Modulation of photochromic properties of spirooxazine bearing sulfobutyl substituent by metal ions

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Chemistry., 2019-02, Vol.371, p.453-460
• Main Authors: Fedorov, Yury V., Shepel, Nikolay E., Peregudov, Alexander S., Fedorova, Olga A., Deligeorgiev, Todor, Minkovska, Stela
• Format: Article
• Language: English
• Subjects: Absorption; Absorption spectra; Acetonitrile; Bearing; Cadmium; Calcium; Calcium ions; Chemical synthesis; Coloration; Complex formation; Complexation; Coordination compounds; Irradiation; Kinetics; Light irradiation; Magnesium; Metal ions; Photochromism; Ring opening; Spectral properties; Spirooxazine; Ultraviolet radiation; Zinc
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/j.jphotochem.2018.10.045

[Display omitted] •Novel sulfobutyl substituent on the indoline fragment of the molecule was synthesized and studied.•The interaction of spirooxazine with Cd2+, Ca2+, Mg2+, Zn2+ or Pb2+ results in the formation of colored complexes of metal ions with merocyanine form.•The thermal build-up reaction is independent of the metal ion thus implying the ring opening is the rate determining step.•UV-irradiation of SP1 produced the colored MC1 which undergoes a thermal relaxation to the colorless SP form with a rate constant k = 1.1 s−1.•The concentration of the complexes of metal ions with merocyanine form can be influenced by light. A novel spirooxazine bearing sulfobutyl substituent on the indoline part of the molecule has been synthesized and its photochromic properties and complex formation with metal ions have been studied. Under UV light irradiation of colorless acetonitrile solution of spirooxazine the open merocyanine form having an absorption band in visible region of the spectrum with λmax = 625 nm is generated. Thermal back reaction of merocyanine form to spirooxazine with the rate constant 1.10 s−1 at 298 K has been observed. Interaction of spirooxazine with Mg2+, Ca2+, Cd2+, Zn2+ or Pb2+ ions in the dark leads to the formation of complexes of merocyanine form demonstrating a visible absorption band shifted from 20 to 8 nm relative to the uncomplexed merocyanine form. The activation energy of metal-induced coloration process in the dark is in the range of 84–88 kJ mol−1 and does not depend on the nature of the metal ions. This suggests that the process of thermal ring opening of the spiro form is the rate limiting step of complex formation. The degree of conversion of spirooxazine to complexed merocyanine form strongly depends on metal ions nature and irradiation wavelength.