INHIBITION OF NEAR-INFRARED PHOTOINDUCED ELECTRON-TRANSFER BETWEEN FREE HEXACYANOFERRATE(II) AND HEXACYANOFERRATE(III) BY TETRAMETHYLAMMONIUM IONS

A recently reported weak 800-nm intervalence absorption band in mixtures of potassium hexacyanoferrate(III) and -(II) was interpreted as photoinduced electron transfer between the free hexacyanoferrate ions. We have investigated the effect of replacing potassium ions by tetraalkylammonium ions on this band using mixtures of the appropriate hexacyanoferrates rather than by adding tetraalkylammonium halides to the potassium hexacyanoferrates. The intervalence band appears to vanish on full replacement. This suggests that the phototransition is likely to be in an ion pair bridge configuration.