Hyponitrite radicals, a stable adduct of nitric oxide and nitroxylстатья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 27 марта 2017 г.
Аннотация:All major properties of the aqueous hyponitrite radicals (ONNO- and ONNOH), the adducts of nitric oxide (NO) and nitroxyl (3NO - and 1HNO), are revised. In this work, the radicals are produced by oxidation of various hyponitrite species in the 2-14 pH range with the OH, N3, or SO4 - radicals. The estimated rate constants with OH are 4 × 107, 4.2 × 10 9, and 8.8 × 109 M-1 s-1 for oxidations of HONNOH, HONNO-, and ONNO2-, respectively. The rate constants for N3 + ONNO2- and SO4 - + HONNO- are 1.1 × 109 and 6.4 × 108 M-1 s-1, respectively. The ONNO - radical exhibits a strong characteristic absorption spectrum with maxima at 280 and 420 nm (ε280 = 7.6 × 103 and ε420 = 1.2 × 103 M-1 cm -1). This spectrum differs drastically from those reported, suggesting the radical misassignment in prior work. The ONNOH radical is weakly acidic; its pKa of 5.5 is obtained from the spectral changes with pH. Both ONNO- and ONNOH are shown to be over 3 orders of magnitude more stable with respect to elimination of NO than it has been suggested previously. The aqueous thermodynamic properties of ONNO- and ONNOH radicals are derived by means of the gas-phase ab initio calculations, justified estimates for ONNOH hydration, and its pKa. The radicals are found to be both strongly oxidizing, E°(ONNO-/ONNO 2-) = 0.96 V and E°-(ONNOH, H+/HONNOH) = 1.75 V, and moderately reducing, E°(2NO/ONNO-) = -0.38 V and E°(2NO, H+/ONNOH) = -0.06 V, all vs NHE. Collectively, these properties make the hyponitrite radical an important intermediate in the aqueous redox chemistry leading to or originating from nitric oxide