Iwona Anusiewicz

BX4- and AlX4- superhalogen anions (X = F, Cl, Br): an ab initio study.

The vertical electron detachment energies (VDEs) of 30 MX 4 (-) (M = B, Al; X = F, Cl, Br) anions were calculated at the OVGF level with the 6-311+G(3df) basis sets. The largest vertical electron binding energy was found for the AlF 4 (-) system (9.789 eV). The strong VDE dependence on the symmetry of the species, ligand type, ligand-central atom distance, and bonding/nonbonding/antibonding character of the highest occupied molecular orbital was observed and discussed.

Superhalogen anions utilizing acidic functional groups as ligands.

The vertical electron detachment energies (VDE) of several NaL(2)(-) and MgL(3)(-) anions (where L= -ClO(4), -ClO(3), -ClO(2), -ClO, -NO(3), -PO(3), -H(2)PO(4), -HSO(4), -HCO(3), -SH) were calculated at the outer valence Green function level with the 6-311++G(3df,3pd) basis sets. It was shown that various acidic functional groups may act as ligands in superhalogen anions whose electronic stabilities always exceed 4 eV. The largest values of the electron binding energies were found for the anions containing -ClO(4) ligands (VDE=7.8-8.9 eV). The VDE dependencies on the origin of the ligand used (whether it is a functional group derived from strong or weak acid), chemical constitution of acidic functional groups and the electronegativity of the ligands central atom were observed and discussed.

Electrophilic Substituents as Ligands in Superhalogen Anions

The vertical electron detachment energies (VDE) of several NaL(2)(-) and MgL(3)(-) anions (where L = -NO(2), -CF(3), -CCl(3), -SHO(3), -COOH, -COOCH(3), -CHO, -CONH(2)) were calculated at the outer valence Green function level with the 6-311++G(3df,3pd) basis sets. It was proposed that some of electrophilic substituents may act as ligands in these species, analogously to halogen atoms in superhalogen anions. The largest values of the electron binding energies were found for the anions containing -SHO(3) ligands (VDE = 6.0-8.2 eV) and -CF(3) groups (VDE = 5.2-6.6 eV).

Theoretical Search for Alternative Nine-Electron Ligands Suitable for Superhalogen Anions

The calculations performed at the OVGF/6-311++G(3df,3pd)//MP2/6-311++G(d,p) level for the representative NaX(2)(-) and AlX(4)(-) anions matching the MX(k+1)(-) superhalogen formula and utilizing 9-electron systems (i.e., consisting of various possible combinations of atoms containing nine electrons when brought together) revealed that the OH, Li(2)H(3), and NH(2) groups might be considered as alternative ligands X due to their thermodynamic stability and large values of electron binding energy (approaching or even exceeding 6 eV in some cases). All aluminum-containing AlX(4)(-) anions (excluding Al(HBLi)(4)(-)) were predicted to be thermodynamically stable, whereas the NaX(2)(-) anions for X = CH(3), HBLi, CLi, BeB, and H(2)BeLi were found to be susceptible to the fragmentations leading to Na(-) loss. Among the MX(k+1)(-) (M = Na, Al; X = Li(2)H(3), OH, H(2)BeLi, BeB, NH(2), HBLi, CH(3), Be(2)H, CLi) anions utilizing systems containing 9 electrons (and thus isoelectronic with the F atom) the largest vertical electron detachment energy of 6.38 eV was obtained for Al(OH)(4)(-).

1,3‐Alternate calix[4]arene‐bonded silica stationary phases. Effect of calixarene skeleton substituents on the retention mechanism and column selectivity

Four novel 1,3-alternate calix[4]arene-bonded silica gel stationary phases possessing different aromatic and aliphatic substituents at the upper rim (CalixNph, CalixBph, CalixHex, and CalixDdc) were prepared and structurally characterized. The comparison and selectivity of these phases were done by using alkylbenzenes, fatty acid p-bromophenacyl esters, aromatic positional isomers, and polynuclear aromatic hydrocarbons as analytes. Quantum chemistry calculations have also been performed (using an ab initio method) to support the experimental findings. The effect of the type and content of organic modifier on the retention and selectivity of the alkylbenzenes was studied. The retention mechanism is also discussed. The results indicate that the stationary phases behave like RP packings. However, inclusion complex formation and hydrophobic and pi-pi interactions seem to be involved in the separation process.

Refinements to the Utah-Washington mechanism of electron capture dissociation.

Ab initio electronic structure calculations on a rather geometrically constrained doubly positivley charged parent peptide ion are combined with experimental data from others on three similar ions to refine understanding of the mechanistic steps in the Utah-Washington model of electron-capture and electron-transfer dissociation. The primary new findings are that (i) the electron need not first attach to a Rydberg orbital and subsequently be extracted by an SS σ* or amide π* orbital (rather, it can be guided directly into the SS σ* or amide π* orbital by the Rydberg orbital) and (ii) Coulomb and dipole potentials within the parent ion alter both the electron binding strengths and radial ranges of Rydberg orbitals located on the positively charged sites, which, in turn, alters the ranges over which the electron can be guided. These same potentials, when evaluated at disulfide or backbone amide sites, determine which disulfide σ* and amide π* orbitals are and are not susceptible to electron attachment leading to SS and N-Cα bond cleavage. Additional experiments on the same parent ions discussed here are proposed to further test and refine the UW model.

The saturation of the gas phase acidity of nHF/AlF3 and nHF/GeF4 (n = 1–6) superacids caused by increasing the number of surrounding HF molecules

The acidic strength of selected Bronsted/Lewis superacids is evaluated on the basis of theoretical calculations carried out at the QCISD/6-311++G(d,p) level. The energies and Gibbs free energies of deprotonation processes for nHF/AlF3 and nHF/GeF4 (n = 1–6) are found to depend on the number (n) of hydrogen fluoride molecules (playing a Bronsted acid role) surrounding the AlF3 and GeF4 Lewis acids. The successive attachment of HF molecules to either AlF3 or GeF4 gradually increases the acidity strength of the resulting superacid, which leads to the saturation achieved for 5–6 HF molecules interacting with either one of these Lewis acids. The importance of the microsolvation of the corresponding anionic species as well as the necessity of considering larger (more structurally complex) building blocks of superacids while predicting their acidity is indicated and discussed.

Electron detachment energies in high-symmetry alkali halide solvated-electron anions

We decompose the vertical electron detachment energies (VDEs) in solvated-electron clusters of alkali halides in terms of (i) an electrostatic contribution that correlates with the dipole moment (μ) of the individual alkali halide molecule and (ii) a relaxation component that is related to the polarizability (α) of the alkali halide molecule. Detailed numerical ab initio results for twelve species (MX)n− (M=Li,Na; X=F,Cl,Br; n=2,3) are used to construct an interpolation model that relates the clusters’ VDEs to their μ and α values as well as a cluster size parameter r that we show is closely related to the alkali cation’s ionic radius. The interpolation formula is then tested by applying it to predict the VDEs of four systems [i.e., (KF)2−, (KF)3−, (KCl)2−, and (KCl)3−] that were not used in determining the parameters of the model. The average difference between the model’s predicted VDEs and the ab initio calculated electron binding energies is less than 4% (for the twelve species studied). It is conclud...

Are HBO− and BOH− electronically stable?

The binding of an excess electron to HBO and BOH was studied at the coupled cluster level of theory with single, double and non-iterative triple excitations and with extended basis sets to accommodate the loosely bound excess electron. The bent BOH molecule, with a dipole moment of 2.803 D, binds an electron by 39cm−1, whereas the linear HBO tautomer possesses a similar dipole moment (2.796 D) yet binds the electron by less than 1 cm−1. It is therefore likely that HBO− is not stable when rotational energies are included whereas BOH− is for low rotational quantum numbers.

Predicting the viscosity and electrical conductivity of ionic liquids on the basis of theoretically calculated ionic volumes

Selected physical properties of the ionic liquids might be quantitatively predicted based on the volumes of the ions these systems are composed of. It is demonstrated that the ionic volumes calculated using relatively simple theoretical quantum chemistry methods can be utilised to estimate the viscosities and electrical conductivities of various commonly used ionic liquids. The fitting formulas of the exponential form are offered and their predictive usefulness is verified. The quality of such predictions is discussed on the basis of several ionic liquids involving [Tf2N]‑ and [BF4]‑ anions and 16 various cations. The dependence of the viscosity and electrical conductivity of the ionic liquids on the temperature is also investigated and the temperature-dependent equations are derived and compared to the experimentally measured values.