The One-Photon and Two-Photon Absorption Properties for Porphyrin-Derived Monomers and Dimers

摘要

Materials possessing large nonlinear optical (NLO) responses have been studied comprehensively for telecommunication information storage, optical switching, and signal processing. Among the various categories of NLO chromophore, porphyrins appear to have unique characteristics that make then superior as NLO materials. These macrocycles with a large polarizable π-conjugated system constitute of two-dimensional framework for electronic communication. By changing the metal center, the axial ligands, and the nature of the substituents at the peripheral sites of the macrocycle, their optical properties can be remodeled. Recently, a great effort has been devoted to the design and synthesis of porphyrins oligomers and polymers. Such porphyrin polymers offer several advantages: the polymers are highly soluble in common organic solvents, the porphyrin subunits have tunable photophysical and electronic properties, and the coplanar conjugated system provides for potential electrical conductivity in the charged state. As for the third-order nonlinear optical properties of porphyrin polymers, there are many experimental observations It is pointed out that the porphyrin polymers have large third-order susceptibilities γ~(5,7,8) it is known that the imaginary component of third-order susceptibilities lmγ controls two-photon absorption (TPA), which is useful for unconverted leasing. optical power limiting, photodynamic therapy, and three-dimensional (3D) microfabrication. By inspecting the above relationship, one can suppose that the porphyrin polymers should show large TPA responses. As a rule, the TPA cross section is regarded as the standard of the magnitude of TPA responses in materials. However, there are few reports about the TPA properties of porphyrin polymers. Herein, we selected monomers and dimers of some porphyrin polymers as a model system and examined theoretically their one-photon absorption properties.