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The benzene molecule serves as a benchmark among the aromatic hydrocarbons and has been the subject of numerous experimental and theoretical studies. Despite such intensive investigations, the precise structure of the benzene cation ([C.sub.6][H.sub.6][sup.+]) is not known. Now, experiments measuring high-resolution state-to-state threshold photoionization spectra of benzene concretely establish the terms of vibronic levels in the distorted cation that are split by higher order Jahn-Teller coupling between its ²[E.sub.1g] electronic ground state and [v.sub.6] [e.sub.eg] in-plane ring-bending vibrational mode. This assignment, in turn, sets the absolute energy phase of the vibronic pseudorotation in this coordinate and thereby offers a definitive experimental determination of the shape of the benzene cation., Molecules with electronically degenerate ground states confound conventional notions of molecular shape and the ball-and-stick separability of electronic and internuclear degrees of freedom. Nuclear motions coupled with electronic degeneracy link [...]

Cations bind to the Π face of an aromatic structure through a surprisingly strong, non-covalent force termed the cation-Π interaction. The magnitude and generality of the effect have been established by gas-phase measurements and by studies of model receptors in aqueous media. To first order, the interaction can be considered an electrostatic attraction between a positive charge and the quadrupole moment of the aromatic. A great deal of direct and circumstantial evidence indicates that cation-Π interactions are important in a variety of proteins that bind cationic ligands or substrates. in this context, the amino acids phenylalanine (Phe), tyrosine (Tyr), and tryptophan (Trp) can be viewed as polar, yet hydrophobic, residues., Noncovalent intermolecular forces play a major role in determining the structures of biological macromolecules and in mediating processes such as receptor-ligand interactions, enzyme-substrate binding, and antigen-antibody recognition. Although the hydrophobic [...]

A tetraphosphabenzene analog of the postulated anti-tricyclohexylene, a singlet biradical valence isomer of benzene, has been isolated. The tricyclic derivative features one-electron phosphorus-phosphorus bonds, which result from the [[Pi].sup.*]-[[Pi].sup.*] interaction […]

Molecular-scale wires have many potential applications in nanotechnology. Such wires may be assembled from molecular units by exploiting intermolecular interactions, such as metal-ligand bonds or hydrogen bonds. Benzene rings may [...]

Electron-rich species such as benzene can interact with low-lying unoccupied orbitals of metal centers, for instance, when benzene adsorbs on metal surfaces. Mercury cations and organomercurials are known to have [...]

The replacement of volatile organic solvents with ionic liquids would reduce emissions of chemicals into the environment as well as promote energy-efficient separations. One concern, however, is that solvent interactions [...]