Hybrid Materials Based on Imidazo[4,5-b]porphyrins for Catalytic Oxidation of Sulfides
, Remi Chassagnon 3 and Alla Bessmertnykh-Lemeune 1,4,*
Round 1
Reviewer 1 Report
Summary- The authors have synthesized and characterized heterogenized metalloporphyrin catalysts by immobilizing meso-tetraarylporphyrins on hydrated mesoporous titanium dioxide through carboxylate and phosphonate anchoring groups. The most stable catalyst, Mn(TMPIP)/TiO2 was evaluated for the selective oxidation of sulfides to sulfoxides with oxygen and isobutyraldehyde. The catalyst was recycled several times for the oxidation of thioanisole and gave comparable yields for the oxidation product.
Comments/Suggestions/Edits-
1. Line 41: The author's name needs to be corrected to Groves in place of Gloves.
2. Line 85-93: References need to be added.
3. Line 197: Please comment on the use of high loadings of TMSBr (30 eq.).
4. Line 206: The solvent that was used to wash Mn(TMPIP)/TiO2 needs to be mentioned here.
5. Line 355: Entry 7 describes the reaction that was done without the transition metal catalyst, not representing the optimized reaction conditions. A reaction entry is missing in Table 1 that corresponds to the optimized results.
6. Line 359: Thioanisole spelling needs to be corrected.
7. Table 2- Did the authors try isolating the sulfoxides from the crude reaction mixtures for any of the substrates to determine the isolated yields? Please comment on the isolation/purification of the final product, sulfoxides from the reaction mixture.
8. Line 431: The authors can rephrase the sentence (that includes "useless") for scientific publication.
9. Did the author test any other type of oxidation reaction with the synthesized catalyst?
10. Line 539: TLC spelling needs to be corrected.
11. Line 562 and 563: Please explain the difference in the [M-Cl+H]2+ m/z calculated (544.21518) and found (554.21526) values for HRMS-ESI for (Mn(TMPIP)).
Author Response
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Author Response.pdf
Reviewer 2 Report
In this manuscript , The authors synthesized 2H(TMPIC) and 2H(TMPIP). Then, the structural characteristics of the mesoporous hybrid materials and the integrity of the immobilized complex were studied. Finally, the catalytic efficiency of the most stable material Mn(TMPIP)/TiO2 and phosphate anchor in the presence of isobutyric aldehyde was studied. The heterocomplex has good catalytic activity and stability in the sulfoxylation of thioanisole. This work is worthy of publication in catalysts if the following comments are suitably handled during the revision.
1. On page 12 line 390, the authors claimed that “Electron rich derivatives are more reactive as compared to compounds with electron deficient aryl group”. However, the authors did not provide sufficient evidence to support this conclusion.
2. The author needs to compare the catalytic effects of the catalyst used in the paper with those used by others, and summarize the advantages of the catalyst used in the paper.
3. The mechanism of thiophene oxidation needs to be described in detail in this paper.
4. Some small errors in this article should be carefully checked. For example, on page 8 line 247, “Scheme 2” might be changed to “Scheme 3”. please modified this.
5. Recent references to this catalytic reaction should be added.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Manuscript ID: catalysts-2166056
Title: Hybrid Materials based on Imidazo[4,5-b]porphyrins for Catalytic Oxidation of Sulfides
The present work should be accepted for publication after major revisions.
Some points needing attention are outlined below:
- Authors need to clarify if they use a Ti/Mn ratio or a Mn/Ti ratio along the manuscript (please refer to pages 6, 7 and 8, where both ratios are referred).
- The amount of catalyst added to the reactions (0.09 mol%) refers to Mn mol%, or to Ti mol%, or to the MN-porphyrin macrocycle mol%?
- Entry 7 (table 1) seems to be mistaken, since the main text (“Finally, adjusting amount of IBA to reach a complete conversion and an appropriate reaction rate, the sulfoxide was obtained in about quantitative yield (entry 7)” - page 11, lines 353-355) do not fit with footnote 3 for entry 7 in table 1 (“The reaction was performed without transition metal catalyst”).
- The authors present a TON = ~1100 and a TOF = ~370, but never explain how these values are obtained. Once again, the precise identity of the species described as mol% of catalyst added is crucial to understand these TON and TOF values. Moreover, all calculations need to be presented.
- The statement on page 12 (lines 392-395) do not correspond to the values given in table 2 (3.3 < 5 equiv.).
- About the putative mechanisms involved, and in relation with the text on lines 453-456, the authors should run an assay with hydrated TiO2 but without the Mn-Porphyrin attached. This could shad some light on the role played by TiO2 itself.
- Finally, the sentence on page 19 (lines 689-691): “TON can be increased to the value which appears be mainly limited by a patience of the experimenter by recycling the catalysts several times owing to exceptional stability of the solid” needs clarification. This seems to be a strange conclusion for a scientific paper.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
The manuscript submitted by Kirill Birin et al., reports the catalytic application of the manganese complexes of two previously synthesized meso-tetraarylporphyrins immobilized on nano-structured TiO2 for the aerobic oxidation of sulfides. At present, it is very difficult to evaluate the importance of work. The following issues should be carefully addressed before making a decision.
1. What are the advantages of the immobilized “moisture-sensitive” manganese porphyrins used in the present study over previous simple manganese porphyrins such as manganese meso-tetra(4-carboxyphenyl)porphyrin? In contrast to 2H(TMPIC) and 2H(TMPIP) synthesized in multi-step reactions, meso-tetra(4-carboxyphenyl)porphyrin is synthesized in a one-step procedure. The complex was found to be moisture-sensitive (Line 203).
2. As was stated “Complexes Mn(TMPIC) and Mn(TMPIP) were found to be soluble in methanol and chlorinated solvents such as chloroform and dichloromethane that is important for their use in material chemistry.” The results of homogeneous reactions are needed. Also, they should be compared with the heterogeneous reactions.
3. Why the catalytic reactions were conducted in toluene? According to the conclusion “this strategy has many potential benefits for sustainable chemistry technologies”, the catalysts were designed to be used in industry. However, this solvent cannot be a convenient solvent.
4. Are the immobilized manganese porphyrins applicable for aqueous oxidation of sulfides?
5. The catalyst leaching has not been reported.
6. The catalyst degradation should be measured and reported.
7. What is the necessity of computational studies?
8. Why the results of computational studies have not been presented in abstract and conclusion?
9. What does the stability mean in the case of Mn(TMPIP)/TiO2? Is it stable towards oxidative degradation or bleaching?
10. The quality of SEM images should be improved. The size of nanoparticles should be determined in the images.
11. The abbreviations should be defined in the abstract before use.
12. The entry 3 of table 1 shows that ca. 50% of sulfoxide is oxidized to sulfone in ca. 0.5 h. On the other hand, ca. 2.5 h is needed for complete oxidation of sulfide to the corresponding sulfoxide. It means that the rate of oxidation of sulfoxide to sulfone is much greater than that of the oxidation of sulfide to sulfoxide. Accordingly, the lack of sulfone (entry 3) in 2.5 h is not acceptable.
13. A control reaction using the sulfoxide as the substrate is required to compare the rate of sulfoxidation and sulfonation.
14. You have just two compounds. More stable should be used instead of the most stable.
15. In this work, “manganese meso-tetraarylporphyrins” were immobilized on hydrated mesoporous titanium dioxide. Manganese should be added to the names e.g. in the abstract.
16. In figure 2, the compounds were mentioned as chromophores. What does it mean? There is no photocatalytic reactions in this manuscript.
17. “Catalytic oxidation is a key technology for converting petroleum-based feedstocks to useful chemicals of a high oxidation state such as alcohols, carbonyl compounds, and epoxides” has been copied from Punniyamurthy, T., Velusamy, S., & Iqbal, J. (2005). Recent Advances in Transition Metal Catalyzed Oxidation of Organic Substrates with Molecular Oxygen. Chemical Reviews, 105(6), 2329–2364. Please check the manuscript. The sentences of other papers or books cannot be used without rewriting them.
18. “This fused porphyrin–heterocycle compounds” should be “these fused …”.
19. The whole manuscript should be checked for typos and bad or less common phrases.
Author Response
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Round 2
Reviewer 3 Report
Title: Hybrid Materials based on Imidazo[4,5-b]porphyrins for Catalytic Oxidation of Sulfides.
The manuscript can be accepted for publication.
Author Response
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Reviewer 4 Report
1- Please check the entry again; the entry 3 of table 1 shows that running the oxidation of methyl phenyl sulfide in 2.5 h gives the corresponding sulfoxide as the sole product. The increase in the reaction time from 2.5 to 3 h led to the over-oxidation of ca. 50 of the formed sulfoxide to methyl phenyl sulfone and a significant decrease in sulfoxide selectivity. It means that the oxidation of methyl phenyl sulfoxide to the corresponding sulfone is much faster than the oxidation of methyl phenyl sulfide to methyl phenyl sulfoxide. Accordingly, the lack of sulfone (entry 3) in 2.5 h is not acceptable. A control reaction using the sulfoxide as the substrate is required to compare the rate of sulfoxidation and sulfonation. The data shows that there is a competition between sulfoxidation and sulfonation.
2- You have just two compounds. The word combination of “more stable” should be used instead of “the most stable”.
Author Response
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