Quenching of triplet states of diazines by H-atom donors. Formation of azyl radicals |
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Authors: | DV Bent E Hayon PN Moorthy |
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Institution: | Pioneering Research Laboratory, U.S. Army Natick Laboratories, Natick, Massachusetts 01760, USA |
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Abstract: | The laser flash photolysis of pyrazine in water and in organic solvents has been examined. The 3(n, π*) state in water has absorption bands at 230, ≈ 260, ≈ 295, ≈ 640, 700 and 810 nm, and decays with k = 2.2 × 105 sec?1. It is quenched by oxygen with kq = 3.2 × 109 M?1 sec?1 and by various H-atom donors, e.g., kq = 1.3 × 108 M?1 sec?1 for isopropyl alcohol. On reaction with H-atom donors, the chemistry of 3(n, π*) pyrazine produces the neutral pyrazyl-radical and the dihydro radical cation, whose characteristic absorption spectra have been identified. These results are discussed by comparison with 3(π, π*) diazines and with 3(n, π*) aromatic carbonyl compounds. |
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