Theoretical studies on one- and two-photon absorption properties of rubrene and its derivatives

One- and two-photon absorption properties of a very intriguing perpendicular π-electron system 5,6,11,12-tetraphenylnaphthacene (rubrene) and its derivatives have been discussed from the theoretical investigation view. Based on the correct geometries, the INDO/SDCI method was adopted to determine the one-photon absorption (OPA) and two-photon absorption (TPA) properties. The elongation of π-conjugation and the perpendicular phenyl groups on two-photon absorption cross section (δmax) of rubrene are investigated in detail. The results show that the extension of π-conjugation plays an important role on the magnitude of δmax. In addition, the perpendicular phenyl groups favor to enhance the δmax of rubrene, which can be seen from the dominant charge transfer (CT) contributing to TPA obviously. This CT process is a symmetrical intramolecular CT process from the pendent phenyl groups to the main π-backbone. At the same time, the relationship between substituents attached to rubrene and two-photon absorption cross section is also systematically discussed.