Theoretical study of two-photon absorption properties of a series of tetra-paracyclophane derivatives

The equilibrium geometries and one- and two-photon absorption (TPA) properties of a series of tetra-paracyclophane derivatives have been determined by using the hybrid B3LYP combined with 6-31G basis set and ZINDO-SOS methods. The results show that the tetra-paracyclophane derivatives have large TPA cross-sections, which are about two times larger than that of the corresponding linear counterparts. The introduction of donor/acceptor groups has improved the TPA cross sections of paracyclophane derivatives. In particular, the increased molecular chain plays a crucial role in increasing TPA cross section, according to the three-state model, due to the larger transition dipole moment between the ground state and intermediate state. The calculated results also reveal that the dimers of D-π-A (D and A denote donor and acceptor, respectively) chromophore have relatively large TPA cross sections among studied compounds.