations show that compared with TMN4-C, TMS4-C have FADH-like feature, which can selectively reduce CO2 to formic acid. Particularly, CoS4-C is the most promising SAN for CO2 reduction, with a low limiting potential of -0.07 V, which exceeds most reported catalysts. Two descriptors of TMX4-C (X = N, S) based on intrinsic and electronic structure properties were proposed to shed light on the origin activity of candidates. The findings presented here will provide new insights into the design of novel enzyme-like catalysts for electrochemical CO2 reduction.

Adsorption free energy of phenol onto coronene: Solvent and temperature effects

Molecular modeling can considerably speed up the discovery of materials with high adsorption capacity for wastewater treatment. Despite considerable efforts in computational studies, the molecular modeling of adsorption processes has several limitations in reproducing experimental conditions. Handling the environmental effects (solvent effects) and the temperature effects are part of the important limitations in the literature. In this work, we address these two limitations using the adsorption of phenol onto coronene as case study. In the proposed model, for the solvent effects, we used a hybrid solvation model, with n explicit water molecules and implicit solvation. We increasingly used n=1 to n=12 explicit water molecules. To account for the temperature effects, we evaluated the adsorption efficiency using the adsorption free energy for temperatures varying from 200 to 400K. We generated initial configurations using classical molecular dynamics, before further optimisation at the ωB97XD/aug-cc-pVDZ level of theory. Polarisable continuum solvation model (PCM) is used for the implicit solvation. The adsorption free energy is evaluated to be -1.3kcal/mol at room temperature. It has been found that the adsorption free energy is more negative at low temperatures. Above 360K, the adsorption free energy is found to be positive.

UV–vis and ECD spectroelectrochemistry of atropisomeric naphthalenediimide derivative

The UV–vis and ECD spectroelectrochemistry (SEC) of a chiral binaphthalenylamine derivative of the N-butyl naphthalenediimide (NDIB-NH2) enantiomers were applied to measure UV–vis and ECD spectra of NDIB-NH2 radicals and dianion formed in the reduction and oxidation processes observed in cyclic voltammetry (CV). The CV curves and EPR spectroelectrochemistry enabled us to establish conditions at which a radical-anion [NDIB-NH2]̇.−, a dianion [NDIB-NH2]2−, and a radical-cation [NDIB-NH2]̇.+ are formed. The DFT restricted open-shell CAM-B3LYP-D3/def2TZVP/PCM calculations demonstrated that in the radical-anion [NDIB-NH2]̇.−, spin is spread over the NDI system while in the radical-cation [NDIB-NH2]̇+ it is spread over the aminonaphthalene moiety. The UV–vis spectra of radical-anion and dianion show the most significant changes in the 400–800 nm range. In that range, the ECD spectra varied with the change of electrode potential more than the UV–vis did and enabled the identification of a new ECD band of [NDIB-NH2]̇.− at ca. 400 nm hidden in the background in the UV spectra at −1000 mV. A broad structured ECD pattern with a maximum at ca. 530 nm was observed for [NDIB-NH2]̇.− (−1000 mV), while a single smooth ECD band of [NDIB-NH2]2− was located at 520 nm (−1750 mV). For the first time, an isosbestic point (455 nm) was found in ECD spectroelectrochemical measurements for the radical-cation [NDIB-NH2]̇.+ in equilibrium with the NDIB-NH2 neutral form. The TD-DFT CAM-B3LYP-D3/6-31G** calculations combined with the hybrid (explicit combined with implicit) solvation model fairly well reproduced the UV–vis and ECD SEC of neutral and redox forms of NDIB-NH2 but the ECD spectrum of [NDIB-NH2]̇.+ above 390 nm.

Solvation energies of ferrous ion in methanol at various temperatures

• Solvated ferrous ion in methanol is hexa-coordinated. • Accurate free energy and enthalpy of the solvated ferrous ion in methanol available. • Binding and clustering energies of the solvated ferrous ion in methanol available. The accurate determination of the solvation free energies or solvation enthalpies of ferrous ion in a given medium is subject to the determination of the most favored structures of the ferrous ion in this medium. In this work, we investigated structures, relative stabilities, clustering energies, binding energies, solvation enthalpies and solvation free energies of the ferrous ion in methanol for temperatures ranging from 20 K to 400 K. It is pointed out that the coordination number of the solvated ferrous ion in methanol is six, but could decrease slightly when the temperature increases. The temperature dependence of the relative stability of different isomers obtained proves that, for T ranging from 20 K to 400 K, the population is dominated by one structure and we noted the presence of fourfold coordinated structures for n > 6. Solvation energies of ferrous ion in methanol were computed following an hybrid solvation scheme. Finally, the solvation free energy of ferrous ion in methanol at room temperature (298.15 K), is −2066.1 kJ mol −1 and the corresponding solvation enthalpy is −2103.5 kJ mol −1 . Taking into account the temperature effects, the solvation free energies are more affected by the change of temperature mainly for temperature higher than 200 K. However, the effect of temperature is insignificant on the solvation enthalpies. At the saturation, the binding electronic energy per methanol molecule, the binding enthalpy per methanol molecule and the binding free energy per methanol molecule of the solvated ferrous ion in methanol are −142.1, −140.3 and −104.0 kJ mol −1 , respectively. For the clustering energies, we reported −6.9, −6.8 and -3.4 kJ mol −1 corresponding respectively to the clustering electronic energy, the clustering enthalpy and the clustering free energy of the solvated ferrous ion in methanol.

Accounting for Dispersion Effects in the DFT Framework of Electrocatalysis: A Hybrid Solvation Model-Based Case Study of the Oxygen Reduction Reaction

Accounting for Dispersion Effects in the DFT Framework of Electrocatalysis: A Hybrid Solvation Model-Based Case Study of the Oxygen Reduction Reaction

Theoretical investigation of the cooperative effect of solvent: a case study

The effect of solvent was investigated at the DFT level, M06-2X/6-31++G(d,p), for the implicit, namely the universal solvent model based on solute electron density (SMD) and hybrid solvation models, and a new pathway for the Markovnikov for the addition of HCl to 1-butene was suggested, incorporating the solvent in the reaction. The results showed that the use of implicit solvent brings greater stabilization for a large part of the reaction coordinates and for the charges of the transition states (TS). Studying the hybrid solvent model, it was shown by quantum mechanics and molecular simulations that although the first solvation shell is composed of approximately 30 solvent molecules, most of the effect comes from just eight solvent molecules explicitly added, with a variation in energy that tends to about -19.3 kJ mol-1. The reaction rates for the hydration of 1-butene were only able to achieve a reasonable accuracy with the addition of three explicit solvent molecules of 5.97 × 10-8 M-1 s-1 and 2.33 × 10-9 M-1 s-1 for the calculated and the experimental values, respectively. This indicates that not only hybrid solvation may be required, but also the number of explicit molecules added may heavily influence the calculated reaction rates. It was found that for the intermediary product of hydration the hydrogen bonds are stronger than average, suggesting a partial covalent characteristic.

First-Principles Modeling of the Electrochemical Kinetics at Solid-Water Interface

Kinetic information, such as the activation energy and transition state, is critical to understanding the reaction. However, the kinetic information of electrochemistry at solid-water interface is challenging to obtain from conventional models of density functional theory (DFT), as they often neglect the presence and/or the dynamics of the surface charge [1] and the solvent configuration, which are further coupled. Here we present a new model that accounts for these effects, by combining hybrid solvation, constant-electron-potential, and slow-growth sampling techniques together. We then apply this model to elucidate the active site structure and the mechanism of electrochemical carbon dioxide reduction catalyzed by single-nickel-atom embedded in graphene, which shows high performance in experiments while is not well understood [2].[1] D. Kim, J. Shi, Y. Liu, J. Am. Chem. Soc. 2018, DOI: 10.1021/jacs.8b03002[2] X. Zhao, Y. Liu, J. Am. Chem. Soc. 2020, DOI: 10.1021/jacs.9b13872

Ion-solvent interaction of 1-decyl-3-methylimidazolium chloride and isopropanol in a quaternary aqueous two phase system for the efficient partitioning of vanillin and L-tryptophan

A novel quaternary aqueous biphasic system (ABS) composed of 1-decyl-3-methylimidazolium chloride ([Dmim]Cl), 2-propanol, and dipotassium hydrogen phosphate (K2HPO4) was determined at 298.15 K, and impact of 2-propanol:[Dmim]Cl mass ratio on the partition of L-tryptophan and vanillin, was investigated systematically. Additionally, the ion-association and solvation behavior of the ionic liquid in a solution of the aqueous-alcoholic mixture was investigated using the electrical conductivity measurement and analyzed with the low-concentration chemical model (lcCM). It is found that ion-association phenomena govern significantly at the top phase, and biomolecules affinity enhanced where it solvated completely by the ionic liquid. The hybrid ion-interaction and solvation model (HIS) coupled with the UNIQUAC model, was implemented to fit liquid-liquid equilibrium (LLE) data and investigate the ion-solvent interaction of ionic and nonionic compounds. The interaction parameter's analysis of the HIS-UNIQUAC model declared the great solvation for the ionic liquid at the bottom phase. At the 2-propanol:[Dmim]Cl mass ratio of 3:1, the highest partition coefficient of vanillin, K = 389.4, was achieved while the highest partitioning of L-tryptophan, K = 66.5, occurs at the 2-propanol:[Dmim]Cl mass ratio of 1:10, respectively. The partition behavior of biomolecules independently describes using the electrostatic and solvation terms of the HIS-UNIQUAC model, and in general, the activity model provided favorable agreement with theoretical concepts and experimental data.

Specific Optical Rotation and Absolute Configuration of Flexible Molecules Containing a 2‐Methylbutyl Residue

Establishing the absolute configuration of flexible molecules is difficult, and specific optical rotation (SOR) might be an optional strategy. However, complex conformation distributions inevitably generate ambiguous results. Herein, the relationship between SORs and the absolute configuration of flexible molecules containing a 2‐methylbutyl residue was studied using quantum chemical calculations. The existence of a nitrogen atom might increase the uncertainty of the predicted SOR. Compared with the optical rotation calculation step, the geometry optimization step is more influential. Computational parameters including hybrid functionals, basis sets, and solvation models could exert a great effect on the Boltzmann distribution, leading to substantial variation in the SORs. To achieve unambiguous SOR prediction results for flexible molecules, the calculation needs to be performed using at least two combinations of different levels.

Effects of counterions and solvents on the geometrical and vibrational features of dinucleoside-monophosphate (dNMP): case of 3',5'-dideoxycytidine-monophosphate (dDCMP).

The effects of the interaction of the monovalent (Li+, Na+, K+) and divalent (Mg2+) counterions hexahydrated (6H2O), with the PO2- group, on the geometrical and vibrational characteristics of 3', 5'-dDCMP, were studied using the DFT/B3LYP/6-31++G(d) method. These calculations were performed using the explicit (6H2O) and hybrid (6H2O/Continuum) solvation models. The optimizations reveal that in the conformation g-g- and in the explicit model of solvation, the small ions (Li+, Na+) deviate from the bisector plane of the angle O1-P-O2 and the large ions (K+ and Mg2+) remain in this plane, whereas in the hybrid model of solvation, the counterions deviate from this plane. However, when the conformer is g+g+, the monovalent counterions deviate and divide the remainder of the plane regardless of the type of solvation model. In addition, the g-g- conformer is the most stable in the presence of the explicit solvent, while the g+g+ conformer is the most stable in the presence of the hybrid solvent. Finally, the normal modes of the conformers g-g- and g+g+ in the presence of the counterions in the hybrid model show a better agreement with the available experimental data of the DNA forms A, B (g-g-), and Z (g+g+) relatively to the explicit model. This very good agreement is illustrated by the very small deviations ≤ 0.08% (g-g-) and ≤ 0.41% (g+g+) observed between the calculated and experimental data for the PO2- (asymmetric) stretching mode in the presence of the counterion K+ in the hybrid model. Graphical abstract.