The Crystal Structure and Crystal Chemistry of Mineral-like Cd5(VO4)2(OH)4, a Novel Isomorph of Arsenoclasite and Gatehouseite
Round 1
Reviewer 1 Report
Comments:
The manuscript describes the synthesis and structure of a new ionic compound containing vanadium and cadmium ions. The synthesis is based on previous literature procedures. The crystal structure of the compound is reported, and the structure is analyzed primarily through the interpretation of vdW radii of the atoms.
An extensive list of bond distances and angles is discussed to contrast previously reported structures and the similarities between the compound presented herein and previous literature structures. The crystal data is supplemented with a cursory examination of the Raman spectrum of the compound.
Overall the manuscript is well-written and the data is adequate for publication. While I personally would have liked to see a deeper examination of the compound (e.g. TGA, DSC, pXRD, etc) this is, of course, limited by the instrumentation available to the researchers.
The reviewer offers two critiques for the authors. I do want to be explicit that these should not disqualify the paper from being published. Merely, these are offered as food for thought and feedback from a humble reader:
1) I would have liked to see more elaboration on the conclusions from the study. For example, the authors state in the introduction that these materials are potentially useful for catalysis or magnetic properties (among other things). Why not test these? Or at least offer their thoughts as to if the authors (who are quite clearly experts in these materials ) believe their compound would be better (or worse or comparable to) than previously reported materials based on their results from their analysis. For example, quoting the geometric parameters of the sample is useful, but does this lead to any knowledge about the potential applicability of the compound? (e.g. do the discussed h-bonds actually point to any reactivity as with other samples?)
2) The authors spend quite a bit of words discussing short metal-metal interactions. This practically begs for a computational study to better understand the electronic structure of the material, particularly based on the introduction.
Finally, a couple of minor typos are listed:
Typos/Editing Notes:
Line 44: “However, the majority of these…”
Line 47: “…proved that hydrothermal methods are effective…” or “…proved that the hydrothermal method is effective…”
Line 157: The authors state the hydrogen bonding may be “weak to moderate.” Unless it is calculated or necessary, simply remove this statement. The phrase still holds without the qualifiers of the hydrogen bonding.
Line 188: “The Raman spectrum…”
Author Response
Dear reviewer,
We appreciate very much your comments and suggestions. As much as we wish to examine the compound deeper using other analytical techniques, such as pXRD and/or TGA, DSC, we are limited with the amount of the synthesized sample. As already indicated in the synthesis part of the manuscript, the end-mixture where the relatively small single-crystals of Cd-vanadate appear is very heterogeneous in its composition and it was not possible to extract Cd-vanadate in the amount big enough to allow the examination using above-mentioned methods. The same applies for the resolving of the physical properties. However, since this manuscript is the part of the Special Edition related to the mineral-related oxy-salts, their synthesis and structural properties we strongly believe that the main goal of our research was fulfilled.
Point 1: I would have liked to see more elaboration on the conclusions from the study. For example, the authors state in the introduction that these materials are potentially useful for catalysis or magnetic properties (among other things). Why not test these? Or at least offer their thoughts as to if the authors (who are quite clearly experts in these materials) believe their compound would be better (or worse or comparable to) than previously reported materials based on their results from their analysis. For example, quoting the geometric parameters of the sample is useful, but does this lead to any knowledge about the potential applicability of the compound? (e.g. do the discussed h-bonds actually point to any reactivity as with other samples?).
Respones 1: As laready mentioned in the general comment to this review, it was not possible to extract Cd-vanadate in the amount big enough to allow its examination using some further experimental methods. The same applies for the resolving of the physical properties. We agree that we can at least give some thoughts on it in the Conclusion part and we have added two new sentences to clarify it and one new reference dealing with vanadium oxides and metal-vanadates, their properties and applications. However, since we are not material scientist and the main scope of the special issue is not the physical properties, but the diversity of the crystal structure and crystal chemistry, we do not think that it is a good idea.
Point 2: The authors spend quite a bit of words discussing short metal-metal interactions. This practically begs for a computational study to better understand the electronic structure of the material, particularly based on the introduction.
Response 2: We fully agree with the reviewer that a computer study would provide a better understanding of the electronic structure of the material, but we have at this time only the results of X-ray structure analysis. These results indicate the existence of the system of weakly bound dimers (two similar pairs of coupled polyhedra V1O4‒Cd5O4(OH)2 and V2O4‒Cd1O5(OH H)2) with intradimer Cd‒V distances of 3.0934(7) and 3.1081(7) Å for V1–Cd5 and V2–Cd1, respectively, which are shorter than the sum of the van der Waals radii of 3.71 Å. Additionaly, the V1–V2 distances of 4.1214(9) Å are also shorter than the sum of the van der Waals radii of 4.26 Å.
Typos/Editing Notes:
Line 44: “However, the majority of these…”
Response: We corrected this typographical error by changing " However, majority of these " to "However, the majority of these ".
Line 47: “…proved that hydrothermal methods are effective…” or “…proved that the hydrothermal method is effective…”
Response: We corrected this typographical error by changing "…proved that hydrothermal method is effective…" to "…proved that the hydrothermal method is effective…".
Line 157: The authors state the hydrogen bonding may be “weak to moderate.” Unless it is calculated or necessary, simply remove this statement. The phrase still holds without the qualifiers of the hydrogen bonding.
Response: We agree with this remark and we deleted "weak to moderate".
Line 188: “The Raman spectrum…
Response: We corrected this typographical error by changing "Raman spectrum…" to "The Raman spectrum…".
Many thanks again for your comments.
Sincerely,
Ljiljana Karanovic and Tamara Dordevic
Reviewer 2 Report
The authors synthesized a Cd-based compound Cd5(VO4)2(OH)4 using a hydrothermal method. Its structure was well solved by the single crystal XRD, giving a noncentrosymmetric space group P212121. And the structure is also compared with other similar compounds with formulas M5(XO4)2(OH)4 in detail. I suggest it can be published after some issues can be addressed.
1. As the authors said that there are some unusal bond lengths such as V–Cd and V-V, I suggest the authors further check the crystal structure with other space groups. For example, Cd5(VO4)2(OH)4 crystallizes in an acentric space group P212121, so it be checked the acentric structure using powder second harmonic generation method.
2. Can the authors prepare other Cd-based compounds such as Cd5(AsO4)2(OH)4, as the authors stated the similar deravites are abundant.
Author Response
Dear reviewer,
We appreciate very much your comments and suggestions. As much as we wish to examine the compound deeper using other analytical techniques, we are limited with the amount of the synthesized sample. As already indicated in the synthesis part of the manuscript, the end-mixture where the relatively small single-crystals of Cd-vanadate appear is very heterogeneous in its composition and it was not possible to extract Cd-vanadate in the amount big enough to allow the examination using above-mentioned methods. The same applies for the resolving of the physical properties. However, since this manuscript is the part of the Special Edition related to the Mineral-related oxy-salts, their synthesis and structural properties we strongly believe that the main goal of our research was fulfilled.
- As the authors said that there are some unusual bond lengths such as V–Cd and V-V, I suggest the authors further check the crystal structure with other space groups. For example, Cd5(VO4)2(OH)4 crystallizes in an acentric space group P212121, so it be checked the acentric structure using powder second harmonic generation method.
Response 1: Please see the general comment in the bieginning of oure “Response”
- Can the authors prepare other Cd-based compounds such as Cd5(AsO4)2(OH)4, as the authors stated the similar deravites are abundant.
Response 2: Although we have already done some research on the Cd-arsenates (Cd2(AsO4)(OH), DOI 10.1007/s00710-012-0235-5; Cd5(AsO4)3Cl0.58(OH), DOI 10.1107/S0108270108023457), we have never obtained Cd5(AsO4)2(OH)4. Nevertheless, we will not stop trying.
Many thanks again for your comments.
Sincerely,
Ljiljana Karanovic and Tamara Dordevic
