Solvation energies of the proton in ammonia explicitly versus temperature

Doping Efficiency of Poly(benzodifurandione) from First Principles

Poly(benzodifurandione) (PBFDO) has emerged as a promising n-type conductive polymer (n-CP) for organic electronic applications, particularly in thermoelectrics (TE), due to its high doping efficiency and environmental stability. Unlike most high-performance p-type polymers, high-efficiency n-CPs are limited, posing a bottleneck in the TE module performance. In this study, we use first-principles electronic structure calculations to investigate the thermodynamic conditions that favor n-doping in PBFDO, focusing on the role of the temperature, chain length, and doping concentration. We compute the change in Gibbs free energy, ΔG, upon doping and explore how it varies with temperature and polymer chain length. Our results show that doping becomes more thermodynamically favorable at lower temperatures and in longer chains, with a strong dependence of ΔG on the doping level emerging as chain length increases. Notably, PBFDO can achieve favorable doping levels across various chain lengths and temperatures, with specific doping thresholds identified for different molecular weights. These findings suggest that lower synthesis temperatures could lead to more heavily doped, higher-conductivity PBFDO, and that chain length significantly influences achievable doping efficiency. This work provides insights for optimizing PBFDO doping strategies to enhance its performance in TE applications, bridging a key gap in organic semiconductor research.

Clusters of solvated ferrous ion in water-ammonia mixture: Structures and noncovalent interactions

The behavior of metal ions is commonly studied in pure solvent although, in our daily life, these metals are involved in mixtures of solvents. In the present study, we investigated structures, relative stabilities and temperature dependance of solvated ferrous ion in water-ammonia mixture solvent at 0K and at various temperatures ranging from 25K to 400K. All the calculations are performed at the MN15 level of theory associated with the aug-cc-pVDZ basis set. For deep understanding of binding patterns in solvated ferrous ion in water-ammonia mixture solvent, noncovalent interactions are presented based on the QTAIM analysis using AIMAll. Our results prove that the ferrous ion is more stable when it is solvated by ammonia instead of water. In addition, hydrogen bonds are weakened by the presence of ammonia molecules. The temperature dependence of the different obtained geometries indicates that from s=6 (s is the sum of water and ammonia molecules around the ferrous ion), when the number of water molecules is almost equal to that of ammonia, the structures with coordination number 5 are dominant. However, the coordination number is six when there are a maximum water molecules (rich water solution) or maximum ammonia molecules (rich ammonia solution) around the ferrous ion (for s≥6). The QTAIM analysis shows that there are two coordination bondings and four hydrogen bondings. Furthermore, it is found that the Fe2+⋯N coordination bondings are stronger than the Fe2+⋯O confirming that the ferrous ion prefers to be solvated by ammonia instead of water.

Solvation energies of the ferrous ion in water and in ammonia at various temperatures

CONTEXT

The solvation of metal ions is crucial to understanding relevant properties in physics, chemistry, or biology. Therefore, we present solvation enthalpies and solvation free energies of the ferrous ion in water and ammonia. Our results agree well with the experimental reports for the hydration free energy and hydration enthalpy. We obtained [Formula: see text] kJ mol[Formula: see text] for the hydration free energy and [Formula: see text] kJ mol[Formula: see text] for the hydration enthalpy of ferrous ion in water at room temperature. At ambient temperature, we obtained [Formula: see text] kJ mol[Formula: see text] as the [Formula: see text] ammoniation free energy and [Formula: see text] kJ mol[Formula: see text] for the ammoniation enthalpy. In addition, the free energy of solvation is deeply affected when the temperature increases. This pattern can be attributed to the rise of entropy when the temperature rises. Besides, the temperature does not affect the ammoniation enthalpies and the hydration enthalpy of the [Formula: see text] ion.

METHOD

All the geometry optimizations are performed at the MP2 methods associated with the 6-31++g(d,p) basis set of Pople. solvated phase structures of [Formula: see text] ion in water or in ammonia are performed using the PCM model. The [Formula: see text] program suite was used to perform all the calculations. The program TEMPO was also used to evaluate the temperature sensitivity of the different obtained geometries.

Hydration of [Formula: see text]aminobenzoic acid: structures and non-covalent bondings of aminobenzoic acid-water clusters

CONTEXT

Micro-hydration of the aminobenzoic acid is essential to understand its interaction with surrounding water molecules. Understanding the micro-hydration of the aminobenzoic acid is also essential to study its remediation from wastewater. Therefore, we explored the potential energy surfaces (PESs) of the para-aminobenzoic acid-water clusters, ABW[Formula: see text], [Formula: see text], to study the microsolvation of the aminobenzoic acid in water. In addition, we performed a quantum theory of atoms in molecules (QTAIM) analysis to identify the nature of non-covalent bondings in the aminobenzoic acid-water clusters. Furthermore, temperature effects on the stability of the located isomers have been examined. The located structures have been used to calculate the hydration free energy and the hydration enthalpy of the aminobenzoic acid using the cluster continuum solvation model. The hydration free energy and the hydration enthalpy of the aminobenzoic acid at room temperature are evaluated to be -7.0 kcal/mol and -18.1 kcal/mol, respectively. The hydration enthalpy is in perfect agreement with a previous experimental estimate. Besides, temperature effects on the calculated hydration enthalpy and free energy are reported. Finally, we calculated the gas phase binding energies of the most stable structures of the ABW[Formula: see text] clusters using twelve functionals of density functional theory (DFT), including empirical dispersion. The DFT functionals are benchmarked against the DLPNO-CCSD(T)/CBS. We have found that the three most suitable DFT functionals are classified in the following order: PW6B95D3 > MN15 > [Formula: see text]B97XD. Therefore, the PW6B95D3 functional is recommended for further study of the aminobenzoic acid-water clusters and similar systems.

METHODS

The exploration started with classical molecular dynamics simulations followed by complete optimization at the PW6B95D3/def2-TZVP level of theory. Optimizations are performed using Gaussian 16 suite of codes. QTAIM analysis is performed using the AIMAll program.

Self-healable polymer complex with a giant ionic thermoelectric effect

In this study, we develop a stretchable/self-healable polymer, PEDOT:PAAMPSA:PA, with remarkably high ionic thermoelectric (iTE) properties: an ionic figure-of-merit of 12.3 at 70% relative humidity (RH). The iTE properties of PEDOT:PAAMPSA:PA are optimized by controlling the ion carrier concentration, ion diffusion coefficient, and Eastman entropy, and high stretchability and self-healing ability are achieved based on the dynamic interactions between the components. Moreover, the iTE properties are retained under repeated mechanical stress (30 cycles of self-healing and 50 cycles of stretching). An ionic thermoelectric capacitor (ITEC) device using PEDOT:PAAMPSA:PA achieves a maximum power output and energy density of 4.59 μW‧m-2 and 1.95 mJ‧m-2, respectively, at a load resistance of 10 KΩ, and a 9-pair ITEC module produces a voltage output of 0.37 V‧K-1 with a maximum power output of 0.21 μW‧m-2 and energy density of 0.35 mJ‧m-2 at 80% RH, demonstrating the potential for a self-powering source.

Solvation of Manganese(III) Ion in Water and in Ammonia

In this work, we have studied the solvation of manganese(III) ion in water and in ammonia using three levels of theory: MP2, MN15, and ωB97XD associated with the aug-cc-pVDZ basis set. The studied systems are constituted of Mn³⁺(H₂O)₆ and Mn³⁺(NH₃)₆ in gas and solvent phases as well as Mn³⁺(H₂O)₁₈ and Mn³⁺(NH₃)₁₈ in the gas phase. Four aspects of the solvation of manganese(III) ion have been examined for the aforementioned systems at the three levels of theory. First, we started by locating the Jahn-Teller elongated and compressed configuration in Mn³⁺(H₂O)₆ and Mn³⁺(NH₃)₆. Second, we calculated the spin state energies and the spin state free energies for temperatures ranging from 50 to 400 K to look at possible spin crossover in the studied systems. Third, we carried out a quantum theory of atoms in molecules (QTAIM) analysis, and we determined the ionic radii of manganese(III) ion in water and in ammonia. Fourth, we calculated the solvation free energies and the solvation enthalpies of manganese(III) ion in water and in ammonia using the cluster continuum solvation model. For these four aspects of the solvation of manganese(III) ion, most of the reported properties are provided in this work for the first time. We particularly found that the calculated solvation enthalpy of the manganese(III) ion in water is in good agreement with an experimental estimate.

Structures, binding energies and non-covalent interactions of furan clusters

Understanding of the furan solvent is subjected to the knowledge of the structures of the furan clusters and interactions taking place therein. Although, furan clusters can be very important to determine the dynamics and the properties of the furan solvent, there has been only a few investigations reported on furan dimer. In this work, we have explored the potential energy surfaces (PESs) of the furan clusters using two incremental levels of theory. Structures have been initially generated using classical molecular dynamics followed by full optimization at the MP2/aug-cc-pVDZ level of theory. The results show that the most stable structure of the furan dimer has a stacking configuration while that of the trimer has a cyclic configuration. We have noted that the structures of the furan tetramer have no definite configurations. In addition, we have performed a quantum theory of atoms in molecule (QTAIM) analysis to identify all possible non-covalent interactions of the furan clusters. The results show that six different types of non-covalent interactions can be identified in furan clusters. We have noted that the CH⋯C and CH⋯O hydrogen bondings are the strongest non-covalent interactions while the H⋯H bonding interaction is found to be the weakest. Furthermore, we have assessed the performance of ten DFT functionals in calculating the binding energies of the furan clusters. The ten DFT functionals (M05, M05-2X, M06, M06-2X, M08HX, PBE0, ωB97XD, PW6B95D3, APFD and MN15) have been benchmarked to DLPNO-CCSD(T)/CBS. The functionals M05-2X and M06 are recommended for further affordable investigations of the furan clusters.

Generalized energy-based fragmentation approach for calculations of solvation energies of large systems

A generalized energy-based fragmentation (GEBF) approach has been combined with a universal solvation model based on solute electron density (SMD) to compute the solvation energies of general large systems (such as protein molecules) in solutions. In the GEBF-SMD method, the solvation energy of a target system could be combined by the corresponding solvation energies of various subsystems, each of which is embedded in the background point charges and surface charges on the surface of solute cavity at the positions of its atoms and neighbouring atoms outside of the subsystem. Our results show that the GEBF-SMD model could reproduce the conventional SMD solvation energies quite well for various proteins in solutions, and could significantly reduce the computational costs for the SMD calculations of large proteins. In addition, the GEBF-SMD approach is almost independent of the basis sets and the types of solvents (including protic, polar, and nonpolar ones). Also, the GEBF-SMD approach could reproduce the relative energies of various conformers of large systems in solutions. Therefore, the GEBF-SMD method is expected to be applicable for computing the solvation energies of a broad range of large systems.

Temperature-dependent oxidation of BSCAPE molecule in methanol medium

Temperature-dependent solvation free energy and oxidation by free energy of ionization of 2-Phenylethyl (2E)-3-(1-benzenesulfonyl-4,5-dihydroxyphenyl) acrylate (BSCAPE) in methanol medium are the concerns of the present work. This molecule is a relevant phenolic acid enclosing multiple bioactivities. The explicit, implicit and discrete-continuum models of solvation were used. The methanol molecules were coordinated to this acid to form cluster complexes. The dual method M06-2X/6-31++G(d,p)//B3LYP/6-31G(d) was employed along with basis set superposition error correction. The results show that, the free energy of coordination and solvation are distant. Both quantities increase with temperature. From discrete-continuum treatment, there is non-spontaneity of solvation process, while coordination yielded spontaneity and non-spontaneity at cold and hot room temperatures, respectively. The ionization potential in gas phase, decreases with temperature. All the solvation models yielded lower ionization potential than that of gas phase. Thus, it follows that, the increase of temperature and methanol medium favours the oxidation of BSCAPE. Consequently, this favours its metabolism processes.

Structures and relative stability of hydrated ferrous ion clusters and temperature effects

Structures of solvated ferrous ion clusters have been investigated in the singlet and quintet spin states of the ferrous ion. Relative stabilities of isomers are also discussed at different temperatures.

Large-Sized Ammonia Clusters and Solvation Energies of the Proton in Ammonia

The absolute solvation energies (free energies and enthalpies) of the proton in ammonia are used to compute the pK_a of species embedded in ammonia. They are also used to compute the solvation energies of other ions in ammonia. Despite their importance, it is not possible to determine experimentally the solvation energies of the proton in a given solvent. We propose in this work a direct approach to compute the solvation energies of the proton in ammonia from large-sized neutral and protonated ammonia clusters. To undertake this investigation, we performed a geometry optimization of neutral and protonated ammonia 30-mer, 40-mer, and 50 mer to locate stable structures. These structures have been fully optimized at both APFD/6-31++g(d,p) and M06-2X/6-31++g(d,p) levels of theory. An infrared spectroscopic study of these structures has been provided to assess the reliability of our investigation. Using these structures, we have computed the absolute solvation free energy and the absolute solvation enthalpy of the proton in ammonia. It comes out that the absolute solvation free energy of the proton in ammonia is calculated to be -1192 kJ mol^-1 , whereas the absolute solvation enthalpy is evaluated to be -1214 kJ mol^-1 . © 2019 Wiley Periodicals, Inc.

Structures of the solvated copper(ii) ion in ammonia at various temperatures

We investigated theoretically the structures and relative stabilities of the solvated copper(ii) ion in ammonia, Cu²⁺(NH₃)_n, n = 1–10.

Ionic radii of hydrated sodium cation from QTAIM

The sodium cation is ubiquitous in aqueous chemistry and biological systems. Yet, in spite of numerous studies, the (average) distance between the sodium cation and its water ligands, and the corresponding ionic radii, are still controversial. Recent experimental values in solution are notably smaller than those from previous X-ray studies and ab initio molecular dynamics. Here we adopt a "bottom-up" approach of obtaining these distances from quantum chemistry calculations [full MP2 with the 6-31++G(d,p) and cc-pVTZ basis-sets] of gas-phase Na⁺(H₂O)_n clusters, as a function of the sodium coordination number (CN = 2-6). The bulk limit is obtained by the polarizable continuum model, which acts to increase the interatomic distances at small CN, but has a diminishing effect as the CN increases. This extends the CN dependence of the sodium-water distances from crystal structures (CN = 4-12) to lower CN values, revealing a switch between two power laws, having a small exponent at small CNs and a larger one at large CNs. We utilize Bader's theory of atoms in molecules to bisect the Na⁺-O distances into Na⁺ and water radii. Contrary to common wisdom, the water radius is not constant, decreasing even more than that of Na⁺ as the CN decreases. We also find that the electron density at the bond critical point increases exponentially as the sodium radius decreases.

Structures of solvated ferrous ion clusters in ammonia and spin-crossover at various temperatures

The solvated ferrous ion in ammonia is hexa-coordinated, irrespective of the temperature.

Ionization of Ammonia Nanoices with Adsorbed Methanol Molecules

Large ammonia clusters represent a model system of ices that are omnipresent throughout the space. The interaction of ammonia ices with other hydrogen-boding molecules such as methanol or water and their behavior upon an ionization are thus relevant in the astrochemical context. In this study, ammonia clusters (NH₃) _N with the mean size N̅ ≈ 230 were prepared in molecular beams and passed through a pickup cell in which methanol molecules were adsorbed. At the highest exploited pickup pressures, the average composition of (NH₃) _N(CH₃OH) _M clusters was estimated to be N: M ≈ 210:10. On the other hand, the electron ionization of these clusters yielded about 75% of methanol-containing fragments (NH₃) _n(CH₃OH) _mH⁺ compared to 25% contribution of pure ammonia (NH₃) _nH⁺ ions. On the basis of this substantial disproportion, we propose the following ionization mechanism: The prevailing ammonia is ionized in most cases, resulting in NH₄⁺ core solvated most likely with four ammonia molecules, yielding the well-known "magic number" structure (NH₃)₄NH₄⁺. The methanol molecules exhibit a strong propensity for sticking to the fragment ion. We have also considered mechanisms of intracluster reactions. In most cases, proton transfer between ammonia units take place. The theoretical calculations suggested the proton transfer either from the methyl group or from the hydroxyl group of the ionized methanol molecule to ammonia to be the energetically open channels. However, the experiments with selectively deuterated methanols did not show any evidence for the D⁺ transfer from the CD₃ group. The proton transfer from the hydroxyl group could not be excluded entirely or confirmed unambiguously by the experiment.

Solvation energies of the proton in methanol revisited and temperature effects

Various functionals assessing solvation free energies and enthalpies of the proton in methanol.