Three mixed-valence Keggin type molybdotungstophosphates have been photochemically synthesized and characterized. These mixed-valence species are products of one electron-reduction, which retain the structural features of their parent polyanions. The research using ^3^1P NMR, EPR and Evans method indicates that the added "blue" electron is delocalized among Mo atoms, and the larger the number of tungsten atoms replaced by molybdenum atoms, the weaker the paramegnetism of the one-electron-reduction species.

Key words: PHOTOCHEMICAL REACTION, CHEMICAL SYNTHESIS, ANION, PHOSPHORUS COMPOUNDS, TUNGSTEN COMPOUNDS, MOLYBDENUM COMPOUNDS, MIXED VALENCE, PARAMAGNETISM