Photolysis of Octacyanomolybdate(IV) and Diethylenetriamine System: Kinetics and Mechanism of the Reaction

Abstract

The lignad field (LF) excitation of [Mo(CN)₈]^4– produces [Mo(CN)₇OH]^4– which reacts with diethylenertiamine (dien) in 3:2 stoichiometry. Rate constants and quantum yields for the formation of the phtoproduct were calculated and found to be depended on pH, ligand and [Mo(CN)₈]^4– concentrations. A reaction mechanism for the photochemical reaction of [Mo(CN)₈]^4– and dien is proposed. Rate constants and quantum yields are maximum at pH 7.4 and pH > 7.4, the reverse reaction generating octacyanocomplex from heptacyano species, is faster, at low pH the ligand is protonated which is less reactive and hence rate of reaction and quantum yield values decrease. At higher concentrations of [Mo(CN)₈]^4– to give eventually a second-order rate constant. The ionic strength does not affect the reaction rate, implying that the mechanism is not dissociative.