Evolution of manganese low-energy photoredox catalysis from high-energy visible light photocatalysis

Domain: chemistry
Published: 2026-01-27
Editorial outcome: minor_revision

Abstract
Reducing the energy input of light in photocatalytic reactions is desirable yet challenging, as modifying the light-absorbing or catalytic properties of a photocatalyst typically requires tedious preparation, resulting in a lengthy development process. Here, we overcome this limitation by achieving manganese-based low-energy photoredox catalysis through the in-situ assembly of simple Mn salts with inexpensive coordinating chemicals, thereby bypassing the need for complex pre-preparation. Assembling Mn(acac)2, 2,2’-bipyridine-6,6’-diamine, and TMSN3 in-situ forms a visible-light-absorbing system that, upon blue-light irradiation, generates azido radicals to drive an anti-Markovnikov hydroazidation of unactivated alkenes with H2O as the hydrogen source. Building on this assembly strategy, the combination of Mn(acac)3 and TMSN3 in CH3CN/HFIP yields a system with a light-absorption range extended to 850 nm; this feature is further leveraged to unlock the selective aerobic hydroxyazidation of alkenes in a single step. These findings pave the way for the development of in-situ-assembled, 3d metal-based low-energy photochemistry.

Introduction
Reducing the consumption of light energy needed in photocatalytic reactions is significant. Excess inputs of light energy into organic chemical reactions not only result in a waste of energy, but also probably cause several intractable issues, such as over-functionalization of reactants and incompatibility with light-sensitive/labile functional groups1–3. In this context, the direct use of high-energy light (λ<500 nm)4—encompassing both the high-energy visible (400–500 nm) and UV (<400 nm) regions—frequently leads to an excessive input of photon energy. Furthermore, the poor penetration depth and biocompatibility of high-energy light significantly limit its applications, particularly in scale-up synthesis and biomedical fields5–7. Therefore, for a given high-energy photocatalytic system, the strategy for reducing its demand for light energy is of great importance7,8. The natural abundance, low toxicity, and versatile catalytic reactivity of 3d metal render 3d metal-catalyzed chemical reactions extraordinarily valuable. Integrating exogenous light energy into 3d metal catalysis provides intriguing opportunities to enrich the diversity of synthetic strategies in organic synthetic chemistry9–11. Indirect visible light-induced 3d metal catalysis, a 3d metal-based light-absorbing system—without any external photocatalyst—drives the entire catalytic cycle (Fig. 1A)12–19. However, current 3d metal-based photoredox catalysis relies heavily on the use of high-energy light to achieve the desired catalytic effect. The unique mildness and deep-tissue penetration of low-energy light (λ>595 nm) motivated us to develop a low-energy, 3d metal-based photocatalytic system7,20–22. Such a system holds great promise for applications across synthetic organic chemistry, biomedicine, and polymer science7,23.

The in-situ assembly of a 3d metal-based photocatalytic system from readily available components—such as metal salts, ligands, or substrates—is a straightforward strategy for controlling both light-absorbing and catalytic properties through modulating the ligand, counterion, or metal oxidation state (Fig. 1B)24,25. This paradigm avoids the preparation process of 3d metal photocatalysts and is expected to enable a rapid shift from prevalent high-energy to low-energy photoredox catalysis platforms25.

We observed that Mn-based photocatalysis still remains in its infancy26–43. To date, CO-coordinated Mn(0) complexes (e.g., Mn2(CO)10) have been extensively studied as robust photocatalysts to mediate atom transfer or single electron transfer processes for the production of various carbon-centered radicals44–48. By contrast, N-centered radicals generated by a Mn(II or III)-based photocatalytic system remain to be developed. Given the privileged status of N-centered radicals in synthetic organic chemistry49–52 and the limitations of existing systems, we questioned whether an effective Mn(II or III)-based photocatalytic platform that allows for the controllable absorption of light energy could be devised using easy-to-access starting materials to yield versatile N-centered radicals53.

Here, we demonstrate that assembling Mn-based photocatalytic systems in situ is an effective strategy to rapidly unlock a low-energy photoredox catalytic system from high-energy visible light-induced Mn catalysis (Fig. 1C). The formation of valuable azido radicals can be achieved not by leveraging high-energy visible light (blue light, λcenter=440 nm), but by using low-energy, near-infrared light (λcenter=850 nm). The blue light-induced Mn photocatalytic system enables the anti-Markovnikov hydroazidation of unactivated alkenes with H2O as the hydrogen source, while the Mn-based low-energy photocatalytic platform allows for the aerobic hydroxyazidation of alkenes in a single step. This showcases the unique catalytic ability of in-situ-assembled, Mn-based photocatalysis.

Results
Evolution of a Mn-based low-energy photocatalytic system via in-situ assembly

Our study began with UV−Vis experiments to probe the in-situ assembly of the Mn-based light-absorbing system for generating desired azido radicals (Supplementary Figs. 13−18). After continuous efforts, we found that the mixture of Mn(acac)2, 2,2′-bipyridine-6,6′-diamine (L1) and TMSN3 exhibited a distinct absorption band at approximately 475 nm, which lies within the high-energy visible light region (Fig. 2A and Supplementary Fig. 13). This peak was eliminated upon removal of any one of the three components. When the mixture was subjected to blue light irradiation (λcenter=440 nm), the intensity of the absorption peak gradually decreased, indicating that the events of electron transfer and azido radical generation along with the valence change of Mn might have occurred (Fig. 2B and Supplementary Fig. 15)25. In addition to the prominent absorption peak at ~475 nm, the absorption tail extended into the low-energy light range. Low-energy light irradiation (λcenter=630 nm) was also able to consume the Mn(II)-based light-absorbing system (Fig. 2C and Supplementary Fig. 17), whereas the consumption rate was markedly lower than that under blue light irradiation. The weaker light absorption in the region of 700−850 nm relative to 630 nm should account for the lower efficiency of the expected redox event (Fig. 2D and Supplementary Fig. 18). We therefore sought a method to enhance its absorption and corresponding photoredox activity in the 700–850 nm region. In principle, raising the valence of Mn from +2 to +3 can improve the oxidizing ability of the Mn center. This stronger oxidizing power may lower the light energy required to drive the redox event, thereby enabling the use of lower-energy light.

With this hypothesis in hand, we examined the absorption spectrum of the mixture of Mn(acac)3, L1 and TMSN3. The spectrum indeed showed stronger absorption in the 700–850 nm low-energy light region (Fig. 2E and Supplementary Fig. 19). It was also worth noting that irradiation of the Mn(III)-based system with an near-infrared light source (760−918 nm, λcenter=850 nm) caused a distinct decrease in absorbance (Fig. 2F and Supplementary Fig. 20). Moreover, L1 was not essential for the absorption of the near-infrared light (Fig. 2G and Supplementary Figs. 21−24). To confirm that light irradiation triggers the formation of the valuable azido radical, we proposed an anti-Markovnikov hydroazidation of alkenes54–63 catalyzed by the Mn-based light-absorbing systems, employing H2O as the hydrogen source (Fig. 2H and Supplementary Figs. 28, 38 and 40). As shown in Fig. 2I, the targeted hydroazidation of the unactivated alkene proceeded in good yield (3, 78%) under the blue light-induced, Mn(II)-based photoredox catalytic system (Supplementary Tables 1−5, Supplementary Fig. 26); the yield of 3 drastically decreased when L1 was absent (Supplementary Figs. 32–34). Furthermore, the deuterioazidation of alkenes was observed when H2O was replaced with D2O (Supplementary Fig. 30), confirming that H2O is the source of hydrogen for the alkene hydroazidation. The low reactivity observed under irradiation at 630 nm and 850 nm might correlate with the relatively weak absorption of low-energy light by the Mn(II)-based photoredox catalytic system (Fig. 2J). The Mn(III)-based, low-energy photoredox catalytic system was also examined. Unfortunately, the yields of the target product 3 were still very low (Fig. 2J). These results led us to reevaluate the plausibility of the Mn(III)-catalyzed hydroazidation of alkenes. From a mechanistic perspective (Supplementary Figs. 40 and 41), the regeneration of [MnIII] from [MnII] is much more difficult under external oxidant-free conditions compared with that of [MnII] from [MnI]. This might be the real reason why the blue light-induced, Mn(II)-based photoredox catalytic system was competent to perform the hydroazidation of alkenes, but the Mn(III)-based, low-energy photoredox catalytic system was ineffective.

To unlock a Mn(III)-based, low-energy photoredox catalytic reaction, the green oxidant O2 was employed to fulfill the regeneration of [MnIII], and the preliminary results of UV−Vis experiments showed that O2 could indeed facilitate the regeneration of the Mn(III)-based light-absorbing system (Fig. 2K and Supplementary Fig. 25). This finding encouraged us to design a step-economic hydroxyazidation of alkene64–70 catalyzed by the Mn(III)-based, low-energy photoredox catalytic platform. We envisioned harnessing a simple alkyl alcohol as cheap reductant to reduce the peroxyl alcohol intermediate in situ, enabling the one-step synthesis of the corresponding β-azido alcohol (Fig. 2L and Supplementary Figs. 39, 42, and 43). It was satisfactory that in the presence of Mn(acac)3 (3.0 mol%), isobutanol (1.0 equiv.), NH4HCO3 (1.0 equiv.), and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as the co-solvent, a good yield 82% for 4 was obtained under the irradiation of low-energy light (λcenter=850 nm) (Fig. 2M, Supplementary Tables 6−13 and Supplementary Fig. 31). This low-energy photoredox catalytic platform did not require the use of bidentate N ligand L1 (Supplementary Figs. 35−37). Notably, the azido radical was captured by butylated hydroxytoluene (BHT) which also inhibited the generation of 4, indicating that azido radical was the crucial intermediate in the low-energy photocatalytic conditions (Fig. 2N, Supplementary Fig. 29). Also, the aerobic hydroxyazidation of alkenes is unlikely to proceed via a radical chain process, as continuous irradiation with low-energy light was necessary to provide the desired product (Fig. 2O, Supplementary Fig. 27).

Scope of substrates

Having identified the optimal conditions of the anti-Markovnikov hydroazidation and aerobic hydroxyazidation of alkenes, we next examined the substrate scope. As shown in Fig. 3, an array of alkenes was successfully converted into value-added alkyl azides in moderate to good yields (6−59). Crucially, quinoline (16), thioether (40), unprotected amine (21 and 42), alcohol (26 and 31−59), thiazole (15) and triazole (29 and 54) functionalities, whose coordination ability might influence the in-situ assembly of the Mn(II/III)-based light-absorbing system, did not hinder the catalytic reactivities, showcasing excellent functionality tolerance. The incorporation of CF3 group (35 and 39) and diverse heterocycles (12−17, 29, 30, 54 and 55) into alkyl azides enhanced their application potential in the field of biomedicine. Although there was a cyclopropyl in the structure of the alkene, a satisfactory yield of the hydroazidation could still be obtained (18 and 19). Subsequently, the late-stage functionalization of a plethora of alkenes that bear more complex molecular skeletons from various pharmaceuticals was evaluated to access new potential drug candidates. Both of the Mn-based photoredox systems generated via the strategy of in-situ assembly showed the ability to unlock complex alkyl azides with useful yields (60−81, 20%−90%) (Fig. 4, Supplementary Tables 16 and 17). In addition, the coexistence of azido and hydroxy functionalities in 74−81 enabled by the Mn-based low-energy photoredox catalysis further attracted the interests of biologists and pharmacologists.

Synthetic utility

The synthetic utility and advantage of the in-situ assembly paradigm for Mn-based photocatalysis were further demonstrated. The hydroazidation and hydroxyazidation of alkenes were both synthetically scalable, and of particular note was that natural sunlight was directly utilized to drive the Mn-based, low-energy photocatalytic hydroxyazidation of alkenes (Fig. 5A, Supplementary Figs. 44 and 45). During the examination of the substrate scope, we found that the alkene 82 containing an anthraquinone moiety, which itself had the ability to absorb high-energy visible light (e.g., purple or blue light), was not a competent substrate for the hydroazidation of C=C double bond (Fig. 5B-i); by contrast, only under the low-energy photocatalytic aerobic conditions (630 or 850 nm), could useful yields toward β-azido alcohol 84 be observed (Fig. 5B-ii). This huge disparity in reactivity between high-energy visible light photocatalysis and the low-energy photocatalysis highlighted the unique functional group tolerance of the Mn-based, low-energy photocatalytic platform. Furthermore, we found that adopting a series of current popular photocatalysts including 4CzIPN (PC1), Ir[dF(CF3)ppy]2(dtbbpy)PF6 (PC2), Ru(bpy)3(PF6)2 (PC3), and [Acr-Mes]+(ClO4)− (PC4) to catalyze the hydroazidation/hydroxyazidation of alkenes was all unsatisfactory (Fig. 5C-i). Meanwhile, the manganese-based photocatalytic system was significantly more effective than its iron-based counterpart in the hydroazidation of alkenes (Fig. 5C-ii, Supplementary Tabs. 14 and 15). Last but not least, the alkyl azide 3 and β-azido alcohol 4 were derivatized into a series of new organic N-containing compounds (85−91), further highlighting the synthetic utility of our protocol (Fig. 5D).

In conclusion, we have shown that a modular in-situ assembly strategy using easily accessible components can rapidly unlock a highly desirable Mn-based, low-energy photoredox catalytic platform, starting from a corresponding high-energy visible light photocatalysis. The Mn-based high-energy visible light photocatalysis achieves an anti-Markovnikov radical hydroazidation of unactivated alkenes with H2O as hydrogen source, and the low-energy photoredox catalytic platform enables a one-step aerobic hydroxyazidation of alkenes. The successful gram-scale synthesis and late-stage functionalization of complex molecules underscore the practical utility and broad applicability of both the Mn-based photocatalytic systems. Further efforts on the development of Mn-based low-energy photocatalytic platforms are still ongoing in our laboratory.

Methods
General procedure for the anti-Markovnikov hydroazidation of alkenes

To a 25.0 mL Schlenk tube that contains a stir bar were added Mn(acac)2 (0.02 mmol, 10.0 mol%) and 2,2’-bipyridine-6,6’-diamine (L1, 0.02 mmol, 10.0 mol%). The mixture was thoroughly degassed via vacuum-nitrogen purging and filled with nitrogen. Alkene (0.2 mmol, 1.0 equiv.), azidotrimethylsilane (TMSN3, 0.6 mmol, 3.0 equiv.), H2O (1.0 mL) and anhydrous 1,2-dichloroethane (DCE, 1.0 mL) were added under nitrogen. Then the reaction was stirred and irradiated with blue light (λcenter=440 nm) at room temperature for 48 h (Supplementary Figs. 1 and 2). After the reaction was complete (monitored by TLC), the reaction mixture was extracted with ethyl acetate (EtOAc) three times. The combined organic layers were dried over Na2SO4 and removed under reduced pressure. The residue was purified by column chromatography on silica gel by eluting with petroleum ether (PE)/EtOAc to afford the products (Supplementary Figs. 11 and 46).

General procedure for the one-step hydroxyazidation of alkenes

To a 25.0 mL Schlenk tube that contains a stir bar were added Mn(acac)3 (0.006 mmol, 3.0 mol%) and NH4HCO3 (0.2 mmol, 1.0 equiv.). The mixture was thoroughly degassed via vacuum-air purging and filled with air. Alkene (0.2 mmol, 1.0 equiv.), TMSN3 (0.6 mmol, 3.0 equiv.), isobutanol (0.2 mmol, 1.0 equiv.), 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP, 1.0 mL) and anhydrous CH3CN (1.0 mL) were added under air and the tube was sealed with parafilm. Then the reaction was stirred and irradiated with low-energy light (λcenter=850 nm) at 30 °C for 48 h (Supplementary Figs. 3−5). After completion of the reaction (monitored by TLC), the solvent was removed under reduced pressure. The residue was purified by column chromatography on silica gel (PE/EtOAc) to afford the products (Supplementary Figs. 12 and 47).

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This manuscript presents an approach to low-energy manganese photoredox catalysis using in-situ assembly of Mn(II/III) salts, ligands, and reagents. The potential shift from high-energy (blue light) to low-energy (NIR, 850 nm) photocatalysis for generating N-centered radicals and enabling alkene functionalizations (hydroazidation, hydroxyazidation) is significant. The demonstration of two distinct transformations—anti-Markovnikov hydroazidation and aerobic hydroxyazidation under different light conditions showcases the versatility and tunability of the system. However, several critical issues must be addressed before the manuscript can be considered for publication.\n1. For the hydroxyazidation reaction under Condition B, it is important to clarify whether the observed reactivity could be influenced by photothermal heating. The irradiation may lead to significant temperature increases in the reaction mixture, it is essential to determine whether the transformation is truly driven by photochemical excitation rather than a thermal process. The authors should provide information on how the reaction temperature was monitored and controlled during irradiation. Was the temperature maintained constant throughout the experiment (e.g., via external cooling or a thermostated reactor)? If not, could the observed conversion be partially or fully attributed to localized heating? For example, running the reaction under identical conditions but in the dark, with heating applied to match the maximum temperature reached during the photoreaction; Comparing the reaction efficiency under irradiation at different light intensities (and corresponding temperatures) to assess the contribution of thermal effects.\n2. In the light on/off experiment shown in Figure 2P, the reaction appears to proceed more slowly during the initial irradiation period (0–3 h) compared to the later stage (6–9 h). Could the authors provide a plausible explanation for this kinetic behavior?\n3. In the catalyst screening section, the authors have evaluated several Mn(II) and Mn(III) salts. To provide a more comprehensive understanding of the oxidation state dependence and the scope of manganese species active in this transformation, it would be valuable to include data on other accessible oxidation states, particularly Mn(I) and Mn(IV) complexes.\n4. The authors have not experimentally verified the proposed valence state changes of the manganese species during the catalytic cycle, and have not provided supporting literature evidence for such transitions. Techniques such as XPS of reaction samples or in-situ/operando spectroscopic methods should be employed to directly monitor and elucidate the manganese valence states throughout the reaction.\n5. The references cited in the main text require careful verification; for example, there are errors in ref No.7 and ref No.50 .\n6. The Supporting Information (SI) contains several inconsistencies and inaccuracies that must be addressed. For instance, the products depicted in \"Fig. S5\" and \"Fig. S7\" are incorrect. Additionally, the NMR spectra 10, 12, 16, 28, 47, 54, 55, and 58 require further purification. There are also significant inaccuracies in the NMR data: for example, the ¹³C NMR spectra for products 67 and 68 are incorrect, and the spectrum for product 78 is erroneous too. Furthermore, inconsistencies in data formatting are observed, such as mismatched significant figures in the ¹H NMR data of spectra 31 and 32. It is strongly recommended that the authors carefully verify all data and NMR spectra in the Supporting Information. Additionally, providing 1–2 sets of single-crystal X-ray diffraction data would be preferable if feasible.", "reviewer_2": "The manuscript submitted by Lan, Zhang, Li, Niu and co-workers, and entitled \"Evolution of manganese low-energy photoredox catalysis from high-energy visible light photocatalysis\" describes the radical hydroazidation and hydroxyazidation of alkenes using interesting manganese photocatalysis. The first part focuses on the development of Mn(II)-based photoredox catalysis to achieve the hydroazidation of non-activated alkenes, which can be considered a more straightforward manner to test the photochemical properties of coordination transition metal complexes in comparison with the isolated photocatalysts. The second part is more intriguing, focusing on the development of the aerobic hydroxyazidation of alkenes in a single step using Mn(acac)3 and visible light at wavelength of 850 nm. The scope of alkenes is broad. It is exciting that the low-energy photocatalytic strategy indeed has unique advantages compared to the high-energy visible light catalysis. Overall, this strategy is truly fascinating. Therefore, I recommend this manuscript to be published in Nature Communications after the minor revision is made.\nEssential revisions:\n1. Can the two Mn-based photochemical systems operate using other azide reagents such as NaN3 and TBAN3? What about the corresponding yields of hydroazidation and hydroxyazidation of alkenes?\n2. For the reaction conditions B, if CH3CN is replaced by C(CH3)3CN or other common solvents that do have unnegligible coordinating ability, what is the influence on yields of hydroxyazidation?\n3. Besides the substrates shown in Figure 3 and 4, the authors should examine the reactivity of phenyl acrylate and vinyl benzoate, which would give some useful insights for the reaction mechanism.\n4. In Figure 5b, it is shown that the good yield of the hydroxyazidation of an alkene bearing the anthraquinone moiety increases with the utility of Mn-based low-energy photocatalysis. Whereas I do appreciate this result, it would be better to compare the catalytic performance of 3d metal iron (Carreira JACS 2023 145, 22347−22353; Shi Nat. Commun 2022 13:7880) under the photochemical conditions.\n5. Regarding the mechanistic studies, this reviewer strongly suggest that the authors should use HRMS to detect the possible intermediates during the initial stage of the two reactions.\n6. Stoichiometric H218O should be added to the reaction system of hydroxyazidation. I want to know whether the -18OH could be detected.\n7. There are also multiple formatting errors in the references and supplementary information. They are not listed here. It is hoped that they will be carefully revised.", "reviewer_3": "In this manuscript, Song and co-workers report a practical manganese-photocatalyzed radical hydroazidation and hydroxyazidation of alkenes, and they establish a paradigm that modular in-situ assembly of readily available Mn catalysts, TMSN₃ and/or bipyridyl ligands can rapidly unlock an effective Mn-based low-energy photoredox system (near-infrared, λ = 850 nm) from the corresponding high-energy visible-light precursor (blue, λ = 440 nm). In the introduction, the authors highlight the advantages of preparing photoactive metal complexes in situ through combination of a first-row transition metal and a ligand. The work is divided into two parts: the first part showcases the development of Mn(II)-based photoredox catalysis that under 440 nm visible light irradiation and using water as the H-source, enables selective anti-Markovnikov hydroazidation of unactivated alkenes; the second part shows how to quickly unlock an intriguing manganese-based low-energy photoredox catalytic system for the direct aerobic hydroxyazidation of alkenes. Considering all the above, I think this work does contain the expected conceptual novelty to justify its publication in Nature Communications. Several minor revisions should be made before the formal acceptance.\n(1) Figure 1 shows that the in situ assembly strategy proposed by the authors involves forming light-absorbing complexes through the in-situ assembly of metal salts, ligands, and solvents, which release radical species upon photoexcitation. However, in the reactions achieved using low-energy light, the authors did not employ ligands. This distinction should be clarified in the introduction.\n(2) In Figures 2A–2D, the authors measured UV-Vis data using DCE as the solvent, but the actual reactions were conducted in a mixed solvent system of DCE and water. To ensure experimental rigor and comprehensiveness, I recommend that the authors supplement the UV-Vis data using either water or a DCE/water mixture to verify or rule out the potential influence of water on the system's light absorption. Additionally, the corresponding UV-Vis experiments for Mn(acac)₃ should also include the data obtained with HFIP or CH₃CN/HFIP as the solvent.\n(3) Although both reactions demonstrate good substrate compatibility with alkenes, I still recommend that the authors present some unsuccessful substrate examples in SI to provide readers with a more comprehensive understanding.\n(4) The following key references should be included for completeness: 10.1021/jacs.4c18366 and 10.1038/s41557-024-01446-8.\n(5) I noticed several grammatical errors, which I won't enumerate here, but I recommend the authors conduct a thorough and meticulous proofreading of the entire text."}, "author_response": "Response to the comments from Reviewer #1.\nComments:\nThis manuscript presents an approach to low-energy manganese photoredox catalysis\nusing in-situ assembly of Mn(II/III) salts, ligands, and reagents. The potential shift from\nhigh-energy (blue light) to low-energy (NIR, 850 nm) photocatalysis for generating N-\ncentered radicals and enabling alkene functionalizations (hydroazidation,\nhydroxyazidation) is significant. The demonstration of two distinct transformations—\nanti-Markovnikov hydroazidation and aerobic hydroxyazidation under different light\nconditions showcases the versatility and tunability of the system.\nOur Response: We sincerely thank the reviewer for the positive comments on our work.\nHowever, several critical issues must be addressed before the manuscript can be\nconsidered for publication.\n1. For the hydroxyazidation reaction under Condition B, it is important to clarify\nwhether the observed reactivity could be influenced by photothermal heating. The\nirradiation may lead to significant temperature increases in the reaction mixture, it is\nessential to determine whether the transformation is truly driven by photochemical\nexcitation rather than a thermal process. The authors should provide information on\nhow the reaction temperature was monitored and controlled during irradiation. Was the\ntemperature maintained constant throughout the experiment (e.g., via external cooling\nor a thermostated reactor)? If not, could the observed conversion be partially or fully\nattributed to localized heating? For example, running the reaction under identical\nconditions but in the dark, with heating applied to match the maximum temperature\nreached during the photoreaction; Comparing the reaction efficiency under irradiation\nat different light intensities (and corresponding temperatures) to assess the contribution\nof thermal effects.\nOur Response: We sincerely thank the reviewer for the insightful comments and\nsuggestions. As shown in Supplementary Figure 3, our low-energy light photochemical\nreactor is equipped with two fans for temperature control, maintaining a maximum\ntemperature of 30 °C during 850 nm irradiation. Regardless of whether the system is\nunder 850 nm light irradiation or kept in darkness (using aluminum foil for shielding),\nthe temperature around the reaction vial is maintained at about 30 °C (Supplementary\nFigure 5). Based on the results of the strict comparison of control experiments (Table\nR1, Supplementary Table 13) and light-on/off experiment (Figure 2O, Supplementary\nFigure 27), we can conclude that photothermal effects do not drive the\nhydroxyazidation under condition B. Instead, the reaction necessitates continuous 850\nnm irradiation.\nSupplementary Figure 3. The photochemical reactor B (λcenter = 850 nm).\nSupplementary Figure 5. Temperature Monitoring in Reaction Processes.\nTable R1. Control experiments\nReaction setup (0.2 mmol-scale): To a 25.0 mL Schlenk flask that contains a stir bar were added Mn(acac)3 (0.006\nmmol, 3.0 mol%) and NH4HCO3 (0.2 mmol, 1.0 equiv.). The flask was evacuated and refilled with air three times\nusing an air balloon. Alkene (0.2 mmol, 1.0 equiv.), TMSN3 (0.6 mmol, 3.0 equiv.), isobutanol (0.2 mmol, 1.0 equiv.),\n1,1,1,3,3,3-hexafluoro-2-propanol (HFIP, 1.0 mL) and anhydrous CH3CN (1.0 mL) were added under air and the\nflask was sealed with parafilm. Then the reaction was stirred and irradiated by 850 nm LEDs for 48 h. Products were\npurified by silica gel chromatography to afford the isolated yields (from Supplementary Table 13 in the revised\nSupplemental Information).\n30\n20\n%)\nd\n(\nel\nYi\n10\n0\n0 2 4 6 8 10 12\nTime (h)\nFigure. 2O Light on/off experiment (See the Supplementary Figure 27 for details).\n2. In the light on/off experiment shown in Figure 2P, the reaction appears to proceed\nmore slowly during the initial irradiation period (0–3 h) compared to the later stage (6–\n9 h). Could the authors provide a plausible explanation for this kinetic behavior?\nOur Response: We are very grateful to the reviewer for pointing out this issue.\nConsidering that the yields of the light on/off experiment were determined by HPLC\nand the accuracy of HPLC yields is usually lower than that of isolated yields, we thus\nhave determined the isolated yields of the light on/off experiment. The isolated yields\nindicated that the reaction progress during the initial irradiation period (0–3 h) was\nalmost the same as that in the later stage (6–9 h) (Supplementary Figure 27). The revised\nresults of light on/off experiment have been shown in Figure 2O in the revised\nmanuscript.\n30\n20\n%)\nd\n(\nYiel\n10\n0\n0 2 4 6 8 10 12\nTime (h)\nSupplementary Figure 27. Light on/off experiment of the hydroxyazidation of alkenes. Reaction setup (0.2 mmol-\nscale): To a 25.0 mL Schlenk flask that contains a stir bar were added Mn(acac)3 (0.006 mmol, 3.0 mol%) and\nNH4HCO3 (0.2 mmol, 1.0 equiv.). The flask was evacuated and refilled with air three times using an air balloon.\nAlkene (0.2 mmol, 1.0 equiv.), TMSN3 (0.6 mmol, 3.0 equiv.), isobutanol (0.2 mmol, 1.0 equiv.), 1,1,1,3,3,3-\nhexafluoro-2-propanol (HFIP, 1.0 mL) and anhydrous CH3CN (1.0 mL) were added under air and the flask was\nsealed with parafilm. Then the reaction was stirred and irradiated by 850 nm LEDs for corresponding time.\nProducts were purified by silica gel chromatography to afford the isolated yields. See the Supplementary Figure 27 for details.\n3. In the catalyst screening section, the authors have evaluated several Mn(II) and\nMn(III) salts. To provide a more comprehensive understanding of the oxidation state\ndependence and the scope of manganese species active in this transformation, it would\nbe valuable to include data on other accessible oxidation states, particularly Mn(I) and\nMn(IV) complexes.\nOur Response: We sincerely thank the reviewer for the insightful comments and\nsuggestions. According to your insightful suggestions, data for several accessible\noxidation states of manganese have now been included in the catalyst screening section\n(Supplementary Tables 1 and 7).\n1. For the anti-Markovnikov hydroazidation of alkenes (Condition A): When Mn(I)\ncatalyst was employed as the initial catalyst, the desired product 3 could still be\ngenerated (Table R2, entries 2 and 3). According to the proposed mechanism\n(Supplementary Figure 40), the whole catalytic cycle involves the interconversion of\n[Mn(II)] and [Mn(I)]. Therefore, the above reactivity is reasonable. In addition, when\nMn(acac) and MnO were used as alternatives to Mn(acac) , they provided product 3\n3 2 2\nin moderate yields (Table R2, entries 4 and 5). This is because their strong oxidizing\npower allows them to be easily reduced by TMSN , leading to the formation of [Mn(II)]\n3\nspecies. Once [Mn(II)] is generated, this reaction proceeds well under the blue light\nirradiation.\nTable R2. Investigation of Mn salt in the Mn(II)-based photoredox system\nReaction setup (0.2 mmol-scale): To a 25.0 mL Schlenk flask that contains a stir bar were added Mn salt (0.02 mmol,\n10.0 mol%) and 2,2'-bipyridine-6,6'-diamine (L1, 0.02 mmol, 10.0 mol%). The mixture was thoroughly degassed\nvia vacuum-nitrogen purging and filled with nitrogen. Alkene (0.2 mmol, 1.0 equiv.), azidotrimethylsilane (TMSN3,\n0.6 mmol, 3.0 equiv.), H2O (1.0 mL) and anhydrous 1,2-dichloroethane (DCE, 1.0 mL) were added under nitrogen.\nThen the reaction was stirred and irradiated by 440 nm LEDs for 48 h. Products were purified by silica gel\nchromatography to afford the isolated yields (from Supplementary Table 1 in the revised Supplemental Information).\n2. For the hydroxyazidation of alkenes (condition B): As shown in Table R3, we found\nthat the Mn(I) catalysts failed to yield the desired product 4 (Table R3, entries 2 and 3).\nBy contrast, raising the valence of Mn to +4 could achieve the desired hydroxyazidation\nof alkenes in a 30% yield (Table R3, entry 4). These findings showed the uniqueness\nof the Mn(III)-based low-energy photocatalytic system (Supplementary Figure 42).\nTable R3. Investigation of Mn salt in the Mn(III)-based low-energy photoredox system\nReaction setup (0.2 mmol-scale): To a 25.0 mL Schlenk flask that contains a stir bar were added Mn salt (0.006\nmmol, 3.0 mol%) and NH4HCO3 (0.2 mmol, 1.0 equiv.). The flask was evacuated and refilled with air three times\nusing an air balloon. Alkene (0.2 mmol, 1.0 equiv.), TMSN3 (0.6 mmol, 3.0 equiv.), isobutanol (0.2 mmol, 1.0 equiv.),\n1,1,1,3,3,3-hexafluoro-2-propanol (HFIP, 1.0 mL) and anhydrous CH3CN (1.0 mL) were added under air and the\nflask was sealed with parafilm. Then the reaction was stirred and irradiated by 850 nm LEDs for corresponding time.\nProducts were purified by silica gel chromatography to afford the isolated yields (from Supplementary Table 7 in\nthe revised Supplemental Information).\n4. The authors have not experimentally verified the proposed valence state changes of\nthe manganese species during the catalytic cycle, and have not provided supporting\nliterature evidence for such transitions. Techniques such as XPS of reaction samples or\nin-situ/operando spectroscopic methods should be employed to directly monitor and\nelucidate the manganese valence states throughout the reaction.\nOur Response: We sincerely thank the reviewer for the suggestions. In the revised\nSupplementary Information, we have provided detailed discussions on the valence state\nchanges of Mn during the catalytic cycle based on the results of UV−Vis, HRMS, and\nXPS experiments (Supplementary Figures 40 and 42).\n1. For the Mn(II)-based blue light photocatalytic system, UV−Vis evidence\n(Supplementary Figures 13 and 15) and radical clock experiment (Supplementary\nFigure 28) demonstrated that blue light irradiation photolyzed the\nMn(acac) /L1/TMSN mixture under a N atmosphere, generating azido radicals. This\n2 3 2\nphotolysis process is concomitant with a reduction in the manganese valence state from\n+2 to +1. The HAT process of radical adduct VIII, which is essential for the\nhydroazidation (Nat. Commun. 2025, 16, 7906), is likely mediated by the unstable\n[Mn(I)] intermediate in the presence of the co-solvent H O (Supplementary Figure 40);\n2\nthe transient nature of this [Mn(I)] species accounts for the exclusive detection of\n[Mn(II)] by XPS (Supplementary Figure 41). Therefore, we proposed that the\nmanganese valence cycles between +2 and +1 during the hydroazidation reaction\nprocess.\nSupplementary Figure 40. Proposed mechanism of the anti-Markovnikov hydroazidation of alkenes.\nSupplementary Figure 41. XPS spectrum of the anti-Markovnikov hydroazidation of alkenes.\n2. For the Mn(III)-based low-energy light photocatalytic system, UV−Vis evidence\n(Supplementary Figures 20−25) and the successful capture of azido radicals by BHT\n(Supplementary Figure 29) demonstrated that the photolysis of the Mn(acac) /TMSN\n3 3\nmixture in CH₃CN/HFIP to generate azido radicals requires only 850 nm low-energy\nlight irradiation. This photolysis process is concomitant with a reduction in the\nmanganese valence state from +3 to +2 (Supplementary Figure 42). The high reactivity\nunder 850 nm low-energy light indicated that the Mn(acac) /TMSN mixture was\n3 3\nextremely unstable. Consequently, only the [Mn(II)] species was observed by XPS\n(Supplementary Figure 43). Similar to Prof. Jiao’s report (J. Am. Chem. Soc. 2015, 137,\n6059–6066), the manganese valence cycling between +3 and +2 for the aerobic\nhydroxyazidation of alkenes is reasonable.\nSupplementary Figure 42. Proposed mechanism of the hydroxyazidation of alkenes.\nSupplementary Figure 43. XPS spectrum of the hydroxyazidation of alkenes.\n5. The references cited in the main text require careful verification; for example, there\nare errors in ref No.7 and ref No.50.\nOur Response: We sincerely thank the reviewer for pointing these format errors on the\nreferences. The formatting of all references in both the revised manuscript and\nsupplementary information has been carefully checked and corrected. All amendments\nhave been highlighted for the reviewer's convenience.\n6. The Supporting Information (SI) contains several inconsistencies and inaccuracies\nthat must be addressed. For instance, the products depicted in \"Fig. S5\" and \"Fig. S7\"\nare incorrect. Additionally, the NMR spectra 10, 12, 16, 28, 47, 54, 55, and 58 require\nfurther purification. There are also significant inaccuracies in the NMR data: for\nexample, the ¹³C NMR spectra for products 67 and 68 are incorrect, and the spectrum\nfor product 78 is erroneous too. Furthermore, inconsistencies in data formatting are\nobserved, such as mismatched significant figures in the ¹H NMR data of spectra 31 and\n32. It is strongly recommended that the authors carefully verify all data and NMR\nspectra in the Supporting Information. Additionally, providing 1–2 sets of single-crystal\nX-ray diffraction data would be preferable if feasible.\nOur Response: We sincerely thank the reviewer for pointing these mistakes in\nsupplementary information, and we also apologized for our carelessness to these\nmistakes. In the revised supplementary information, we have made a diligent effort to\nensure that all inconsistencies and inaccuracies have been thoroughly addressed\n(Supplementary Figures 6 and 10). Following your advice, we have confirmed the\nstructures of the hydroazidation and hydroxyazidation products (S15 and 84,\nrespectively) by single-crystal X-ray diffraction (Supplementary Tables 16 and 17). Of\nparticular note, because hydroazidation product 73 is a colorless liquid, we converted\nit into triazole S15 via a Click reaction to facilitate subsequent single-crystal X-ray\ndiffraction analysis.\nAdditionally, we have undertaken repurification and reacquired the NMR spectra for\nproducts 10, 12, 16, 28, 47, 54, 55, 58, 67, 68, and 78. The spectral quality for products\n16, 28, 47, 54, 55, 58, 67, 68, and 78 has been successfully improved to a satisfactory\nlevel (Figures R1−R18). However, despite extensive efforts using various purification\nmethods, the NMR spectra for products 10 and 12 still show minor signals from a\npersistent unknown impurity that we could not eliminate. It is worth noting that this\nimpurity has also been observed in the supporting information of both Prof. Carreira's\n(J. Am. Chem. Soc. 2023, 145, 22347) and Prof. West's (Nat. Commun. 2025, 16, 7906)\nwork. Thus, we speculated that this impurity may originate from the nucleophilic azide\nreagents (NaN and TMSN ) under the radical azidation conditions of alkenes. To\n3 3\npresent a high-quality supplementary information for publication, we have deleted the\nproducts 10 and 12 and renumbered the products in the revised manuscript (Figure 3)\nand supplementary information.\nSupplementary Figure 6. Method A for the synthesis of non-activated alkenes.\nSupplementary Figure 10. Method E for the synthesis of non-activated alkenes.\nSupplementary Table 16. Crystal data and structure refinement for S15\nCCDC number 2500507\nEmpirical formula C H N O\n29 31 7\nFormula weight 493.61\nTemperature [K] 150.00(10)\nCrystal system monoclinic\nSpace group (number) P2 /c (14)\n1\na [Å] 21.3513(10)\nb [Å] 8.1784(4)\nc [Å] 14.4340(5)\nα [°] 90\nβ [°] 91.352(4)\nγ [°] 90\nVolume [Å3] 2519.76(19)\nZ 4\nρ [gcm−3] 1.301\ncalc\nμ [mm−1] 0.083\nF(000) 1048\nCrystal size [mm3] 0.15×0.2×0.22\nCrystal colour colourless\nCrystal shape block\nRadiation Mo K (λ=0.71073 Å)\nα\n2θ range [°] 5.65 to 48.27 (0.87 Å)\n−24 ≤ h ≤ 24\nIndex ranges\n−9 ≤ k ≤ 9\n−16 ≤ l ≤ 16\nReflections collected 11660\nIndependent reflections 3863, R = 0.0495, R = 0.0541\nint sigma\nCompleteness to θ = 24.136° 96.0 %\nData/Restraints/Parameters 3863/0/335\nAbsorption correction T /T (method) 0.0132/1.0000, (multi-scan)\nmin max\nGoodness-of-fit on F2 0.919\nFinal R indexes [I≥2σ(I)] R = 0.0652, wR = 0.1505\n1 2\nFinal R indexes [all data] R = 0.0880, wR = 0.1608\n1 2\nLargest peak/hole [eÅ−3] 0.21/−0.23\nSupplementary Table 17. Crystal data and structure refinement for 84\nCCDC number 2499393\nEmpirical formula C H N O\n21 19 3 5\nFormula weight 393.39\nTemperature [K] 100.00(10)\nCrystal system triclinic\nSpace group (number) P1 (2)\na [Å] 8.1742(3)\nb [Å] 9.1962(4)\nc [Å] 13.1379(5)\nα [°] 84.150(3)\nβ [°] 75.197(4)\nγ [°] 81.424(4)\nVolume [Å3] 942.04(7)\nZ 2\nρ [gcm−3] 1.387\ncalc\nμ [mm−1] 0.836\nF(000) 412\nCrystal size [mm3] 0.06×0.1×0.12\nCrystal colour clear light colourless\nCrystal shape block\nRadiation Cu K α (λ=1.54184 Å)\n2θ range [°] 6.97 to 133.19 (0.84 Å)\n−9 ≤ h ≤ 9\nIndex ranges −10 ≤ k ≤ 10\n−15 ≤ l ≤ 15\nReflections collected 16482\nIndependent reflections 3324, R = 0.0482, R = 0.0292\nint sigma\nCompleteness to θ = 66.593° 99.7 %\nData/Restraints/Parameters 3324/1/274\nAbsorption correction T /T (method) 0.6377/1.0000 (multi-scan)\nmin max\nGoodness-of-fit on F2 1.056\nFinal R indexes [I≥2σ(I)] R = 0.0853, wR = 0.2612\n1 2\nFinal R indexes [all data] R = 0.1000, wR = 0.2768\n1 2\nLargest peak/hole [eÅ−3] 0.67/−0.33\nFigure R1. 1H NMR spectrum of 12. 1H NMR (400 MHz, Chloroform-d) δ 4.46 (dd, J = 8.7, 5.4 Hz, 1H), 4.20 –\n4.10 (m, 2H), 4.03 (q, J = 7.1 Hz, 1H), 3.96 – 3.88 (m, 1H), 3.26 (t, 2H), 2.35 – 2.21 (m, 1H), 2.09 – 1.85 (m, 3H),\n1.74 – 1.54 (m, 4H), 1.50 – 1.32 (m, 4H).\nFigure R2. 13C NMR spectrum of 12. 13C NMR (101 MHz, Chloroform-d) δ 173.55, 76.84, 69.42, 64.82, 51.38,\n30.29, 28.79, 28.53, 26.41, 25.53, 25.31.\nHRMS (ESI, m/z) calcd for C11H19N3O3Na+, [M+Na]+: 264.1319, found: 264.1320.\nFigure R3. 1H NMR spectrum of 24 (Sci. China. Chem. 2019, 62, 1537−1541).1H NMR (400 MHz, Chloroform-d)\nδ 7.20 (t, J = 8.0 Hz, 2H), 7.14 – 7.04 (m, 3H), 3.18 (t, 2H), 2.55 (t, J = 7.9 Hz, 2H), 1.70 – 1.57 (m, 2H), 1.57 –\n1.41 (m, 2H).\nFigure R4. 13C NMR spectrum of 24 (Sci. China. Chem. 2019, 62, 1537−1541). 13C NMR (101 MHz, Chloroform-\nd) δ 141.92, 128.48, 128.47, 126.00, 51.42, 35.46, 28.55.\nFigure R5. 1H NMR spectrum of 43. 1H NMR (400 MHz, Chloroform-d) δ 8.26 (d, J = 7.7 Hz, 1H), 7.91 (d, J = 7.8\nHz, 1H), 7.81 (d, J = 7.2 Hz, 1H), 7.69 (d, J = 7.2 Hz, 1H), 7.50 (t, J = 7.6 Hz, 1H), 7.33 (t, J = 7.4 Hz, 2H), 4.42 (t,\nJ = 5.9 Hz, 2H), 3.80 (s, 1H), 3.39 (d, J = 12.4 Hz, 1H), 3.34 – 3.18 (m, 1H), 2.37 (s, 1H), 1.94 – 1.79 (m, 2H), 1.74\n– 1.47 (m, 4H).\nFigure R6. 13C NMR spectrum of 43. 13C NMR (101 MHz, Chloroform-d) δ 193.04, 166.73, 143.99, 143.15, 136.01,\n135.55, 135.18, 134.37, 129.84, 128.67, 127.25, 127.11, 126.21, 124.16, 70.58, 65.46, 57.17, 33.87, 28.61, 22.18.\nHRMS (ESI, m/z) calcd for C20H19N3O4Na+, [M+Na]+: 388.1268, found: 388.1271.\nFigure R7. 1H NMR spectrum of 50. 1H NMR (400 MHz, Chloroform-d) δ 3.92 – 3.82 (m, 1H), 3.36 (dd, J = 12.4,\n3.2 Hz, 1H), 3.23 (dd, J = 12.3, 7.4 Hz, 1H), 2.04 (s, 1H), 1.84 – 1.59 (m, 5H), 1.53 – 1.35 (m, 2H), 1.33 – 1.07 (m,\n4H), 1.04 – 0.81 (m, 2H).\nFigure R8. 13C NMR spectrum of 50. 13C NMR (101 MHz, Chloroform-d) δ 68.48, 57.78, 42.04, 34.17, 34.02,\n32.91, 26.59, 26.39, 26.22.\nHRMS (ESI, m/z) calcd for C9H17N3ONa+, [M+Na]+: 206.1264, found: 206.1261.\nFigure R9. 1H NMR spectrum of 51. 1H NMR (400 MHz, Chloroform-d) δ 3.65 (t, J = 7.7 Hz, 1H), 3.50 (td, J =\n9.3, 8.7, 2.6 Hz, 1H), 2.54 (s, 1H), 2.05 – 1.90 (m, 1H), 1.90 – 1.81 (m, 1H), 1.80 – 1.67 (m, 4H), 1.66 – 1.42 (m,\n6H).\nFigure R10. 13C NMR spectrum of 51. 13C NMR (101 MHz, Chloroform-d) δ 74.37, 68.83, 31.88, 28.26, 25.93,\n25.74, 24.33, 24.01.\nHRMS (ESI, m/z) calcd for C8H15N3ONa+, [M+Na]+: 192.1107, found: 192.1105.\nFigure R11. 1H NMR spectrum of 54. 1H NMR (400 MHz, Chloroform-d) δ 7.90 – 7.76 (m, 2H), 7.44 – 7.31 (m,\n2H), 4.74 (t, J = 6.9 Hz, 2H), 3.91 – 3.65 (m, 1H), 3.31 (dd, J = 12.4, 3.5 Hz, 1H), 3.22 (dd, J = 12.4, 7.3 Hz, 1H),\n2.82 (d, J = 4.1 Hz, 1H), 2.25 – 2.03 (m, 2H), 1.61 – 1.46 (m, 3H), 1.46 – 1.33 (m, 1H).\nFigure R12. 13C NMR spectrum of 54. 13C NMR (101 MHz, Chloroform-d) δ 144.02, 126.23, 117.72, 70.16, 56.81,\n56.08, 33.44, 29.58, 22.39.\nHRMS (ESI, m/z) calcd for C12H16N6ONa+, [M+Na]+: 283.1278, found: 283.1274.\nFigure R13. 1H NMR spectrum of 63. 1H NMR (400 MHz, Chloroform-d) δ 7.21 (d, J = 8.1 Hz, 2H), 7.12 (d, J =\n8.1 Hz, 2H), 4.06 (t, J = 6.5 Hz, 2H), 3.69 (q, J = 7.2 Hz, 1H), 3.22 (t, J = 6.9 Hz, 2H), 3.12 (dd, J = 13.9, 4.1 Hz,\n1H), 2.51 (dd, J = 13.9, 9.5 Hz, 1H), 2.42 – 2.26 (m, 2H), 2.19 – 2.03 (m, 2H), 2.02 – 1.88 (m, 1H), 1.82 – 1.68 (m,\n1H), 1.64 – 1.50 (m, 5H), 1.48 (d, J = 7.2 Hz, 3H), 1.38 – 1.24 (m, 4H).\nFigure R14. 13C NMR spectrum of 63. 13C NMR (101 MHz, Chloroform-d) δ 174.62, 138.80, 138.45, 129.06,\n127.50, 64.48, 51.26, 50.95, 45.14, 38.16, 35.17, 29.21, 28.68, 28.37, 26.24, 25.35, 20.53, 18.44, 18.43.\nHRMS (ESI, m/z) calcd for C21H29N3O3Na+, [M+Na]+: 394.2101, found: 394.2105.\nFigure R15. 1H NMR spectrum of 64. 1H NMR (400 MHz, Chloroform-d) δ 7.91 (s, 1H), 7.79 (d, J = 7.6 Hz, 1H),\n7.42 (d, J = 7.9 Hz, 1H), 7.34 (t, J = 7.7 Hz, 1H), 4.32 (t, J = 6.6 Hz, 2H), 3.27 (t, J = 6.8 Hz, 2H), 2.51 (s, 3H), 1.87\n– 1.71 (m, 2H), 1.69 – 1.57 (m, 2H), 1.51 – 1.39 (m, 4H).\nFigure R16. 13C NMR spectrum of 64. 13C NMR (101 MHz, Chloroform-d) δ 169.18, 165.59, 150.61, 131.92,\n129.40, 126.93, 126.25, 122.76, 65.09, 51.29, 28.72, 28.53, 26.37, 25.60, 21.00.\nHRMS (ESI, m/z) calcd for C15H19N3O4Na+, [M+Na]+:328.1268, found: 328.1271.\nFigure R17. 1H NMR spectrum of 74. 1H NMR (400 MHz, Chloroform-d) δ 7.81 – 7.71 (m, 3H), 7.63 (d, J = 7.6\nHz, 1H), 7.60 – 7.50 (m, 2H), 7.49 – 7.37 (m, 3H), 4.14 – 3.97 (m, 2H), 3.78 (q, J = 7.2 Hz, 1H), 3.66 (s, 1H), 3.22\n(qd, 2H), 2.68 (s, 1H), 1.63 – 1.54 (m, 2H), 1.51 (d, J = 7.2 Hz, 3H), 1.46 – 1.36 (m, 3H), 1.33 – 1.23 (m, 1H).\nFigure R18. 13C NMR spectrum of 74. 13C NMR (101 MHz, Chloroform-d) δ 196.77, 174.12, 140.99, 137.85,\n137.34, 132.65, 131.59, 131.55, 130.10, 129.12, 129.08, 129.03, 128.50, 128.34, 70.53, 64.70, 56.93, 45.43, 33.78,\n28.39, 21.86, 18.32.\nHRMS (ESI, m/z) calcd for C22H25N3O4Na+, [M+Na]+: 418.1737, found: 418.1740.\nResponse to the comments from Reviewer #2.\nComments:\nThe manuscript submitted by Lan, Zhang, Li, Niu and co-workers, and entitled\n\"Evolution of manganese low-energy photoredox catalysis from high-energy visible\nlight photocatalysis\" describes the radical hydroazidation and hydroxyazidation of\nalkenes using interesting manganese photocatalysis. The first part focuses on the\ndevelopment of Mn(II)-based photoredox catalysis to achieve the hydroazidation of\nnon-activated alkenes, which can be considered a more straightforward manner to test\nthe photochemical properties of coordination transition metal complexes in comparison\nwith the isolated photocatalysts. The second part is more intriguing, focusing on the\ndevelopment of the aerobic hydroxyazidation of alkenes in a single step using\nMn(acac) and visible light at wavelength of 850 nm. The scope of alkenes is broad. It\n3\nis exciting that the low-energy photocatalytic strategy indeed has unique advantages\ncompared to the high-energy visible light catalysis. Overall, this strategy is truly\nfascinating. Therefore, I recommend this manuscript to be published in Nature\nCommunications after the minor revision is made.\nOur Response: Thank you very much for your supportive and insightful comments\nregarding our manuscript.\n1. Can the two Mn-based photochemical systems operate using other azide reagents\nsuch as NaN and TBAN ? What about the corresponding yields of hydroazidation and\n3 3\nhydroxyazidation of alkenes?\nOur Response: We sincerely thank the reviewer for the insightful comments. After\ncareful identification, we found that neither NaN nor TBAN serves as an effective\n3 3\nazide reagent in the two manganese photochemical systems (Supplementary Tables 4\nand 8).\nSupplementary Table 4. Investigation of azide source in the Mn(II)-based photoredox system\nReaction setup (0.2 mmol-scale): To a 25.0 mL Schlenk flask that contains a stir bar were added Mn(acac)2 (0.02\nmmol, 10.0 mol%) and 2,2'-bipyridine-6,6'-diamine (L1, 0.02 mmol, 10.0 mol%). The mixture was thoroughly\ndegassed via vacuum-nitrogen purging and filled with nitrogen. Alkene (0.2 mmol, 1.0 equiv.), azide source (0.6\nmmol, 3.0 equiv.), H2O (1.0 mL) and anhydrous 1,2-dichloroethane (DCE, 1.0 mL) were added under nitrogen. Then\nthe reaction was stirred and irradiated by 440 nm LEDs for 48 h. Products were purified by silica gel chromatography\nto afford the isolated yields.\nSupplementary Table 8. Investigation of azide source in the Mn(III)-based low-energy photoredox system\nReaction setup (0.2 mmol-scale): To a 25.0 mL Schlenk flask that contains a stir bar were added Mn(acac)3 (0.006\nmmol, 3.0 mol%) and NH4HCO3 (0.2 mmol, 1.0 equiv.). The flask was evacuated and refilled with air three times\nusing an air balloon. Alkene (0.2 mmol, 1.0 equiv.), azide source (0.6 mmol, 3.0 equiv.), isobutanol (0.2 mmol, 1.0\nequiv.), 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP, 1.0 mL) and anhydrous CH3CN (1.0 mL) were added under air\nand the flask was sealed with parafilm. Then the reaction was stirred and irradiated by 850 nm LEDs for 48 h.\nProducts were purified by silica gel chromatography to afford the isolated yields.\n2. For the reaction conditions B, if CH CN is replaced by C(CH ) CN or other common\n3 3 3\nsolvents that do have unnegligible coordinating ability, what is the influence on yields\nof hydroxyazidation?\nOur Response: Thank you very much for your insightful comments and suggestions.\nFor the Mn-based low-energy light photocatalytic system, our HRMS results provided\nevidence for the participation of CH CN in the in-situ assembly of the photoactive\n3\nmore sterically hindered C(CH ) CN decreased the yield of the hydroxyazidation\n3 3\nproduct (Table R4, entry 2). This suggested that the increased steric bulk of C(CH ) CN\n3 3\nmay hinder the in-situ assembly of the Mn(III)-based photocatalytic system. Other\ncommonly-used solvents with non-negligible coordinating ability, such as acetone and\nDMF, were unsuitable for the hydroxyazidation of alkenes (Table R4, entries 3, 4).\nThese results have been incorporated into the revised Supplementary Information\n(Supplementary Table 9).\nSupplementary Figure 36. ESI-HRMS spectrum of Species IV. Species IV may be a low-energy light-absorbing\nintermediate for the generation of the azido radical. It was detected in positive-ion mode (as its sodium adduct) by\nHRMS.\nTable R4. Investigation of solvent in the Mn(III)-based low-energy photoredox system\nReaction setup (0.2 mmol-scale): To a 25.0 mL Schlenk flask that contains a stir bar were added Mn(acac)3 (0.006\nmmol, 3.0 mol%) and NH4HCO3 (0.2 mmol, 1.0 equiv.). The flask was evacuated and refilled with air three times\nusing an air balloon. Alkene (0.2 mmol, 1.0 equiv.), TMSN3 (0.6 mmol, 3.0 equiv.), isobutanol (0.2 mmol, 1.0 equiv.)\nand solvent (2.0 mL) were added under air and the flask was sealed with parafilm. Then the reaction was stirred and\nirradiated by 850 nm LEDs for 48 h. Products were purified by silica gel chromatography to afford the isolated yields\n(from Supplementary Table 9 in the revised Supplemental Material).\n3. Besides the substrates shown in Figure 3 and 4, the authors should examine the\nreactivity of phenyl acrylate and vinyl benzoate, which would give some useful insights\nfor the reaction mechanism.\nOur Response: We sincerely thank the reviewers for their valuable comments. We have\ninvestigated the reactivity of vinyl benzoate S5 and phenyl acrylate S7 in our two\nsystems. The corresponding results and discussions have been presented below.\n1. Under the Mn(II)-based blue light photocatalytic system for hydroazidation of\nalkenes, the yields of desired product of both vinyl benzoate S5 and phenyl acrylate S7\nwere very low (Supplementary Figure 38), accompanied by the production of numerous\ncomplex and inseparable byproducts. From a mechanistic viewpoint (Supplementary\nFigure 40), compared to the radical adduct VIII, the more stable radical adduct\ngenerated by S5 or S7 is less likely to undergo HAT with our proposed H-donor\nintermediate IX. This lower reactivity may account for the poor reaction selectivity.\nSupplementary Figure 38. Reactivity assessment under condition A. Reaction setup (0.2 mmol-scale): To a 25.0 mL\nSchlenk flask that contains a stir bar were added Mn(acac)2 (0.02 mmol, 10.0 mol%) and 2,2'-bipyridine-6,6'-diamine\n(L1, 0.02 mmol, 10.0 mol%). The mixture was thoroughly degassed via vacuum-nitrogen purging and filled with\nnitrogen. Alkene S5 or S7 (0.2 mmol, 1.0 equiv.), TMSN3 (0.6 mmol, 3.0 equiv.), H2O (1.0 mL) and anhydrous 1,2-\ndichloroethane (DCE, 1.0 mL) were added under nitrogen. Then the reaction was stirred and irradiated by 440 nm\nLEDs for 48 h.\nSupplementary Figure 40. Proposed mechanism of the anti-Markovnikov hydroazidation of alkenes.\n2. Under the Mn(III)-based low-energy light photocatalytic system for\nhydroxyazidation of alkenes, the desired products from both vinyl benzoate (S5) and\nphenyl acrylate (S7) were not detected (Supplementary Figure 39). From a mechanistic\nviewpoint (Supplementary Figure 42), compared to the radical adduct VIII, the\nnucleophilicity of the radical adduct generated by S5 or S7 is attenuated by the ester\ngroup, thereby impeding the subsequent reactions with electrophilic O .\nSchlenk flask that contains a stir bar were added Mn(acac)3 (0.006 mmol, 3.0 mol%) and NH4HCO3 (0.2 mmol, 1.0\nequiv.). The flask was evacuated and refilled with air three times using an air balloon. Alkene S5 or S7 (0.2 mmol,\n1.0 equiv.), TMSN3 (0.6 mmol, 3.0 equiv.), isobutanol (0.2 mmol, 1.0 equiv.), 1,1,1,3,3,3-hexafluoro-2-propanol\n(HFIP, 1.0 mL) and anhydrous CH3CN (1.0 mL) were added under air and the flask was sealed with parafilm. Then\nthe reaction was stirred and irradiated by 850 nm LEDs for 48 h. Products were purified by silica gel chromatography\nto afford the isolated yields.\nSupplementary Figure 42. Proposed mechanism of the hydroxyazidation of alkenes.\n4. In Figure 5b, it is shown that the good yield of the hydroxyazidation of an alkene\nbearing the anthraquinone moiety increases with the utility of Mn-based low-energy\nphotocatalysis. Whereas I do appreciate this result, it would be better to compare the\ncatalytic performance of 3d metal iron (Carreira JACS 2023 145, 22347−22353; Shi\nNat. Commun 2022 13:7880) under the photochemical conditions.\nOur Response: We sincerely thank the reviewer for the insightful comments and\nsuggestions. Attempts to apply Carreira's FeCl ·6H O or Shi's Fe(NO ) ·9H O system\n3 2 3 3 2\nto the low-energy-light-mediated hydroxyazidation of substrate 82 were unsuccessful.\nEven under higher-energy blue light irradiation, the desired product 84 was not formed\n(Supplementary Tables 14 and 15).\nSupplementary Table 14. Comparison of catalytic performance between FeCl3·6H2O and Mn(acac)3 under condition\nB\nReaction setup (0.2 mmol-scale): According to the literature (Carreira et al. J. Am. Chem. Soc. 2023, 145,\n22347−22353), to a 25.0 mL Schlenk flask that contains a stir bar were added FeCl3·6H2O (0.006 mmol, 3.0 mol%)\nand NH4HCO3 (0.2 mmol, 1.0 equiv.). The flask was evacuated and refilled with air three times using an air balloon.\nAlkene 82 (0.2 mmol, 1.0 equiv.), TMSN3 (0.6 mmol, 3.0 equiv.), isobutanol (0.2 mmol, 1.0 equiv.), 1,1,1,3,3,3-\nhexafluoro-2-propanol (HFIP, 1.0 mL) and anhydrous CH3CN (1.0 mL) were added under air and the flask was\nsealed with parafilm. Then the reaction was stirred and irradiated by 440 nm or 850 nm LEDs for 48 h. Products\nwere purified by silica gel chromatography to afford the isolated yields.\nSupplementary Table 15. Comparison of catalytic performance between Fe(NO3)3·9H2O and Mn(acac)3 under\ncondition B\nReaction setup (0.2 mmol-scale): According to the literature (Shi et al. Nat. Commun. 2022, 13, 7880), to a 25.0 mL\nSchlenk flask that contains a stir bar were added Fe(NO3)3·9H2O (0.006 mmol, 3.0 mol%) and NH4HCO3 (0.2 mmol,\n1.0 equiv.). The flask was evacuated and refilled with air three times using an air balloon. Alkene 82 (0.2 mmol, 1.0\nequiv.), TMSN3 (0.6 mmol, 3.0 equiv.), isobutanol (0.2 mmol, 1.0 equiv.), 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP,\n1.0 mL) and anhydrous CH3CN (1.0 mL) were added under air and the flask was sealed with parafilm. Then the\nreaction was stirred and irradiated by 440 nm or 850 nm for 48 h. Products were purified by silica gel\nchromatography to afford the isolated yields.\n5. Regarding the mechanistic studies, this reviewer strongly suggest that the authors\nshould use HRMS to detect the possible intermediates during the initial stage of the two\nreactions.\nOur Response: Thank you very much for your insightful suggestions. During the initial\nstages of both reactions, we performed detailed HRMS studies to identify potential\nintermediates. In the hydroazidation of alkenes, we detected the presence of\nintermediates I and II (Supplementary Figures 33 and 34). Among them, II is a\nproposed light-absorbing intermediate responsible for azido radical production. For the\nhydroxyazidation of alkenes, intermediates III, IV, and V were detected\n(Supplementary Figures 35−37). Based on corresponding UV−Vis studies, all three are\npotential light-absorbing species (Supplementary Figures 21−23).\n1. HRMS experiments for the Mn(II)-based photoredox reaction (condition A):\nSupplementary Figure 33. ESI-HRMS spectrum of Species I. Species I may be formed through the in-situ assembly\nof Mn(acac)2 with L1. It was successfully detected in positive-ion mode (as its sodium adduct) by HRMS.\nSupplementary Figure 34. ESI-HRMS spectrum of Species II. Species II may be a blue light-absorbing intermediate\nfor the generation of the azido radical. It was detected in positive-ion mode (as its proton adduct) by HRMS.\n2. HRMS experiments for the Mn(III)-based photoredox reaction (condition B):\nSupplementary Figure 35. ESI-HRMS spectrum of Species III. Species III may be a low-energy light-absorbing\nintermediate for the generation of the azido radical. It was detected in positive-ion mode (as its sodium adduct) by\nHRMS.\nSupplementary Figure 36. ESI-HRMS spectrum of Species IV. Species IV may be a low-energy light-absorbing\nintermediate for the generation of the azido radical. It was detected in positive-ion mode (as its sodium adduct) by\nHRMS.\nSupplementary Figure 37. ESI-HRMS spectrum of Species V. Species V may be a low-energy light-absorbing\nintermediate for the generation of the azido radical. It was detected in positive-ion mode (as its sodium adduct) by\nHRMS.\n6. Stoichiometric H 18O should be added to the reaction system of hydroxyazidation.\nwant to know whether the -18OH could be detected.\nOur Response: We sincerely thank the reviewer for the comment. When H 18O was\n2\nadded to the hydroxyazidation reaction system, the desired β-azido alcohol was\nobtained in 40% yield after 48 hours. However, HRMS analysis did not detect any 18O-\nlabeled product (4-18O). This result suggests that the oxygen atom in the hydroxyl group\nindeed originates from O (Supplementary Figure 31).\n7. There are also multiple formatting errors in the references and supplementary\ninformation. They are not listed here. It is hoped that they will be carefully revised.\nOur Response: We sincerely thank the reviewer for pointing the mistakes in references\nsupplementary information, and we also apologized for our carelessness to these\nmistakes. In the revised supplementary information, we have made a diligent effort to\nensure that all inconsistencies and inaccuracies have been thoroughly addressed.\nFollowing your advice, we have double-checked the references and confirmed the all\nerrors have been corrected. Many thanks for the reviewer’s strong support for our work.\nResponse to the comments from Reviewer #3.\nComments:\nIn this manuscript, Song and co-workers report a practical manganese-photocatalyzed\nradical hydroazidation and hydroxyazidation of alkenes, and they establish a paradigm\nthat modular in-situ assembly of readily available Mn catalysts, TMSN₃ and/or\nbipyridyl ligands can rapidly unlock an effective Mn-based low-energy photoredox\nsystem (near-infrared, λ = 850 nm) from the corresponding high-energy visible-light\nprecursor (blue, λ = 440 nm). In the introduction, the authors highlight the advantages\nof preparing photoactive metal complexes in situ through combination of a first-row\ntransition metal and a ligand. The work is divided into two parts: the first part showcases\nthe development of Mn(II)-based photoredox catalysis that under 440 nm visible light\nirradiation and using water as the H-source, enables selective anti-Markovnikov\nhydroazidation of unactivated alkenes; the second part shows how to quickly unlock an\nintriguing manganese-based low-energy photoredox catalytic system for the direct\naerobic hydroxyazidation of alkenes. Considering all the above, I think this work does\ncontain the expected conceptual novelty to justify its publication in Nature\nCommunications. Several minor revisions should be made before the formal\nacceptance.\nOur Response: We sincerely thank the reviewer for the positive comments on our work.\n(1) Figure 1 shows that the in situ assembly strategy proposed by the authors involves\nforming light-absorbing complexes through the in-situ assembly of metal salts, ligands,\nand solvents, which release radical species upon photoexcitation. However, in the\nreactions achieved using low-energy light, the authors did not employ ligands. This\ndistinction should be clarified in the introduction.\nOur Response: We thank the reviewer again and we do completely agree with this\nviewpoint. As you suggested, we have revised the Introduction to clarify the description\nof the in-situ assembly of metal-based light-absorbing systems. The revised text now\nreads: “The in-situ assembly of a 3d metal-based photocatalytic system from readily\navailable components—such as metal salts, ligands, or substrates—is a straightforward\nstrategy for controlling both light-absorbing and catalytic properties through\nmodulating the ligand, counterion, or metal oxidation state” (Page 3, paragraph 2).\n(2) In Figures 2A–2D, the authors measured UV-Vis data using DCE as the solvent, but\nthe actual reactions were conducted in a mixed solvent system of DCE and water. To\nensure experimental rigor and comprehensiveness, I recommend that the authors\nsupplement the UV-Vis data using either water or a DCE/water mixture to verify or rule\nout the potential influence of water on the system's light absorption. Additionally, the\ncorresponding UV-Vis experiments for Mn(acac)₃ should also include the data obtained\nwith HFIP or CH₃CN/HFIP as the solvent.\nOur Response: Many thanks for your insightful comments and suggestions. To\ninvestigate the influence of the co-solvent on the light-absorbing properties of the two\nsystems, further UV−Vis experiments have been conducted.\n1. For the Mn(II)-based blue light photocatalytic system, H O is used as the co-\n2\nsolvent. However, due to the immiscibility between DCE and H O, phase separation\n2\noccurred. Therefore, we directly examined the absorption spectrum of the mixture of\nMn(acac) , L1, and TMSN in H O and compared it with that in DCE. The two spectra\n2 3 2\nwere distinct (Figure R19). Irradiation of the mixture of Mn(acac) , L1, and TMSN₃ in\n2\nwater at 440 nm did not cause a significant change in the absorption spectrum (Figure\nR19, right; Supplementary Figure 14). Furthermore, the desired hydroazidation of\nalkenes could not be achieved when H O was used as the sole solvent (Supplementary\n2\nof the Mn(II)-based blue light photocatalytic system.\nFigure R19. The comparison of UV–Vis absorption spectra of the Mn(II)-based photochemical system in DCE and\nH2O. See the Supplementary Figures 13 and 14 for details.\n2. For the Mn(III)-based low-energy light photocatalytic system, we found that\nirradiation of the Mn(acac) and TMSN mixture at 850 nm produced a significant\n3 3\nchange in the absorption spectrum, regardless of whether the solvent was CH CN,\n3\ndemonstrated the broad solvent tolerance of the Mn(III)-based low-energy light\nphotocatalytic system. Considering the nonnegligible coordination ability of CH CN\n3\nand HFIP and based on the in-situ HRMS detection (Supplementary Figures 36 and\n37), we proposed that both solvents might be involved in the in-situ assembly of the\nMn(III)-based low-energy light photocatalytic system for the hydroxyazidation of\nalkenes (Supplementary Figure 42). The superior hydroxyazidation reactivity of\nalkenes in the CH CN/HFIP mixture compared to that in DCE supports this proposal\n3\n(Supplementary Table 9).\nFigure R20. UV–Vis monitoring of the Mn(acac)3 and TMSN3 mixture upon 850 nm irradiation in different solvents.\nSee the Supplementary Figures 21−24 for details.\n(3) Although both reactions demonstrate good substrate compatibility with alkenes, I\nstill recommend that the authors present some unsuccessful substrate examples in SI to\nprovide readers with a more comprehensive understanding.\nOur Response: We sincerely thank the reviewer for the comments and suggestions. We\nagree that negative results are also important. Examples of unsuccessful reaction\nsubstrates have been included in the Supplementary Figures 46 and 47. Of particular\nnote, the anthraquinone moiety in substrate 82 absorbs blue light, which likely hinders\nthe hydroazidation of the alkene double bond by our Mn(II)-based photocatalytic\nsystem.\nSupplementary Figure 46. Unsuccessful substrates under condition A.\nSupplementary Figure 47. Unsuccessful substrates under condition B.\n(4) The following key references should be included for completeness:\n10.1021/jacs.4c18366 and 10.1038/s41557-024-01446-8.\nOur Response: We sincerely thank the reviewer for the suggestions. In the revised\nmanuscript, the citation for the sentence “We observed that Mn-based photocatalysis\nstill remains in its infancy” has been expanded to include the two recent references\n(ref. 38: 10.1038/s41557-024-01446-8, ref. 42: 10.1021/jacs.4c18366).\n(5) I noticed several grammatical errors, which I won't enumerate here, but I\nrecommend the authors conduct a thorough and meticulous proofreading of the entire\ntext.\nOur Response: We sincerely thank the reviewer for the suggestions. In the revised\nmanuscript, we have carefully corrected the language with the help of an English native\nspeaker. Many thanks for the reviewer’s strong support for our work.\nResponse to the comments from Reviewer #1.\nThe revisions made by the authors have fully addressed all the points I raised. In my opinion this\nhas resulted in an improved paper which suitably highlights and discusses the important new\nfindings. I therefore recommend publication.\nOur Response: Thank you very much for your great support for our work. We are deeply grateful\nfor your recognition of the significance of our work in the field and your support for its\npublication in Nature Communications.\nOne minor suggestion: it would be helpful to clearly indicate what the different colored curves in\nthe XPS spectra represent.\nOur Response: We sincerely thank the reviewer for the insightful suggestions. We have added the\nfigure captions to clearly indicate what each colored curve in the XPS spectra represents.\nMn 2P XPS spectrum for sample\nfitting curve of the XPS spectrum\nMn 2P3/2 baseline\n[Mn(II)] 640.75 satellite peak 1 of Mn(II)\nsatellite peak 2 of Mn(II)\nMn 2P3/2\n642.42 multiplet splitting peak 1 of Mn 2P\n1/2\nc/ s sate fo l 6 l r i 5 t e M 7 . p n 7 e ( 9 I a I) k 1 M 6 n 5 2 3 P .8 1 3 /2 M 6 n 5 2 2 s P a .4 t 1 e 2 / l 2 lite p 6 e 4 a 6 k . 1 2 1 for Mn(II) m m u u l l t t i i p p l l e e t t s s p p l l i i t t t t i i n n g g p p e e a a k k 2 1 o o f f M M n n 2 2 P P 1 3 / / 2 2\nmultiplet splitting peak 2 of Mn 2P\n3/2\n660 655 650 645 640 635 630\nBinding Energy (eV)\nSupplementary Figure 41. XPS spectrum of the anti-Markovnikov hydroazidation of alkenes.\nMn2p XPS spectrum for sample\nfitting curve of the XPS spectrum\n[Mn(II)]\nM\n6\nn\n4\n2\n.1\n3\n2\n/2\nbaseline\nsatellite peak 1 of Mn(II)\nMn 2P3/2 satellite peak 2 of Mn(II)\n642.74 multiplet splitting peak 1 of Mn 2P\nc/ s sate fo l 6 l r i 5 t e M 8 . p n 6 e ( 7 I a I) k 1 M 6 n 5 2 4 P .1 1 4 /2 M\n6\nn\n5\n2\n2\ns P\n.\na\n1\n1 t\n8\ne /2 llite p 6 e 4 a 6 k . 2 2 7 for Mn(II) multiplet splitting peak 2 of Mn 2P 1 1 / / 2 2\nmul tiplet splitting peak 1 of Mn 2P\n3/2\nmultiplet splitting peak 2 of Mn 2P\n3/2\n660 655 650 645 640 635 630\nBinding Energy (eV)\nSupplementary Figure 43. XPS spectrum of the hydroxyazidation of alkenes.\nResponse to the comments from Reviewer #2.\nThe authors have addressed all the comments and concerns. I suggest it be accepted for\npublication.\nOur Response: We sincerely thank you for your valuable suggestions regarding our work and for\nplaying a critical role in supporting its publication in Nature Communications.\nResponse to the comments from Reviewer #3.\nThe manuscript is recommended to publish as its current version.\nOur Response: We sincerely thank you for guiding us in the revision process. We are also\nparticularly grateful for your invaluable support in publishing our manuscript in Nature\nCommunications."}, {"round": 2, "reviewer_comments": {"reviewer_1": "The revisions made by the authors have fully addressed all the points I raised. In my opinion this has resulted in an improved paper which suitably highlights and discusses the important new findings. I therefore recommend publication.\nOne minor suggestion: it would be helpful to clearly indicate what the different colored curves in the XPS spectra represent.", "reviewer_2": "The authors have addressed all the comments and concerns. I suggest it be accepted for publication.", "reviewer_3": "The manuscript is recommended to publish as its current version."}, "author_response": ""}]

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