Highly Efficient and Selective Photocatalytic Oxidation of Sulfide by a Chromophore–Catalyst Dyad of Ruthenium-Based Complexes

Abstract

Electronic coupling across a bridging ligand between a chromophore and a catalyst center has an important influence on biological and synthetic photocatalytic processes. Structural and associated electronic modifications of ligands may improve the efficiency of photocatalytic transformations of organic substrates. Two ruthenium-based supramolecular assemblies based on a chromophore-catalyst dyad containing a Ru-aqua complex and its chloro form as the catalytic components were synthesized and structurally characterized, and their spectroscopic and electrochemical properties were investigated. Under visible light irradiation and in the presence of [Co(NH3)5Cl]Cl2 as a sacrificial electron acceptor, both complexes exhibited good photocatalytic activity toward oxidation of sulfide into the corresponding sulfoxide with high efficiency and >99% product selectivity in neutral aqueous solution. The Ru-aqua complex assembly was more efficient than the chloro complex. Isotopic labeling experiments using (18)O-labeled water demonstrated the oxygen atom transfer from the water to the organic substrate, likely through the formation of an active intermediate, Ru(IV)═O.

Photoassisted Oxidation of Sulfides Catalyzed by Artificial Metalloenzymes Using Water as an Oxygen Source

“…This could indicate that the insertion of 1-Mn into the hydrophobic pocket of Xln10A [18] hinders the electron transfer from the manganese center to the photo-activated ruthenium complex. The results observed in the presence of 1-Mn-Xln10A are, however, comparable to those obtained under the same conditions for the oxidation of thioanisole catalyzed by an Mn-corrole complex and Mn-corrole-BSA artificial metalloenzyme, which respectively lead to the chemoselective formation of the corresponding sulfoxide with 32 ± 3 and 21 ± 7 TON ( [22,23].…”

Sulfur‐Center‐Involved Photocatalyzed Reactions

“…(118)]. [83] EPR experiments confirmed the existence of Cu I species, and the involvement of copper oxygen-activated species was verifiedw hen a1 :10 mixture of the reduced Cu I catalyst and 4-bromothioanisolgave sulfoxide in 70 %yield with respect to the Cu I catalysti na nhydrous acetonitrile under air. Additionally,n anosecond time-resolved absorption spectroscopy under catalytic conditions supported the oxidative quenching of the 3 MLCT (metal-to-ligand charge transfer) state, which led to ap hotoinduced electron transfer to Cu II from the ruthenium photosensitizer in its excited state.…”

“…In 2017, MacMillan and co-workers developed an efficient photocatalyzed deuterium-and tritium-labeling method,a nd achieved the modificationo f1 8 drug molecules with thiols as important H/D-or H/Tatom transfer reagents [Eq. (83)]. [56] For deuteration, D 2 Ow as used as the hydrogen isotope source, which helped to achieve the corresponding transformations on ag ram scale.…”

Photocatalytic Oxygenation Reactions Using Water and Dioxygen

“…[35][36][37][38][39][40][41][42][43][44][45][46][47] [Ru(bpy) 3 ] 3 + was used as ao neelectron oxidant to produce high-valent metal-oxo complexes, but it can be replaced by much milder oxidants such as [Co III (NH 3 ) 5 Cl] 2 + under photoirradiation. [48][49][50][51][52][53][54][55][56][57][58] Scheme2 shows the catalytic cycle of the photocatalytic oxygenation of watersoluble substrates (S) with [Co III (NH 3 ) 5 Cl] 2 + as an oxidanta nd [Ru(bpy) 3 ] 2 + as ap hotocatalyst and am anganese(III)-hydroxo porphyrin ([(Por)Mn(OH)]) as an oxygenation catalyst. [58] The photocatalytic oxygenation is started by photoinduced ET from [Ru(bpy) 3 ] 2 + *( where *d enotes the excited state) to [Co III (NH 3 ) 5 Cl] 2 + to produce [Ru(bpy) 3 ] 3 + ,w hich oxidizes [(Por)Mn(OH)] by ET to produce [(Por)Mn IV (O)].…”

“…[47] When the TMP ligand was replaced by TDCPP, [(TDCPP)Mn III ] + acts as a more reactive catalyst for the oxygenation of cyclohexene and styrene than [(TMP)Mn III (H 2 O) 2 ](PF 6 ), because of the smaller steric effect of the TDCPP ligand as comparedw ith that of TMP ligand and the high redox potential. [48][49][50][51][52][53][54][55][56][57][58] Scheme2 shows the catalytic cycle of the photocatalytic oxygenation of watersoluble substrates (S) with [Co III (NH 3 ) 5 Cl] 2 + as an oxidanta nd [Ru(bpy) 3 ] 2 + as ap hotocatalyst and am anganese(III)-hydroxo porphyrin ([(Por)Mn(OH)]) as an oxygenation catalyst. [47] Av ariety of high-valent metal-oxo complexes were produced by ET oxidation of metal complexes by one-electron oxidants, such as [Ru(bpy) 3 ] 3 + and cerium(IV) ammonium nitrate (CAN), with H 2 O, catalyzing oxygenation of substrates by using H 2 Oa sa no xygen source.…”