Лако-красочные материалы — производство

The thermal fading of the colored form follows first-order kinetics.1 The substituent effects in the pyran component obey Hammett-type corre — lation.2 For example, the value of p for the thermal fading rate of spiroin — dolinobenzopyrans having substitution only in the pyran portion is — 1.8 to — 3.45. The electron-donating group in the indoline component stabilizes the colored form by decreasing the thermal fading rate which is also dependent on solvent, temperature, substituent groups, and heterocyclic components. The rate constant for thermal fading of the spiroindolino — benzopyran without a substituent group in the 3-position is generally 1.4 x 10-3-4.8 x 10-2s-1 in toluene.1

The substituent effect in the phenyl group at the 3-position is also observed in the benzothiazoline series.2,17 The thermal fading rate increases with the bulky group at the 3-position, but the colored forms of 3-methoxy and 3-phenoxy derivatives are largely stabilized by an intramolecular interaction with 5-hydrogen atom.2

The chelation of the colored form with metal ion is possible for spirobenzopyrans having a donor substituent group at the 8-position, acting as bidentate ligand groups. These groups can be —OCH3, —CH2OH, —CH2OR, —CH2NR2, —CH=NR, or —N=N—Ar.18 The formation of the stable chelates of the colored form with divalent metals, e. g., Zn2+, CO2+, Ni2+, and Cu2+, has been qualitatively demonstrated. The structures of these complexes are not always established. In the spiroindolino — and spirobenzothiazolino-benzopyrans with such substituent groups, the C—O bond in the colorless form can be broken by metal salts to give complexes.’ Spiropyran possessing a bidentate ligand forms two bonds with a metal ion, giving metal complex, 11a or 11b which depends on the substituent group at the 3-position due to steric hindrance. Metals such as cobalt give a

mixture of monomeric and dimeric complexes. The geometry of the dimeric complex consists of polyhedral coordinations to the Co ion19; however, the heterocyclic plane and phenyl ring maintain a bent conformation (like a cisoid form) and the nonbonding C2—O1 distance (2.65A) in this metal complex is within the van der Waals radii.

Instead of metal chelation, an intramolecular hydrogen bonding be­tween the oxygen atom of phenolate and a hydrogen atom of a carboxylic acid in the 8-position leads to stabilization of the colored form, such as compound 12.20,21 This spiropyran exhibits reversed photochromism, which means that thermally stable species change from the spiro form to the colored form, and thus the colorless form produced by photoirradiation soon converts to thermally stable colored form.

In the presence of acid, unsubstituted BIPS assumes a thermally stable protonated colored form, and shows reversed photochromism, in which the phenolate form changes to a phenol.20,22 In this case, the absorption band remarkably shifts to the short wavelength. For example, in the presence of acid the absorption band of 6-nitro-BIPS occurs at 405 nm in acetone.

The spiropyran containing a quinoline ring forms a stable chelate 13 by reacting Cu2+ or Fe3+ ions with the colored form, produced by photoirradiation, or by irradiation of a solution of spiropyridopyran con­taining a metal ion.23,24 7-Amino-spiropyridopyran also gives a colored complex with guanosine derivative by intermolecular hydrogen bonding.25