Calculations of third-order optical properties of titanyphthalocyanine polymorphs

We report the dynamic third-order nonlinear optical susceptibilities χ(3) using the INDO/SDCI method coupled with the SOS method for the different forms of PcTiO films. The calculated values of χ(3) at a low frequency are found to decrease in the order α-PcTiO>Y-PcTiO>β-PcTiO, and well corresponded to the varied trends in the measurements. A low space symmetrical structure of α-PcTiO film has the largest magnitude of χ(3), which is the contribution from the intermolecular interaction. The electron transfers from macrocycle π orbitals to metal Ti 3d orbital make a substantial contribution to the third-order NLO response for the PcTiO.