Direct spectroscopic evidence for (1)Delta O-g(2) production from the photolysis of vanadium(V)-peroxo complexes in aqueous solution

The chemiluminescence of (1)Delta(g)O(2) expelled from the UV photolysis of vanadium(V)-peroxo (VP) complexes in aqueous solution was observed for the first time. Using phenalenone photosensitization as a standard reference, the O-1(2) quantum yields from the photolysis of 12 TTP complexes were meas ured. No good correlation was found between the relative DNA-photocleavage activities and the O-1(2) quantum yields of these complexes. This lack of c orrelation underscores the significant contribution of the complex-DNA bind ing interaction in determining the observed DNA-photocleavage activity of t he complex. The small O-1(2) quantum yields observed in these complexes wer e interpreted in terms of the minor O-1(2) photoelimination channel relativ e to other more efficient relaxation processes.