A Neutral Heteroleptic Molybdenum Cluster trans-[{Mo6I8}(py)2I4]
, Anton A. Ivanov 1, Ilia V. Eltsov 2, Natalia V. Kuratieva 1 and Michael A. Shestopalov 1,*Round 1
Reviewer 1 Report
The information provided by Michael Shestopalov’s team in this work contributes elegantly to the state of the art of the chemistry of molybdenum cluster octahedral iodides. This manuscript is written in a concisely and consistently, and the techniques used support the full characterization of the compounds obtained. I consider that this manuscript should be accepted in this journal after reviewing after consider few aspects, which I cite below:
1. Some references should be revised. References [18,19] suit better as sterilizing or antimicrobial materials. Revise the state of the art in the field of O2 sensors and catalysis, the literature should be updated.
2. In the materials and methods section, there is a misunderstanding in the following sentence: “The excitation (λem = 700 nm) and emission (λex = 350 nm)”; it should be just the opposite.
3. In Synthesis subsection, the amount of pyridine added (in mols) as well its purity should be included.
4. The meaning of the last sentence in page 3 (“Nevertheless, the presence of the initial dianion [{Mo6I8}I6]2– in the crystals due to its high solubility in pyridine is highly unlikely”) is not very clear. If the compound is highly soluble in pyridine, it should be a reason enough to be co-crystallized. Authors should clarify this or the sentence should be written with other words.
5. Authors describe exclusively the Mo6 clusters with halides, although they refere to Mo6 clusters in general (line 135) However, there are similar synthetic and crystallographic works in this field for similar Mo6S8 clusters with pyridine and pyridine-related ligands. Authors should cite the following works: Inorg. Chem. 1994, 33, 9, 1822–1832 and J. Chem. Soc., Dalton Trans., 2002, 3096-3100.
6. In page 6, lines 222-3, authors suggest that stronger Mo-N bonds are found in Mo6I8 cluster compounds in comparison to reported halide clusters. This feature is interesting, and should be noted and described in the conclusion section. This is also de driving force the reaction, despite the natural competition of iodine to be bonded to Mo6I8 units.
7. In page 6, regarding the [{Mo6X8}(N-base)2X4] formula, and following the description of reference [42], apical X could be Cl, Br or I, and inner X correspond to Cl. Clarify this.
8. At the beginning of the “optical properties” subsection, authors describe the optical properties measured in the solid state and in pyridine solution. Explain the reason for choosing this solvent, considering that DMSO has been sufficient to ensure the solubility of the compound, as shown in the NMR experiments.
9. In page 7, authors cite “a decrease in intercluster interactions in solution, thus reducing the efficiency of nonradiative energy transfer”. Explain what kind of intercluster interactions are expected.
10. Define abbreviations, and avoid multiple terms for the same abbreviation, such as “single crystal XRD” (introduction) and SCXRD (conclusions section).
Author Response
Referee 1
The information provided by Michael Shestopalov’s team in this work contributes elegantly to the state of the art of the chemistry of molybdenum cluster octahedral iodides. This manuscript is written in a concisely and consistently, and the techniques used support the full characterization of the compounds obtained. I consider that this manuscript should be accepted in this journal after reviewing after consider few aspects, which I cite below:
Answer: Thank you for your positive feedback and relevant suggestions, which we address below.
Dear authors,
After reading your manuscript I concluded that:
- Some references should be revised. References [18,19] suit better as sterilizing or antimicrobial materials. Revise the state of the art in the field of O2 sensors and catalysis, the literature should be updated.
Answer: Relevant references in the field of O2 sensors and catalysis were added. References [18,19] were moved to self-sterilizing materials.
- In the materials and methods section, there is a misunderstanding in the following sentence: “The excitation (λem = 700 nm) and emission (λex = 350 nm)”; it should be just the opposite.
Answer: The sentence was correct: λem = 700 nm meant that we monitored emission at 700 nm, and λex = 350 nm meant that excitation wavelength was set at 350 nm. To avoid discombobulation the sentence was rephrased as follows: “The excitation (monitored at λem = 700 nm) and emission (excitation wavelength was 350 nm)”.
- In Synthesis subsection, the amount of pyridine added (in mols) as well its purity should be included.
Answer: Corresponding data was added.
- The meaning of the last sentence in page 3 (“Nevertheless, the presence of the initial dianion [{Mo6I8}I6]2– in the crystals due to its high solubility in pyridine is highly unlikely”) is not very clear. If the compound is highly soluble in pyridine, it should be a reason enough to be co-crystallized. Authors should clarify this or the sentence should be written with other words.
Answer: The sentence was rephrased as follows: “According to probability calculation, the content of [{Mo6I8}I6]2– is low, and thus the formula of the compound can be designated as (pyH)0.2[{Mo6I8}(py)1.8I4.2]·1.8py.”
- Authors describe exclusively the Mo6 clusters with halides, although they refer to Mo6 clusters in general (line 135) However, there are similar synthetic and crystallographic works in this field for similar Mo6S8 clusters with pyridine and pyridine-related ligands. Authors should cite the following works: Inorg. Chem. 1994, 33, 9, 1822–1832 and J. Chem. Soc., Dalton Trans., 2002, 3096-3100.
Answer: We are sorry for misunderstanding, since we meant only halide Mo6 clusters. This is a typo. The sentence was rephrased as follows: “To the best of our knowledge, only four articles on preparation of halide Mo6-clusters with N-heterocyclic ligands are reported.”
- In page 6, lines 222-3, authors suggest that stronger Mo-N bonds are found in Mo6I8 cluster compounds in comparison to reported halide clusters. This feature is interesting, and should be noted and described in the conclusion section. This is also de driving force the reaction, despite the natural competition of iodine to be bonded to Mo6I8 units.
Answer: Thank you for the comment. We added corresponding discussion in conclusion section: “TGA data revealed higher temperatures of pyridine ligands loss in comparison with literature, which indicates stronger Mo-N bonds in the Mo6 iodide clusters. This can be additional driving force of the reaction, despite the natural competition of iodine to be bonded to Mo6I8 units.”
- In page 6, regarding the [{Mo6X8}(N-base)2X4] formula, and following the description of reference [42], apical X could be Cl, Br or I, and inner X correspond to Cl. Clarify this.
Answer: Corresponding formulae were corrected according to the article: “J. Kraft and H. Schäfer in 1985 described preparation of heteroleptic clusters [{Mo6X8}(py)2X4] (X = Cl, Br) and [{Mo6Cl8}(N-base)2X4] (N-base = 2,2’-bipyridine and 2-phenylpyridine; X = Cl, Br, I).”
- At the beginning of the “optical properties” subsection, authors describe the optical properties measured in the solid state and in pyridine solution. Explain the reason for choosing this solvent, considering that DMSO has been sufficient to ensure the solubility of the compound, as shown in the NMR experiments.
Answer: Thank you for the comment. While studying the cluster composition via NMR we tried to increase cluster concentration in DMSO by heating the solution. This indeed resulted in more colored solution, but on the NMR spectra only free pyridine molecules were detected (corresponding spectra and discussion were added to the main text and ESI). Thus, dissolution of the cluster leads to competitive reaction of pyridine and DMSO molecules, and in excess of DMSO the substitution of pyridine occurs. To avoid partial substitution, we studied optical properties in pyridine solution.
- In page 7, authors cite “a decrease in intercluster interactions in solution, thus reducing the efficiency of nonradiative energy transfer”. Explain what kind of intercluster interactions are expected.
Answer: Here we meant the distances between inner and apical iodide ligands. It is known from the literature, that close I-I distances strongly affects optical properties and especially luminescence, which is probably due to nonradiative energy transfer. Corresponding I-I distances, discussion, and illustrative figure were added to the main text and in ESI.
- Define abbreviations, and avoid multiple terms for the same abbreviation, such as “single crystal XRD” (introduction) and SCXRD (conclusions section).
Answer: Single crystal XRD was replaced by SCXRD.
Reviewer 2 Report
Shestopalov et al. report on a new heteroleptic octahedral iodide molybdenum cluster complex with a pyridine ligand. The chemical story is interesting, although a bit thin, more complexes could be reported to make the story round. Another base might be tested.
The language needs a complete rewriting process. Sometimes, it is hard to understand. Hence, the manuscript needs a major revision.
Author Response
Referee 2
Shestopalov et al. report on a new heteroleptic octahedral iodide molybdenum cluster complex with a pyridine ligand. The chemical story is interesting, although a bit thin, more complexes could be reported to make the story round. Another base might be tested.
Answer: Thank you for your positive feedback. We conducted a series of experiments with other N-base compounds, but no positive results were obtained yet. Also, we extend discussion on NMR and optical properties.
The language needs a complete rewriting process. Sometimes, it is hard to understand. Hence, the manuscript needs a major revision.
Answer: English language was thoroughly corrected and edited.
Round 2
Reviewer 2 Report
When no further results are there, it is ok to publish it. The language should be checked allover.
