Two-photon absorption of a series of V-shape molecules: the influence of acceptor's strength on two-photon absorption in a noncentrosymmetric D–π–A–π–D system

A series of V-shape D–π–A–π–D molecules were synthesized based on pyrimidine as the acceptor. The strength of the acceptor (A) in these molecules was systematically adjusted through changing the substituent group in pyrimidine. Their two-photon absorption properties were measured by two-photon induced fluorescence techniques with a mode-locked Ti:sapphire laser (100 fs, 80 MHz) in the range of 720 to 880 nm. The results indicate that the strength of the acceptor has an important influence on the two-photon absorption properties of this noncentrosymmetric D–π–A–π–D system, and a molecule with a strong acceptor is liable to display a large two-photon absorption cross-section.