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In homogeneous catalysis solvent is an inherent part of the catalytic system. As such, it must be considered in the computational modeling. The most common approach to include solvent effects in quantum mechanical calculations is by means of continuum solvent models. When they are properly used, average solvent effects are efficiently captured, mainly those related with solvent polarity. However, neglecting atomistic description of solvent molecules has its limitations, and continuum solvent models all alone cannot be applied to whatever situation. In many cases, inclusion of explicit solvent molecules in the quantum mechanical description of the system is mandatory. The purpose of this article is to highlight through selected examples what are the reasons that urge to go beyond the continuum models to the employment of micro-solvated (cluster-continuum) of fully explicit solvent models, in this way setting the limits of continuum solvent models in computational homogeneous catalysis. These examples showcase that inclusion of solvent molecules in the calculation not only can improve the description of already known mechanisms but can yield new mechanistic views of a reaction. With the aim of systematizing the use of explicit solvent models, after discussing the success and limitations of continuum solvent models, issues related with solvent coordination and solvent dynamics, solvent effects in reactions involving small, charged species, as well as reactions in protic solvents and the role of solvent as reagent itself are successively considered.

Gamma‐Valerolactone (GVL) has emerged as a promising biomass‐derived solvent for the catalytic conversion of sugars into furan chemicals such as 5‐hydroxymethylfurfural and furfural. Although GVL‐based solvent systems have demonstrated superior performance, the mechanistic roles of GVL are often described qualitatively and remain insufficiently clarified. This review systematically synthesizes recent advances and organizes insights from the literature to elucidate the roles of GVL in sugar‐to‐furan conversion. The effects of GVL‐based solvents are summarized into several interconnected aspects, including enhanced substrate solubility, regulation of reaction pathway selectivity, stabilization of key transition states, mediation of reactant enrichment, and facilitation of product separation. These insights highlight GVL as a multifunctional reaction medium rather than an inert solvent and provide guidance for the rational design of solvent systems for efficient biomass valorization. Gamma‐Valerolactone (GVL) is a promising bio‐based solvent for tandem biomass sugars conversion into furan chemicals, yet its specific roles remain unclear. This review disentangles the multiroles of GVL in sugar‐to‐furan reactions, highlighting how solvent effects, including solubility, pathway regulation, transition‐state stabilization, reactant enrichment, and product separation, govern catalytic efficiency.

The choice of solvent plays a crucial role in aldol reactions, often affecting both the conversion rate and stereoselectivity. In this study, we investigated the influence of solvents (water, methanol and hydroalcoholic) on the proline-catalyzed aldol reactions. We focused on elucidating the solute–solvent interactions at the rate-determining step and the stereoselective step. Our theoretical finding suggests, hydroalcoholic-mediated reaction exhibits a higher conversion rate as compared to pure water and pure methanol-mediated system with the generation of most stable transition state structure. This can be attributed to the existence of strong hydrogen bonding and the formation of stable six-membered transition state structures in hydroalcoholic-mediated system. In addition to this, our research demonstrates that the choice of solvent plays a crucial role in determining the percentage of enantiomeric excess in the reaction. Theoretical finding suggest that the anti-product is preferentially formed in the presence of water and hydroalcoholic media as solvents. Pure water and hydroalcoholic solvents surprisingly showed a higher enantiomeric excess for the anti-product due to formation of strong hydrogen bonding between reaction moiety and solvents. In contrast, methanol-assisted reactions resulted in a racemic mixture, consistent with experimental observations. Results reported in the present study contribute to the broader understanding of solvent effects in organic reactions and offer valuable insights for the design of organic reactions.

Evaluating the effects of a solvent on the properties of a solute molecule is important to understand its behavior in a solution of that solvent; this, in turn, is important because most reactions—including all the reactions in biological systems—occur in solution. In its most common definition, aromaticity is a property of molecules with delocalized electrons in a ring. It significantly influences their behavior and, therefore, it is important to evaluate the effects of a solvent on it. The most powerful magnetic criterion to estimate aromaticity considers magnetically induced current densities in the ring. The present work applies this approach to adducts of hydroxybenzenes with explicit water molecules. Hydroxybenzenes are selected as the simplest aromatic systems capable of forming solute–solvent hydrogen bonds with water molecules. Hydroxybenzenes without consecutive OH groups are selected to avoid the influence of intramolecular hydrogen bonds between OHs. Current densities are calculated focusing on the aromatic rings, and the effect of the solvent is highlighted by the density changes caused by the presence of the water molecules attached to the hydroxybenzene molecule. The results show that the strength of the ring current decreases as the number of OH groups in the molecule increases. The strength does not change greatly in the adducts with respect to the isolated molecules: the change extent and direction depend mostly on the arrangement of water molecules around the central molecule. The current density maps show that the water molecules may also be involved in the current flow.

The aim of this research is the identification of the changes in anion- and solvent-dependent polaronic transitions and the ratio of acid to monomer during the polymerization of new poly( ortho -methoxyaniline) nanosilica-supported sulfuric acid emeraldine salt1/salt2 (POMA-NSSSA-ES1/ES2) nanocomposites. The synthesis is done by doping poly( ortho -methoxyaniline)-emeraldine base (POMA-EB) in the presence of nanosilica-supported sulfuric acid (NSSSA) under solid-state condition. The structure, size, and morphology of all samples were identified using spectroscopy methods. Effect of acid concentration (0.5, 1.5, and 2.0) and low- and high-valent sulfate anion (H 2 SO 4 /HSO 4 − Vs. HSO 4 − /SO 4 2− ) on polaronic transitions of poly( ortho -methoxyaniline) nanocomposites in different solvents (NMP, MCR, DMSO, and MeOH), and conductivity were studied. Afterwards, changes in polaron mutations under changing conditions were analyzed. Increasing the acid concentration compared to the monomer increases the absorption number (λ max ) in the UV–Vis study along with hypsochromic effect (blueshift) and bathochromic effect (redshift) in low acid concentration for polaronic transition. The anion effect proved that by increasing the negative charge of the anion (SO 4 2− ) due to the limiting potential of the polaron and bipolaron structures, it prevents the creation of delocalized polaron structure with no change in the POMA-NSSSA-ES2 nanocomposite conductivity. Results showed that the average size of nanocomposite particle obtained by this method was a range of 40–50 nm and the morphology of nanocomposites was spherical (nanospheres). POMA-NSSSA nanocomposites were completely in a doped state and the emeraldine salt from of POMA. During this research, for the first time, the polaronic orbital energy level was determined. Graphical abstract

In this minireview, weak interactions that occur in supramolecular polymers are discussed. Combination of weak and strong interactions plays an important role in the construction of supramolecular polymers. It is beneficial to separate the contributions of the weak interactions, as well as each solvent effect on the weak interactions. However, it is generally difficult to observe each solvent effect separately at work in each interaction. Small molecular probes are useful to estimate the contributions of the weak interaction. But, the results should be treated with caution when applied to supramolecular polymer systems. To overcome the problems, a new solvent parameter, solvation ability (SA), is introduced, which was determined on the balance point of extended and stacked forms of porphyrin‐based interconvertible supramolecular polymers. Solvent impact on polymers: Solvents affect the strength of non‐bonding interactions, which control the formation of supramolecular polymers in solution. Solvent effects and parameters measured in supramolecular polymer systems are selectively reviewed. A new solvent scale, solvation ability (SA), based on the balance point between extended and stacked polymers is introduced.

In the search to cover the urgent need to combat infectious diseases, natural products have gained attention in recent years. The caespitate molecule, isolated from the plant Helichrysum caespititium of the Asteraceae family, is used in traditional African medicine. Caespitate is an acylphloroglucinol with biological activity. Acylphloroglucinols have attracted attention for treating tuberculosis due to their structural characteristics, highlighting the stabilizing effect of their intramolecular hydrogen bonds (IHBs). In this work, a conformational search for the caespitate was performed using the MM method. Posteriorly, DFT calculations with the APFD functional were used for full optimization and vibrational frequencies, obtaining stable structures. A population analysis was performed to predict the distribution of the most probable conformers. The calculations were performed in the gas phase and solution using the implicit SMD model for water, chloroform, acetonitrile, and DMSO solvents. Additionally, the multiscale ONIOM QM1/QM2 model was used to simulate the explicit solvent. The implicit and explicit solvent effects were evaluated on the global reactivity indexes using the conceptual-DFT approach. In addition, the QTAIM approach was applied to analyze the properties of the IHBs of the most energetically and populated conformers. The obtained results indicated that the most stable and populated conformer is in the gas phase, and chloroform has an extended conformation. However, water, acetonitrile, and DMSO have a hairpin shape. The optimized structures are well preserved in explicit solvent and the interaction energies for the IHBs were lower in explicit than implicit solvents due to non-covalent interactions formed between the solvent molecules. Finally, both methodologies, with implicit and explicit solvents, were validated with 1H and 13C NMR experimental data. In both cases, the results agreed with the experimental data reported in the CDCl3 solvent.

Interaction of an oxadiazole derivative, 5-(3,4-dimethoxyphenyl)-3-(3-methoxyphenyl)-1,2,4-oxadiazole (DPMO) with Ag/Au/Cu and graphene quantum dots with different solvents, is reported theoretically. The adsorption energy is maximum for the Cu 6 cluster and minimum for the Ag 6 cluster. The asymmetric charge redistribution between DPMO and M 6 s produces an improvement in dipole moment values. The decrease in energy gaps of complexes increased conductivity and metal clusters can be used as a drug sensor. The solvation energies are more negative in solvent media than in the gaseous media, indicating an enhancement in the solvent medium’s stability. Wave function studies show that there exist significant noncovalent interactions between metal clusters and oxadiazole that facilitate cluster formation. DPMO is found to form stable clusters with graphene which is evident from the enhancement of Raman activity of the system through SERS also enabling it for sensing DPMO in a mixture.

The solubility data of spectinomycin dihydrochloride pentahydrate (SDP) in three binary solvents were determined over a temperature range of 278.15–318.15 K by the gravimetric method. Among the selected binary solvents, the solubility of SDP increased with the rise in temperature and initial methanol composition of binary solvents, and the general order of solubility of SDP under the same conditions was: (methanol + ethanol) > (methanol +  n- propanol) > (methanol +  i- propanol). Subsequently, solubility–temperature models including van’t Hoff equation, λh equation, Yaws equation, and Apelblat equation; solubility–solvent composition models including general single model; solubility–temperature and solvent composition models including NRTL equation and modified Jouyban–Acree model were used to correlate the solubility data. Regarding the application of the NRTL equation in binary solvent systems, the influence of solvent composition on model parameters was first taken into account by introducing a solvent composition correction factor, thereby exhibiting an enhancement in fitting accuracy. To gain deeper insights into the dissolving behavior of SDP, molecular electrostatic potential surface, Hirshfeld surface analysis and the KAT-LSER model were applied to analyze the molecular interactions between SDP molecules and the solvent effects. Meanwhile, entire solubility data in three binary solvent systems at 298.15 K were associated as a function of solvent properties on the basis of KAT-LSER model. The results revealed that SDP primarily acts as hydrogen bond acceptors in solution, and polar interactions between SDP and solvent molecules can play a crucial role in promoting the dissolution of SDP.

Solvent-induced shifts in the absorption spectrum of N,N-diethyl-4-nitroaniline were studied by quantum-chemical methods in water, dimethylsulfoxide, acetonitrile and acetone. TDDFT methodology and semiempirical ZINDO/S and PM6-CIS approaches were used to calculate excitation energies. Solvent effect was modeled in implicit solvent model by different variants of the PCM approach. Classical molecular dynamics was applied to obtain solute–solvent geometries used in explicit solvent modeling. Most implicit solvent models fail to reproduce the sequence of solvatochromic shifts for four studied solvents, usually yielding too small effect for water. The best result of the PCM method was obtained with SMD atomic radii. Semiempirical quantum-chemical methods in explicit solvent model did not provide satisfactory description of solvatochromic shifts with the largest disagreement to experiment observed for water. TDDFT explicit solvent calculations performed the best in modeling of spectral shifts. Problems with reproduction of experimental data were attributed to specific interactions.