Reactions of e(-)(aq), CO(2)(*)(-), HO(*), O(2)(*)(-) and O(2)((1)delta(g)) with a dendro[60]fullerene and C(60)[C(COOH)(2)](n) (n = 2-6).
Using pulse radiolysis and laser flash photolysis, we have investigated the reactions of the deleterious species, e(-)(aq), HO&z.rad;, O(2)(*)(-) and O(2)((1)Delta(g)) with 10 water-soluble cyclopropyl-fused C(60) derivatives including a mono-adduct dendro[60]fullerene (d) and C(60) derivatives based on C(60)[C(COOH)(2)](n=2-6), some of which are known to be neuroprotective in vivo. The rate constants for reactions of e(-)(aq) and HO&z.rad; lie in the range 0.5-3.3 x 10(10) M(-1) s(-1). The d and bis-adduct monoanion radicals display sharp absorption peaks around 1000 nm (epsilon = 7 000-11 500 M(-1) cm(-1)); the anions of the tris-, tetra-, and penta-adduct derivatives have broader, weaker absorptions. The monohydroxylated radicals have their most intense absorption maxima around 390-440 nm (epsilon = 1000-3000 M(-1) cm(-1)). The anion and hydroxylated radical absorption spectra display a blue-shift as the number of addends increases. The radical anions react with oxygen (k approximately 10(7)-10(9) M(-1) s(-1)). The reaction of O(2)(*)(-) with the C(60) derivatives does not occur via an electron transfer. The rate constants for singlet oxygen reaction with the dendrofullerene and eee-derivative in D(2)O at pH 7.4 are k approximately 7 x 10(7) and approximately 2 x 10(7) M(-1) s(-1) respectively, in contrast to approximately 1.2 x 10(5) M(-1) s(-1) for the reaction with C(60) in C(6)D(6). The large acceleration of the rates for electron reduction and singlet oxygen reactions in water is due to a solvophobic process.
Bensasson
R V
RV
Laboratoires de Biophysique et de Photobiologie, Muséum National d'Histoire Naturelle, CNRS UMR 8646, INSERM U201, Paris Cedex, France. rvb@mnhn.fr
Brettreich
M
M
Frederiksen
J
J
Göttinger
H
H
Hirsch
A
A
Land
E J
EJ
Leach
S
S
McGarvey
D J
DJ
Schönberger
H
H
D002244:Carbon / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry*; D037741:Fullerenes; D017665:Hydroxyl Radical / Q000737:chemistry*; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry*; D010782:Photolysis; D011675:Pulse Radiolysis; D013329:Structure-Activity Relationship
D005609:Free Radicals; D037741:Fullerenes; D017665:Hydroxyl Radical; D002244:Carbon; C069837:fullerene C60; D010100:Oxygen