Indolino spiropyrans

Photochromism Based on Electrocyclic Reactions. The most common general class of photochromic systems involves reversible electrocychc reactions. Within this general class, the most weU-studied compounds are the indolino spiropyrans and indolino spiroxa2ines. 

Benzothiazolinospiropyrans 77 have been extensively studied by Gugliel-metti s group.31 Studies were carried out on aerated toluene solutions, and photodegradation was quantified in terms of V /2- The effect of substituents on both the benzothiazoline and chromene moieties was assessed. Photocolorability (Eapp) of this class of photochromes is, in general, lower than that of indolino-spiropyrans (Table 8). 

N. P. Ernsting, B. Dick, and T. Arthen-Engeland, The primary photochemical reaction step of unsubstituted indolino-spiropyrans, Pure Appl. Chem. 62, 1483-1488 (1990). 

V S. Marevtsev, L. L. Zaichenko, V D. Ermakova, S. I. Beshenko, V. A. Linskii, A. T. Gradyushko, and M. I. Cherkashin, Effect of electron-donating and electron-accepting substituents on photo- and thermochromic properties of indolino-spiropyrans, Bull. Acad. Sci. USSR, Chem. Sci. 29, 1591— 1596 (1980) Chem, Abstr. 94, 29901 (1980). 

The number of papers on this topic is also small. The potential, limitations, and detailed comparisons with other typ>es of systems have been discussed for the newly introduced indolizines . Another published lecture describes the use of ps pulses to study primary photochemical steps in unsubsdtuted indolino-spiropyrans. A new photochromic system which has been described is mesoxaldehyde 1-allyl-l-phenyl-2-phenylosazone. ... 

The nitro spiropyrans are susceptible to fatigue which has limited their appHcation. Indolino spiroxa2ines exhibit photochromism by way of a mechanism that is very similar to that of the spiropyrans. 

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 order to demonstrate the usefulness of the method, SERS spectra of indolino-spironaphthopyran (SPP, 4) and indolino-spironaphthoxazine (SPOX, 3) (see Scheme 7) were recorded at low concentration (10 7-10-8 A/) and their spectral characteristics analysed.48 Figure 8 shows the SERS spectrum of 4 in Ag colloids (spectrum a) along with the corresponding near-infrared Fourier transform (NIR-FT) Raman spectrum of the neat compound (spectrum b). Strong differences between the SERS and spontaneous Raman spectra are apparent. As stated above, these differences arise mainly from the particular orientation of the adsorbed spiropyran with to the metal surface in SERS experiments. 

Other reports have dealt with the photochromism of the acridine spiropyrans (53) and of several chromene derivatives, (54) and (55)7 In some instances the photochromic properties are poor. The influence of heteroatoms and ring size upon the photodegradation of some [2H]-chromenes has been investigated. A study of the photochromism of some 2,2-diarylsubstituted pyridoannelated [2H]-chromenes has been published. Photochromism is also exhibited by the indolino-naphthoxazine (56) in toluene. The photo-chromicity of 1,3,3-trimethylspiro[indoline-2,3 -[3H]-naphth-[2,1 -b][l, 4]-... 

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