The photochromic, electrochemical and third-order nonlinear optical properties of the novel naphthopyran derivatives

A series of novel naphthopyran derivatives featuring nonplanar and spiro-conjugation structure have been successfully synthesized and characterized. In this paper, we investigated the effects of the electron donating ability and volume of substituents on the photochromic and third-order nonlinear properties of novel naphthopyran derivatives. The UV-Vis absorption spectroscopy was used to analyse the photophysical and photochromic properties. Under the dual role of electron-donating group and bulky substituent group, maximum absorption peaks (lambda(max)) of the closed form and the open-form of the naphthopyran derivatives were both red shifted, and all molecules showed relatively good photochromic properties and fatigue resistance. The electrochemical properties have been investigated by the cyclic voltammetry (CV) measurement, the band gap of NP-C, NP-O and NP-N narrowed in sequence, and the level of HOMO decreased in turn. The third-order nonlinear optical (NLO) properties of the compounds were studied by the Z-scan techniques at 532 nm, which indicated that all molecules showed the reverse saturable absorption (RSA) behavior and the optical susceptibility chi((3)) reached 10(-14). These interesting findings provide a new insight on the practical application of naphthopyran molecules and the design of the NLO materials.