Two-photon absorption properties of two (dicyanomethylene)-pyran derivatives

The two-photon absorption (TPA) properties of two fluorophores 4-(dicyanomethylene)-6-methyl-2-[2-[4-(diphenylamino)phenyl]-ethenyl]-4H-pyran (DCM-TPA) and [2,6-bis[2-[4-(diphenylamino)phenyl]-ethenyl]-4H-pyran-4-ylidene]propanedinitrile (DADP) have been investigated. Both of them exhibit intense up-converted luminescence and large two-photon absorption cross-sections σ2 in the femtoseconds regime (σ2 of DADP is as high as 1298 × 10−50 cm4 s photon−1 molecule−1 with 80 fs laser pulses). The increase of σ2 values from DCM-TPA to DADP is about five times. This could be ascribed to the extended π-delocalization system and its two-dimensional charge transfer character.