Theoretical study of the one- and two-photon absorption properties of two series of fluorene derivatives

A dipolar molecule and two series of fluorene derivatives have been theoretically studied with B3LYP/6-31G(d) associated with ZINDO–SOS method. The different peripheral groups and lengthening the bridge have effect on the one-photon absorption. The maximum two-photon absorption cross sections δmax for the fluorene derivative (1B) is more than three times as that of the dipolar counterpart (S1). The δmax are obviously increased as the conjugation length increases from the series 1 molecules to the series 2 counterparts. Meanwhile, the δmax are increased with the stronger electron-donating (accepting) capability.