Лако-красочные материалы — производство

Spirooxazines are generally colorless compounds whose absorption bands lie in the UV region, and show photochromism in solution, plastic resin, and films. The quantum yield of the photocoloration of spiroindo- linonaphthooxazine in ethanol is very high (>0.90). In contrast to spiro- pyrans, the photocoloring reaction of spironaphthooxazine proceeds via an excited singlet state. For photocoloring reaction, photosensitization by benzophenone has not been observed. Recently, two stereoisomers (analog­ous to C and D in Figure 1.1) of the colored form are suggested based on

thermal fading Kinetics,78 and detected by picosecond Raman and absorp­tion spectroscopy technique.84

The spiroindolinonaphthooxazine is generally very stable toward UV light, compared with spirobenzopyran. However, replacement of the indo — line ring with benzoxazine significantly reduced its photostability.

Like other spiropyrans, the colored form of spirooxazines generated by UV irradiation, reconverts to the colorless form. However, it is possible to measure the thermal decay rates and activation energies at ambient tem­perature, since this fading reaction obeys first-order kinetics in solution. The thermal decay rate constant for spiroindolinonaphthooxazine has been found to be 0.02-0.15s-1 in ethanol and 0.1-1.4s-1 in toluene, although this may vary according to the substituent groups.72,77 However, these values are smaller than those of the spironaphthopyran series.

Colored forms of 5′,8′-disulfonate derivatives of 33 chelate with divalent metal ions, e. g., Ca2+, Cu2+, and Pb2+, causing blueshift.85 The order of blueshift and thermal stability of the chelated photomerocyanine is as follows: Ca2+ < Cu2+ < Pb2+. 5′-Methoxy derivative of 33 also gives Ni2+ complexes. This chelation significantly stabilizes photomerocyanine, com­pared with the nonchelating colored form. In contrast to sulfonate deriva­tives, chelation of 5′-methoxy derivatives with Ni2+ causes redshift (ca. 40 nm), but their structures are not clear.

Thermochromism of spiroindolinonaphthooxazine is observed only in high-concentration solution.77 A high concentration ( 10-3 M) of 33 in ethanol produces a bluish solution, and its color intensity increases as the temperature of such concentrated solution increases. This thermal equilib­rium is also affected by substituent groups. Donor substituent groups promote the formation of the colored form.