Isobenzothiophene-bridged molecules for significantly enhanced two photon absorption properties

Abstract Isobenzothiophene-bridged molecules featured with a D-π-D type structure were designed and synthesized for developing new compounds with excellent two photon absorption (2PA) properties. Compared with a series of compounds based on thiophene and acene with different peripheral fused benzene rings as conjugated bridges, isobenzothiophene-based ones exhibited significantly enhancement in both of the 2PA cross section (σ 2 ) and the value of σ 2 per molecular weight (σ 2 /MW) due to their outstanding electron-rich property and quinoid character. Theoretical calculations further elucidated that the efficient intramolecular charge-transporting property and increased delocalization of the isobenzothiophene ring facilitated the 2PA performance of these molecules. With the benefits to 2PA, isobenzothiophene can serve as a valid unit for designing novel 2PA chromophores, especially for biological imaging.