Andreas Gügel

Covalent attachment of various substituents in closest proximity to the C60-core: A broad synthetic approach to stable fullerene derivatives

Abstract α-Substttulcd o-quinodimethanes facihtate the covlcnt attachment of many attractive molecules in closest proximity to the C 60 -core Thermal isomcrizalion of various (±)-hydroxyben/ocyclobutenc esters 4. 8. 10 and 13 in the presence of C 60 provided the corresponding fullerene adducts 5(n). 7(n). 9(n). 11(n) and 12(n) in high yields Using a dumbbell shaped bis-o-quinodimethane precursor 19 . accessible from (±)-7-hydroxybenzocyclobutcne and dodccancdicarboxyhc acid dichloride. a soluble C 60 -contaimng polymer 20 was formed

High-yield reactive extraction of giant fullerenes from soot

By the common Soxhlet extraction with 1,2,4-trichlorobenzene a mere 8 mass % of virgin fullerene soot can be dissolved. The extracted soot was subjected to a reactive extraction with 5-hexadecanamido-1,3-dihydro-2-benzothiophene 2,2-dioxide(4), an ortho-quinodimethane precursor. Through an irreversible Diels–Alder cycloaddition an additional 12 mass % was solubilized. Mass spectrometry, vapour pressure osmometry and elemental analysis indicate that the soluble material consists of multiple adducts of fullerenes C 60 –C 418 .

The repetitive Diels-Alder reaction: A new approach to [60]fullerene main-chain polymers

Abstract Maindashchain polymers with incorporated [60]fullerene units are accessible by reaction of buckminsterfullerene with functionalized bis -o- quinodimethanes . Cross linking can be effectively suppressed by carefully directed admixing of a mono -o- quinodimethane . The polymer 11(n) of high molecular weight and excellent solubility, consisting of 80 [60]fullerene units on the average, is affordable. This polymer can be processed to thin amorphous films of high quality by spin coating.

Photoconductivity of an Inorganic/Organic Composite Containing Dye-Sensitized Nanocrystalline Titanium Dioxide

The photophysical properties of solid films of an inorganic/organic composite composed of dye-sensitized nanocrystalline titanium dioxide (TiO2) particles, a conjugated polymer, and a [60] fullerene derivative have been investigated. Large charge collection efficiencies of up to 10% at a field of only 10 V/μm were observed. The photoaction spectrum of the composite is interpreted in terms of three major contributions: a weak photocurrent due to the absorption of photons by the polymer, photogeneration of charges involving the fullerene, and a broad region below the onset of the polymer absorption which involves photophysical processes in the dye-loaded TiO2 nanoparticles.

Separation of C60 and C70 on polystyrene gel with toluene as mobile phase

Abstract The separation of C 60 and C 70 on polystyrene gel using toluene as mobile phase is described. A fully automated system was designed that permits the separation of 5–10 g of C 60 C 70 mixture within 24 h on a column of only 20 mm I.D. The purity of the isolated C 60 is greater than that achieved by standard procedures (separation on alumina) and the recovery is nearly 100%.

Anion radicals of [60]-fullerene and its ortho-quinodimethane adducts generated by cathodic reduction and photochemical electron transfer: an EPR and vis-near-IR study

Abstract [60]-Fullerene and its four ortho-quinodimethane adducts, one of them in oligomeric form, were reduced by three different methods, (a) by cathodic reduction, (b) in photoexcited TiO2 suspension, and (c) quenching photoexcited fullerene by triethylamine donor. The radicals obtained were mainly investigated by EPR and also characterized by vis—near-IR measurements. All three methods of generation gave two identical radical products: the primary radical A, which is a fullerene mono-anion, with EPR spectral parameters gA = 2.0000 and peak-to-peak width ppA = 0.09 mT for [60]-fullerene, ppA = 0.105 for its adducts and ppA = 0.19 mT for the fullerene oligomer. The near-IR band of A at 1077 nm for [60]-fullerene shiftd into the region of 1010 nm for its ortho-quinodimethane adducts. As a consecutive product of A, radical B was found with gB = 2.0006 and ppB = 0.07 mT for all [60]-fullerene adducts. The EPR signal of B converts to A after stopping photogeneration, resulting in a total increase of the spin susceptibility in the form of fullerene mono-anion A. The formation of fullerene di-anion or fullerene associates is considered as an alternative.

Covalent incorporation of an alkoxysilyl-substituted [60]fullerene derivative in sol-gel matrices

A [60]fullerene adduct bearing a reactive triethoxysilyl functional group has been synthesized. The high solubility of this adduct in polar solvents enables its covalent incorporation into a sol-gel silica matrix. In comparison to the conventional admixing of ‘naked’ fullerene to silica sols, this approach has the following distinct advantages: (i) even with an adduct content of up to 2 wt% (related to SiO 2 ), the reaction mixture remains homogeneous during the entire sol-gel process, and (ii) the covalently attached fullerene adduct is fixed in the silica matrix and therefore cannot migrate.

Triplet-EPR spectroscopy on the Diels-Alder adduct of C60 and 4,5-dimethoxy-o-quinodimethane in frozen solution

Pulsed-EPR spectroscopy was used to study a modified C60 molecule (1) in its photoexcited triplet state. The analysis of the triplet EPR lineshape shows a break of the high symmetry of the lowest populated triplet state of C60 due to the modification of the C60 unity. The reported temperature dependence of the spectra is influenced by relaxation effects. Lineshape simulations based on a triplet Hamiltonian including anisotropic T1/T2 relaxation were performed. The results are discussed in relation to the behaviour of pure 3C60.

Efficient charge carrier transfer from m-LPPP to C60 derivatives

Abstract The improvement of dissociation of singlet excitons by electron or hole capturing species like C 60 is essential for efficient photovoltaic cells based on conjugated systems. We investigate the charge transfer in blends of methyl-substituted ladder type poly-(paraphenylene) (m-LPPP) with new well soluble C 60 derivatives, which are characterized by sidegroups of different electronic properties (donor, acceptor nature). It is shown, that the electronic properties of the C 60 sidegroups strongly influence the efficiency of the charge transfer in these blends and hence significant different behaviours in the photocurrent and photoinduced absorption is observed.

Preparative separation of fullerene adducts by liquid chromatography on polystyrene gel

SummaryThe preparative separation of numerous fullerene adducts by liquid chromatography on polystyrene gel is described. These adducts can be resolved on a scale of 10–40 g/day on a 600×20 mm column. Both toluene and chloroform can be used as mobile phases; toluene offers better solubility for the adducts and chloroform better peak resolution.