Spectral Properties and Photochromic Characteristics of Spiropyran Dyes1

A bis-benzospiropyran(BBSP) and nitro-substituted indoline spirobenzopyrans(SBP) were prepared by following a simple procedure. The reaction mechanism of synthesizing bis-benzospiropyran is discussed. A comparative analysis of the spectral and photochromic properties between SBP and BBSP was carried out with the aid of a PMMA film. The results indicate that chemical structures and UV irradiation played an important role in the spectral and photochromic properties of SBP and BBSP, which would readily affect λmax of the colored forms and the reversibility. The IR spectra and 1H NMR spectra of these compounds are used to interpret the photochromic phenomena under different UV irradiation and determine the configurations of SBP and BBSP.