Synthesis, H-1 and C-13 NMR assignment and electrochemical properties of novel thiophene-thiazolothiazole oligomers and polymers

International audienc

A three-step synthetic approach to asymmetrically functionalized 4H-cyclopenta[2,1-b3,4-b′]dithiophenes

A convenient and efficient three-step route toward both symmetrically and asymmetrically functionalized 4H-cyclopenta[2,1-b:3,4-b′]dithiophenes has been developed. Using this method a broad collection of functionalized bridged bithiophenes can smoothly be accessed. Starting from 3-bromo-2,2′- bithiophene, prepared by Kumada coupling of 2-thienylmagnesium bromide with 2,3-dibromothiophene under Pd(dppf)Cl2 catalysis, lithiation and subsequent reaction with dialkyl ketones afforded (a)symmetrically dialkylated tertiary alcohol derivatives. By means of final Friedel-Crafts dehydration cyclization in sulfuric acid medium, these derivatives were converted to 4,4-dialkyl-4H-cyclopenta[2,1-b:3,4-b′]dithiophenes. Upon replacement of the dialkyl ketone reagent by ethyl levulinate, an ester-functionalized 4H-cyclopenta[2,1-b:3,4-b′]dithiophene was prepared, representing an attractive precursor for variously functionalized cyclopentadithiophene compounds.</p

Combined experimental-theoretical NMR study on 2,5-bis(5-aryl-3- hexylthiophen-2-yl)-thiazolo[5,4-d]thiazole derivatives for printable electronics

Four 2,5-bis(5-aryl-3-hexylthiophen-2-yl)thiazolo[5,4-d]thiazole derivatives have been synthesized and thoroughly characterized. The extended aromatic core of the molecules was designed to enhance the charge transport characteristics, and solubilizing hexyl side chains were introduced on the thiophene subunits to enable possible integration of these semiconducting small molecules in printable electronics. Complete elucidation of the chemical structures by detailed one-dimensional/two-dimensional NMR spectroscopy is described, providing interesting input for chemical shift prediction software as well, because limited experimental data on these types of compounds are currently available. Furthermore, theoretical calculations have assisted experimental observations-giving support for the chemical shift assignment and providing a springboard for future screening and predictions-demonstrating the benefits of a coordinated theoretical-experimental approach

Reaction of 4H-cyclopenta[2,1-b:3,4-b′]dithiophenes with NBS - A route toward 2H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6(4H)-diones

In this paper we present a detailed study of the bromination reaction of cyclopentadithiophene (CPDT) derivatives, by means of NBS, giving access to either 2,6-dibromo-4H-cyclopenta[2,1-b:3,4-b′]dithiophenes or 2H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6(4H)-diones (CPDT-2,6-diones). The CPDT-2,6-diones are fully characterized, including an X-ray single crystal structure of one of the representative materials. A mechanism leading to the formation of the latter, which arise as a new class of compounds within the CPDT family, is proposed and is supported by Gibbs free energy calculations. The influence of the solvent, reaction time, and the number of equivalents of NBS on the selectivity of the reaction is discussed