Quadrupolar Benzobisthiazole-Cored Arylamines as Highly Efficient Two-Photon Absorbing Fluorophores

A computer-aided design of novel
D−π–A−π–D
styrylamines containing five isomeric benzobisthiazole moieties as
the electron-accepting core has revealed the linear centrosymmetric
benzo­[1,2-d:4,5-d′]­bisthiazole
as the most promising building block for engineering chromophores
displaying high two-photon absorption (TPA) in the near-IR region,
as also confirmed experimentally. The ease of synthesis of quadrupolar
derivatives thereof, combined with extraordinarly high TPA action
cross sections (δTPAΦf > 1500
GM),
makes these heteroaromatic systems particularly attractive as diagnostic
agents in 3D fluorescence imaging.