Synthesis and Radiation Sensitivity of Phenoxazine Type Color Formers Including Thiol Ester Protective Group

ABSTRACT

3,7-Bis(N,N-diethylamino)-10-(phenylthio)carbonylphenoxazine (1a) and its analogs (1b–f) were synthesized and the color change after γ irradiation was investigated. The color change of acetonitrile solutions of 1a ([1a]₀ = 1.0 × 10⁻³ M) after γ irradiation was identified by naked eyes at the dose of 20 Gy. Phenylthio-substituted compound 1a showed more significant absorbance increase than phenoxy-substituted compound, 3,7-bis(N,N-diethylamino)-10-phenoxycarbonylphenoxazine (2a). The C‒S cleavage in 1a by γ irradiation was revealed to occur more easily than the C‒O cleavage in 2a. The sensitivity of the color formers (1a–f) to γ rays was correlated with the stability of the thiyl radicals generated in the reaction.

Keywords:

• γ rays
• color former
• dosimetry system
• phenoxazine dyes
• substituent effect