No 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 [ *~] , unpublished results.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.

Abstract:The synthesis of the first fullerene cryptate 7 with a sodium ion bound to a benzo[2.2.2]cryptand covalently attached to a methanofullerene[60] is described. The amphiphilic properties of 7 as well as of a variety of other covalent fullerene derivatives with polar functional groups and the ability of these compounds to form Langmuir monolayers at the air-water interface were investigated C,, and methanofullerenes, four of which are fullerene C-glycosides. The films at the water surface were characterized by their surface pressure versus molecular area isotherms, compression and expansion in a systematic study. Among these S l o d g C t t~derivatives are Diels-Alder adducts of

CommunicationsVCH Verlagsgesell.scha/t n?hH, 0-49469 Weinhelm, 1993 0935-Y648/93/0606-0458 $ 5.00+ ,2510 Ade. Mater. 1993, 5 , No. 6 c ) VCH Vei/u~sjirsclls(huft mhH. D 6'145'1 Wrmheim 1YY3 OY35-U64CijU3~0605-(i45(~ X S 0 0 1 2510