A Ruthenium(II)–Copper(II) Dyad for the Photocatalytic Oxygenation of Organic Substrates Mediated by Dioxygen Activation

Abstract

Dioxygen activation by copper complexes is av aluable method to achieve oxidation reactions for sustainable chemistry.T he development of ac atalytic system requires regeneration of the From an environmental point of view,t here is ag rowing interest in designing catalysts capable of using O 2 as oxygen atom source to perform oxidation reactions to avoid strong, toxic, and expensive oxidants.[1] Indeed, O 2 is nowadays considered as an appealing oxidant for sustainable oxidation chemistry.N ature has developed al arge panel of metalcontaining enzymes to perform selective and efficient oxidation reactions through dioxygen activation.[2] O 2 activation at am etal center generally entails its two-electron reduction to the peroxo state and subsequent OÀOb ond cleavage.I n dinuclear centers,t he second metal ion acts as ar eductant, while in mononuclear active sites,anexternal electron donor is required. This is the case for copper metalloenzymes such as dopamine b-monooxygenase (DbM), peptidylglycine ahydroxylating monooxygenase (PHM), and the recently identified insect tyramine b-monooxygenase (TbM) that are involved in the transformation of various substrates by Cu I /O 2 chemistry.[3] Thec atalytic activity is achieved owing to the presence,i nc lose proximity,o fareducing co-factor that allows aregeneration of the active Cu I species from the final inactive Cu II state (Scheme 1, top). Several bio-inspired mono and dinuclear copper complexes have been reported, but few of them act catalytically in homogeneous conditions. [4] This assessment might originate from the competitive reduction of the active Cu II (O 2 )o xidative species (that is,s uperoxo or peroxo) by the additional sacrificial reductant (Scheme 1, top) that would short-circuit the catalytic cycle.E xploiting our expertise in the development of eco-aware photocatalysts for small molecules activation (such as water [5]

Understanding the Synergistic Effects Observed When Using Tethered Dual Catalysts for Heat and Light Activated Catalysis

“…[18][19][20][21][22][23] These 'heavy atoms' promote intersystem crossing (ISC) from the singlet to the triplet excited state of the photocatalyst, with this approach widely used to promote reactive singlet oxygen ( 1 O 2 ) generation through triplet-triplet energy transfer ( Figure 1). As such, a variety of tethered photocatalyst-metal complexes have been developed and used in applications that require singlet oxygen generation, such as photocatalysis [24][25][26][27][28] and photodynamic therapy. [26,[29][30] Despite the increasing use of tethered catalysts that feature both a photocatalyst and a transition metal catalyst, [23,25,28,[31][32][33][34] there have been limited mechanistic investigations into the origins of the synergistic effects between the catalytic centres.…”

“…As such, a variety of tethered photocatalyst-metal complexes have been developed and used in applications that require singlet oxygen generation, such as photocatalysis [24][25][26][27][28] and photodynamic therapy. [26,[29][30] Despite the increasing use of tethered catalysts that feature both a photocatalyst and a transition metal catalyst, [23,25,28,[31][32][33][34] there have been limited mechanistic investigations into the origins of the synergistic effects between the catalytic centres. For example, our group recently developed a series of complexes that feature an organic photocatalyst (1,3,5,7tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene, BDP 1) tethered to an Ir complex ligated with a bis(pyrazolemethane) (bpm) ligand, Ir(I) 2 ( Figure 2).…”

Sulfur‐Center‐Involved Photocatalyzed Reactions

“…Ap roposed mechanism similart op reliminary HAT reactions is depicted in Scheme 31:t he catalysts are activated by blue light and then oxidizea mine 225, which undergoes facial deprotonation at the a-position to give a-aminor adical A.A tt he same time, In 2017, Kanai et al made use of at ernary hybrid catalytic acceptorless dehydrogenation system, which included an acridinium photoredox catalyst, apalladium metal catalyst, and at hiophosphoric imide organocatalyst,t oc onstructn aphthalenes by releasing two molar equivalents of hydrogen gas from tetrahydronaphthalenes [Eq. (84)]. [57] The authors proposed the mechanism in Scheme32: the excited PC is quenched by RSH, then the generated RSC can abstract ab enzylic hydrogen atom from 232 a to produce benzyl radical A.T he combination of A and palladium generates organometallic species B,w hich can be reducedt oC.S ubsequent b-hydride elimination of C could produce unsaturated dihydronaphthalene 234 and metal hydride speciesM n H. At this stage, one molecule of hydrogen can evolve by the combination of M n Ha nd the protong enerated in the organocatalystc ycle.…”

“…(119)]. [84] Both catalysts showed significant activity,w ith TONs of up to 1000 and high product selectivity (> 99 %). Notably,n itro anda mine groups could be tolerated in this system.I sotopic labeling experiments with H 2 18 Od emonstrated transfer of the oxygen atom from water to the organic substrate, and an active Ru IV =Os pecies was proposed as ak ey intermediate.…”

Ru(II)–Pd(II) dinuclear complexes of di(pyridin-2-yl)amino-substituted 1,10-phenanthrolines: synthesis, characterization and application for catalysis

“…The advantages of the dinuclear photoactive complexes was thoroughly studied in such processes as hydrogen photogeneration [17][18][19] , CO 2 photoreduction 14,20,21 and photoaccelerated polymerization [22][23][24][25] . In recent years Ir-Pd 26,27 , Ru-Pd 28,29 , Ru-Au 30 , Ru-Cu 31,32 and Ir-Ni 33 dinuclear complexes have been successfully employed for the oxydation reactions and carbon-carbon and carbon-element bond formation reactions under visible light irradiation. The structure of the bridging ligand is one of the most important parameters controlling the interaction between the photocatalyst and the metal complex catalyst in the dinuclear complex and thus governing the efficiency of the dual catalyst.…”