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Density functional theory is used for studying the structure and stability of a set of [(CF).sub.60] isomers. The relative energy per CF unit of the most stable isomer to graphite fluoride [(CF).sub.n] is 3.7 kcal/mol, which is smaller than that of [C.sub.60] fullerene per carbon to graphite.

A synthetic strategy was developed to perform synthesis of porphyrins containing between one and four stereogenic centers, such that their molecular weights vary only as a result of methyl groups which give the chiral forms. The self-assembly and chiral structure of the aggregates of porphyrin molecules are observed to be significantly influenced by the number of stereogenic centers.

Chiral domains are formed at liquid/solid interface by achiral diarylethenes due to surface-induced atropoisomerism. Molecular dynamics have shown that these dimers of diarylethenes are chiral dimers, rather than prochiral dimers.

A new process combining double-miniemulsion/emulsion polymerization with Sol-gel technology to synthesize monodispersed hydrophilic magnetic nanospheres that exhibit a much higher saturation magnetization due to a large fraction of magnetite is developed. The superparamagnetic properties of nanospheres would allow them to serve as ideal candidates for biomedical applications such as nucleic acid extraction, cancer diagnosis and treatment, biosensors, and drug delivery.

The structures and energies of isolobal (CH)n and (BCO)n polyhedral species are computed at the B3LYP density functional theory level. Unlike the (CH)n cages, the most stable (BCO)n polyhedra (n greater than equal to 10) prefer structures with the largest numbers of three-membered rings.

A synthetic strategy was developed for the preparation of porphyrins containing between one and four stereogenic centers, such that their molecular weights vary only as a result of methyl groups which give the chiral forms. The low-dimensional nanoscale aggregates of these compounds reveal the profound effects of this varying molecular chirality on their supramolecular structure and optical activity. The number of stereogenic centers influences significantly the self-assembly and chiral structure of the aggregates of porphyrin molecules described here. A scanning tunneling microscopy study of monolayers on graphite shows that the degree of structural chirality with respect to the surface increases almost linearly with the number of stereogenic centers, and only one handedness is formed in the monolayers, whereas the achiral compound forms a mixture of mirror-image domains at the surface. In solution, four hydrogen bonds induce the formation of an H-aggregate, and circular dichroism measurements and theoretical studies indicate that the compounds self-assemble into helical structures. Both the chirality and stability of the aggregates depend critically on the number of stereocenters. The chiral porphyrin derivatives gelate methylcyclohexane at concentrations dependent on the number and position of chiral groups at the periphery of the aromatic core, reflecting the different aggregation forces of the molecules in solution. Increasing the number of stereogenic centers requires more material to immobilize the solvent, in all likelihood because of the greater solubility of the porphyrins. The vibrational circular dichroism spectra of the gels show that all compounds have a chiral environment around the amide bonds, confirming the helical model proposed by calculations. The morphologies of the xerogels (studied by scanning electron microscopy and scanning force microscopy) are similar, although more fibrous features are present in the molecules with fewer stereogenic centers. Importantly, the presence of only one stereogenic center, bearing a methyl group as the desymmetrizing ligand, in a molecule of considerable molecular weight is enough to induce singlehanded chirality in both the one and two-dimensional supramolecular self-assembled structures. [ABSTRACT FROM AUTHOR]

The article presents a process to obtain monodispersed, nanoscale and superparamagnetic magnetite or polystyrene spheres. By uniquely combining modified miniemulsion/emulsion polymerization and the sol-gel technique, the surfaces of monodispersed nanospheres functionalized to be hydrophilic through silica coating. Aside from also serving as a buffer, the silica coating protected the magnetite nanoparticles from dissolving in the application environments.

The structure and stability of a set of (CF)60 isomers have been computed at the B3LYP/6-31G-(d) density functional theory level. The most stable isomer (6, F4@C60F56) has tube-like structure with four endo C-F bonds and fused five-membered rings at the end of the tube, while the reported most stable cage structure (2, F8@C60F52) with eight endo C-F bonds is higher in energy by 22.6 kcal/mol. This is in contrast to the isolated pentagon rule for the stability of fullerenes. The mean bond dissociation energy of 6 is larger than those of the experimental known C60F36, C60F48, and graphite fluoride. The relative energy per CF unit of 6 to graphite fluoride (CF)n is 3.7 kcal/mol, which is smaller than that of C60 fullerene per carbon to graphite (about 9-10 kcal/mol). [ABSTRACT FROM AUTHOR]

An oligo(p-phenylenevinylene) (OPV)-substituted hexaarylbenzene has been synthesized and fully characterized. Recycling gel permeation chromatography appeared to be a powerful technique to obtain the OPV molecules in a very pure form. X-ray analysis and polarization optical microscopy revealed that the OPV molecule is plastic crystalline at room temperature with an ordered columnar superstructure. In apolar solvents, the molecules self-assemble via a highly cooperative fashion into right-handed chiral superstructures, which are stable even at high temperatures and low concentration. Atomic force microscopy revealed right-handed fibers with a diameter of 6 nm, indicating π-stacked aggregates; on a silicon oxide substrate, supercoiled chiral structures were observed. STM studies on a liquid-solid interface showed that the star-shaped OPV molecule forms an organized monolayer having a chiral hexagonal lattice. [ABSTRACT FROM AUTHOR]