A novel molecular design strategy for efficient two-photon absorption materials

This paper describes a novel molecular design strategy for obtaining efficient two-photon absorption (TPA) materials. The most popular strategy for enhancing the TPA cross-section (σ(2)) of a molecule is to enhance its transition dipole moment. However, this strategy also red shifts the one-photon absorption (OPA) band. Consequently, molecules with large transition dipole moments typically exhibit strong OPA at visible wavelengths, making it difficult to use such molecules for TPA-related applications in the visible wavelength region. Therefore, an alternative molecular design principle for TPA materials to enhance the transition dipole moment is strongly required. The present paper describes a novel molecular design strategy for reducing the detuning energy by incorporating an azulenyl moiety in a large, planar π- electron system. This strategy enhances σ(2) without significantly red shifting the OPA band.