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Publication costs assisted by the National Science FoundationThe reaction of 2,2'-bipyridine (bpy), 1,lO-phenanthroline (phen), and their monoprotonated cations (bpyH+ and phenH+) with radiation-generated one-electron reducing agents yields radicals, the spectra, kinetics, and acid-base properties of which have been established. BpyH2+. has a pK, of 5.6 and exhibits an intense absorption maximum at 375 nm ( e 4.5 X lo4 M-l cm-' 1; bpyH. shows A, , , 365 nm ( E 3.0 X lo4 M-' cm-'). BpyH. decays via second-order kinetics (2h = 4.0 X lo9 M-' sd) representing primarily a disproportionation reaction. BpyH2+. appears to decay via concurrent first-and second-order reactions; the processes are complicated by unidentified dose-dependent sequences. Irrespective of pH, the final isolatable product is a pale yellow solid which can be identified by elemental analysis, molecular weight determination, and IR spectrum as a trimer of dihydrobipyridine isomers. PhenHz+. shows A,, 370 nm (e 7.8 X lo3 M-' cm-l ) and 510 nm ( e 3.8 X lo3 M-l cm-' ) and pK, = 6.3 while phenH. exhibits A, , , 350 nm ( E 5.8 X lo3 M-' cm-' ) and 475 nm (t 3.0 X lo3 M-' cm-l ).PhenH. protonates to form phenHz+-with k = 8.3 X lo9 M-' s-' a nd phenHz+. decays via second-order kinetics (2k = 1.6 x lo9 M-l s-l ). In alkaline solution (pH 10-13) the decay of phenH. is first order ( k = 2 X IO3 9-l).The bimolecular reaction appears to proceed predominantly via combination; a product has been isolated with the empirical formula C12HllN2C104. The behavior of the one-electron reduction products is compared with that of species believed to be similar arising from the photoreduction of bpy and phen in aqueous solution.

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