James P. Parakka

Furan- and pyrrole-containing analogs of α-quinquethiophene: spectroscopic and electrochemical properties

Abstract A series of pentacyclic analogs of α-quinquethiophene containing one or two furan or pyrrole units has been synthesized. The synthesis is based on the cyanide-catalyzed Stetter reaction, providing the ketonic precursors to the pentacycles. Spectral and electrochemical investigations show that the redox-stable mixed pentacycles display hypsochromic shifts in their absorption maxima, as well as a greater ease of oxidation, in comparison to α-quinquethiophene.

Synthesis of α,ω-long chain disubstituted sexithiophenes

Abstract The synthesis and electrochemistry of three new symmetrical α,ω-disubstituted sexithiophene derivatives 1–3 substituted by heptadecyl, hexadecyloxymethyl, and trans -heptadecenyl groups is described.

GEOMETRICALLY CONSTRAINED THIOPHENE-PYRROLE OLIGOMERS

Abstract A series of novel mixed thiophene-pyrrole penta- and heptacyclic oligomers has been prepared in which two pyrrole nitrogens of each oligomer are connected by a polymethylene bridge. The steric constraints produced in these bridged compounds are reflected in their spectroscopic and electrochemical properties.

Understanding of molecular assembly with scanning tunneling microscopy at solid/liquid interfaces

Abstract Scanning tunneling microscopy (STM) was used to resolve molecular packing structures of mixed thiophene-N-alkylpyrrole oligomeric molecules at the solid/liquid interfaces. We have systematically synthesized several mixed thiophene-pyrrole oligomers to understand the nature of grains, shapes, and crystalline orientations. The resulting STM images were compared with the structure generated by MM3 molecular modeling simulation. The basal plane of highly oriented pyrolytic graphite (HOPG) surface was used to deposit the molecules.

The oxidation of 3-aminocarbazole and its N-ethyl derivative

Abstract Chemical oxidation of 3-aminocarbazole by peroxydisulfate gives only a low yield of an insulating polymer under standard conditions employed for the preparation of polyaniline from aniline or p -aminodiphenylamine. Similar oxidation of N -ethyl-3-aminocarbazole gives no appreciable polymer, but a major ( c . 40%) crystalline oxidized dimer assigned the structure of a bis(indolo)phenoxazone. In contrast, electrochemical oxidation of 3-aminocarbazole affords a reversibly oxidizable film with an oxidation potential of c . 0.29 V.