Photochemistry and Photophysics of Thienocarbazoles¶

Abstract

Two methylated thienocarbazoles and two of their synthetic nitro-precursors have been examined by absorption, luminescence, laser flash photolysis and photoacoustic techniques. Their spectroscopic and photophysical characterization involves fluorescence spectra, fluorescence quantum yields and lifetimes, and phosphorescence spectra and phosphorescence lifetimes for all the compounds. Triplet-singlet difference absorption spectra, triplet molar absorption coefficients, triplet lifetimes, intersystem crossing S1 --> T1 and singlet molecular oxygen yields were obtained for the thienocarbazoles. In the case of the thienocarbazoles it was found that the lowest-lying singlet and triplet excited states, S1 and T1, are of pi,pi* origin, whereas for their precursors S1 is n,pi*, and T1 is pi,pi*. In both thienocarbazoles it appears that the thianaphthene ring dictates the S1 --> T1 yield, albeit there is less predominance of that ring in the triplet state of the linear thienocarbazole, which leads to a decrease in the observed phiT value.

Palladium-catalyzed amination and cyclization to heteroannellated indoles and carbazoles

“…The latter were obtained by palladium-catalyzed amination 5,7 performed on both rings of the benzo [b]thiophene moiety and were submitted to palladium-catalyzed intramolecular cyclization under Sakamoto's 6 or Jeffery's 8 conditions as required. The tetracyclic compounds prepared may have biological activity or/and may be used as biomarkers due to their fluorescence already studied by us 9 and possible DNA intercalation which is in study. The presence of methoxy groups in this type of compounds showed to be important for biological activity, the 9-methoxyellipticine 10 being much more active than the ellipticine itself.…”

Regio- and stereoselective synthesis of dispirooxindole-pyrrolocarbazole hybrids via 1,3-dipolar cycloaddition reactions: Cytotoxic activity and SAR studies

“…For example, glybomine B and C showed significant antitumor-promoting activity, which was confirmed by the inhibiting effect of these alkaloids in conjunction with the tumor promoter 12-o-tetradecanoylphorbol-13-acetate (TPA) [32], while heptaphylline and 7-methoxyheptaphylline displayed strong cytotoxicity against NCI-H187 and KB cell lines [33]. In addition carbazole arrests the tumor cell cycle at the M phase and induces apoptotic cell death by increasing expression of p-53 and promoting bcl-2 phosphorylation [34,35] (Figure 1).…”

Energy transfer from fluorene‐based conjugated polyelectrolytes to on‐chain and self‐assembled porphyrin units

“…The 8.60 ns component is assigned to emission from the DPP units, in agreement with the values published for PPV and PF doped with porphyrins. 34,63 TPPS Self-Assembled with PBS-PFP via Calcium (II) Binding With PBS-PFP-DPP, the porphyrin is expected to be collinear with the PF units. We will now discuss the second PFporphyrin energy transfer system, in which the anionic porphyrin meso-tetrakisphenylporphyrinsulfonate (TPPS) is selfassembled by calcium(II) ions to the homopolymer PBS-PFP (Scheme 2) and the PF and porphyrin units are expected to be cofacial.…”