Resonance Raman (RR) spectroscopy has been used to probe theinteraction between dipyridophenazine(dppz) complexes of ruthenium(II),[Ru(L)
2(dppz)]
2+ (L = 1,10-phenanthroline(
1) and 2,2-bipyridyl (
2)), and calf-thymus DNA.
Ground electronic state RR spectra at selected probewavelen
gths reveal enhancement patterns whichreflect perturbation of the dppz-centered electronic transitions in theUV-vis spectra in the presence of DNA.Comparison of the RR spectra recorded of the short-lived MLCTexcited states of both complexes in aqueous solutionwith those of the lon
ger-lived states of the complexes in the DNAenvironment reveals chan
ges to excited statemodes, su
ggestin
g perturbation of electronic transitions of the dppzli
gand in the excited state as a result of intercalation.The most prominent feature, at 1526 cm
-1, appears inthe spectra of both
1 and
2 and is a convenientmarker bandfor intercalation. For
1, the excited state studieshave been extended to the
![](/ima<font color=)
ges/
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![](/ima<font color=)
ges/entities/L
gr.
gif"> enantiomers. The markerbandappears at the same frequency for both but with different relativeintensities. This is interpreted as reflectin
g thedistinctive response of the enantiomers to the chiral environment ofthe DNA bindin
g sites. The results, to
getherwith some analo
gous data for other potentially intercalatin
g complexes,are considered in relation to the more
generalapplication of time-resolved RR spectroscopy for investi
gation ofintercalative interactions of photoexcited metalcomplexes with DNA.