Spiropyran-carrying

It is well known that the conjugation of proteins to chemical polymers can be used to improve protein stability or change its solubility. Ito et al. conjugated subtilisin to spiropyran carrying polymethacrylate... 

Early picosecond studies were carried out by Schneider et al, [63] on the parent spiro-oxazine (NOSH in Scheme 8) and similar derivatives. In a back-to-back work, they also described a complimentary CARS (coherent anti-Stokes Raman spectroscopy) investigation [69], Simply put, these authors found that the closed spiro-oxazine ring opened in 2-12 psec after laser excitation. The reaction was slower in more viscous solvents. An intermediate state formed within the excitation pulse and preceded the formation of merocyanine forms. This transient was named X in deference to the X transient named by Heiligman-Rim et al. for the spiropyran primary photoproduct [8], (See also the previous section.) The name X has since been adopted by other workers for the spiro-oxazines [26,65],... 

Clearly, the TC isomer has its spectrum red-shifted compared to the TT isomeric form. Although spectra for individual isomeric forms of spiro-oxazine and spiropyran merocyanines are not available, it has been shown that the different isomers have very different spectra. In fact, Abe and co-workers [89] have shown that the merocyanine of spiro-oxazine can be converted photochemically between two states having different absorption spectra. Even earlier work carried out at low temperature and or with visible-light irradiation suggested that the spiropyran merocyanine isomers also exhibit significant differences between their absorption spectra [6-8]. 

The third approach is useful when the spiropyran itself (or, more correctly, its intermediates) is easily available, the necessary substituted intermediates are not, and the spiropyran tolerates the chemical transformations involved. Halogenation and nitration of BIPS and spiro(dinaphthopyrans) can be carried out by standard methods bromo substituents replaced by cyano or lithium, nitro substituents reduced to amino, etc. For example, the aldehyde group in 6-formylBIPS can be reduced, oxidized, caused to react with organometallics, condensed with active methylene groups, converted to cyano, and derivatized to give a wide variety of 6-substituted BIPS. These reactions cannot be usefully carried out directly on 5-formylsalicylal-... 

The preparation, filtration, washing, and drying of the spiropyran should, of course, be carried out in the absence of direct or diffuse daylight, and if possible under incandescent or gold (minus blue) fluorescent lamps. There is sufficient UV radiation available from ordinary fluorescent lamps to significantly color a still-damp filter cake of a sensitive compound. 

Like azobenzenes (III.A), polypeptides carrying spiropyrans have been studied to control the conformations of polypeptides. In polar solvents such as hexafluoropropanol, the colored merocyanine form is thermally more stable than the spiro form. Therefore it shows reverse (or negative) photochromism irradiation by visible light on the colored species bleaches it, while the spiro form formed... 

The photochromism of spirobenzopyrans is a well-documented phenomenon that arises from the photoinduced reversible isomerization between spiropyran and merocyanine forms . In spirobenzopyrans carrying a crown ether moiety (e.g., Ill), this interconversion process is affected by metal ion complexation. A strong interaction of the crown ether unit with a metal ion caused the thermal isomerization of the spirobenzopyran residue to the corresponding merocyanine form with simultaneous suppression of the UV-induced isomerization process (negative photochromism) (Scheme 3). Conversely, a weak metal ion interaction induced a positive photochromism <2001JOC1533, 2002EJ0655>. 

Chapter 7 (Structural Studies by X-ray Diffraction). The geometric parameters of photochromic compounds have been determined by X-ray diffraction on single crystals and yield interesting correlations with photochromic behavior (colorability, thermal bleaching rates, or absorption spectrum of the colored species). More intensive studies have been carried out on members of the spiropyran series (indolinospiropyrans), examining both closed spiranic forms and permanent merocyanines. The latter served as models of open photomer-ocyanines, the transient species produced by UV irradiation of spiropyrans. 

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). 

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