PANI Branches onto Donor-Acceptor Copolymers: Synthesis, Characterization and Electroluminescent Properties of New 2D-Materials.

A new series of two-dimensional statistical conjugated polymers based on aniline and 9,9-dihexylfluorene as donor units and benzo- or naphtho-quinoxaline/thiadiazole derivatives as acceptor moieties, possessing PANI segments as side chains, were designed and synthesized. To investigate the effects of the perpendicular PANI branches on the properties of the main chain, the optical, electrochemical, morphological and electroluminescence properties were studied. The 2D materials tend to possess lower molecular weights and to absorb and to emit light red-shifted compared to the trunk 1D-polymers, in the yellow-red region of the visible spectrum. The 1D- and 2D-conjugated polymers present optical band gaps ranging from 2.15⁻2.55 eV, HOMO energy levels between -5.37 and -5.60 eV and LUMO energy levels between -3.02 and -3.29 eV. OLED devices based on these copolymers were fabricated. Although the performances were far from optimal due to the high turn-on voltages for which electroluminescence phenomena occur, a maximum luminescence of 55,100 cd/m² together with a current density of 65 mA/cm² at 18.5 V were recorded for a 2D-copolymer, PAFC6TBQ-PANI.

A facile and efficient four-step enantioselective synthesis of (+)-vernolepin from (+)-minimolide, the major germacranolide of Mikania minima.

Enantiomerically pure (+)-vemolepin was semi-synthesized for the first time using the synthon (6S,7R,8S)-8,14-diacetoxy-15-hydroxygermacra-1(10),4,11(13)-trien-6, 12-olide [(+)-minimolide], the major sesquiterpene lactone of the Argentinean vine Mikania minima. After performing four consecutive reactions (Cope rearrangement, two oxidations, and selective hydrolysis of the acetate groups) on the synthon (+)-minimolide, a (+)-vernolepin yield of ca. 40% was achieved, proving to be a suitable semi-synthetic strategy for the production of quantities between 0.5-1.0 g of (+)-vernolepin. The transformations described here mimetize the biogenetic pathway for the production of (+)-vernolepin in the genus Vernonia. The synthesized (+)-vernolepin, but not its precursors, shows antifungal activity similar to amphotericin B. The semi-synthesis reported here combines affordable and easily available chemical reagents with classical organic methodologies.

Electropolymerization of 3',4'-disubstituted 2,2':5',2″-terthiophene derivatives. A theoretical and photovoltaic characterization.

In the present work a series of ß-substituted thiophenes have been synthesized and their electrochemical behavior studied. The products obtained by electro-oxidation are highly dependent on the substituent, affording sometimes conducting polymers, insulating layers or soluble species. This behavior has been ascribed to specific electronic and/or steric factors. Theoretical calculations at the density functional theory level confirm the experimental findings and assess the use of reactivity descriptors for modeling complex chemical systems with specific polymerization patterns. In particular, the analysis of the polymerization sites of terthiophene derivatives using the dual descriptor for chemical reactivity and selectivity allows one to predict the specific sites able for reaction and explains correctly the observed polymerization pattern.