Polarographisches Verhalten einiger Chromkomplexe VI. Komplexe von Chrom mit Äthylendiamin

Reactions of chromium(III) complexes of 1,10-phenanthroline, 2,2′-bipyridyl, and oxalate with the pulse radiolytically generated aquated electron, zinc(I), and cadmium(I)

“…Pulse radiolysis experiments were performed with a van de Graaff electron accelerator which delivered electron pulses (3 p) at ca. 1 MeV (1 eV = 1.60 x lW19 J) through the thin wall of a cell with a 1-cm optical path, as previously de~cribed. '~ Dosimetry was performed with an aerated aqueous solution of potassium thiocyanate, employing values of E = 7600 dm3 mol-' cm-' at 480 nm and G(0H) = G[(CNS),*-] = 2.8; a dose of approximately 40 Gy was observed.…”

“…Redox reactions between chromium(rI1) complexes and zinc (1) or cadmium(r) were initiated by pulse radiolysis of 0.01 mol dm-, solutions of zinc(1r) or cadmium(rr) sulphate and containing variable amounts of chromium(m), but always < 10-4 mol dm-3. Variation of the pseudo-first-order decay at 310 nm was monitored, and this rate was first order in [Cr"'], allowing the electron-transfer rate constant to be determined from the slope of kobs.…”

“…The metal(1) ions can be generated essentially exclusively from radiolysis of solutions containing at least a 100-fold excess of metal@) ions over chromium(rI1) ions. Decay of both zinc(1) and cadmium@) is a process readily monitored at 310 nrn,I9 and this decay rate is mediated by electron transfer between zinc@) or cadmium (1) and any oxidant present, such as the chromium(r1r) complexes. Observed second-order rate constants for the redox reactions between cadmium(1) or zinc (1) and the chromium(II1) complexes are all close to 2 x lo9 dm3 mol-I s-', with no significant variation with charge or ligand type apparent.…”