Abstract

--- - New pi-conjugated Schiff base oligomers (o-AZdAN1Th and o-AZdAN2Th) based on a binaphthalene core and containing thiophene or bithiophene units in their backbone were synthesized from the reaction between [1,1 '-binaphthalene]-4,4 '-diamine with thiophene-2,5-dicarbaldehyde and [2,2 '-bithiophene]-5,5 '-dicarbaldehyde by a high-temperature polycondensation method. These new materials were slightly soluble in non-protic polar solvents, such as chloroform and dichloromethane. From GPC analysis of the CHCl3-soluble fraction, o-AZdAN1Th was found to be a tetramer, whereas o-AZdAN2Th was a trimer with 1.4 kDa and 1.3 kDa average molecular weight (Mn), respectively. Both samples exhibited high thermal stability with T5% values of 452 degrees C and 456 degrees C and relatively high Tg values of 346 degrees C and 384 degrees C, for o-AZdAN1Th and o-AZdAN2Th, respectively. The samples showed absorptions in the deep-blue (o-AZdAN1Th) and blue (o-AZdAN2Th) regions of the visible spectrum, and emission responses at 387 nm and 447 nm, respectively, with moderate Stokes shifts (77-95 nm). Their optical and electronic properties were similar to those described for thiophene-based materials, with optical bandgap values close to 2.4 eV. HOMO energy values of -5.98 and -5.95 eV and LUMO energy values of -3.87 eV and -3.84 eV were obtained for o-AZdAN1Th and o-AZdAN2Th, respectively. Theoretical DFT and TD-DFT calculations were used to compare the effect of increasing thiophene units along the backbone for the real and also theoretical o-AZdANxTh samples (x = 3 and 4 thiophene units). According to our study, these two new thiophene-based can be proposed for optoelectronic applications. - Schiff base oligomers based on a binaphthalene core were synthesized from [1,1 '-binaphthalene]-4,4 '-diamine with thiophene-2,5-dicarbaldehyde and [2,2 '-bithiophene]-5,5 '-dicarbaldehyde by a high-temperature polycondensation method.