Yves Rubin

The Higher Fullerenes: Isolation and Characterization of C76, C84, C90, C94, and C70O, an Oxide of D5h-C70.

The toluene extract of the fluffy carbon material produced by resistive heating of graphite contains a variety of molecules larger than C60 and C70 in a total amount of 3 to 4% by weight. Repeated chromatography of this material on neutral alumina has led to the isolation of stable solid samples of C76, C84, C90, and C94. The characterization, which includes mass spectrometry, 13C nuclear magnetic resonance, electronic absorption (ultraviolet/visible) and vibrational (infrared) spectroscopy identifies these all-carbon molecules as higher fullerenes. In addition, C70O, a stable oxide, has been isolated that is structurally and electronically closely related to D5h-C70. This compound forms during the resistive heating process and probably has an oxygen atom inserted between two carbon atoms on the convex external surface of the C70 skeleton.

Sequence-specific modification of guanosine in DNA by a C60-linked deoxyoligonucleotide: Evidence for a non-singlet oxygen mechanism

Abstract A C60-linked deoxyoligonucleotide (C60-DON-1) was prepared from bromoacetate 3. This C60-oligonucleotide conjugate was hybridized to a complementary single-stranded DNA. This system reacted with light and oxygen to damage only guanosines in the single-stranded region which are closest to C60. The damage did not involve 1O2 as the active species but rather resulted from a single electron-transfer mechanism between guanosine and 3C60, as shown by comparison experiments with eosin-attached DON-1 and by the use of singlet oxygen quenchers.

All-Carbon Molecules: Evidence for the Generation of Cyclo[18]carbon from a Stable Organic Precursor

The unambiguous structural characterization of a single-sized all-carbon molecule requires its chemical synthesis. For cyclo[18]carbon, ab initio calculations predict a relatively stable, cyclic D9h ground state geometry with alternating C-C (1.36 angstroms) and C≡C (1.20 angstroms) bonds. The synthesis and x-ray crystal structure of a direct precursor to C18 are described. The analysis of laser flash heating experiments on this precursor by time-of-flight mass spectroscopy shows a sequence of retro-Diels-Alder reactions leading to C18 as the predominant fragmentation pattern. Structural evidence is provided for the generation of an all-carbon molecule from a well-characterized organic precursor.

Self-assembling fullerenes for improved bulk-heterojunction photovoltaic devices.

The fullerene adducts 1a and 1b, whose molecular shapes either promote or hinder the formation of 1-D stacks, have been examined for their potential to form 1-D wire-like domains in bulk-heterojunction organic solar cells. The photovoltaic efficiency of solar cells based on blends of the stacking fullerene 1a with regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) is greatly enhanced compared to nonstacking model fullerene 1b.

Ring Opening Reactions of Fullerenes: Designed Approaches to Endohedral Metal Complexes

Endohedral complexes of fullerenes are some of the most attractive targets of research in fullerene chemistry and physics. An overview of the field is provided with a focus on endohedral complexes incorporating lanthanide metals, noble gases, and atomic nitrogen. Although the present approaches have been successful in providing the first members of this class of fullerenes, their preparation is still difficult and limited to a few elements. It is argued that ring opening reactions within fullerene shells have the potential to provide easy access to endohedral metallofullerenes on a large scale, including those with transition metals which are potentially the most interesting elements in regard to their materials properties. Current ring opening reactions within fullerene shells are reviewed. An outlook on ring opening reactions leading to effectively large apertures is presented.

Formation of an Effective Opening within the Fullerene Core of C60 by an Unusual Reaction Sequence

A large hole in a fullerene: The addition of dioxygen to the highly reactive 1,4-diaminobutadiene moiety of 1, formed from the reaction of C(60) with a rigid diazidobutadiene, results in the very efficient formation of an open fullerene (see the space-filling model) with the largest orifice created so far on a fullerene. The opening may be large enough to allow the smallest atoms, molecules, or ions to pass through.

Acetylenic Cyclophanes as Fullerene Precursors: Formation of C60H6 and C60 by Laser Desorption Mass Spectrometry of C60H6(CO)12

A logical precursor of macrocycle C60 H6 , cyclophane C60 H6 (CO)12 (1) represents a building block in a possible total synthesis of C60 . In Fourier transform ion cyclotron resonance laser desorption mass spectroscopic experiments in the negative-ion mode, 1 fragments to C60 H6 (2) under successive loss of CO. Further loss of six H atoms and rearrangement gives C60 ions with a fullerenic structure.

Reversible switching of molecular second-order nonlinear optical polarizability through proton-transfer

Abstract Reversible switching of the molecular second-order nonlinear optical (NLO) polarizability has been achieved by means of proton-transfer. The NLO molecule is an azafulleroid, based on a homoconjugated fullerene moiety as the acceptor as a new attractive building block for organic NLO materials. The electron-donor (proton–acceptor) group is the dimethylamino group. The NLO response was dramatically reduced upon protonation, and completely restored after deprotonation. Analogies and differences between this proton-transfer based switching and earlier reported electron-transfer based switching are discussed, along with the implications for third-order NLO materials based on a composite material comprised of a second-order NLO molecule and a photoaddressable proton donor.

Atomic Force Microscope Studies of Fullerene Films: Highly Stable C60 fcc (311) Free Surfaces

Atomic force microscopy and x-ray diffractometry were used to study 1500 �-thick films of pure C60 grown by sublimation in ultrahigh vacuum onto a CaF2 (111) substrate. Topographs of the films did not reveal the expected close-packed structures, but they showed instead large regions that correspond to a face-centered cubic (311) surface and distortions of this surface. The open (311) structure may have a relatively low free energy because the low packing density contributes to a high entropy of the exposed surface.

1,3,5 / 2,4,6-Differentiated hexaalkynylbenzenes: absorption and fluorescence properties of a D3h-symmetric donor-substituted system

Abstract The synthesis of 1,3,5 / 2,4,6 differentially functionalized hexaethynylbenzene derivatives is described. Interesting solvatochromic behavior was observed for 9b in the absorption and emission spectra. A twisted intramolecular charge transfer (TICT) state in polar solvents appears to be involved.