Protonation Equilibria in Excited State Tris(Bipyrazine) Ruthenium(II).
Abstract
The Tris(bipyarazine)ruthenium(II) cation has six peripheral uncoordinated nitrogen atoms potentially available for protonation in acidic media. Studies of the absorption and emission spectroscopy of the ruthenium cation in media ranging from neutral water to concentrated sulfuric acid, show that it is, indeed, possible to sequentially protonate these six nitrogen atoms. As the acidity is increased, a series of isosbestic points are seen in the absorption spectra, and these shift as the equilibria change upon increasing acidity. The parallel studies of emission show six different protonated species with distinct emission maxima and lifetimes ranging from 27 to 520ns. The first three protonation steps, to three different bipyrazine rings on the cation have MLCT excited states which are stronger bases than the ground state, while for the second set of three protonation species, the MLCT excited states are weaker bases than the ground state. pKa and pKa* values for many of the species are reported. Protonation equilibria with the free base bipyrazine are also included. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 21, 1982
- Accession Number
- ADA121016
Entities
People
- Alfred Beverley Philip Lever
- N. Kress
- R. J. Crutchley
Organizations
- University of York