One-electron reduction of aromatic nitrogen heterocycles in aqueous solution. 2,2'-bipyridine and 1,10-phenanthroline

Journal Article · Thu Jun 14 04:00:00 EDT 1979 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100475a006· OSTI ID:6137015

Mulazzani, Q G ^[1]; Emmi, S; Fuochi, P G; Venturi, M; Hoffman, M Z; Simic, M G

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1. Laboratorio di Fotochimica e Radiazioni d'Alta Energia del C.N.R., Bologna, Italy

The reaction of 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), and their monoprotonated cations (bpyH/sup +/ and phenH/sup +/) with radiation-generated one-electron reducing agents yields radicals, the spectra, kinetics, and acid-base properties of which have been established. BpyH/sub 2//sup +/. has a pK/sub a/ of 5.6 and exhibits an intense absorption maximum at 375 nm (epsilon 4.5 x 10/sup 4/M/sup -1/cm/sup -1/); bpyH. shows lambda/sub max/365 nm (epsilon 3.0 x 10/sup 4/M/sup -1/cm/sup -1/). BpyH. decays via second-order kinetics (2k = 4.0 x 10/sup 9/M/sup -1/s/sup -1/) representing primarily a disproportionation reaction. BpyH/sub 2//sup +/. 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. PhenH/sub 2//sup +/. shows lambda/sub max/370 nm(epsilon 7.8 x 10/sup 3/M/sup -1/cm/sup -1/) and 510 nm (epsilon 3.8 x 10/sup 3/M/sup -1/cm/sup -1/)and pK/sub a/ = 6.3 while phenH. exhibits lambda/sub max/350 nm (epsilon 5.8 x 10/sup 3/M-/sup 1/cm/sup -1/) and 475 nm (epsilon 3.0 x 10/sup 3/M/sup -1/cm/sup -1/). PhenH. protonates to form phenH/sub 2//sup +/. with k = 8.3 x 10/sup 9/M/sup -1/s/sup -1/ and phen H/sub 2//sup +/. decays via second-order kinetics (2k = 1.6 x 10/sup 9/M/sup -1/s/sup -1/). In alkaline solution (pH 10-13) the decay of phenH. is first order (k = 2 x 10/sup 3/s/sup -1/). The bimolecular reaction appears to proceed predominantly via combination; a product has been isolated with the empirical formula C/sub 12/H/sub 11/N/sub 2/.ClO/sub 4/. 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. 10 figures, 1 table.

• OSTI ID: 6137015
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 83:12; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400600* -- Radiation Chemistry
AQUEOUS SOLUTIONS
AROMATICS
AZINES
BIPYRIDINES
CATIONS
CHARGED PARTICLES
CHEMICAL PROPERTIES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
DISPERSIONS
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
HETEROCYCLIC COMPOUNDS
IONS
IRRADIATION
KINETICS
LEPTONS
MIXTURES
NITROGEN COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDATION
PHENANTHROLINES
PULSED IRRADIATION
PYRIDINES
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
RADIOLYSIS
REDUCTION
SOLUTIONS
SPECTRA