Mechanism of Redox Reactions between SO₃^•- Radicals and Transition-Metal Macrocyclic Complexes:  Oxidative Addition to the Ligand and Outer-Sphere Electron Transfer

Abstract

Reactions of SO 3 •radicals with complexes of Ni(II and I) and Cu(II and I) were investigated under anaerobic conditions. Reactions of CuCR + , Cu(TIM) + , and Ni(Me 6 [14]dieneN 4 ) + with SO 3 •radicals were investigated by time-resolved spectroscopy. The kinetics of the processes is in accordance with an outer-sphere electrontransfer mechanism. Intermediates with a ligand-radical nature were observed in SO 3 •reactions with Cu(2,9-dimethyl-1,10-phenanthroline) 2 + , Cu(Me 6 [14]dieneN 4 ) 2+ , NiCR 2+ , or NiCRH 4 2+ . Two products were isolated in the reaction of NiCR 2+ with SO 3 •radicals, one product with a sulfonated macrocycle and the other product with one additional double bond in the macrocycle. These products confirmed the attack of the ligand by SO 3 •radicals and the formation of intermediates with a ligand-radical nature. A mechanism based on the oxidative addition of SO 3 •radicals to the ligand accounts also for the kinetics of product formation.

On the redox reactions of radicals with AlIII(phthalocyaninate) pendants covalently bonded to poly(ethyleneamide). Mechanistic alterations when radicals are formed inside pockets of micelle‐like polymer aggregates

“…In the second step of the mechanism, eq 5, insertion of the SO 3 •− radical into the phthalocyanine macrocycle forms a phthalocyanine radical, that is, the long‐lived intermediate. In some regards, the addition process bears a resemblance with the formation of an adduct in the reaction of the SO 3 •− radical with Ni II CR + 18. Marked differences can be seen between the spectrum of the radical and the spectra of those formed in reactions where radicals function as electron donors, for example, e aq − , CO 2 •− and (CH 3 ) 2 C • OH, or acceptors, for example, HCO 3 • and N 3 • .…”

“…Pulse radiolysis experiments were carried out with a model TB‐8/16‐1S electron linear accelerator following previously described methods 7, 18. The instrument and computerized data collection for time‐resolved UV‐Vis spectroscopy, and reaction kinetics have been described elsewhere in the literature 19.…”

Observations on the mechanisms of the thermal and photoinduced oxidation of D-mannitol and fucoidan by transition metal complexes and inorganic radicals

“…Although the reactions of these carbohydrates with radicals are relatively slow, coordination to a toxin such as the Ni(III) complex, 3 [31], kinetically enhances the antioxidant response. Except for the reactions of D-mannitol and fucoidan with O .À 2 , the rate constants for the scavenging of various radicals in table 1 show that D-mannitol and fucoidan are not as good scavengers of radicals as ascorbic acid.…”

Harnessing no-photon exciton generation chemistry to engineer semiconductor nanostructures

“…Finally, we used the mechanism of NPEGEC to find suitable etchant for 6H-SiC, too. The dithionate (S 2 O 6 2− ) ion decomposes above 70 °C 32 and various ions and radicals can form 33 , 34 including SO 3 2− with a reduction potential of −1.36 ± 0.24 V at the SO 3 2− /S 2 O 4 2− redox couple 35 that can inject electrons into the CB of 6H-SiC. Figure 2E shows the absorption and emission spectra of 6H-SiC NPs made by NPEGEC etching of 6H-SiC in HF:K 2 S 2 O 6 electrolyte.…”