Narrow Results

The viability of facile oxidation and cycloaddition of fullerene C₆₀ with ruthenium tetraoxide (RuO₄) has been confirmed by means of density functional theory calculations. Owing to the powerful capability of RuO₄ as an oxidant, the addition process has been found to occur readily in the absence of organic base as a catalyst, which is in remarkable contrast to the base-catalyzed osmylation of C₆₀ with osmium tetraoxide (OsO₄). Significantly, we have found that boron can be employed as an effective promoter for enhancing the cycloaddition and complexation of transition metal oxides, e.g. RuO₄ and OsO₄, with C₆₀, in which the base is not needed at all. Our results suggest that boron doping into the lattice of fullerenes and carbon nanotubes would provide a well-defined approach for anchoring transition metal oxides.

The mechanism of cycloaddition reaction between ethylene and the Si dimer on Si(100) is discussed from our recent experimental results using high-resolution electron energy loss spectroscopy and valence photoelectron spectroscopy at ~50 K. The weakly adsorbed π-complex state is identified as a precursor for di-σ bond formation and the activation barrier is roughly estimated to be ~0.2 eV. A different reaction route may exist since a di-σ species is also observed at low temperature. Using cycloaddition reaction, unsaturated organic molecules are chemically attached to the dimer on Si(100), and the adsorbed species are relatively stable. Thus, scanning tunneling spectroscopy (STS) measurements of a single adsorbed molecule can be carried out at room temperature. We report the STS results of 2-butyne adsorbed on Si(100).

A symmetrical β,β′-tetrasulfoleno-corrole is described here as an excellent and selective precursor to highly reactive corrole-β,β′-dienes, opening a selective route to specific β,β′-functionalized corroles via cycloaddition chemistry. The β,β′-tetrasulfoleno-corrole was prepared by acid catalyzed condensation of tolylaldehyde and a β,β′-disulfoleno-dipyrromethane, which was obtained by standard procedures. Crystalline deep green β,β′-tetrasulfoleno-corrole was isolated in 8–10% yield. Thermolysis of the corrole at 140 °C and in presence of an excess of C₆₀-fullerene gave a difullereno-corrole selectively (> 80% yield). The spectroscopic data indicated attachment of the two fullerene units at the "western," directly connected pyrrole rings. The tetrasulfoleno-corrole thus showed a remarkable preference for loss of sulphur dioxide and subsequent cycloaddition at the two "western" rings. In the difullereno-adduct, two sulfolene groups in the remaining "eastern" β,β″-disulfoleno-pyrroles still are available as "caged dienes" for further thermal diene formation, and attachment of additional groups via [4 + 2]-cycloaddition reactions.

Click chemistry has become a very popular and efficient concept for synthetic chemists for the construction of new molecules. Among the click chemistry approaches known to date, it is undoubted that the copper-catalyzed alkyne-azide 1,3-dipolar cycloaddition (CuAAC) has played a key role. Such reactions in general offer virtually unlimited possibilities to prepare new molecules for $e.g$. materials science applications. As such, the synthesis of porphyrin–fullerene conjugates obtained via CuAAC are summarized within the present review article.

In the age when the miniaturization trend that has driven the semiconductor industry is reaching its limits, organic modification of semiconductors is emerging as a field that could give much-needed impetus. We review the current state of understanding of the functionalization of C(100), Si(100), and Ge(100) surfaces through chemisorption of alkenes and alkynes, focusing on adsorbate structural control. While reactions on C(100) show most of the properties expected for concerted cycloaddition reactions such as [2+2] and [4+2] (Diels–Alder) processes, reactions on Si(100) present a wide range of variant behavior, including in some cases the prominence of non-cycloaddition products. More general stepwise free-radical addition processes are seen to provide a better description of reactions on Si(100), their prominence being attributed to either the non-existence or ineffectiveness of π bonding within surface silicon dimers. The investigations of these systems provide not only insight into driving mechanisms for chemisorption but also motivation for the development of new techniques of organic functionalization on semiconductors.