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A series of donor-acceptor p-nitro-p'-alkoxy (OR) substituted (E,E,E)-1,6-diphenyl-1,3,5-hexatrienes were prepared and their properties and crystal structures investigated. The flouresence spectra of these crystals were red-shifted relative to those for the solutions in low polar solvents, which can be attributed to the planarization of molecules in the solid state and to the strong intermolecular interactions in crystals.

The quantitative information on the formation on ionic aggregates in room-temperature Ionic Liquids (RTILs) based on the ratios of molar conductivity values ([A.sub.imp]/[A.sub.NMR], where [A.sub.imp] is the molar conductivity obtained by electrochemical impedance measurements and [A.sub.NMR] is that calculated from the pulse-field-gradient spin-echo NMR (PGSE-NMR) ionic self-diffusion coefficients and the Nernst-Einstein equation is reported. A decrease in ([C.sub.eff]) effective ionic concentration of the RTILs is well correlated with the normal boiling point and distillation rate, whereas the liquid-state dynamics is controlled by a subtle balance between the electrostatic and other intermolecular forces.

The CCSD(T) level interaction energies of CH/pi complexes at the basis set limit are estimated. The weak directionality has indicated that the hydrogen atom of the interacting C-H bond is not essential for the attraction and that the typical CH/pi interaction does not play a key role in determining the molecular orientation in molecular assemblies.

A series of room-temperature ionic liquids (RTILs) were prepared with different cationic structures, combined with an anion and the thermal property, density, self-diffusion coefficients of the cation and anion, viscosity, ionic conductivity were measured over a wide temperature range. It was found that the relative cationic and anionic self-diffusion coefficients for the RTILs appear to be influenced by the shape of cationic structure and that the microscopic ion dynamics and ionic state significantly contributes to the macroscopic physicochemical properties of the ionic liquids.

The ARS-E model was used for calculating the intermolecular interaction energy of hexafluorobenzene-benzene. The largest and most negative energy of -5.38 kcal/mol was observed in the slipped-parallel complex.

Single crystal of a series of (Z,E,Z)-1,6-diphenylhexa-1,3,5-triene 4,4'-dicarboxylic acid dialkyl esters that were prepared and their crystal structures and photoisomerization behaviors that were systematically investigated is described. The conformational flexibility of the alkyl chains made the large change in the trienegeometry in the lattice possible, leading to the enhancement of the photoreactivity in the crystalline state.

(Super 1)H and (super 13)C NMR studies have proved interactions between a thicarbonyl group and a pyridinium nucleus, and between a carbonyl group and a pyridinium nucleus. The experimental results suggested the existence of attractive (C=S)...Py(super +) and (C=O)...(Py(super +) interactions in solution and in crystal.

The interaction energies of the alkaline-earth-metal dication/benzene complexes were calculated at the MP2 level using the 6-311G-basis set. The calculations of benzene under an electric field show that the electric field produced by the diction is a cause of the C-C bond elongation in the alkaline-earth-metal dication/benzene complexes.

Calculation of intermolecular interaction energies of 14 orientation CHF3 dimers is done with electron correlation correction by the MP2 method. Electron correlation correction increases the attraction considerably, which indicates that the dispersion interaction is important for the attraction.

The interaction energy calculation of the thiophene dimmer is presented by using very large basis sets near saturation. The estimation of MP2 and CCSD(T) level interaction energies at the basis set limit are described by using model chemistry.

Research is presented concerning the use of density functional theory calculations to investigate the intermolecular interaction energy of the water-crownophane complex. The binding energy of the water is discussed.

Interactions between the pi face of benzene and ammonia are reported as a model of NH/pi interaction.

High-level ab initio calculations were used to evaluate the CH/varPi interaction of model systems and benzene.

High-level ab initio calculations have been used to investigate the torsional potentials of methoxy and hydroxyl groups of omichron-hydroxyanisole. It was established that the intramolecular bond significantly stabilizes the energy minimum structure.

Estimation of the intermolecular interaction energies has been carried out by means of ab initio calculations of C (sub)2 H (sub)4 - CH (sub)4 and C (sub)2 H (sub)6 - CH (sub)4 dimer orientations. The role of the electrostatic, dispersion and charge transfer interactions between aliphatic C-H bond and pi-system has been discussed.

Two medium-size basis sets, aug(d,p)-6-311G** and aug(df,pd)-6-311G**, are developed to analyze the dispersion interactions of hydrocarbon molecules. Intermolecular interaction energies of methane, ethane, propane, ethylene, acetylene and benzene dimers calculated with the basis sets are compared with those from the Sadlej's basis set and Dunning's correlation-consistent basis sets. Results show that the aug(d,p)-6-311G** set is more effective than Sadlej's basis set in evaluating dispersion energy. The aug(df,pd)-6-311G** basis set is also smaller than Dunning's basis sets.

Ab initio methods using basis sets of up to 6-311G(2d) quality, with MP2 level electron correlation energy correction were used to examine the intermolecular interaction potential of the corannulene dimer in a parallel (D5h) orientation. Results indicate that the dispersion interaction is the dominant principle in the interaction of the corannulene dimer. Findings also suggest that the intermolecular interaction potential obtained from the corannulene dimer will outperform atom-atom potentials for molecular dynamics studies of the bulk properties of fullerenes.

The role of neutral species and metal coordination in the enzymatic cleavage of RNA have been investigated. The results showed that the cleavage occurs via a cyclic pentacoordinate oxyphosphane intermediate/transition state. The metal coordination produces an electrostatic field that allows in-line attack and departure process. This also prevents pseudorotations for the positional exchanges of ligands of pentacoordinate oxyphosphorane intermediate/transition state.

Studies of oxyphosphoranes such as neutral pentahydroxyphosphorane, dianionic trihydroxyphosphorane and trimethoxyphosphorane suggest that conformation of the P-O3 bond and its effect on reactivity are in accord with stereoelectronic effect-based predictions. The 'n-sigma asterisk interaction' is not crucial for the stereoelectronic control of the oxyphosphorane system.

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.

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.