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The intermolecular interaction energies of naphthalene dimers have been calculated by using an aromatic intermolecular interaction model (a model chemistry for the evaluation of intermolecular interactions between aromatic molecules). The CCSD(T) (coupled cluster calculations with single and double substitutions with noniterative triple excitations) interaction energy at the basis set limit has been estimated from the second-order Møller–Plesset perturbation interaction energy near saturation and the CCSD(T) correction term obtained using a medium-size basis set. The estimated interaction energies of the set of geometries explored in this work show that two structures emerge as being the lowest energy, and may effectively be considered as isoenergetic on the basis of the errors inherent in out extrapolation procedure. These structures are the slipped-parallel (C[sub i]) structure (-5.73 kcal/mol) and the cross (D[sub 2d]) structure (-5.28 kcal/mol). The T-shaped (C[sub 2v]) and sandwich (D[sub 2h]) dimers are substantially less stable (-4.34 and -3.78 kcal/mol, respectively). The dispersion interaction is found to be the major source of attraction in the naphthalene dimer. The electrostatic interaction is substantially smaller than the dispersion interaction. The large dispersion interaction is the cause of the large binding energies of the cross and slipped-parallel dimers. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The π/π interaction (stacking) and N(B)–H/π interaction of the borazine (B[sub 3]N[sub 3]H[sub 6]) dimer were theoretically studied. In contrast to the benzene dimer, the gauche parallel-stacked dimer of borazine was energetically minimum, and total interaction energy was about 1 kcal/mol more negative than that of the parallel-stacked dimer of benzene. The gauche parallel-stacked dimer of borazine was more stable than slipped parallel-stacked dimers and T-shape dimers. The syn parallel-stacked dimer of borazine was energetically unstable and it was less stable than the slipped syn parallel-stacked structures. The electron correlation effect at higher than the second-order Møller–Plesset (MP2) level on the molecular interaction energy was quite small. The dispersion term and the charge transfer term had large contribution in almost all the borazine dimer formations, except the syn parallel-stacked dimer. In the case of syn parallel-stacked dimer, contribution of the dispersion term was dominant. The electrostatic term had only small contribution for all the dimer formations. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The energy profile of the interconversion path between the T-shape and slipped-parallel dimers has been studied by high level ab initio calculations. The CCSD(T) (coupled cluster calculation with single and double substitutions with noniterative triple excitations) interaction energy at the basis set limit has been estimated from the MP2 (the second-order Møller-Plesset calculation) interaction energy near the basis set limit and the CCSD(T) correction term using the 6-311G[sup *] basis set. The calculated CCSD(T) level energy profile has shown that the potential is very flat and the interconversion barrier height is very small (around 0.2 kcal/mol). The MP2 calculations using large basis sets near the basis set limit considerably overestimate the attraction of the slipped-parallel dimer, which indicates the importance of higher level electron correlation correction for studying the potential energy surface of the benzene dimer. [ABSTRACT FROM AUTHOR]

Intermolecular interaction energies of eight orientation CF[sub 4] dimers and seven orientation C[sub 2]F[sub 6] dimers were calculated with electron correlation correction by the second-order Moller-Plesset perturbation (MP2) method. The D[sub 3d] CF[sub 4] dimer and C[sub 2h] C[sub 2]F[sub 6] dimer have the largest binding energies. Electron correlation correction increases the attraction considerably, while the effects of electron correlation beyond MP2 are small. Electrostatic and induction energies are not large in all cases. This indicates that dispersion interaction is mainly responsible for the attraction. The calculated binding energy of the CF[sub 4] dimer (0.69 kcal/mol) is about 60% larger than that of the CH[sub 4] dimer (0.44 kcal/mol), while the binding energy of the C[sub 2]F[sub 6] dimer (1.02 kcal/mol) is close to that of the C[sub 2]H[sub 6] dimer (0.90 kcal/mol). The intermolecular separations (C···C distance) in the CF[sub 4] and CH[sub 4] dimers at the potential minima are close (4.0 and 3.8 Å, respectively), while the separation in the C[sub 2]F[sub 6] dimer (4.8 Å) is appreciably larger than that in the C[sub 2]H[sub 6] dimer (4.0 Å). The larger intermolecular separation in the C[sub 2]F[sub 6] dimer reduces dispersion energy. Therefore the binding energies of the C[sub 2]F[sub 6] and C[sub 2]F[sub 6] dimers are not largely different. The molar volume of C[sub 2]F[sub 6] is substantially larger than that of C[sub 2]F[sub 6] due to bulky fluorine atoms. The small difference of the binding energies suggests that the large molecular volume of perfluoroalkanes is the cause of their small heats of vaporization per volume. [ABSTRACT FROM AUTHOR]

Ab initio molecular orbital calculations are used for studying the interactions of the lithium bis(trifluoromethylsulfonyl)amide (LiTFSA) complex with N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium (DEME), 1-ethyl-3-methylimidazolium (EMIM) cations, neutral dithylether (DEE) and the DEMETFSA complex. The attraction between the DEME cation and the LiTFSA complex has shown that the interaction between the Li cation and the oxygen atom of DEME cation has played key roles in determining the mobility of the Li cation in DEME-based room temperature ionic liquids.

Conformational energies are calculated for the butyl group of 1-butyl-3-methylimidazolium (bmim) is calculated by high level ab initio methods. The studies have shown that the GT rotamer of bmim is the most stable in ionic liquids and the positive charge on the imidazolium ring has not changed the conformational energies.

The electronic conductivity of the neat N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)amide (DEME-TFSA) and DEME-TFSA-Li doped with different concentrations of lithium salt (LiTFSA) is measured and correlated with NMR measurements of the diffusion coefficients and the spin-lattice relaxation times. The lithium one-jump distance has changed with the temperature and salt concentration and has provided information on lithium transfer.

A series of ring-fluorinated (E,E,E)-1,6-diphenyl-1,3,5-hexatrienes (DPHs) are synthesized and their solid-state absorption, fluorescence properties and the crystal structures are examined. The difference in the fluorescence origin is attributed to the difference in the strength of orbital-orbital interaction between molecular [pi]-planes in the ground and excited states in crystals.

The study explains the origin of attraction, magnitude and directionality of interaction energies in various benzene complexes having different pyridinium cations. The attraction between the benzene-pyridine complexes is found to be a result of the dispersion [pi]-[pi] interaction in the pyridine complex.

The intermolecular interaction between an aliphatic C-H bond and a pi-electron system (C-H/pi interaction) is characterized on the basis of infrared spectroscopy and high level ab initio calculations. The [S.sub.1]/[S.sub.0] electronic transition of the aromatic moiety is observed, indicating low-frequency shifts upon cluster formation, and these results have supported the dominance of the dispersion interaction over the electrostatic and charge-transfer terms in the aliphatic C-H/pi interaction.

The accurate CH/pi interaction energy of the benzene-methane model system was experimentally and theoretically determined. The mass analyzed threshold ionization (MATI) technique was applied to benzene-methane cluster and the calculated binding energy after the vibrational zero-point energy correction was similar to the experimental value.

The isolation and X-ray structural characterization of two 16 pi electron octaethyl- and octaisobutyl-tetraphenylporphyrins are reported. The X-ray analysis of octaisobutyl-tetraphenylporphyrins showed a very similar distorted nonplanar structure to that of octaethyl, but in this case, H2O was found in the center of the core instead of CH2Cl2.

The membranes of a perfluorosulfonic acid polymer swollen in 10-80 wt % methanol solution were investigated to elucidate the methanol effect on their morphologies, such as size of the solvent cluster, solvent location, and polymer structure, by using isothermal-isobaric molecular dynamics simulations. The partial radial distribution functions between solvent oxygen and fluorocarbons that were composed of the main chain show that methanol was located closer to the polymer matrix than water.

The intermolecular interaction energies of nine ion pairs of room temperature ionic liquids were studied by MP2/6-311G** level ab initio calculations. Experimental ionic conductivities show that the magnitude and directionality of the interaction energy of the ion pairs play a crucial role in determining the ionic/dissociation dynamics in the ionic liquids.

Molecular dynamics simulations of the swollen membrane of perfluorinated ionomer were undertaken to analyze the static and dynamic properties of the water and the side chain in the membrane. The results indicated that in a low water uptake membrane, the dynamics of water is substantially restricted due to strong attractive interactions with acidic sites.

Intermolecular interaction energies of n-butane, n-pentane, and n-hexane dimers were calculated at the MP2 level with large basis set including multiple polarization functions. A comparison of the calculated interaction energies of five orientations of dimers for each n-alkane molecule showed that the interaction between the two n-alkane chains has strong anisotropy.

A molecular interaction between the fluorine atom and r -system of the hexafluorobenzene is examined. It is concluded that there is a very weak repulsive interaction between them.

Studies the effects of basis set and electron correlation on the calculated interaction energies of hydrogen bonding complexes. Use of the Dunning's correlation consistent basis sets in the study; Effects of electron correlation; Effects of basis set; Interaction energies at the basis-set limit.

Calculates the internal rotational barrier heights of biphenyl with the Dunning correlation consisted basis sets and the electron correlation correction by the second order Moller-Plesset method. Calculations of benzene dimers suggesting that the dispersion interaction increased the relative stability of the coplanar conformer.

In order to identify the key factor governing the transport properties and extent of proton transfer in protic ionic liquids (PILs), a series of PILs were prepared by simple neutralisation of a super-strong acid, bis(trifluoromethanesulfonyl)amide acid (H[NTf2]), with a range of amines comprising diverse structures, including secondary and tertiary amines. The bulk physicochemical properties of the resulting PILs with a wide variation in the ΔpKa values of the constituent acid and protonated bases were compared to those of previously reported PILs derived from a super-strong base, 1,8-diazabicyclo[5.4.0]-7-undecene (DBU), and different acids (M. S. Miran, H. Kinoshita, T. Yasuda, M. A. B. H. Susan and M. Watanabe, Phys. Chem. Chem. Phys., 2012, 14, 5178–5186) with emphasis on the thermal stability, vibrational spectroscopy, density, viscosity, conductivity, and ionicity characteristics. The thermal stability of all PILs, as analysed by thermogravimetric analysis (TGA), was found to linearly increase with the ΔpKa values. However, isothermal TGA measurements for an extended duration indicated that [NTf2]-based PILs exhibit higher thermal stability than [DBU]-based PILs at low ΔpKa values (＜15). PILs with secondary amines showed higher viscosity and lower ionic conductivity than those with tertiary amines because of the formation of multiple hydrogen bonds. The evaluated ionicity suggested that all [NTf2]-based PILs are “good PILs”, irrespective of the basicity of the amines, and have higher ionicity than [DBU]-based PILs particularly at low ΔpKa values (＜15). [ABSTRACT FROM AUTHOR]

Investigates the intermolecular interaction potential of the carbon dioxide dimer. Absence of an inversion barrier; Calculation of the energy difference of the dimer; Use of diffuse polarization in evaluating the essential attractive interactions.

The energy profiles for the internal bond rotation of substitutes methyl radicals, X-CH2 (X= BH2, CH3, NH2, and OH) are examined with B3LYP/6-31G(d) calculations. The computed rotational energy profiles, as well as the calculated values for the geometrical parameters, the vibrational frequencies, the ionization potential, are found to be reasonable in agreement with previously reported experimental and theoretical results.

The interaction energies of the cation/pi complexes were calculated at the MP2/6-311G level. The calculated potential suggests that the major source of the attraction in the cation/pi interaction is long-range interactions such as induction and electrostatic.