3-Aminoperylene and ascorbate in aqueous SDS, one green laser flash … and action! Sustainably detoxifying a recalcitrant chloro-organic

Abstract

The hydrated electron represents a "super-reductant" in water, providing 2.9 eV of reductive power, which suffices to decompose nonactivated aliphatic halides. We show that 3-amino-perylene in SDS micelles, when combined with the bioavailable ascorbate as an extramicellar sacrificial donor, sustainably produces hydrated electrons through photoredox catalysis with green light, from a metal-free system, and at near-physiological pH. Photoionization of the amine with a 532 nm laser yields an extremely long-lived radical cation as the by-product, and a subsequent reaction of the latter with the sacrificial donor across the micelle/water interface regenerates the catalyst. The regeneration step involves parallel reactions between differently protonated forms, causing a bell-shaped pH dependence in basic medium. We have separated these processes kinetically. Employing this catalytic cycle for the laboratory-scale decomposition of chloroacetate, an accepted model compound for toxic and persistent halo-organic waste, gave turnover numbers of about 170. Even though both the substrate and the sacrificial donor compete for the hydrated electron, their consumption ratio is practically independent of the initial concentration ratio because the formal radical anion of the ascorbate undergoes secondary scavenging by the chloroacetate. In the course of the reaction, the initial hydrophobic catalyst is converted into a secondary species that is hydrophilic and still exhibits catalytic activity.

Generating Hydrated Electrons for Chemical Syntheses by Using a Green Light‐Emitting Diode (LED)

“…As in previous systems affording e À aq with pulsed lasers, [1][2][3] we used chloroacetate ClAc for this purpose.T he value of benchmarking different electron generators with the same test compound is obvious;n o other reductant accessible by photoredox catalysis is known to decompose ClAc,hence this standard provides astringent yardstick;and this bulk chemical with amarket approaching 10 6 tonnes per year combines ah igh acute toxicity with high persistence,soits remediation is an environmentally relevant task. As in previous systems affording e À aq with pulsed lasers, [1][2][3] we used chloroacetate ClAc for this purpose.T he value of benchmarking different electron generators with the same test compound is obvious;n o other reductant accessible by photoredox catalysis is known to decompose ClAc,hence this standard provides astringent yardstick;and this bulk chemical with amarket approaching 10 6 tonnes per year combines ah igh acute toxicity with high persistence,soits remediation is an environmentally relevant task.…”

“…This has been successfully exploited for laboratory transformations of otherwise inert substrates [1][2][3] as well as remediations of industrial pollutants, [4][5][6][7] with particular emphasis on recalcitrant halogenated waste. This has been successfully exploited for laboratory transformations of otherwise inert substrates [1][2][3] as well as remediations of industrial pollutants, [4][5][6][7] with particular emphasis on recalcitrant halogenated waste.…”

“…This has been successfully exploited for laboratory transformations of otherwise inert substrates [1][2][3] as well as remediations of industrial pollutants, [4][5][6][7] with particular emphasis on recalcitrant halogenated waste. [1][2][3] Each of these compromises has specific deficiencies.I onizing radiation incurs safety hazards and regulatory problems;U V-Ci s absorbed so strongly by other components of typical samples as to bar its penetration;and lasers are expensive.Herein we present, characterize,and apply the first catalytic system that is free from these weaknesses.I ta ffords laboratory-scale amounts of the super-reductant e À aq ,y et operates with lowintensity green light from aL ED (light-emitting diode); moreover,i tc onsumes only the approved food additive vitamin C. [1][2][3] Each of these compromises has specific deficiencies.I onizing radiation incurs safety hazards and regulatory problems;U V-Ci s absorbed so strongly by other components of typical samples as to bar its penetration;and lasers are expensive.Herein we present, characterize,and apply the first catalytic system that is free from these weaknesses.I ta ffords laboratory-scale amounts of the super-reductant e À aq ,y et operates with lowintensity green light from aL ED (light-emitting diode); moreover,i tc onsumes only the approved food additive vitamin C.…”

“…[14][15][16][17][18][19][20] Photoredox catalysis hinges on ap hotoinduced electron transfer between al ight-absorbing catalyst and as ubstrate;f or the latter, this redox activation unlocks the door to the realm of radical-ion chemistry;a nd the cycle is completed by catalyst regeneration through at hermal electron transfer involving as ubstrate-derived intermediate or as acrificial additive.R egarded from the storage perspective,the photon energy is distributed between ac atalyst-based and as ubstrate-based radical, which must normally recombine by asecond-order reaction. [2,23] Thec atalyst of this work is the popular ruthenium-trisbipyridyl ion [Ru(bpy) 3 ] 2+ . Hence,photoredox catalysis is inherently well-suited for accommodating photon pooling as an accessory; [3,21,22] and it is expected to perform this function better than two-photon processes without intervening electron transfer, [1] even when they are catalytic.…”

Laser‐Induced Wurtz‐Type Syntheses with a Metal‐Free Photoredox Catalytic Source of Hydrated Electrons

“…[9][10][11] Second, we prepare e À aq in high local concentration such that its rapid interceptionb yachloro-organic to give ac hloride ion and a carbon-centred radicalf avoursd imerization of the latter over the usual decay pathwayso fh ydrogen abstraction from a donor or addition to ac oupling component. Figure 1a displays the two subtypes of the general mechanism of e À aq production [15,16] explored herein. Figure 1a displays the two subtypes of the general mechanism of e À aq production [15,16] explored herein.…”