Survey of Vibrational Studies on Spiropyran and Spirooxazine Photochromes

SURVEY OF VIBRATIONAL STUDIES ON SPIROPYRAN AND SPIROOXAZINE PHOTOCHROMES 

In the early seventies, Arnold and Paal published a detailed IR study on a series of 16 photochromic compounds.8 In this paper the authors reported a comparative assignment of the main vibrations of indolino- and benzothiazolino-spiropyrans along with the corresponding spirooxazines. IR data from benzox-azolinospiropyrans were also included for comparison. Thus, this study provided an interesting data base which includes the vibrational characteristics of the two popular parent spiro compounds (since they have been used so often in various 

In view of the difficulties encountered in direct interpretation of the vibrational spectra of spiropyrans, Davin-Pretelli et al.w proposed a more rational approach. They investigated first the IR and Raman spectra of the two constituent moieties of the photochrome under study. Thus, from a preliminary IR and Raman study of benzothiazolines and 2/f-chromenes, which served as models, they were able to give a satisfactory assignment of the spectra of a series of benzothiazolinic spiropyrans.9 Moreover, on the basis of the vibrational data for 2//-chromenes, the set of bands at ca. 1250 cm-1 was unambiguously assigned to vibrations involving 

Attempts to detect the main structural changes occurring in the ring-opening/ closing process in spiropyrans, using IR vibrational spectroscopy, were reported by Schiele and Arnold for a series of indolinonitrospiropyrans12 and later by 

In the next part of this chapter, we will consider vibrational studies of organic photochromes in dilute solutions using time-resolved Raman techniques. 

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