Synthesis and characterization of two-photon active chromophores based on asymmetrically substituted tetrathienoacene scaffolds

Four new asymmetric donor-π-acceptor (D-π-A) fused-thiophene based chromophores were developed and characterized for a two-photon absorption study. In the chromophores the alkylated tetrathienoacene served as a π spacer, p-methoxytriphenylamine was used as an electron donor, and a cyanoalkyl acetate unit was employed as the acceptor. To investigate the effect of elongated conjugation on this system, thiophene units were systematically incorporated between the central core and each capped ends. The thermal, optical, and electrochemical properties of these compounds were investigated. The photo-physical, electrochemical and electronic properties of these molecules were compared, and all four chromophores exhibit strong fluorescence and high thermal stability. The elucidated structure-property correlations are in agreement with the theoretical calculations based on the density functional theory. The compound containing a thiophene unit between the donor and spacer exhibits a maximal two-photon absorption cross-section value of 1130 GM.