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Permanent merocyanine

Two permanent merocyanines have been reported for the spiro-oxazines [85]. These were NOSH heteroanellated by imidazo [l,2-a]pyridine and imidazo [l,2-a]pyrimadine. Several tests have been conducted to determine the nature of these species. H -NMR data show that the indoline nitrogen is not highly charged and the crystal structure indicates that the ground state is essentially the quinoidal form. The most stable form was found to be the TTC isomeric form by x-ray analysis. The dipole moment of these permanent spiro-oxazine merocyanines was around 3.84 D, which is much lower than the values reported for spiropyran merocyanines. [Pg.382]

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. [Pg.7]

The Structure of Permanent Merocyanines—Models of the Open Forms of Indolinospiropyrans... [Pg.306]

Guiliano et al. for benzothiazolinonitrospiropyrans9 (Spiro., Scheme 2). In the latter study, the photochromic conversion was performed by UV-irradiating the spiropyrans, dispersed in a solid matrix or dissolved in carbon disulfide (CS2), leading to thermodynamically stable colored species. The IR spectra ofthe colored states thus obtained were compared to those of a stable benzothiazoline photo-merocyanine in the solid state (R=OCH3) and a permanent merocyanine (R=H), (Mero., Scheme 2). From a detailed analysis ofthe IR spectra, it appeared that two... [Pg.362]

M. Delamar, J. Aubard, J. L. Albert, and J. E. Dubois, XPS study ofabenzoxazolinic spiropyran and a related permanent merocyanine, J. Electron. Spectrosc. Relat. Phenom. 28, 289-293 (1983). [Pg.389]

Overall, the quantum yield of ring closure is reported to be low when measured in toluene [100] and this is in accordance with the transient studies. Further, in the transient study by Bohne et al. [71,72], the dye laser used to bleach the merocyanine form was rather powerful at 100-300 mJ/pulse. Even using this strong laser pulse on a merocyanine solution with an absorbance of 0.25, they only permanently bleached the mero-form absorbance by one-third in acetonitrile and one can, therefore, imagine that the bleaching yield is also rather low in acetonitrile. [Pg.394]


See other pages where Permanent merocyanine is mentioned: [Pg.314]    [Pg.373]    [Pg.376]    [Pg.314]    [Pg.373]    [Pg.376]    [Pg.384]    [Pg.125]    [Pg.342]    [Pg.161]    [Pg.125]    [Pg.6270]   
See also in sourсe #XX -- [ Pg.372 , Pg.373 ]




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