OPTICAL-DETECTION OF THE LOWEST TRIPLET EXCITED-STATE OF OLIGOTHIOPHENES AND ANTHRYLOLIGOTHIOPHENES

The lowest excited triplet state of all-trans oligothiophenes T-n (n = 2...5), 9-anthryl-oligothiophenes A-T-n (n = 1...3) and 9-anthryl-bit hienylpyridine A-T-2-Py in the crystalline phase has been investigated by delayed fluorescence detected high resolution photoexcitation spec troscopy. For the T-n molecules a 1/n dependence of the triplet energi es is observed. On the other hand, the triplet stares of the anthracen e substituted compounds A-T-n and A-T-2-Py do not differ much in energ y. Their spectra reflect predominant anthracene character, independent of the chain length.