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Influence of the ionic strength on O2(1Δg) quenching by azide

1992; Elsevier BV; Volume: 66; Issue: 2 Linguagem: Inglês

10.1016/1010-6030(92)85209-d

1873-2666

Marı́a A. Rubio, Daniel O. Mártire, Silvia E. Braslavsky, E. A. Lissi,

Analytical Chemistry and Sensors

The quenching of singlet molecular oxygen O2(1Δg) by N3− in polar solvents is strongly influenced by the ionic strength (I) of the solution. In D2O the quenching rate constant is increased from kq = (3 ± 0.5) × 108 M−1 s−1 for I = 0 to (7.9 ± 0.4) × 108 M−1 s−1 or (7.1 ± 0.6) × 108 M−1 s−1 for I = 3 for [N(CH3)4] Cl or NaCl as electrolyte respectively. In ethanol the increase is more pronounced. This effect is in line with the proposed charge-transfer intermediate between O2(1Δg) and N3− whose rate of formation should be influenced by the presence of charged species in the medium and explains, at least in part, the increased deactivation rate of O2(1Δg) by N3− in cationic micelles due to the high local ionic strength at the micellar surface.