Reaction of Buckminsterfullerene with ortho‐Quinodimethane: a New Access to Stable C₆₀ Derivatives

Abstract

0.041 0.W 0.043 ) o.054 0.012 0.046 ) -0.012 1+ Fig. 4 The experimentally determined spin-density distribution of cation radical I'+ (top) and anion radical 1.- (bottom). The radii of the circles are proportional to the spin density; unfilled circles represent negative spin densities.vides a new alternative to the description of the doping behavior of polythiophenes and conducting polymers in general. Thus, the formation of corresponding dimeric species complementary to polarons and bipolarons, can now be considered as the first mechanistic step during doping. This fact easily explains the observation that the ESR activity of polarons in conducting and cation radicals in longer o l i g~m e r s [~"~ is detected only at unexpectedly low levels of doping, in the first case, or not at all, in the second. Nevertheless, the findings described here d o not necessarily disagree with the existence of polaronic and bipolaronic bands in highly doped conjugated polymers. In addition, the anionic redox states of 1 are the first models for negatively charged defects in thiophene chains. The n-doping of polythiophene is possible otherwise only under extreme condit i o n~. [ *~] , unpublished results. In the X-ray structures of sexithiophene I and the related precursor 3'-dodecyl-2,2:5',2'-terthiophene both have the same torsion angle with a value of 10.8 and 11.0". respectively. for the thiophene rings which are sterically hindered by the alkyl side chains. In the case of I not all of the bond lengths and angles have yet been obtained with satisfactory precision because of the small size of the crystals examined and the resulting weak reflections. For this reason the X-ray structure is not discussed further here.[XI Oxidations of I were measured in dichloromethane, reductions in tetrahydrofuran a t a concentration of 5 x mol L-' with tetrabutylammonium hexdfluorophoSphate (0.1 M) as the supporting electrolyte. The working electrode was a platinum disk 1 mm in diameter, the counterelectrode a platinum wire. and the reference electrode a Ag/AgCl electrode which was calibrated with ferrocene after each measurement. 260. 191 We measured the oxidation potential of polythiophene under identical [lo] J. ] Since the absorption bands of the dimer (I):+ are blue-shifted relative to those of I " . we suspect that another charge-transfer absorption exists in the near-IR region ( E < 0.6 eV), which cannot be observed because of the solvent absorptions in this region. [22] Since ENDOR measurements were not possible and selectively deuterated compounds not available, the spin-density distribution and hyperfine coupling constants were calculated with an INDO program (M. Plato. E. Trknkle. W. Lubitz, F. Lendzian, K. Mobius, Chem. P l r~s . 1986. 107, 185 ~ 196). Assignment ofthe fitted hyperfine values was possible by comparison to those obtained by theoretical calculations. A detailed presentation of the ESR results will be published in due course (D. Huttenlocher. A. Grupp, P. Bluerle, M. Mehring, unpublished results).[23] R.

Efficient Preparation of Monoadducts of [60]Fullerene and Anthracenes by Solution Chemistry and Their Thermolytic Decomposition in the Solid State

“…[15,16] The FAB-mass spectra of the monoadducts all showed only a weak signal due to the molecular ion, indicating the efficient fragmentation of [4 2]-cycloadducts of 1, as also noted elsewhere. [19,22] The positions of the characteristic and well separated signals in the 1 H NMR spectra of the aromatic hydrogen atoms (d 7.4 ± 7.8), the bridgehead (d 5.5 ± 6) and methyl group hydrogen atoms (d 1.42 for rac-9, 2.3 ± 2.9 otherwise) were shifted by 0.2 ± 0.4 ppm to lower field (by the fullerene), when compared to the spectra of other 9,10-dihydro-9,10-ethanoanthracenes.…”

“…[17] Several laboratories have expanded on Wudls exploratory work [3a,b] on organic cycloaddition reactions with [60]fullerene (1) and have exploited the dienophilic reactivity of this electrophilic, [18] polyunsaturated carbon molecule in [4 2]-cycloaddition reactions. [4,5,8,10,15,16,19,20] Cyclic dienes, anthracenes and other polycyclic aromatics proved to represent useful addends in mono-and multiple cycloaddition processes with C 60 . [10b,c, 19, 20] Without exception [4 2]-cycloaddition reactions have been found to occur at one of the 30 equivalent (6,6)-bonds of 1.…”

Synthesis and Metal Ion Complexation Studies of [60]Fullerene Derivatives of Tetrathiafulvalene Crown Ethers

“…The dienes are generated in situ by iodine-induced 1,4-elimination of Br 2 from the corresponding bis(bromomethyl)TTF derivatives 5a-c, using either KI in the presence Scheme 1. Synthetic procedures for compounds 3a (n ϭ 0), 3b (n ϭ 3), and 3c (n ϭ 5) of 18-crown-6 as the phase transfer reagent, developed by Müllen et al, [10] or Bu 4 NI as described by Diederich et al [3] We compared these two different reagents for the synthesis of 3a. The yields of the Diels-Alder products were comparable.…”

Electronic properties of charged fullerenes characterized by EPR and Vis-NIR spectroscopy

“…In order to find out the specific influence of organic substituents on the electronic characteristics of C 60 we have chosen the Diels-Alder monoadduct of 0-xylylenes 1 [28] with C 60 [14b, 14c] (Fig. 4).…”