NewIr PhenN O-PC™
Dihydrophenazine photocatalysts (PhenN O-PC™) are some of the strongest visible light reductants.1 Here are the ranges of photo and electrochemical properties for dihydrophenazine PC derivatives:
|Excited state redox potential||Eo(2PC●+/1PC*) = -1.5 V to -1.9 V vs. SCE|
|Ground state oxidation potential||E1/2(2PC●+/1PC) = -0.1 V to 0.5 V vs. SCE|
|Excited state energy||E(singlet) = 1.9 to 2.2 eV|
|λmax,abs||340 – 390 nm|
|εmax,abs||4,000 – 22,000 M-1cm-1|
Compared to phenoxazine PCs, dihydrophenazine PCs oxidize more readily even at ground state.2 For example, PhenN O-PCTM B0301 oxidizes at E1/2(2PC●+/1PC) = 0.21 V vs. SCE, as compared to E1/2(2PC●+/1PC) = 0.65 V vs. SCE for Phenox O-PCTM A0202. Notably, it will even oxidize before the well-known ferrocene/ ferrocenium redox couple [E1/2(FeIII/FeII) = 0.39 V vs. SCE]. Demonstrating its redox reversibility, PhenN O-PCTM B0301 possesses highly reversible CV; it also forms a stable radical cation that is isolatable. Accessing the charge transfer excited state with the display of extensive solvatochromism3 is the hallmark of dihydrophenazine PCs. As a result, the photophysical properties of dihydrophenazine PCs depend strongly on solvent polarity. For example, in DMF, PhenN O-PCTM B0301 has τ(triplet) = 4.3 µs, φ(triplet) = 2%.2
Dihydrophenazine PCs are strong excited state reductants capable of reducing alkyl and aryl halides via an electron transfer mechanism.1,2 The alkyl radicals formed can partake in substitution or addition reactions on unsaturated vinyl or aromatic groups e.g., atom transfer radical polymerization, atom transfer radical addition, trifluoromethylation and ring-opening polymerization.1,2,4 Dihydrophenazine PCs can also activate an Ni co-catalyst for C-N cross-coupling reactions.2 They also outperformed many precious metal PCs in decarboxylative olefination.5 In recent advances, dihydrophenazines PCs were functionalized at the core positions enabling further redox and photophysical tuning. These core-functionalized dihydrophenazine PCs support controlled ATRP polymerization at ppm level catalyst loading.6
PhenN O-PC™ B0301
1. Theriot, J. C.; Lim, C.-H.; Yang, H.; Ryan, M. D.; Musgrave, C. B.; Miyake, G. M., Organocatalyzed atom transfer radical polymerization driven by visible light. Science 2016, 352, 1082.
2. Du, Y.; Pearson, R. M.; Lim, C.-H.; Sartor, S. M.; Ryan, M. D.; Yang, H.; Damrauer, N. H.; Miyake, G. M., Strongly Reducing, Visible-Light Organic Photoredox Catalysts as Sustainable Alternatives to Precious Metals. Chem. Eur. J. 2017, 23, 10962.
3. Lim, C.-H.; Ryan, M. D.; McCarthy, B. G.; Theriot, J. C.; Sartor, S. M.; Damrauer, N. H.; Musgrave, C. B.; Miyake, G. M., Intramolecular Charge Transfer and Ion Pairing in N,N-Diaryl Dihydrophenazine Photoredox Catalysts for Efficient Organocatalyzed Atom Transfer Radical Polymerization. J. Am. Chem. Soc. 2017, 139, 348.
4. Chen, D.-F.; Boyle, B. M.; McCarthy, B. G.; Lim, C.-H.; Miyake, G. M., Controlling Polymer Composition in Organocatalyzed Photoredox Radical Ring-Opening Polymerization of Vinylcyclopropanes. J. Am. Chem. Soc. 2019, 141, 13268.
5. Tlahuext-Aca, A.; Candish, L.; Garza-Sanchez, R. A.; Glorius, F., Decarboxylative Olefination of Activated Aliphatic Acids Enabled by Dual Organophotoredox/Copper Catalysis. ACS Catal.2018, 8, 1715.
6. Cole, J. P.; Federico, C. R.; Lim, C.-H.; Miyake, G. M., Photoinduced Organocatalyzed Atom Transfer Radical Polymerization Using Low ppm Catalyst Loading. Macromolecules 2019, 52, 747.