Alkyl, aryl, and alkynyl as well as heteroatom derivatives of sym-pentasubstituted corannulenes have been synthesized from sym-pentachlorocorannulene. These units form potential building blocks for future work on superstructures based on corannulene. Absorption/emission properties follow expected trends from the parent 1. sym-Pentasubstitution gives rise to variations in the chemical dynamics of bowl inversion. van der Waals attraction is cited to explain an anomalously high barrier to bowl inversion in 10.

We have investigated novel model systems for photo-induced intramolecular electron-transfer processes. The molecules presented here are of the structure T5–C60 or A–T5–C60, i.e., fullerene C60 is used as acceptor, and quinquethiophene (T5) or anthracene (A) can act as a donor. From theoretical considerations we learn that a charge transfer should occur after excitation of the quinquethiophene or anthracene part, whereby an energy transfer is still not excluded. Optical absorption spectra show the electronic independence of the fullerene from the substituent and hint at isolated molecules in solutions. After laser-flash excitation of frozen solutions of the molecules, we used pulsed electron spin resonance (ESR) to detect the radical signals of the charge-separated state. In both the diad and the triad, we observe at low temperatures a free induction decay (FID) and a broad spin-echo spectrum with the same lifetime of 1–2 μs. The signals can be assigned to the C60− anion (FID) and the T5+cation (spin echo) by the g factor and the linewidth.

Donor-acceptor substituted α -oligothiophenes with anthracene as donor and C 60 -fullerene as acceptor were synthesized via [4+2]-cycloaddition of C 60 -fullerene with the heteroanalogous o -quinodimethanes of anthryloligothiophenes. The o -quinodimethanes were generated in situ by cheletropic extrusion of SO 2 of the corresponding cyclic sulfones. The oligothienosulfones have been prepared successively starting from 4,6-dihydrothieno[3,4-b ]thiophene 5,5-dioxide via brominations and metal-catalyzed Suzuki coupling reactions. Several oligothienylfullerenes without anthracene as terminal group have been synthesized in the same way."Supermolecules" which consist of various molecular subunits play an important role for studying photochemical and photophysical processes. The photosynthesis is one example in nature, where the transformation of light energy into chemical energy occurs in a "supermolecule". The synthesis of model compounds and investigations of their optical and electrical properties for possible applications as devices for information transfer and storage at a molecular level, is a great challenge for chemists and physicists alike. In the present publication syntheses of model compounds consisting of subunits for a photoinduced intramolecular electron transfer are described.In terminally donor-acceptor substituted conjugated polyenes a nearly quantitative intramolecular energy transfer from the excited donor to the acceptor could be shown. 2 An interruption of this energy transfer through insertion of a saturated spacer fails, which can be explained by Förster energy transfer. 3 Substitution of the polyene chain by oligothiophenes in these energy transfer systems led to an improvement of the selectivity of excitation but most importantly to a drastic increase of quantum yields. 4a An interruption of the energy transfer in these molecules by introduction of saturated spacers into the oligothiophene chain also fails. 4bAs a result of these investigations, an interruption or switching of energy transfer in this type of compounds seems to be not possible. We have therefore developed and investigated similar compounds for an intramolecular electron transfer. The described model compounds for an energy transfer had to be varied in such a way, that they are suitable for an intramolecular electron transfer. For that reason the terminal porphyrin group was substituted by a pyridinium group as acceptor. 5 A photoexcited electron transfer in these compounds could be proved by transient absorption of the anthryl radical cation. 5b The proof of a pyridine radical, however, fails. 5bIt was therefore the aim of this work to synthesize terminally donor-acceptor substituted oligothiophenes with anthracene as donor and C 60 -fullerene as acceptor. In case of an intramolecular electron transfer the experimental proof of fullerene radical anion besides the anthryl radical cation should be possible.Fullerenes have a moderate electron affinity, which has been shown by theoretical studies 6a as well as by electrochemical mea...

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