Protonation studies of reduced Ruthenium(II) complexes with polypyridyl ligands
Journal Publication ResearchOnline@JCUAbstract
The pKa values associated with protonation of the one-electron reduced forms of series of [L¢2RuIIL]2+ complexes {L¢ ) bidentate polypyridyl ligand; L ) bidentate polypyridyl ligand with additional uncoordinated N atoms in the aromatic ring system: e.g., dpp ) 2,3-bis(2-pyridyl)pyrazine, bpz ) 2,2¢-bipyrazine} were assessed using pulse radiolysis techniques by the measurement of spectral variations as a function of pH. A linear correlation was observed between pKa and E°(RuL¢2L2+/+) for complexes in which the protonatable ligand was at the same time the site of reduction. In complexes where one or more of the nonprotonatable ligands (L¢) had very low ð* energy levels {e.g. (CF3)4bpy}, reduction occurs on a nonprotonatable ligand and a dramatic decrease in the pKa values was observed for the reduced species. In complexes where the energies of the protonatable and nonprotonatable ligands were comparable, the protonation behavior was consistent with some orbital mixing/ delocalization of the electronic charge.
Journal
Inorganic Chemistry
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Volume
39
ISBN/ISSN
1520-510X
Edition
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Issue
13
Pages Count
8
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Publisher
American Chemical Society
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EISSN
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DOI
10.1021/ic991070d