Electron density analysis of 1-butyl-3-methylimidazolium chloride ionic liquid

Theoretical insights on the development of a 55-77 graphene sheet by embedding Agn=1-4 and Pdn=1-4 metal nanoclusters for efficient CO2 capture

Recent advancements in two-dimensional (2D) allotropes of carbon materials and their usage as superior CO2 adsorbents can decrease the detrimental impact of CO2 on climate change. With the use of quantum chemical calculations, the effect of metal clusters (Agn = 1-4 and Pdn = 1-4) on the structural and electrical characteristics of 55-77 2D graphene sheet is examined in the current work with an aim towards enhancing CO2 capture capacity. The findings revealed that the binding energy (Eb) of the 55-77 sheet decoration with Pdn = 1-4 metal clusters are greater owing to chemisorption by 1.17 eV, 1.69 eV, 0.27 eV, and 1.58 eV than the decoration with Agn = 1-4 clusters. Moreover, CO2 molecules adsorb on the Pdn = 1-4 cluster decorated systems having -0.35 eV, 0.83 eV, 1.53 eV, and -0.98 eV greater adsorption energies than on the Agn = 1-4 decorated 55-77 sheet due to a stronger charge transfer. Further, the findings of an atoms in molecules (AIM) study show that the interaction between CO2 and Pdn = 1-4 decorated 55-77 sheet is partially covalent and non-covalent, confirming the greater charge transfer between the CO2 molecule and Pdn = 1-4 decorated 55-77 systems. Moreover, the CO2 adsorption on Pdn = 1-4 decorated 55-77 systems is clearly demonstrated by non-covalent interaction (NCI) analysis to be a strong electrostatic interaction at sign(λ2)ρ = -0.05 a.u, and this is further supported by an electron localization function (ELF) map. The highest CO2 adsorption capacity is obtained for 55-77/Pd1+CO2 with the value of 6.27 wt % which concludes 55-77 sheet with Pdn decoration is a more suitable structure for CO2 adsorption than the Agn decorated system.

Understanding the Hsp90 N-terminal Dynamics: Structural and Molecular Insights into the Therapeutic Activities of Anticancer Inhibitors Radicicol (RD) and Radicicol Derivative (NVP-YUA922)

Heat shock protein 90 (Hsp90) is a crucial component in carcinogenesis and serves as a molecular chaperone that facilitates protein maturation whilst protecting cells against temperature-induced stress. The function of Hsp90 is highly dependent on adenosine triphosphate (ATP) binding to the N-terminal domain of the protein. Thus, inhibition through displacement of ATP by means of competitive binding with a suitable organic molecule is considered an attractive topic in cancer research. Radicicol (RD) and its derivative, resorcinylic isoxazole amine NVP-AUY922 (NVP), have shown promising pharmacodynamics against Hsp90 activity. To date, the underlying binding mechanism of RD and NVP has not yet been investigated. In this study, we provide a comprehensive understanding of the binding mechanism of RD and NVP, from an atomistic perspective. Density functional theory (DFT) calculations enabled the analyses of the compounds' electronic properties and results obtained proved to be significant in which NVP was predicted to be more favorable with solvation free energy value of -23.3 kcal/mol and highest stability energy of 75.5 kcal/mol for a major atomic delocalization. Molecular dynamic (MD) analysis revealed NVP bound to Hsp90 (NT-NVP) is more stable in comparison to RD (NT-RD). The Hsp90 protein exhibited a greater binding affinity for NT-NVP (-49.4 ± 3.9 kcal/mol) relative to NT-RD (-28.9 ± 4.5 kcal/mol). The key residues influential in this interaction are Gly 97, Asp 93 and Thr 184. These findings provide valuable insights into the Hsp90 dynamics and will serve as a guide for the design of potent novel inhibitors for cancer treatment.

Nonbonding interaction analyses on PVDF/[BMIM][BF4] complex system in gas and solution phase

The present study provides a detailed quantum chemical description of the physicochemical interactions between poly-vinylidene fluoride (PVDF) and 1-butyl-3-methyl-imidazolium tetrafluoro borate ([BMIM][BF₄]) ionic liquid (IL). Geometry optimization and frequency calculations are carried out for four monomer units of α- and β-PVDF, [BMIM][BF₄], and PVDF/[BMIM][BF₄] using dispersion corrected density functional theory. The effects of solvation on the systems under study are demonstrated for three polar aprotic solvents, namely tetra-hydrofuran (THF), acetone, and n,n-dimethyl formamide (DMF) using the integral equation formalism polarizable continuum model (IEFPCM). Calculated negative solvation free energy values suggest solution phase stability of the systems under study. Binding and interaction energies for β-PVDF/IL are found higher in magnitude than those for α-PVDF/IL. The nonbonding interaction phenomenon of β-PVDF/[BMIM][BF₄] is elucidated on the basis of natural bond orbital (NBO), Bader's quantum theory of atoms in molecules (QTAIM), delocalization indices, Hirshfeld surface, and reduced density gradient (RDG) analyses. Both anions and cations of ionic liquids are found to show weak van der Waals interaction with PVDF molecule but the anion ([BF₄]^-)/PVDF interaction is found to be stronger than cation ([BMIM]⁺)/PVDF interaction. Inter-unit C-H⋯F type hydrogen bonds are found to show improper (causing blue shifts in vibrational frequencies) nature. Frontier molecular orbital analysis is carried out, and different chemical parameters like electronegativity, chemical potential, chemical hardness and softness, and electrophilicity index are calculated using Koopmans' theorem. Thermochemical calculations are also performed, and the variation in different standard thermodynamic parameters with temperature is formulated. Graphical abstract (a) Hirshfeld surface mapped onto electron density and (b) NCI isosurfaces showing inter-unit interactions of β-PVDF/[BMIM][BF₄].

Theoretical Probing of Weak Anion-Cation Interactions in Certain Pyridinium-Based Ionic Liquid Ion Pairs and the Application of Molecular Electrostatic Potential in Their Ionic Crystal Density Determination: A Comparative Study Using Density Functional Approach

A comprehensive study on the structure, nature of interaction, and properties of six ionic pairs of 1-butylpyridinium and 1-butyl-4-methylpyridinium cations in combination with tetrafluoroborate (BF₄^-), chloride (Cl^-), and bromide (Br^-) anions have been carried out using density functional theory (DFT). The anion-cation interaction energy (ΔE_int), thermochemistry values, theoretical band gap, molecular orbital energy order, DFT-based chemical activity descriptors [chemical potential (μ), chemical hardness (η), and electrophilicity index (ω)], and distribution of density of states (DOS) of these ion pairs were investigated. The ascendancy of the -CH₃ substituent at the fourth position of the 1-butylpyridinium cation ring on the values of ΔE_int, theoretical band gap and chemical activity descriptors was evaluated. The ΔE_int values were negative for all six ion pairs and were highest for Cl^- containing ion pairs. The theoretical band gap value after -CH₃ substitution increased from 3.78 to 3.96 eV (for Cl^-) and from 2.74 to 2.88 eV (for Br^-) and decreased from 4.9 to 4.89 eV (for BF₄^-). Ion pairs of BF₄^- were more susceptible to charge transfer processes as inferred from their significantly high η values and comparatively small difference in ω value after -CH₃ substitution. The change in η and μ values due to the -CH₃ substituent is negligibly small in all cases except for the ion pairs of Cl^-. Critical-point (CP) analyses were carried out to investigate the AIM topological parameters at the interionic bond critical points (BCPs). The RDG isosurface analysis indicated that the anion-cation interaction was dominated by strong H_cat···X_ani and C_cat···X_ani interactions in ion pairs of Cl^- and Br^- whereas a weak van der Waal's effect dominated in ion pairs of BF₄^-. The molecular electrostatic potential (MESP)-based parameter ΔΔV_min measuring the anion-cation interaction strength showed a good linear correlation with ΔE_int for all 1-butylpyridinium ion pairs (R² = 0.9918). The ionic crystal density values calculated by using DFT-based MESP showed only slight variations from experimentally reported values.

Role of 6-Mercaptopurine in the potential therapeutic targets DNA base pairs and G-quadruplex DNA: insights from quantum chemical and molecular dynamics simulations

The theoretical studies on DNA with the anticancer drug 6-Mercaptopurine (6-MP) are investigated using theoretical methods to shed light on drug designing. Among the DNA base pairs considered, 6-MP is stacked with GC with the highest interaction energy of -46.19 kcal/mol. Structural parameters revealed that structure of the DNA base pairs is deviated from the planarity of the equilibrium position due to the formation of hydrogen bonds and stacking interactions with 6-MP. These deviations are verified through the systematic comparison between X-H bond contraction and elongation and the associated blue shift and red shift values by both NBO analysis and vibrational analysis. Bent's rule is verified for the C-H bond contraction in the 6-MP interacted base pairs. The AIM results disclose that the higher values of electron density (ρ) and Laplacian of electron density (∇²ρ) indicate the increased overlap between the orbitals that represent the strong interaction and positive values of the total electron density show the closed-shell interaction. The relative sensitivity of the chemical shift values for the DNA base pairs with 6-MP is investigated to confirm the hydrogen bond strength. Molecular dynamics simulation studies of G-quadruplex DNA d(TGGGGT)₄ with 6-MP revealed that the incorporation of 6-MP appears to cause local distortions and destabilize the G-quadruplex DNA.

Sodium-ion electrolytes based on ionic liquids: a role of cation-anion hydrogen bonding

Recent success of the sodium-ion batteries fosters an academic interest for their investigation. Room-temperature ionic liquids (RTILs) constitute universal solvents providing non-volatility and non-flammability to electrolytes. In the present work, we consider four families of RTILs as prospective solvents for NaBF4 and NaNO3 with an inorganic salt concentration of 25 and 50 mol%. We propose a methodology to rate RTILs according to their solvation capability using parameters of the computed radial distribution functions. Hydrogen bonds between the cations and the anions of RTILs were found to indirectly favor sodium solvation, irrespective of the particular RTIL and its concentration. The best performance was recorded in the case of cholinium nitrate. The reported observations and correlations of ionic structures and properties offer important assistance to an emerging field of sodium-ion batteries. Graphical Abstract Sodium-ion electrolytes.

Self-interaction error in DFT-based modelling of ionic liquids

The modern computer simulations of potential green solvents of the future, involving the room temperature ionic liquids, heavily rely on density functional theory (DFT). In order to verify the appropriateness of the common DFT methods, we have investigated the effect of the self-interaction error (SIE) on the results of DFT calculations for 24 ionic pairs and 48 ionic associates. The magnitude of the SIE is up to 40 kJ mol(-1) depending on the anion choice. Most strongly the SIE influences the calculation results of ionic associates that contain halide anions. For these associates, the range-separated density functionals suppress the SIE; for other cases, the revPBE density functional with dispersion correction and triple-ζ Slater-type basis is suitable for computationally inexpensive and reasonably accurate DFT calculations.

Interactions in the ionic liquid [EMIM][FAP]: a coupled experimental and computational analysis

IR spectroscopy and DFT calculations were combined to explore the anion conformers and access the hydrogen-bonding phenomenon in RTIL [EMIM][FAP].

Hydrogen bonding in ionic liquids

Ionic liquids (IL) and hydrogen bonding (H-bonding) are two diverse fields for which there is a developing recognition of significant overlap. Doubly ionic H-bonds occur when a H-bond forms between a cation and anion, and are a key feature of ILs. Doubly ionic H-bonds represent a wide area of H-bonding which has yet to be fully recognised, characterised or explored. H-bonds in ILs (both protic and aprotic) are bifurcated and chelating, and unlike many molecular liquids a significant variety of distinct H-bonds are formed between different types and numbers of donor and acceptor sites within a given IL. Traditional more neutral H-bonds can also be formed in functionalised ILs, adding a further level of complexity. Ab initio computed parameters; association energies, partial charges, density descriptors as encompassed by the QTAIM methodology (ρBCP), qualitative molecular orbital theory and NBO analysis provide established and robust mechanisms for understanding and interpreting traditional neutral and ionic H-bonds. In this review the applicability and extension of these parameters to describe and quantify the doubly ionic H-bond has been explored. Estimating the H-bonding energy is difficult because at a fundamental level the H-bond and ionic interaction are coupled. The NBO and QTAIM methodologies, unlike the total energy, are local descriptors and therefore can be used to directly compare neutral, ionic and doubly ionic H-bonds. The charged nature of the ions influences the ionic characteristics of the H-bond and vice versa, in addition the close association of the ions leads to enhanced orbital overlap and covalent contributions. The charge on the ions raises the energy of the Ylp and lowers the energy of the X-H σ* NBOs resulting in greater charge transfer, strengthening the H-bond. Using this range of parameters and comparing doubly ionic H-bonds to more traditional neutral and ionic H-bonds it is clear that doubly ionic H-bonds cover the full range of weak through to very strong H-bonds.

Non-covalent interactions in ionic liquid ion pairs and ion pair dimers: a quantum chemical calculation analysis

Weak non-covalent interactions were studied by means of QTAIM and NCI approaches in ion pairs and ion pair dimers of 1-alkyl-3-methylimidazolium cations coupled with perfluorinated anions.

Hydrogen bonding and π–π interactions in imidazolium-chloride ionic liquid clusters

The importance of 1° and 2° hydrogen-bonding and anion–π⁺ interactions for ionic liquid structuring.

Effect of dielectric constant on estimation of properties of ionic liquids: an analysis of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Influence of dielectric constant values in estimation of thermodynamical properties (vapor pressure, vaporization enthalpy, density and viscosity) of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids with COSMO-RS.