Pulse radiolytic studies on cis-dichlorobis(2,2'-bipyridine)cobalt(III) and cis-dichlorobis(1, 10-phenanthroline)cobalt(III) complexes

摘要

The reactions of hydrated electron (e(aq)(-)) with Co(III) polypyridyl complexes of file type [Co(NN)(2)Cl-2]Cl where NN = 2,2'-bipyridine (bpy), and (phen) have been Studied by pulse radiolysis. The rate constants for the reactions at 300 K have been evaluated to be (7.6 +/- 0.2)x10(10), and (6.9 +/- 0.2) x 10(10) dm(3) mol(-1) s(-1) , respectively. Time resolved transient absorption spectra show two broad peaks at 360 and 610 nm for the bpy complex and a single broad peak at 420 nm for the phen complex at 1 mu s. Comparison with reported transient spectra of the anion radicals of ligands indicates that the electron is located on the complex as a whole. The anion radicals of both the complexes initially produced, decay in the time scale of similar to 80 mu s. Steady State absorption spectra on irradiation point out to breakdown of the phen complex, and the bpy-Co(III) complex is reduced to Co(II) complex. Conductance of the solution substantially increases on irradiation for both the complexes and can be attributed to aquation/de-ligation of the phen complex. The phen complex anion radical undergoes aquation/de-ligation by intramolecular electron transfer leading to dissociation of the complex. For bpy complex the conductance increases due to the release of chloride ions and reduction to Co(II) complex Species Is observed.