The radiation-chemical processes in aqueous solutions of dichromates, isopolymolybdates and isopolytungstates have been studied.
The radiation reduction of Cr(VI) to Cr(III), Mo(VI) to Mo(V) and W(VI) to W(V) takes place. Molybdenum and tungsten blues
are the products of the last two processes in acid solutions. The yields of reduction decrease significantly with the increase
of pH. The mechanisms of the processes have been discussed. The photochemical reduction of Mo(VI) and W(VI) for the production
of corresponding 5-valent states have been used to the study of their electron scavenging efficiencies. It has been shown
that these efficiencies decrease in the order: Mo(V)>W(V)>Cr(VI)>Mo(VI)>W(VI).
The kinetics of radiation reduction of Mo(VI) and W(VI) in aqueous formic acid or acidified methanol solutions has been studied. The rate constants of radiation-chemical processes have been measured by pulse radiolysis technique. It has been shown that the reduction of polytungstates in aqueous formic acid solutions, contrary to polymolybdates whose reduction proceeds via lower oxidation states, leads directly to W(V) compounds. In acidified aqueous methanol solutions the isopolymetallate blues are the only optically detected products of the reduction.
Authors:E. Kalecińska, J. Kaleciński, and F. Pruchnik
Radiation reduction of binuclear [Rh2(OAc)2(phen)2(H2O)2](OAc)2, [Rh2(OAc)(tpy)2Cl2]Cl·2H2O and [Rh2Cl2(HCOO)2(bpy)2]·4H2O complexes in aqueous-methanol solution have been studied. The reduction yields as equal to ca. 6 equiv/100eV and the rate
constants of reactions: complex+e
as equal to 2.9·1010, 3.2·1010 and 3.7·1010 M−1·s−1, respectively, have been determined. On the basis of electronic spectra it has been shown that Rh(II) compounds were reduced
giving several Rh(I) complexes being in equilibrium. The mechanism of the processes has been discussed.