RESUMEN
A series of thienoindolizine structural isomers have been synthesized in a one-pot, two-step procedure starting from easily accessible gem-difluoroalkene functionalized bromothiophenes. The developed method gives easy access to a range of thienoindolizine products containing thieno[3,2-g]-, thieno[3,4-g]- and thieno[2,3-g]indolizine core structures. The described synthesis strategy consists of a base mediated, transition metal free nucleophilic substitution of fluorine atoms by nitrogen containing heterocycles followed by a Pd catalyzed intramolecular cyclization. A series of 22 final product examples has been obtained with yields ranging from 29 % to 95 %. UV/Vis absorption, fluorescence spectroscopy, fluorescence lifetime measurements and cyclic voltammetry were carried out with selected final products to evaluate structural effects on photophysical and electrochemical properties. (TD)DFT and NICS calculations were performed to provide insight into the electronic properties of the four core molecular structures.
RESUMEN
Thieno[2',3',4':4,5]naphtho[1,8-cd]pyridines, S,N-doped pyrene analogs, were prepared by combination of Pd catalyzed cross-coupling reactions and acid-mediated cycloisomerization. The modular scope of the synthesis allowed for access to a variety of functionalized derivatives. The photophysical properties have been studied in detail by steady-state and femtosecond transient absorption accompanied by cyclic voltammetry and (TD)-DFT calculations. The introduction of a five-membered thiophene into the 2-azapyrene scaffold leads to redshifted emission and substantial effects on the excited state dynamics, e.g., quantum yield, lifetime, decay rates, and the ISC ability, which can be further tuned by the substitution pattern of the heterocyclic scaffold.