Multistimuli Luminescence and Anthelmintic Activity of Zn(II) Complexes Based on 1H-Benzimidazole-2-yl Hydrazone Ligands
and Wolfgang Linert 3,*Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsLinert et al report a study of mechanochromic, vapochromic and anthelminthic properties of three different Zn(II) complexes having 1H-benzimidazole-2-yl hydrazones as ligands. The manuscript is well-supported by experimental/theoretical data and the study is in line with the aim of Inorganics, however, in my opinion, some revisions are needed before publication:
1) Scheme 1 is related to the synthesis of Zn(II) complex 1, in contrast with the relative caption.
2) The 4th paragraph, related to the thermal analyses, is quite unclear. “Unsolvated sample” is Zn(II) complex 1 without MeOH coordinated or Zn(II) complex 2, as reported in Fig. S1? Where is the comment relative to the TGA of Zn(II) complex 2? Moreover, in contrast with the mention in the paragraph “Materials and Methods”, DSC data seem be absent.
3) Considering that the mechanochromic and vapochromic properties of Zn(II) complex 1 are not related of the crystallinity of structure, it is plausible to think that ground samples of Zn(II) complexes 2 and 3, in absence of DMF and DMSO, possess mechanochromic and vapochromic properties such as Zn(II) complex 1. Could you comment this aspect in the manuscript?
Author Response
We thank the Referee for interest in our work and for helpful comments and constructive suggestions that will greatly improve the quality of this manuscript. As indicated below, we have checked all the general and specific comments provided by the Referee and have made necessary changes according to their indications (the reviewer’s comments are in italics).
Reviewers' comments:
Reviewer #1:
Linert et al report a study of mechanochromic, vapochromic and anthelminthic properties of three different Zn(II) complexes having 1H-benzimidazole-2-yl hydrazones as ligands. The manuscript is well-supported by experimental/theoretical data and the study is in line with the aim of Inorganics, however, in my opinion, some revisions are needed before publication:
1) Scheme 1 is related to the synthesis of Zn(II) complex 1, in contrast with the relative caption.
A: We are grateful for this comment. We have corrected Scheme 1
2) The 4th paragraph, related to the thermal analyses, is quite unclear. “Unsolvated sample” is Zn(II) complex 1 without MeOH coordinated or Zn(II) complex 2, as reported in Fig. S1? Where is the comment relative to the TGA of Zn(II) complex 2? Moreover, in contrast with the mention in the paragraph “Materials and Methods”, DSC data seem be absent.
A: We agree with the reviewer that the phrase is unfortunate and needs to be corrected. The expression Unsolvated sample meant the residue of complex 1 after removal of solvent molecules during thermal analysis. You have corrected the text to avoid ambiguity. As for the data for complex 2 - it is in the text, but due to a typo it was not clear. We have corrected the text in this respect also. DSC data for this study turned out to be uninformative, so we removed references to them
3) Considering that the mechanochromic and vapochromic properties of Zn(II) complex 1 are not related of the crystallinity of structure, it is plausible to think that ground samples of Zn(II) complexes 2 and 3, in absence of DMF and DMSO, possess mechanochromic and vapochromic properties such as Zn(II) complex 1. Could you comment this aspect in the manuscript?
A: We appreciate the reviewer's good point. Indeed complexes 2 and 3 related to complex 1 were considered as candidates for the manifestation of mechanochromic properties. However, as follows from our reasoning, the unique properties of complex 1 are just related to the removal of a rather volatile methanol molecule under mechanical action. In addition, the relative ease of removal of methanol from the crystal lattice by heating allows us to obtain an unsolvated sample and study its properties. Unfortunately, it was not possible to obtain non-solvated samples for complexes 2 and 3 due to the low volatility of solvated DMF and DMSO molecules. Therefore, we cannot evaluate this aspect of the work at this stage. However, we continue to work in this direction by varying the solvent molecules for a same complex
Reviewer 2 Report
Comments and Suggestions for AuthorsIn the manuscript, three Zn(II) mononuclear complex with general formula ZnL2Cl2 have been prepared, which demonstrate the emissions dependent on the excitation. This is an interesting work; however, the following issues need to be clarified before acceptance.
1. The origins of the emission bands at ~400 nm and ~520 nm are unclear, and as an important topic of this manuscript, it must be improved. I suggest comparing the absorption and emission spectra of the crystals and ligands to rule out the possibility that the ~400 nm emission bands come from the ligands.
2. According to Fig. S4, the absorption bands at ca. 260-266 nm and ca. 336-354 nm overlap and are difficult to be distinguished.
3. Only Zn complex with L1 is shown in Scheme 1.
4. The infrared spectra and PL decays mentioned in the paper are missing.
Comments on the Quality of English Language
Moderate editing of English language required.
Author Response
We thank the Referee for interest in our work and for helpful comments and constructive suggestions that will greatly improve the quality of this manuscript. As indicated below, we have checked all the general and specific comments provided by the Referee and have made necessary changes according to their indications (the reviewer’s comments are in italics).
Reviewer #2:
In the manuscript, three Zn(II) mononuclear complex with general formula ZnL2Cl2 have been prepared, which demonstrate the emissions dependent on the excitation. This is an interesting work; however, the following issues need to be clarified before acceptance.
- The origins of the emission bands at ~400 nm and ~520 nm are unclear, and as an important topic of this manuscript, it must be improved. I suggest comparing the absorption and emission spectra of the crystals and ligands to rule out the possibility that the ~400 nm emission bands come from the ligands.
A: We thank the reviewer for a question regarding the key insight of the study. We believe that the reason for the dual luminescence of complexes is the change of LUMO energy upon introduction/removal of solvent molecules into the crystal lattice. This may be due to both the change in the conformation of the organic ligands of the complexes and the formation of exciplexes for the complex-solvent pair. Thus, the presence of two bands originated with the presence of two luminescence centers - solvated complexes and non-solvated ones. It is important to note that this assumption is consistent with theoretical calculations showing a shift to the blue region of the emission spectrum of the complex when solvent molecules are introduced into the lattice. As for the comparison of luminescence of ligands and complexes, it should be noted that in the solid state ligands demonstrate weak (two orders of magnitude weaker than complexes) emission with a maximum of 498-504 nm, which was not studied in detail in this work
- According to Fig. S4, the absorption bands at ca. 260-266 nm and ca. 336-354 nm overlap and are difficult to be distinguished.
A: We agree with this observation as well, however, we were not able to achieve an improvement in spectrum resolution when the measurement conditions were changed. Nevertheless, we believe that the two types of signals are quite clearly registered in the spectrum (in the form of a shoulder in the case of the short-wave signal). We have made appropriate clarifying edits to the text
- Only Zn complex with L1 is shown in Scheme 1.
A: We are grateful for this comment. We have corrected Scheme 1
- The infrared spectra and PL decays mentioned in the paper are missing.
A: The corresponding data has been inserted into ESI
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors have responded exhaustively to all my comments, so the manuscript, in my opinion, can be published in its current form.
Reviewer 2 Report
Comments and Suggestions for AuthorsAccording to the response and content of the revised manuscript, I suggest that it can be published.
