Pulse radiolysis ligand labilization

Pulse radiolysis is the radiation chemical analogue of flash photolysis. It is a fast-kinetics technique that enables transitory processes, initiated by the absorption of ionizing radiation, to be observed in time frames as short as the submicrosecond region. It permits the detection and characterization of short-lived intermediates, the determination of the kinetics of their decay, and a probing of reaction mechanisms. The technique finds use in the study of radiation effects on materials, and as a tool for the examination of mechanistic details. For inorganic systems, pulse radiolysis is used to characterize metal complexes in unusual oxidation states, to examine the kinetics and rates of ligand-labilization reactions and to elucidate the mechanism of electron transfer. 

The products of these reactions may be short lived, but they often have characteristic absorption spectra that can be detected by pulse radiolysis. Subsequent reactions, such as electron transfer and ligand labilization, can be followed kinetically with the appropriate detection technique. Reviews of the spectra, kinetics and mechanisms of complexes in unusual and unstable oxidation states are available A compilation of rate constants for the reactions of metal ions in unusual valency states is available ... 

Pulse radiolysis is useful in determining the dynamics of labile Co(II) complexes owing to the ease of effecting rapid reduction of the corresponding Co(IlI) species. The first three NHj ligands in [CofNHj) ] are labilized in < 1 /as followed by ... 

Aquation of [M (acac)3]. —The kinetics of ligand exchange in labile complexes can be readily obtained using pulse radiolysis combined with conductivity measurements. For the complexes [M(acac)3]- (M = Co +, Cr, or Ru2 acac =acetylacetonate) the conductance changes in the pH range 3.1—7.0 are in accord with the following reactions ... 

---