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The dimers involving benzene or other substituted [pi] systems were investigated to examine the relevance of the magnitudes of their attractive and repulsive interaction energy components in governing the geometries of several [pi]-[pi] systems. The findings suggest that the presence of substituents on the aromatic ring, irrespective of their electron withdrawing or donating nature leads to an increase in the binding energy.

The structures of neutral and anionic gold-silver binary clusters and pure gold and silver clusters are investigated. It is shown that the calculated electronic properties and dissociation energy of both pure and binary clusters are in agreement with the available experimental data.

Research discusses the origin of the fast diffusion reactivity and the role of low activation barrier in the catalytic mechanism in the context of preorganization, short strong hydrogen bond, and the charge buffering/dissipation of the catalytic residues. Results show that the charge buffering by the catalytic residues reduces negative charge accumulation.

Research examines a new family of ionophores, [n]beltenes, which possess a cation-olefinic pi type interaction as opposed to [n]collarenes exhibiting cation-aromatic pi interaction. Data indicate that the [n]beltenes have binding affinities to metal cations and also show delicate ion selectivity properties.

The interactions of first-row hydrides with ethene and benzene are investigated with regard to olefinic vs aromatic pi-H interactions.

The authors review the publications on the weakly bound van der Waals complexes of pi-systems and their properties. The topics of interest include the theoretical methods, the salient results obtained from the ab initio calculations for different pi-complexes and the results obtained via empirical and semiempirical calculations for the larger pi-complexes.

This research focuses on a comparison of the electronic properties, vibrational frequencies, binding energies, and the geometries of the minimal energy conformers of the C6H6-AlX3 and the corresponding C2H4-AlX3 systems.

Research was conducted to predict the binding energies and geometries of benzene-BX3 and ethene-BX3 complexes using quantum mechanical ab initio calculations. Single point measurements at a much higher correlation level and larger basis sets were also performed. Results based on binding energies indicate that all the complexes were weakly bound van der Waals complexes except for the C2H4-BH3 complex. There was also a strong evidence of an unusual increase in the nucleophilicity of one of the benzene carbons in the lowest energy conformer of systems involving benzene.

A study was conducted to analyze the role of Lewis acid(AlCl3)-aromatic ring interactions in Friedel-Craft's reaction. High-level ab initio computations were carried out on two model systems. Findings showed unusual molecular orbital interactions during the ring interactions. Results also indicated that Lewis acid supports a critical role in the activation of the aromatic substrate prior to attack by the electrophile.

The nature of the interaction and saturation of hydrogen molecules on small titanium clusters is examined by using ab initio calculations. The peaks in the experimental mass and photoelectron spectra of hydrogen saturated titanium clusters are attributed to structures possessing hydrogen multicenter bonds, which are in turn ascribed to the origin of the broad shoulder in the vibrational spectra of hydrogen cycled Ti-doped NaAl[H.sub.4].

Cation-pi and the corresponding anion-pi interactions are investigated as binary complexes. Compared to cation-pi-anion ternary complexes, the magnitude of the cation-pi interaction in pi-cation-anion ternary complexes is markedly lower due to the charge transfer from the anion to the cation.

The role of the metal electrode influencing the structure and electronic properties of semiconducting carbon nanotubes near the interface at low bias is examined. The calculations at the density functional level of theory, including full geometry optimizations, indicates that bonds are formed between the metal atoms of the electrode and the carbon atoms of the nanotubes.

The edge-to-face interactions for either axially or facially substituted benzenes are investigated by using ab initio calculation. The predicted maximum energy difference between substituted and unsubstituted systems is ~ 0.7 kcal/mol.

The theoretical studies yield several insights into the interactions prevailing in aqueous clusters of monovalent alkali metal, ammonium, and hydronium cations. The second order Moller-Plesset (MPs) and density functional levels of theory are used for the calculations of the structures, thermodynamic energies and IR spectra of several plausible conformers.

The interaction of various anions with many representative pie systems is investigated. The results of this research can be effectively employed to generate crafted molecular systems for size-and molecule-selective processes.

The use of femtosecond time-resolved, which degenerates four-wave mixing rotationally resolved spectroscopy to obtain very accurate structural information on the symmetric top cyclohexane is reported. Since, in the chair conformation belongs to the point D3d, it is not possible to employ microwave spectroscopy, which is the most precise structural method in the gas phase for small- and medium-sized molecules.

The authors have investigated alpha-amino acids exhibited by cobalt(III) metal complex. They report that the stereospecific and regiospecific recognition of these acids has been rationalized from the structural characteristics via the use of density functional calculations.

The nature of the cation-Pi interaction was examined by carrying out high level ab initio calculations of metallic and organic cations with different classes of Pi systems. The calculations included a rigorous decomposition of the interaction energies indicating that the interaction of the Pi systems with the metal cations was characterized by contributions from electrostatic and induction energies.

The synthesis of calix[4]hydroquinone nanotube arrays self-assembled with infinitely long one-dimensional (1-D) short hydrogen bonds and aromatic-aromatic interactions is presented. The competition between H-bonding and displaced pi-pi stacking in the assembling process is described.

A new type of interaction between silane (SiH4) and borane (BH3) using high level ab initio calculations were investigated that might have a hitherto unknown role in the mechanism of chemical vapor deposition (CVD), which is employed in the fabrication of boron doped silicon semiconductor materials. It is also noted that the SiH4-BH3 complex would dissociate to form SiH3 and BH4 radicals.