Two Photon Absorption Study of Low-Bandgap, Fully Conjugated Perylene Diimide-Thienoacene-Perylene Diimide Ladder-Type Molecules

A new series of donor-acceptor ladder-type molecules were synthesized via Scholl reaction. These molecules contain up to 25-fused rings but still show good air stability and good solubility. The ring-fusing reaction is found to be sensitive to the nature of the side-chain in donor units. The molecular conformations were investigated by 2D NMR and DFT calculations. The photophysical properties were investigated and an intense intramolecular charge-transfer was observed. All of the molecules exhibit two-photon absorption (TPA) activity, and their TPA cross-section shows a linear relationship with increasing conjugation length of the thienoacene-PDI derivatives.