Electron transfer properties of bisphenol derivatives in relation to their developing properties in silver salt photothermographic systems

Electron transfer properties of a series of bisphenol derivatives were examined in relation to their developing properties in silver salt photothermography. A t-butyl-substituted bisphenol derivative exhibited the highest developing reactivity among bisphenol derivatives investigated in this study. The substituent effects of bisphenol derivatives on the one-electron oxidation potentials and the rates of electron transfer with one-electron oxidants have revealed that the deprotonation step from the bisphenol radical cation, to produce a phenoxyl radical, plays an important role in determining the overall oxidation reactivity in the two-electron oxidation process. The ESR spectra of phenoxyl radicals derived from bisphenol derivatives indicate formation of an intramolecular hydrogen bond between oxygen and OH group of phenoxyl radicals. The reactivity of the bisphenol derivatives during the oxidation process is controlled by the hydrogen bond formation. The high oxidation reactivity of the t-butyl-substituted bisphenol derivative is ascribed to its low ionization potential and low deprotonation energy, as compared with the other alkyl-substituted bisphenol derivatives.