Theoretical Description of Hydride-hydride Interactions in Selected Hydrogen Storage Materials.

In recent years there has been growing interest in the use of metal hydrides as hydrogen rich sources. The high content of hydride-hydride contacts H⋅⋅⋅H in these materials appears to be relevant for hydrogen formation. At present time there is no consensus whether these contacts are attractive or repulsive.

Ab Initio Molecular Dynamics Simulations of Aqueous LiTFSI Solutions─Structure, Hydrogen Bonding, and IR Spectra.

Simulations of Density Functional Theory-based ab initio molecular dynamics (AIMD) have been performed for a series of aqueous lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) solutions with concentrations ranging from salt-in-water to water-in-salt systems. Analysis of the structure of electrolytes has revealed a preference of Li cations to interact with water molecules. In concentrated LiTFSI solutions, water molecules form small associates.

In Vitro and In Silico Studies of Functionalized Polyurethane Surfaces toward Understanding Biologically Relevant Interactions.

The solid-aqueous boundary formed upon biomaterial implantation provides a playground for most biochemical reactions and physiological processes involved in implant-host interactions. Therefore, for biomaterial development, optimization, and application, it is essential to understand the biomaterial-water interface in depth. In this study, oxygen plasma-functionalized polyurethane surfaces that can be successfully utilized in contact with the tissue of the respiratory system were prepared and investigated.

Explicit and Hybrid Solvent Models for Estimates of Parameters Relevant to the Reduction Potential of Ethylene Carbonate.

Using ethylene carbonate as a sample solvent, we investigated two molecular parameters used to estimate the reduction potential of the solvent: electron affinity, and the energy of the lowest unoccupied molecular orbital (LUMO). The results showed that the values of these parameters are inconsistent for a single ethylene carbonate molecule in vacuum calculations and in the continuous effective solvent. We performed a series of calculations employing explicit or hybrid (explicit/continuous) solvent models for aggregates of solvent molecules or solvated salt ions.

Hydrogen Bonding and Infrared Spectra of Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide/Water Mixtures: A View from Molecular Dynamics Simulations.

Simulations of ab initio molecular dynamics have been performed for mixtures of ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) ionic liquid and water. Statistics of donors and acceptors of hydrogen bonds has revealed that with increasing water content, hydrogen bonds between EMIM cations and TFSI anions are replaced by bonds to water molecules. In the mixture of liquids, the total number of bonds (from EMIM cations or water molecules) formed by TFSI acceptors increases.

How Temperature, Pressure, and Salt Concentration Affect Correlations in LiTFSI/EMIM-TFSI Electrolytes: A Molecular Dynamics Study.

Classical polarizable molecular dynamics simulations have been performed for LiTFSI solutions in the EMIM-TFSI ionic liquid. Different temperature or pressure values and salt concentrations have been examined. The structure and dynamics of the solvation shell of Li cations, diffusion coefficients of ions, conductivities of the electrolytes, and correlations between motions of ions have been analyzed.

NaFSI and NaTFSI Solutions in Ether Solvents from Monoglyme to Poly(ethylene oxide)-A Molecular Dynamics Study.

Classical molecular dynamics simulations have been performed for a series of electrolytes based on sodium bis(fluorosulfonyl)imide or sodium bis(trifluoromethylsulfonyl)imide salts and monoglyme, tetraglyme, and poly(ethylene oxide) as solvents. Structural properties have been assessed through the analysis of coordination numbers and binding patterns. Residence times for Na-O interactions have been used to investigate the stability of solvation shells.

MeTFSI (Me = Li, Na) Solvation in Ethylene Carbonate and Fluorinated Ethylene Carbonate: A Molecular Dynamics Study.

Classical and ab initio molecular dynamics (MD) simulations have been performed for electrolytes based on LiTFSI and NaTFSI solutions in ethylene carbonate and its mono- and difluoro derivatives. Differences between electrolytes with Li or Na ions and the effect of fluorination on the structure and transport properties have been analyzed. The observed differences are related to the strength of Me-carbonate binding, which is weaker for the Na cation and/or fluorinated solvents.

Estimates of Electrical Conductivity from Molecular Dynamics Simulations: How to Invest the Computational Effort.

Although the electrical conductivity of an electrolyte can be estimated from the molecular dynamics trajectory, it is often a challenging task because of the need to obtain a substantial amount of data to ensure sufficient averaging. Here, we present an analysis on the convergence of results with the number of simulated trajectories. A series of molecular dynamics simulations have been performed for a model electrolyte (NaCl in water) and the Einstein relation has been used to calculate the electrical conductivity.

Quantum-Chemical and Molecular Dynamics Investigations of Magnesium Chloride Complexes in Dimethoxyethane Solutions.

Quantum-chemical calculations and classical and ab initio molecular dynamics simulations have been performed to study the Mg-conducting electrolytes based on Mg(TFSI)/MgCl solutions in dimethoxyethane. It has been shown that depending on the TFSI/Cl ratio, the MgCl or MgCl complexes are preferred as stable ion aggregates. In the initial stages of the ion association process, MgCl, MgCl, and MgCl are formed as intermediate species.

Molecular Dynamics Investigation of Correlations in Ion Transport in MeTFSI/EMIM-TFSI (Me = Li, Na) Electrolytes.

Classical molecular dynamics simulations have been performed in polarizable and nonpolarizable force fields for series of electrolytes based on MeTFSI (Me = Li, Na) salts dissolved in EMIM-TFSI ionic liquid. Structure and dynamics of the solvation shell of Me ions have been investigated. Contributions to the total conductivity of the electrolyte arising from motions of different ions and cross-correlations between them have been analyzed.

Understanding the Structure of the Hydrogen Bond Network and Its Influence on Vibrational Spectra in a Prototypical Aprotic Ionic Liquid.

Analysis of the hydrogen bond network in aprotic ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) has been performed based on structures obtained from ab initio or classical molecular dynamics simulations. Statistics of different donor and acceptor atoms and the amount of chelating or bifurcated bonds has been presented. Most of the hydrogen bonds in EMIM-TFSI are formed with oxygen atoms as hydrogen acceptors; and the most probable bifurcated bonds are those with a mixed pair of oxygen and nitrogen acceptors.

Molecular Dynamics Simulations of Ionic Liquid Based Electrolytes for Na-Ion Batteries: Effects of Force Field.

Classical molecular dynamics simulations were performed for Na conducting electrolytes based on EMIM-TFSI ionic liquid and NaTFSI salt. Several parametrizations of force fields have been tested, including polarizable fields with dipole polarizabilities or Drude-type polarization. Trajectories up to 1 μs long have been used to estimate viscosities, diffusion coefficients, and conductivities of electrolytes with increasing amount of sodium salt.

Alternative Route Toward Nitrones: Experimental and Theoretical Findings.

Nitrones are important building blocks for natural and biologically active compounds, used as spin-trap reagents and therapeutic agents. All this makes nitrones intriguing and valuable compounds for fundamental studies and as useful chemicals in various synthetic strategies. Therefore, nitrones are still of great interest and in the limelight of researches.

Explicit Solvent Modeling of IR and UV-Vis Spectra of 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide Ionic Liquid.

Explicit solvent modeling of absorption spectra of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide has been performed. Fourier transform of the autocorrelation function of the dipole moment calculated from ab initio molecular dynamics (AIMD) simulations has been used to obtain the IR spectrum of the bulk liquid. A sequential molecular dynamics (MD)/time-dependent density functional theory procedure has been applied to calculate the UV-vis spectrum.

Influence of the Homopolar Dihydrogen Bonding C-H⋅⋅⋅H-C on Coordination Geometry: Experimental and Theoretical Studies.

The reaction of the N-thiophosphorylated thiourea (HOCH2 )(Me)2 CNHC(S)NHP(S)(OiPr)2 (HL), deprotonated by the thiophosphorylamide group, with NiCl2 leads to green needles of the pseudotetrahedral complex [Ni(L-1,5-S,S')2 ]⋅0.5 (n-C6 H14 ) or pale green blocks of the trans square-planar complex trans-[Ni(L-1,5-S,S')2 ]. The former complex is stabilized by homopolar dihydrogen C-H⋅⋅⋅H-C interactions formed by n-hexane solvent molecules with the [Ni(L-1,5-S,S')2 ] unit.

Explicit Solvent Modeling of Solvatochromic Probes in Ionic Liquids: Implications of Solvation Shell Structure.

Calculations of absorption spectra have been performed for three solvatochromic dyes (para-nitroaniline, N,N-diethyl-para-nitroaniline, and Reichardt's dye) in four ionic liquids based on 1-ethyl-3-methylimidazolium cation. Different variants of explicit solvent model have been used: fully explicit representation of solvent ions, charge embedding method, and mixed approach. Electrostatic solute-solvent interactions have been shown to induce structuring of the solvation shell around dipolar solute, causing significant and nonmonotonic dependence of calculated transition energies on the number of ion pairs included in calculations.

Li(+)-Oligoglyme Association in the Presence of Ionic Liquid Studied by Molecular Dynamics and Explicit or Implicit Solvent Model.

Molecular dynamics simulations have been applied to study properties of ternary oligoglyme/ionic liquid/lithium salt electrolytes. Different types of lithium coordination and phase behavior have been observed depending on the liquid/salt anion: from full phase separation and Li(+) coordination exclusively to anions in systems with BF4(-) to rather homogeneous systems and prevailing Li(+)-hexaglyme coordination for FSI(-) or B(CN)4(-) anion. Observed structural properties have been successfully correlated to the binding energies of Li(+)-glyme complexes in solution calculated within an explicit solvent model.

An anion induced multisignaling probe for Hg(2+) and its application for fish kidney and liver tissue imaging studies.

3',6'-Bis(diethylamino)-2-(pyridin-2-ylmethyl)spiro[isoindoline-1,9'-xanthen]-3-one () was synthesized for the selective fluorescence and colorimetric recognition of Hg(2+) at pH 6.0. In addition, was useful for imaging Hg(2+) in fish kidney and liver tissues using a fluorescence microscope.

Ratiometric sensing of lysine through the formation of the pyrene excimer: experimental and computational studies.

Several pyrene based fluorescent probes undergo lysine assisted monomer to excimer conversion in a ratiometric manner. Intracellular lysine is detected using fluorescence microscopy.

Stability of ion triplets in ionic liquid/lithium salt solutions: insights from implicit and explicit solvent models and molecular dynamics simulations.

Binding energies of ion triplets formed in ionic liquids by Li(+) with two anions have been studied using quantum-chemical calculations with implicit and explicit solvent supplemented by molecular dynamics (MD) simulations. Explicit solvent approach confirms variation of solute-ionic liquid interactions at distances up to 2 nm, resulting from structure of solvation shells induced by electric field of the solute. Binding energies computed in explicit solvent and from the polarizable continuum model approach differ largely, even in sign, but relative values generally agree between these two models.

Quantum-chemical and molecular dynamics study of M+ [TOTO]- (M = Li, Na, K) ionic liquids.

Quantum-chemical calculations and classical molecular dynamics simulations with the Optimized Potentials for Liquid Simulations-All Atom (OPLS-AA) force field are presented for ionic liquids based on 2,5,8,11-tetraoxatridecan-13-oate anion (TOTO) and alkali cations (Li, Na, K). Complexation energies decrease with increasing cation radius from Li to K. Cation interactions with carboxylate oxygen atoms are preferred over complexation to ether oxygens.

Complexation properties of N-thiophosphorylated thiourea 2-PyNHC(S)NHP(S)(OiPr)2 towards Ni(II).

Reaction of the deprotonated N-thiophosphorylated thiourea 2-PyNHC(S)NHP(S)(OiPr)2 (HL) with NiCl2 leads to the complex [Ni{2-PyNHC(S)NP(S)(OiPr)2}2] ([NiL2]) with unprecedented 1,5,7-N,N′,S-coordination of the ligand. Recrystallization of [NiL2] from a mixture of CH2Cl2–n-hexane or acetone–n-hexane leads to [Ni(L-1,5,7-N,N′,S)2]·CH2Cl2 and [Ni(L-1,5,7-N,N′,S)2], respectively. The latter complex, in turn, shows a temperature-induced polymorphism.

Molecular dynamics study on the effect of Lewis acid centers in poly(ethylene oxide)/LiClO4 polymer electrolyte.

Molecular dynamics simulations employing a polarizable force field have been performed for the model poly(ethylene oxide)/LiClO(4) electrolytes with boron or aluminum centers. Influence of Lewis acid centers on radial distribution functions, coordination numbers, percentage of free cations, diffusion coefficients and conductivity has been investigated. Results confirm the effect of acid centers on ion complexation and show that the properties of the electrolyte result from interplay of different interactions.

Steric and electronic effects in the host-guest hydrogen bonding in clathrate hydrates.

Clathrate hydrates with polar guest molecules (dimethyl ether, ethylene oxide, trimethylene oxide, tetrahydrofuran, and tetrahydropyran) were studied by means of the density functional theory. A model of a large cage of structure-I clathrate was employed. Optimal configurations of encaged guests were investigated with a focus on the host-guest hydrogen bond formation.