Capturing the antiaromatic (#6094) C68 carbon cage in the radio-frequency furnace

Although all fullerenes do not satisfy the classical aromaticity condition, as a result of their nonplanar nature, they experience effective stabilization due to extensive cyclic π-electron delocalization and exhibit pronounced "spherical aromaticity". This feature has raised the question of the opposite phenomenon, that is, the existence of antiaromatic carbon cages. Here the first experimental evidence of the existence of antiaromatic fullerenes is reported. The elusive (#6094)C(68) was effectively captured as C(68)Cl(8) by in situ chlorination in the gas phase during radio-frequency synthesis. The chlorinated cage was separated by means of multistage HPLC, and its connectivity unambiguously determined by single-crystal X-ray analysis. Halogen-stripped pristine (#6094)C(68) was monitored by mass spectrometry of the chlorinated C(68)Cl(8) cage. Quantum chemical calculations reveal the highly antiaromatic character of (#6094)C(68), in accordance with all geometric, energetic, and magnetic criteria of aromaticity. Chlorine addition leads to substantial stabilization of the cage owing to aromatization in the resulting C(68)Cl(8), which explains its high abundance in the primary fullerene soot. This work provides new insights into the process of fullerene formation and better understanding of aromaticity phenomena in general.     

Preparation of α-oxygenated ketones by the dioxygenation of alkenyl boronic acids

Two in two: Dioxygenation of alkenyl boronic acids has been achieved with N-hydroxyphthalimide. The two-step process involves etherification of an alkenyl boronic acid with N-hydroxyphthalimide followed by a [3,3] rearrangement. The dioxygenated product can then be hydrolyzed to form either the corresponding α-hydroxy ketone or the α-benzoyloxy ketone.     

Large-area organization of pNIPAM-coated nanostars as SERS platforms for polycyclic aromatic hydrocarbons sensing in gas phase

Here, a new surface enhanced Raman spectroscopy (SERS) platform suitable for gas phase sensing based on the extended organization of poly-N-isopropylacrylamide (pNIPAM)-coated nanostars over large areas is presented. This system yields high and homogeneous SERS intensities, and simultaneously traps organic chemical agents as pollutants from the gas phase. pNIPAM-coated gold nanostars were organized into parallel linear arrays. The optical properties of the fabricated substrates are investigated, and applicability for advanced sensing is demonstrated through the detection in the gas phase of pyrene traces, a well-known polyaromatic hydrocarbon.     

Cellular uptake of a fluorescent vanadyl sulfonylcalix[4]arene

Vanadyl bearing calix[4]arene ligands have undergone evaluation against several cell lines, and show varying degrees of toxicity. For vanadyl complexed to a sulfonylcalix[4]arene, monitoring of the strong blue fluorescence revealed slow uptake kinetics. The complex is exclusively found in the cytoplasm of the cells and uptake is not due to active endocytotic mechanisms.     

Multistep scattering in the 160 MeV208Pb(α, α′) reaction

New experimental data has been obtained for the²⁰⁸Pb(α, α′) reaction induced by 160 MeV alpha particles, for inelastic scattering to forward angles. We use these data to investigate the applicability of the multistep scattering theory of Feshbach, Kerman, and Koonin for describing this reaction. The mechanism we study, following the work of Gadioli et al. [1], is of the incident alpha particle remaining intact throughout the scattering process, exciting nucleon particle-hole pairs through multistep process. We conclude that this mechanism, combined with compound nucleus decay at low emission energies, can account for much of the observed data. However, there are indications that other processes also contribute at energies above the compound nucleus emission regime, and we outline future theoretical analyses that are needed.     

Magnetic and crystallographic properties of several C1b type Heusler compounds

The compounds NiMnSb and IrMnGa were studied by neutron diffraction. The former compound has the cubic Cl_b crystal structure with an ideal site occupancy of the atoms. Below 750 K the compound is ferromagnetically ordered. The magnetic moments are confined to the Mn atoms (4.0μ_B/Mn). The compound IrMnGa has a crystal structure related to the C1_b type but characterized by a high atomic disorder. Results of magnetic measurements are presented for NiMnSb, CuMnSb and IrMnGa. The results of these measurements are in accord with the occurrence of high atomic ordering in the first two compounds but point to high atomic disorder in the latter material. Total energies and Mn moments derived from band-structure calculations are presented for three different types of site occupancies in NiMnSb. The lowest total energy as well as the correct value for the Mn moment correspond to the site occupancy found by means of the neutron diffraction.     

From color glass to color dipoles in high-energy onium–onium scattering

Within the Color Glass formalism, we construct the wavefunction of a high energy onium in the BFKL and large-N_c approximations, and demonstrate the equivalence with the corresponding result in the Color Dipole picture. We propose a simple factorization formula for the elastic scattering between two non-saturated “color glasses” in the center-of-mass frame. This is valid up to energies which are high enough to allow for a study of the onset of unitarization via multiple pomeron exchanges. When applied to the high energy onium–onium scattering, this formula reduces to the Glauber-like scattering between two systems of dipoles, in complete agreement with the dipole picture.