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  • Hanan A. A. Althobaiti,
  • Benson M. Kariuki and
  • Grace Lancey
  • et al.

Reviewer 1: Anonymous Reviewer 2: Anonymous

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article under the title “Stereocontrol in Zn(II) and Cd(II) Complexes of Tetraamines 2 with Azacyclic Cores” by Althobaiti and coworkers presents results on the synthesis and structural characterization of novel Zn(II) and Cd(II) complexes, with the ligand-dictating stereoselectivity. The authors have presented these results well with the inclusion of complete spectroscopic characterization. The article could be of potential interest to the readers of the Inorganics, although there are some points that should be addressed before the final decision. Therefore, my recommendation is MAJOR REVISION.

 

The authors should answer the following:

  1. The abstract should be more informative, as the support in results of the claims in the last sentence should be presented.
  2. The authors should formulate the aims of the study better by including the used methodology
  3. Examples of the compounds that support the discussion should be included, as this way the introduction is very general and does not allow deeper understanding of the subject of the study
  4. The authors should mention previous studies and methods applied for the examination of SAM complexes
  5. The authors should verify that the selected level of theory was appropriate for the optimization of the obtained compounds by presenting references for similar compounds
  6. The applicability of the selected level of theory can be proven by comparing the experimental and theoretical bond lengths and angles
  7. The authors could use the theoretical data to support the experimental claims and preferability of the compounds towards specific geometry, this could be done by examining the effect of halide on the structural preferences.
  8. The authors should more clearly outline the effect of central metal ion on the geometry of the obtained complexes.
  9. What is the experimental/theoretical reason for the higher stability of specific isomers, based on the sentences in lines 153-154, the authors should give a plausible explanation.

 

Author Response

First and foremost we are grateful for the time and efforts that the reviewers’ have invested in assessing our manuscript and thank them for their insightful and appropriate comments and suggestions. Our response is as follows and we hope that it answers all of their queries.

Reviewer 1

  1. The abstract should be more informative, as the support in results of the claims in the last sentence should be presented. We have adjusted the abstract (lines 8,9,13,14) to better inform the reader of the content.
  2. The authors should formulate the aims of the study better by including the used methodology. We have attempted to answer points 2-4 by expanding the introduction by the inclusion of lines 37-44, 46-52 and 55-58 and included a greater number of appropriate references [7-14] .
  3. Examples of the compounds that support the discussion should be included, as this way the introduction is very general and does not allow deeper understanding of the subject of the study. Please see comments under point 2.
  4. The authors should mention previous studies and methods applied for the examination of SAM complexes. Please see comments under point 2.
  5. The authors should verify that the selected level of theory was appropriate for the optimization of the obtained compounds by presenting references for similar compounds. Another excellent comment. The approach is standard for molecules of this size and has been commented on in a final sentence in the DFT section of the materials and methods which includes a further reference [35]. We have also added a separate section on the DFT calculations (section 2.6, lines 241-260) as an aid to the reader and to address this issue.
  6. The applicability of the selected level of theory can be proven by comparing the experimental and theoretical bond lengths and angles. We have included comparison of experimental and theoretical M-N bond lengths in Table S5 and included a further table S7 in the ESI.
  7. The authors could use the theoretical data to support the experimental claims and preferability of the compounds towards specific geometry, this could be done by examining the effect of halide on the structural preferences. We have added the section on DFT(section 2.6, see point 5) with appropriate comment and table S7 to help clarify this.
  8. The authors should more clearly outline the effect of central metal ion on the geometry of the obtained complexes. We have adapted the abstract and included a conclusions section (lines 569-576) to highlight the metal ion dependence. We hope this provides the necessary clarification.
  9. What is the experimental/theoretical reason for the higher stability of specific isomers, based on the sentences in lines 153-154, the authors should give a plausible explanation. We have provided an explanation in the DFT section 2.6. It is not an easy question to answer fully but there is evidence to support adoption of the cis-alpha form as highlighted in the final part of this section (2.6).

Sincerely,

Paul D. Newman.

 

 

Reviewer 2 Report

Comments and Suggestions for Authors

The authors describe the stereoselective synthesis of well-defined chiral-at-metal cationic Zn(II) and Cd(II) complexes based on chiral tetramine ligands with a pyrrolidine and piperidine core. The complexes obtained were characterized, including X-ray analysis. Overall, I found the paper to be well-written and easy to understand the material. However, the next issues should be addressed before publication:

  • The description from the template should be deleted (lines 532-534; 536-537; 612-613).
  • Scheme 1. The yields of the products for each step need to indicate.
  • Optical rotations for all new chiral compounds and complexes should be recorded.
  • Experimental section: The mass-spectra need to check, as the masses for L1 and L2 may not be the same. Same goes for L3 and L4. They should be different.
  • The yields for [Zn(L1)Cl2] and [Zn(L2)Cl2] are the same. Need to check.
  • The mass of the yields needs to provide for all complexes, not just as a percentage.
  • It would be interesting to see the CD spectra of the complexes obtained.
  • A Conclusion part is missing and should be included.
  • In the experimental section, there is information about DFT calculations, but I don't see any mention of this in the main text or any discussion of the results.
  • All 1H NMR spectra in SI file should be integrated.
  • Atom coordinates or an xyz file should be provided to check the accuracy of DFT calculations.
  • 12-15. No titles of the paper are provided.

Author Response

First and foremost we are grateful for the time and efforts that the reviewers’ have invested in assessing our manuscript and thank them for their insightful and appropriate comments and suggestions. Our response is as follows and we hope that it answers all of their queries.

Reviewer 2

  • The description from the template should be deleted (lines 532-534; 536-537; 612-613). This has been done.
  • Scheme 1. The yields of the products for each step need to indicate. Many thanks for highlighting this omission. These have now been added.
  • Optical rotations for all new chiral compounds and complexes should be recorded. Unfortunately the in-house polarimeter is not functional and we could not get reliable data.
  • Experimental section: The mass-spectra need to check, as the masses for L1 and L2 may not be the same. Same goes for L3 and L4. They should be different. They are different (as noted in the ESI): L1 C17H22N3 (268.1814); L2 C18H24N3 (282.1971); L3 C16H21N4 (269.1776); L4 C17H23N4 (283.1936).
  • The yields for [Zn(L1)Cl2] and [Zn(L2)Cl2] are the same. Need to check. There was an error which has been corrected. We thank the reviewer for highlighting this.
  • The mass of the yields needs to provide for all complexes, not just as a percentage. This has been done.
  • It would be interesting to see the CD spectra of the complexes obtained. We do not have access to a CD spectrometer.
  • A Conclusion part is missing and should be included. This has been added in lines 569-576..
  • In the experimental section, there is information about DFT calculations, but I don't see any mention of this in the main text or any discussion of the results. We have included a new section 2.6 on DFT (lines 241-260) to address this, supported by data in Tables S5/S6/S7. We hope this adds the necessary clarification.
  • All 1H NMR spectra in SI file should be integrated. We have checked all of these and all appear to be integrated.
  • Atom coordinates or an xyz file should be provided to check the accuracy of DFT calculations. These have been provided in Tables S8-10 in the ESI.
  • 12-15. No titles of the paper are provided. Titles have been added.

Sincerely,

Paul D. Newman.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have answered all of the questions properly. The manuscript is suitable for publication in the present form. 

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have mostly addressed my comments, and for this reason, the manuscript can be considered for publication.