Photochemical studies of the alkylammoniun molybdates. Part 5. Photolysis in weak acid solutions

Abstract

Solution photolysis of hexakis(isopropylammonium) heptamolybdate(VI) trihydrate, [NH₃Prⁱ]₆[Mo₇O₂₄]·3H₂O (1), at pH 5.4 leads to reduction to Mo^V with involvement of hydroxy-radicals, followed by decomposition to yellow and blue species. Propylene and acetone were detected as oxidation products but quantum yields for their formation were much lower than that for Mo^V formation. The irradiated single-crystal e.s.r. spectra revealed the formation of Mo^VO₅(OH) in a MoO₆ octahedral site, which corresponded to the primary event in the solution photolysis. E.s.r. and Raman spectroscopy and flash photolysis were employed to elucidate the mechanism of these reactions.