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Computational study for three isomeric nitroanilines was carried out to find a nonempirical model to predict their relative ionization efficiencies compared to the corresponding experimental logIE values. The CBS-QB3 method was used for the gas-phase calculations of protonated nitroanilines, and the SCC-DFTB method for the calculations of spherical droplets, containing one protonated nitroaniline molecule, one hydronium cation, and 48 acetonitrile molecules, randomly generated by the PACKMOL program. The obtained results show that neither the gas-phase energy of protonated nitroaniline (or gas-phase basicity) nor the average energy of droplets can be used to predict the ionization efficiency ordering of those isomers. However, the difference of gas-phase and droplet energies gives a good correlation with logIE values and, thus, can be used for the prediction of relative ionization efficiencies.

Data on the gas-phase energetics of anion/cation interactions are relatively scarce. In this work, gas-phase alkali metal cation basicity (AMCB) scales were established for a series of 15 benzoate ions XC6H4COO- with Li+, Na+, K+, Rb+, and Cs+ on the basis of mass spectrometry experiments and high-level calculations. A wide range of electron-donating and electron-withdrawing substituents were included in the study. The thermochemical values were calculated by ab initio methodologies and extrapolated to the complete basis set limit. For each metal cation, the experimental relative cation basicity values of the anions were established quantitatively by applying the Cooks' kinetic method to the cation-bound heterodimers [(XC6H4COO-)M+(YC6H4COO-)]-, generated by electrospray ionization. The self-consistency of these AMCB scales was ascertained by multiple overlap of the individual relative basicities. In parallel, the proton gas-phase basicities (GBs) of the benzoate anions (gas-phase acidities of the respective benzoic acids) were calculated in order to compare the results of the theoretical method with known experimental GB values. The experimental and calculated GB values agree quite accurately (average absolute deviation = 3.2 kJ mol-1). The relative experimental AMCB scales and the absolute calculated AMCB scales are highly correlated, and the two sets agree by better than 4 kJ mol-1. It is also demonstrated that the five series of calculated AMCBs are highly correlated with the calculated GB.

Chiral cyclohexanohemicucurbit[n]urils (n = 6, 8) (cycHCs) are able to bind guests through multiple "outer surface interactions", which in the case of planar zinc porphyrins leads to induction of chirality. Crystal structures of complexes of complementary sized hosts revealed social self-sorting, while in the solution phase one cycHC can accommodate up to three porphyrin molecules with log Ktotal 9.

We report a mass spectrometry study of the interaction between three representative Au(I) catalysts containing the ligands L = JohnPhos (2-biphenylyl[bis(2-methyl-2-propanyl)]phosphine), TPP (PPh3, triphenylphosphine), the N-heterocyclic carbene IPr (carbene form of 1,3-bis(2,6-diisopropylphenyl)-2,3-dihydro-1H-imidazole), and 27 organic molecules S (substrates) bearing organic functionalities often present in reactants (alkenes, alkynes, allenes, enol ethers, aldehydes, ketones, epoxides). An experimental scale of gas-phase relative binding energy between three L(Au +) ions and the organic substrates was established by energy-resolved experiments of the 81 cationic two-coordinate gold adducts L(Au +)S using a quadrupole ion trap mass spectrometer. The experimental scale is expressed in units of normalized collision energy for 50% dissociation (NCE50) of the precursor ion. In parallel, the gas-phase bond dissociation energetics and the structure of adducts were probed by DFT calculations. The experimental affinity order of each substrate for the three cationic gold complexes L(Au +), IPr(Au +) > TPP(Au +) > JohnPhos(Au +), is well reproduced by the calculated bond dissociation energies ΔE. At the computational level used in this study, the agreement between the calculated ΔE and the experimental NCE50 values is limited to series of substrates with the same functionality, and reasonable correlations NCE50 vs. ΔE are observed within series. The DFT-optimized structures are discussed and compared with available X-ray crystal structures. Although no general trend can be observed between bond lengths, or their changes upon coordination with the L(Au +) cations, and dissociation energies, a significant correlation between Au-O distance (S = O-bases) and ΔE is observed.

A literature curated dataset containing 24 distinct metal oxide (MexOy) nanoparticles (NPs), including 15 physicochemical, structural and assay-related descriptors, was enriched with 62 atomistic computational descriptors and exploited to produce a robust and validated in silico model for prediction of NP cytotoxicity. The model can be used to predict the cytotoxicity (cell viability) of MexOy NPs based on the colorimetric lactate dehydrogenase (LDH) assay and the luminometric adenosine triphosphate (ATP) assay, both of which quantify irreversible cell membrane damage. Out of the 77 total descriptors used, 7 were identified as being significant for induction of cytotoxicity by MexOy NPs. These were NP core size, hydrodynamic size, assay type, exposure dose, the energy of the MexOy conduction band (EC), the coordination number of the metal atoms on the NP surface (Avg. C.N. Me atoms surface) and the average force vector surface normal component of all metal atoms (v&perp, Me atoms surface). The significance and effect of these descriptors is discussed to demonstrate their direct correlation with cytotoxicity. The produced model has been made publicly available by the Horizon 2020 (H2020) NanoSolveIT project and will be added to the project&rsquo, s Integrated Approach to Testing and Assessment (IATA).

Bromine formation in the mixture of solid NaBr and KNO3 was observed and the process was studied in different acidified organic solvent–water mixtures by monitoring the bromination of acetanilide and other compounds, containing activated aromatic substituents. This assay is based on fast bromination reaction of these aromatic compounds, as differently from the assay of Br2, the brominated aromatics can be easily determined by conventional gas chromatography–mass spectrometry (GC–MS) methods. It was found that bromine was generated autocatalytically on the surface of salt crystals and the reaction was characterized by a lag period, the duration of which depended on reaction conditions, and importantly on the type of the organic solvent in the reaction mixture. As the bromine formation could be easily controlled by reaction conditions, it was suggested that the studied reaction might have practical applications as an environmentally friendly and economically feasible bromination method. It was also shown that the bromination of aromatics followed the mechanism of classical electrophilic aromatic substitution reaction.

Background: Human immunodeficiency virus type 1 (HIV-1) is the causative agent of AIDS occurs across mucosal surfaces or by direct inoculation. Objective: The objective of this study was to consider chemically diverse scaffold sets of HIV-1 Reverse Transcriptase Inhibitors (HIV-1 RTI) subjected to ideal oriented QSAR with large descriptor space. Method: We generated a four-parameter QSAR model based on 111 data points, which provided an optimum prediction of HIV-1 RTI for overall 367 experimentally measured compounds. Results: The robustness of the model is demonstrated by its statistical validation (N training = 111, R 2 = 0.85, Q 2 lmo = 0.84) and by the prediction of HIV-1 inhibition activity for experimentally measured compounds. Conclusion: Finally, 5 novel hit compounds were designed in silico by using a virtual screening approach. The new hits met all the pharmacophore constraints and predicted pIC 50 values within the binding ability of HIV-1 RT protein targets.

Mechanism of an efficient and easily applicable catalytic system for the copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) reaction, consisting of phosphane-ligated CuI carboxylates and apolar/aprotic solvent was investigated by means of 1H NMR reaction monitoring techniques, isotope exchange studies, and DFT calculations (at the M06L/6-311++G(d,p)//B97D/cc-pVDZ (SDD) level of theory). Kinetic analysis indicates 1st order kinetics with respect to [Azide] and nonlinear positive order in [Cu]. H/D scrambling between alkynes reveals a quickly reached equilibrium existing between CuI–carboxylates and CuI–acetylides and that proton transfer processes are mediated by acetate/acetic acid system. According to the computational results, the Cu–triazolide forms a dinuclear structure that equalizes the copper atoms in the catalytic complex.

The typical Gibbs free energy difference between hydrocarbon substituted isocyanides and the corresponding cyanides is 25 to 28 kcal/mol in favor of the cyanides and is mostly independent of the substituent. Triple bonded species with a ―C ≡ C―RN,C (RN,C = CN, NC) structure can be considered as exceptions. Because isocyanide and cyanide species have very similar structures, the relative energy is independent of the pressure and temperature conditions. Theoretical and experimental gas-phase investigations show that basicity of isocyanides ranges from 182.1 to 198.2 kcal/mol which is 14.0 to 19.7 kcal/mol higher than the basicity of respective cyanides. The most favored protonation centers are located on isocyanide or cyanide group depending on the species. The biggest increase of basicity was caused by bulkier substituents. The substitutions have greater influence on the basicity of cyanides than on the basicity of isocyanides. In regard to deprotonation, the cyanides are more acidic than the corresponding isocyanides. For most of the unsaturated cyanide and isocyanide species the (N,C)-CHR′ hydrogen (the one connected to the carbon next to cyanide/isocyanide group) is the most acidic. Our work suggests that for derivatives bearing unsaturated substituent the favored deprotonation center may be different and some cyanides and isocyanides are unstable towards gas-phase deprotonation equilibrium as the formed anion tends to isomerize. Copyright © 2016 John Wiley & Sons, Ltd.

Criteria that have been used to describe alkene strain can be divided into energetic and geometrical criteria. An overview of strain criteria from both groups is given, and altogether, 16 different criteria have been calculated with the DFT M062X/TZVP method for several strained alkene series. Factor analysis was used to judge whether these strain criteria measure the same underlying phenomena. The factor analysis showed that for systematically substituted ethene derivatives (series A) all the studied criteria were describing the same thing. The factor analysis showed that for series B, where the double bonds geometry is fixed with a cyclic backbone, at least two different criteria (e.g. gas-phase basicity and hydrogenation reaction enthalpy) are needed to describe the overall strain. We propose that these two different expressions of strain describe strain related to reactivity and thermodynamics. Those two strains were well-correlated in the first series.

The complexation reactions between lanthanide 3+ cations and 2,9-bis(1,2,4-triazin-3-yl)-1,10-phenanthroline and its derivatives were studied with density functional theory Perdew-Burke-Ernzerhof functionals. The complexes consisted of one lanthanide cation and two ligand molecules. Complexation reactions were found to be exothermic and spontaneous in the gas phase. Absolute values of complextion energy and enthalpy increase in the lanthanide series and follow linear trends of lanthanide atomic number. All the bond lengths decrease in the lanthanide series with increasing charge density.

In the search for novel tools to combat cancer, nanoparticles (NPs) have attracted a lot of attention. Recently, the controlled release of cancer-cell-killing metal ions from doped NPs has shown promise, but fine tuning of dissolution kinetics is required to ensure specificity and minimize undesirable toxic side-effects. Theoretical tools to help in reaching a proper understanding and finally be able to control the dissolution kinetics by NP design have not been available until now. Here, we present a novel set of true nanodescriptors to analyze the charge distribution, the effect of doping and surface coating of whole metal oxide NP structures. The polarizable model of oxygen atoms enables light to be shed on the charge distribution on the NP surface, allowing the in detail study of the factors influencing the release of metal ions from NPs. The descriptors and their capabilities are demonstrated on a Fe-doped ZnO nanoparticle system, a system with practical outlook and available experimental data. ispartof: Nanoscale vol:10 issue:46 pages:21985-21993 ispartof: location:England status: Published online

The kinetics of the reaction of n-butyl- and isopropylmagnesium chloride with alkyltriethoxysilanes (RSi(OEt)3) in diethyl ether were determined. The rate constants correlate well with the steric p...

Steric strain, caused by forced deformation of double bond geometry, has significant impact on alkene reactivity, as was shown by a study of the gas-phase basicity of (E)-1-methyl-2-(1-methyl-2-adamantylidene)adamantane. The Gibbs free energy of the strain effect in this compound was 42 kJ/mol. This analysis was made based on adamantylideneadamantane as a congeneric reference compound with a planar double bond. It was concluded that gas-phase basicity could serve as a valuable alternative indicator for quantification of steric strain in alkenes. Copyright © 2015 John Wiley & Sons, Ltd.

Hydrazine-borane and hydrazine-diborane contain, respectively, 15.4 and 16.9 wt% of hydrogen and are potential materials for hydrogen storage. In this work we present the gas-phase complexation energies, acidities, and basicities of hydrazine-borane and hydrazine-bisborane calculated at MP2/6-311 + G(d,p) level. We also report the release of dihydrogen from both protonated complexes (ΔGhydrazine-borane = −20.9 kcal/mol and ΔGhydrazine-bisborane = −27.2 kcal/mol) which is much more exergonic than from analogues amine-boranes. The addition of the first BH3 to the hydrazine releases 17.1 kcal/mol, and the second addition releases 15.8 kcal/mol. The attachment of BH3 also increases the N―H acidity of hydrazine by 46.3 kcal/mol. It was found that the B―H deprotonation leads to intramolecular rearrangement. The basicity values for hydrazine-borane and -bisborane are 180 and 172.8 kcal/mol, respectively. For both complexes the protonation centres are located at the boron moiety. The protonated structure of hydrazine-bisborane is cyclic and can be described as H2 captured between a negatively charged B―H hydrogen and positive boron (B―H••H2••B). Atoms in molecules analysis are used to investigate bond paths in concerning structures. Copyright © 2015 John Wiley & Sons, Ltd.

The development and implementation of safe-by-design strategies is key for the safe development of future generations of nanotechnology enabled products. The safety testing of the huge variety of nanomaterials that can be synthetized is unfeasible due to time and cost constraints. Computational modeling facilitates the implementation of alternative testing strategies in a time and cost effective way. The development of predictive nanotoxicology models requires the use of high quality experimental data on the structure, physicochemical properties and bioactivity of nanomaterials. The FP7 Project MODERN has developed and evaluated the main components of a computational framework for the evaluation of the environmental and health impacts of nanoparticles. This chapter describes each of the elements of the framework including aspects related to data generation, management and integration; development of nanodescriptors; establishment of nanostructure-activity relationships; identification of nanoparticle categories; hazard ranking and risk assessment.

We present the gas phase stabilities, acidities and basicities for several previously uninvestigated phosphine–boranes, and compare them to respective amine–boranes. Although both species seem to be very similar, it was found that only acidities correlate in a reasonable manner (R2 = 0.874). According to MP2/6-311+G(d,p) calculations the P-substitutions increase the stability of the H3P⋯BH3 complex up to 14 kcal/mol. Phosphorine–borane was the only complex less stable than the unsubstituted H3P⋯BH3. Replacing the phosphine with respective amine decreases the acidity but raises the basicity of the complexes. A complex that can be described as R 1 R 2 R 3 P ⋯ BH 2 + ⋯ H 2 forms upon protonation and the dihydrogen removal from such species is an exergonic process. Typical ΔG for the dissociation reaction ranges from 0.1 to −2.6 kcal/mol but there are notable exceptions. For example, the protonated benzyl phosphine–borane contains a B⋯H–H⋯π interaction which is replaced with stronger B–Cπ interaction upon hydrogen removal thus leading to more favorable H2 removal. The bonds and interactions present in protonated species have been studied using Bader’s Atoms in Molecules approach.

The complete basis set (CBS) extrapolation is used at Hartree-Fock and second-order Møller-Plesset perturbation theory levels and with the def2-xZVP x-ζ basis set (x = 2-4). This approach leads to general, robust, and well-calibrated methods, especially when Hartree-Fock energy (E(HF)) and correlation energies (E(CE)) are extrapolated separately. Indeed, the absolute deviations between theoretical and experimental data are usually smaller than the reported experimental errors. We also point out the need to change usual parameters utilized in CBS methods when calculations involve atoms from third and subsequent rows. The best CBS scheme studied in the current work for obtaining energies for the estimation of alkali metal cation affinities and basicities is E(CBS)[∞] = 1.10529·E(HF)[4] - 0.10529·E(HF)[2] + 0.92703·E(CE)[4] - 0.07297·E(CE)[2], where E(HF)[2], E(HF)[4], E(CE)[2], and E(CE)[4] are the Hartree-Fock energy (E(HF)) and MP2 correlation energies (E(CE)) obtained with def2-QZVP (x = 4) and def2-SV(p) (x = 2) basis sets.

International audience; The effect of Cs+ ligation on the decarboxylation of malonic acids (unsubstituted and methyl-, dimethyl-, ethyl-, and phenyl-substituted) in their carboxylate form was studied in the gas phase using tandem mass spectrometry. The study is based on the comparison of the decarboxylation of the bare monoanion (hydrogen malonates) and of the cesium adduct of the cesium salt (Cs+[cesium hydrogen malonates]) under collisional activation. Energy-resolved dissociation curves of the negative and positive ions exhibit major differences. Decarboxylation of the cationic adducts of substituted malonic acid salts occurs at significantly lower collisional activation than for the corresponding bare hydrogen malonate anions. The conclusions from these experiments are supported by DFT calculations. The calculated activation parameters (enthalpy and Gibbs energy) confirm that the cesium cation coordination assists the decarboxylation of the carboxylate form.

International audience; Complexation energies and acidities of 19 primary, secondary and tertiary amine-boranes were investigated using MP2/6-311+G(d,p) and B3LYP/6-311+G(d,p) methods. Gas phase acidities for free amines were also calculated. Acidity values for studied complexes range from 327.3 to 349.1 kcal mol(-1) and the most acidic are the ones with direct connection between deprotonation center and a π-system. Results obtained by both computational methods are in good agreement with each other and with known experimental data. Addition of BH3 increases the acidity of amines by 30 to 50 kcal mol(-1). This enhancement effect was compared to the respective effect witnessed in phosphine-boranes and traced back to changes of charge delocalization on nitrogen. A question about the structural stability of several deprotonated amine-borane anions in the gas phase was also raised.

The interaction between the cesium cation and fulvic or humic acids is supposed to play a role in cesium mobility in the environment, which is of importance in the context of geographical dispersion or concentration of the corresponding radionuclides. Among the singly charged positive clusters generated by electrospray ionization of mixtures of carboxylic acids (AH) and cesium salts (nitrate, iodide, or trifluoroacetate), the cluster [A- Cs+ ]Cs+ [A'- Cs+ ] was subjected to collision-induced dissociation. The fragmentation into Cs+ [A- Cs+ ] and Cs+ [A'- Cs+ ] was treated using the kinetic method. A gas-phase basicity ladder was built by a step-by-step addition of the relative basicity data. The relative basicity scale deduced from the kinetic method was calibrated using the affinity and basicity (the enthalpy and Gibbs energy scales, respectively) obtained from DFT calculations. The enhanced basicity of the polyacid salts, relative to their monoacid salts, as well as the substituent effects on aliphatic and aromatic structures, are discussed.

Measuring the relative sensitivity factors (Sr) in Bayard-Alpert ion gauge is technically demanding and time-consuming. Moreover, the accuracy deterioration in the low pressure range (high vacuum) becomes problematic. Experimental Sr values are reported for 91 molecules of diverse molecular structures. A three-descriptor QSPR model based on experimental data is established. The model obtained, which explains more than 93% of the data variance, has a good statistical validity and stability. The three selected molecular descriptors, Kier & Hall index, charge difference on the molecular surface, and count of H donor sites appropriately describe the physicochemical background of the relative sensitivity factors. The model developed in this work is freely accessible through the web: http://www.ut.ee/qsar .

While metal oxide nanoparticles (NPs) are one of the most commonly used nanomaterials, the theoretical models used to analyze and predict their behavior have been mostly based on just the chemical composition or the extrapolation from small metal oxide clusters’ calculations. In this study, a set of novel, theoretical full-particle descriptors for modeling, grouping or read-across of metal oxide NP properties and biological activity was developed based on the force-field calculation of the potential energies of whole NPs. The capability of these nanodescriptors to group the nanomaterials acoording to their biological activity was demonstrated by Principal Component Analysis (PCA). The grouping provided by the PCA approach was found to be in good accordance with the algal growth inhibition data of well characterized nanoparticles, synthesized and measured inside the consortia of the EU 7FP framework MODERN project.

Basicities of a number of ring-substituted N,N-dimethylanilines (DMA) and some related bases in water, acetonitrile, and THF and in the gas phase have been experimentally determined. Gas-phase basicities of DMAs and related bases were calculated at DFT B3LYP 6-311+G** and G3(MP2) levels. Structure–Basicity relationships in these four media were discussed. By comparison of gas-phase basicity shifts induced by stepwise substitution, starting from ammonia and ending at triphenylamine, it was observed that solvent effects of water and acetonitrile exceed the structural effects on intrinsic basicity. It was shown that the influence of substituents in the phenyl ring on DMA basicity is reduced by two to three times when going from the gas phase into the abovementioned condensed media. In the gas phase, 4-NO, 4-NO2, 4-CN, 4-COMe, and 4-CHO substituted DMAs protonate on substituent, whereas in solvents, only 4-NO-DMA probably protonates on substituent. The sensitivity of DMA basicity toward substitution in the phenyl ring was compared with the related family of phenylphosphazene bases, and it was found that the substituent effect is stronger in DMAs by 1.35 times in acetonitrile, 1.45 times in the gas phase, 2.0 times in THF, and 2.6 times in water. Copyright © 2012 John Wiley & Sons, Ltd. Supporting information may be found in the online version of this paper

The copper-free Sonogashira cross-coupling reaction consisting of oxidative addition, cis–trans isomerization, deprotonation, and reductive elimination was computationally modeled using the DFT B97D/cc-pVDZ method for reaction between phenyl bromide and phenylacetylene. Tetrakis(triphenylphosphano)palladium was used as a catalyst and sec-butylamine as a base. The reaction mechanism was studied in dichloromethane solution. Oxidative addition proceeds through the biligated pathway, and the catalytically active palladium species is Pd(PPh3)3. Amines, present in the reaction mixture, can inhibit oxidative addition by coordinating to Pd(PPh3)3.

The gas-phase acidities of ca. 60 monosubstituted anilines (with acidity span of almost 50 kcal mol(-1)) have been calculated using density functional theory (DFT) at the B3LYP/6-311+G** level. At this relatively simple level of theory the calculated (ΔG(calc)) and available experimental (ΔG(exp)) acidities are in reasonable quantitative correlation according to the following equation: ΔG(obs) = a + bΔG(calc), where a=20.79, b=0.942, n=27, R(2)=0.990, and s=0.78 kcal·mol(-1). The slope is not far from its ideal value. Substituent effects on the acidities were dissected separately into those operating in the neutral acid molecule and in its conjugated anion using the isodesmic homodesmotic reactions. All in all, both forms, neutral and anionic, are contributing in combination to make up the gross acidity of anilines. However, the contributions of the anions into the gross substituent effects are much larger than the substituent effects in the neutral anilines. Some of the systems were used in testing a relatively new theoretical model, COSMO-RS (conductor-like screening model for real solvents), using it for the prediction of pK(a) values in DMSO. The method proved to be rather accurate for showing pK(a) trends (R(2)=0.980 in DMSO). However, the predicted absolute pK(a) values were all somewhat lower (rmsd=2.49 kcal·mol(-1)) than the respective experimental values.

This work employs Fourier transform ion cyclotron resonance (FT-ICR) and the Gaussian quantum chemistry composite methods W1 and G2 to experimentally and computationally analyze gas-phase basicities (GB) for a series of weak bases in the basicity region around and below water. The study aims to clarify the long-standing discrepancy between reported GB values for weak bases obtained via high-pressure mass spectrometry (HPMS) and ICR; the ICR scale is observed to be more than 2 times contracted compared to the HPMS scale. The computational results of this work support published HPMS data. This agreement improves with increasing sophistication of the computational method and is excellent at the W1 level. Several equilibria were also re-examined experimentally using FT-ICR. In the experiments with some polyfluorinated weak bases (hexafluoro-2-propanol and nonafluoro-2-methyl-2-propanol), it was found that two protonation processes compete in the gas phase: protonation on oxygen and protonation on fluorine. In these species, protonation on fluorine proceeds faster and is statistically favored over protonation on oxygen but leads to cations that are thermodynamically less stable than oxygen-protonated cations. The process may also lead to the irreversible loss of HF. The rearrangement of fluorine-protonated cations to oxygen-protonated cations is very slow and is further suppressed by the process of HF abstraction. These results at least partially explain the discrepancy between published HPMS data and earlier FT-ICR findings and call for the utmost care in using FT-ICR for gas-phase basicity measurements of heavily fluorinated compounds. The narrower dynamic range of ICR necessitates the measurement of several problematic bases and produces some differences between the ICR results in the present work and the published HPMS data; the wider dynamic range allows HPMS to overcome these difficulties in connecting the ladder.

Substituent effects on the formation of cesium cation complexes with a series of 17 benzoic acids (AH), benzoates (A–), and the ion pairs (Cs+A–) are studied by density functional theory (DFT) and mass spectrometry. This study is positioned in the context of the fate of cesium in the environment, with emphasis of the influence of natural organic matter and humic substances. The bond length Cs+-(carboxylic O) in the various adduct geometries are discussed as regards the interaction strength, but quantitative relationships are limited by secondary effects arising mostly from long-distance interactions in systems bearing polar groups in meta-position. Relative cesium cation affinities of [Cs+A–] were experimentally determined by the kinetic method, i.e. by dissociating the required cesium cluster formed by electrospray ionization in a quadrupole ion-trap. Experiments and calculations are in agreement, except for the adducts derived from 3- and 4-hydroxybenzoic acids. A change in the localization of the negative charge is proposed as a possible explanation for the divergence.

The computational investigation of interactions of different acid–base pairs regarding the nature and extent of spontaneous proton transfer was carried out at B3LYP/6-311 + G** level. The selected acid–base pairs include the interactions of strong base (K2O) with acids of different strength (HClO4, HCl, and HF), and strong acid (HClO4) with bases ranging from K2O (GB = 322.8 kcal/mol) to H2O (GB = 157.6 kcal/mol). It was shown that spontaneus, unassisted proton transfer can take place in the gas-phase reactions of strong neutral Bronsted acids and bases. The reaction might be barrierless as in case of interactions between strong acids and bases, for example perchloric acid and alkali metal oxides or potassium oxide and halogen hydrides, or involve the encounter complex (hydrogen bonded acid–base cluster), which is separated from ion-pair by the transition state. Copyright © 2008 John Wiley & Sons, Ltd.

This review focuses on the quantitative data related to cesium cation interaction with neutral or negatively charged ligands. The techniques used for measuring the cesium cation affinity (enthalpies, CCA), and cesium cation basicities (Gibbs free energies, CCB) are briefly described. The quantum chemical calculations methods that were specifically designed for the determination of cesium cation adduct structures and the energetic aspects of the interaction are discussed. The experimental results, obtained essentially from mass spectrometry techniques, and complemented by thermochemical data, are tabulated and commented. In particular, the correlations between cesium cation affinities and lithium cation affinities for the various kinds of ligands (rare gases, polyatomic neutral molecules, among them aromatic compounds and negative ions) serve as a basis for the interpretation of the diverse electrostatic modes of interaction. A brief account of some recent analytical applications of ion/molecule reactions with Cs+, as well as other cationization approaches by Cs+, is given.

Performance of 18 DFT functionals (B1B95, B3LYP, B3PW91, B97D, BHandHLYP, BMK, CAM-B3LYP, HSEh1PBE, M06-L, mPW1PW91, O3LYP, OLYP, OPBE, PBE1PBE, tHCTHhyb, TPSSh, wB97xD, VSXC) in combinations with six basis sets (cc-pVDZ, aug-cc-pVDZ, cc-pVTZ, aug-cc-pVTZ, IGLO-II, and IGLO-III) and three methods for calculating magnetic shieldings (GIAO, CSGT, IGAIM) was tested for predicting 1H and 13C chemical shifts for 25 organic compounds, for altogether 86 H and 88 C atoms. Proton shifts varied between 1.03 ppm to 12.00 ppm and carbon shifts between 7.87 ppm to 209.28 ppm. It was found that the best method for calculating 13C shifts is PBE1PBE/aug-cc-pVDZ with CSGT or IGAIM approaches (mae = 1.66 ppm), for 1H the best results were obtained with HSEh1PBE, mPW1PW91, PBE1PBE, CAM-B3LYP, and B3PW91 functionals with cc-pVTZ basis set and with CSGT or IGAIM approaches (mae = 0.28 ppm). We found that often larger basis sets do not give better results for chemical shifts. The best basis sets for calculating 1H and 13C chemical shifts were cc-pVTZ and aug-cc-pVDZ, respectively. CSGT and IGAIM NMR approaches can perform really well and are in most cases better than popular GIAO approach.

Performance of 18 DFT functionals (B1B95, B3LYP, B3PW91, B97D, BHandHLYP, BMK, CAM-B3LYP, HSEh1PBE, M06-L, mPW1PW91, O3LYP, OLYP, OPBE, PBE1PBE, tHCTHhyb, TPSSh, wB97xD, VSXC) in combinations with six basis sets (cc-pVDZ, aug-cc-pVDZ, cc-pVTZ, aug-cc-pVTZ, IGLO-II, and IGLO-III) and three methods for calculating magnetic shieldings (GIAO, CSGT, IGAIM) was tested for predicting (1)H and (13)C chemical shifts for 25 organic compounds, for altogether 86 H and 88 C atoms. Proton shifts varied between 1.03 ppm to 12.00 ppm and carbon shifts between 7.87 ppm to 209.28 ppm. It was found that the best method for calculating (13)C shifts is PBE1PBE/aug-cc-pVDZ with CSGT or IGAIM approaches (mae = 1.66 ppm), for (1)H the best results were obtained with HSEh1PBE, mPW1PW91, PBE1PBE, CAM-B3LYP, and B3PW91 functionals with cc-pVTZ basis set and with CSGT or IGAIM approaches (mae = 0.28 ppm). We found that often larger basis sets do not give better results for chemical shifts. The best basis sets for calculating (1)H and (13)C chemical shifts were cc-pVTZ and aug-cc-pVDZ, respectively. CSGT and IGAIM NMR approaches can perform really well and are in most cases better than popular GIAO approach.

A quantitative structure-property relationship study of the infinite-dilution activity coefficients for a set of 38 organic compounds in ionic liquids such as 1-methyl-3-ethylimidazolium bis((trifluoromethyl)sulfonyl)imide, 1,2-dimethyl-3-ethylimidazolium bis((trifluoromethyl)-sulfonyl)imide, and 4-methyl-N-butylpyridinium tetrafluoroborate. QSPR study was carried out using the CODESSA PRO program. A general three-parameter QSPR model was obtained. Three orthogonal theoretical molecular descriptors satisfactorily correlate with the activity coefficients. The descriptors, such as the complementary information content, the fractional partial negative surface area and the count of hydrogen donor sites describe the dilution process in ILs.

The molecular geometry of cumulene chains H2CnH2 have been optimized using LCAO-SCF MO method (contracted Gaussian basis set of triple zeta valence quality TZVP and the more extended Dunning's correlation consistent basis set aug-cc-PVDZ), density functional theory at different basis set levels, and the highly parametrized MNDO(PM3) method. The bond lengths have no remarkable alternation within the chain and converge to the asymptotic limit as the value of n is getting larger. The total charges calculated by Mulliken population analysis yield unrealistic values if the split valence basis set was employed. In contrast, using NBO analysis the net charges of the individual atoms converge very rapidly to their asymptotic limits with almost zero charges on central atoms. The comparison of the different basis set results to test the reliability of proton affinities calculated from the differences in molecular enthalpies of the parent chain and the corresponding anions was carried out. The increase of the number of C C bonds in the chain decreases these differences asymptotically. The concept of ‘terminal charge repulsion’ is developed for the explanation of energy effects in long chains. The role of this concept in explanation of dependence of proton affinities on the chain length was discussed. The studied compounds are the best available building blocks in bimetallic compounds with useful properties in molecular electronics and nonlinear optics.

The high acidity of cubylamine ( 1 NH 2 ) seems to originate in the release of strain energy attending the breaking of some C–C bonds in 1 NH − . This process is greatly facilitated by the strong stereoelectronic interactions in 1 NH − . The anionic species thus formed are less strained, and their corresponding conjugate acids seem unable to ‘borrow strength’ from the residual strain, at least within the time-scale of the FT ICR experiments.

The three-layer ONIOM(B3LYP/6-311+G**:HF/3-21G*:MNDO) method was used to model the vibrational frequencies of acid sites in zeolite ZSM-5. Bridged OH and OD groups (both types 1 and 2) in eight crystallographically different locations were studied. The calculated anharmonic stretching vibrational frequencies of bridged hydroxyl groups are in good accordance with experimental measurements. The results of calculations point to the heterogeneity of acid sites due to different aluminium sites in zeolite lattice, and due to several probable locations of acid sites around aluminium atoms.

A quantitative structure−property relationship (QSPR) study of the gas-phase lithium cation basicity of a diverse set of 205 compounds provided a general six-parameter QSPR model (R2 = 0.801; R2cv = 0.785; F = 133.11; s2 = 8.78) using the CODESSA PRO program. Theoretical molecular descriptors, such as the minimum net atomic charge, highest occupied molecular orbital energy, total point-charge component of the molecular dipole, etc., logically explain the reaction equilibrium and electrostatic interaction between a lithium cation and a base.

The complexation of MgX 2 , MeMgX, and Me 2 Mg (X=Cl, Br) with propyne have been studied both in the gas phase and in the presence of dimethyl ether (Me 2 O) by means of the density functional theory B3LYP/6-31+G* method. Solvation was modeled using the supermolecule approach. The complex formation between disolvated magnesium compound and alkyne is connected with replacement of a coordinated solvent molecule by the alkyne, being necessary for the reaction to proceed to the end. The reaction towards end products, an acetylenic Grignard reagent and an alkane, is exothermic. The transition state has a cyclic structure, which is almost triangular with practically linear proton transfer. The transition state resembles more the reagents than the products.

The Schlenk equilibrium involving RMgX, R2Mg, and MgX2 (R = Me, Et, Ph and X = Cl, Br) has been studied both in the gas phase and in diethyl ether (Et2O) and tetrahydrofuran (THF) solutions by means of the density functional theory (DFT) B3LYP/6-31+G* method. Solvation was modeled using the supermolecule approach. The stabilization due to interaction with solvent molecules decreases in the order MgX2 > RMgX > R2Mg and among the groups (R and X) Ph > Me > Et and Cl > Br. Studied magnesium compounds are more strongly solvated by THF compared to Et2O. The magnesium halide is solvated with up to four solvent molecules in THF solution, assuming that trans-dihalotetrakis(tetrahydrofurano)magnesium(II) complex forms. The formation of cis-dihalotetrakis(tetrahydrofurano)magnesium(II) is energetically less favorable than the formation of corresponding disolvated complexes. The predominant species in the Schlenk equilibrium are RMgX in Et2O and R2Mg + MgX2 in THF, which is consistent with experimental data.

B3LYP and PBE0 density functional calculations with different effective core potentials (ECP) and basis sets were used to investigate gas-phase geometries, basicities, and proton affinities of alkali metal oxides M 2 O and hydroxides MOH (M=K, Rb, Cs). The alkali metal oxides and hydroxides were all found to be linear. We suggest the gas phase proton affinities for Rb 2 O and Cs 2 O to be 331.9 and 324.4 kcal/mol, respectively. Our calculations show that the most accurate method for calculating geometries of potassium, rubidium and cesium oxides and hydroxides is PBE0 density functional with CRENBL ECP and basis set (augmented with Glendening's polarization functions) on alkali metal, Dunning's double-zeta basis augmented with set of polarization and diffuse functions on oxygen, and Dunning's double-zeta plus polarization basis on hydrogen, while for proton affinities the B3LYP functional (with the same ECP/basis set combination) is marginally better.

The performance of the ONIOM method was tested in reproducing the properties of the acid sites of the zeolite ZSM-5. The acid sites in three crystallographic locations (Al3–O19(H)–Si6, Al6–O18(H)–Si9 and Al7–O17(H)–Si4) have been modelled by three combinations of two-layer ONIOM method with varied size (two and eight T atoms) and calculation method (ab initio and DFT) used for the chemically important (active) part. The best correspondence with experimental data was achieved in case of Al6–O18(H)–Si9 site calculated with ONIOM(B3LYP/6-311+G∗∗:MNDO) method using eight T atoms in model system for the following properties: stretching vibrational frequencies, 1H NMR chemical shifts of the bridged hydroxyl groups, vibrational frequency shifts and changes in 1H NMR chemical shifts of the hydroxyl groups upon adsorption of CO.

Kinetic studies were carried out on the reaction of phenylmagnesium bromide with hex-1-yne in diethyl ether, and in binary mixtures of diethyl ether with toluene, chlorobenzene and dichloromethane. The reaction was accelerated by addition of non-donating solvents. The replacement of a coordinated solvent molecule by the alkyne is necessary for the reaction to proceed, according to density functional theory (DFT) calculations with B3LYP/6–31 + G* method. The non-donating solvents accelerate the reaction by shifting the replacement equilibrium in favour of the complex formation. An analysis in terms of the Koppel–Palm equation revealed a rate decrease with increase in solvent polarity and polarizability. Copyright © 2002 John Wiley & Sons, Ltd.

The applicability of 12 different quantum chemical calculation methods, including density functional theory (DFT) and ab initio methods, for describing strained alkenes and modeling their gas-phase basicities (GB), hydrogenation enthalpies, and double bond geometries was studied for a series of systematically defined compounds R1R2C = CR3R4. The calculated values were compared to experimental data that had been compiled from literature for several compounds within the series. The closest relationship between the computational results and experimental data occurred with the G2MP2 ab initio method. The best DFT method for GB values was M062X and for hydrogenation enthalpies PBEPBE. At the same time, the relative effects of compound structure variations on the calculated values were similar among all 12 of the calculation methods tested. The double bond length was relatively insensitive to the sizes of the R substituents in R1R2C = CR3R4, but the torsion angles changed significantly in response to structural changes to the compounds when none of the groups R1–R4 was hydrogen.