Correlation between Slow Magnetic Relaxations and Molecular Structures of Dy(III) Complexes with N5O4 Nona-Coordination
, Masayoshi Nakano 2,3 and Takashi Kajiwara 1,*Round 1
Reviewer 1 Report
The paper by Kobayashi et al deals with the synthesis, structural characterization through X-ray diffraction studies and magnetic characterization through dc and ac measurements of three nona-coordinated dysprosium(III) compounds of general formula [DyL(A)2](anion), where L is a Schiff base N5 ligand that occupies the equatorial positions around the lanthanide ion and A/anion = NO3/NO3 (compound 1), AcO/CF3SO3 (compound 2) and acac/CF3SO3 (compound 3). The three A anions coordinate disprosium(III) as O2-donor bidentate ligands in the equatorial positions.
I found the paper well written, suitably cited all along the manuscript, very clear structural descriptions (which nicely introduce to the magnetic anisotropy of the disprosium ions in the three compounds with modulated A) and precise description of the magnetic features as well.
I have only two main concerns:
1 - regarding the compound 2, there is no mention of the solvent molecule(s) present in the crystal structure, and the hydrogen bonds present between the coordinated AcO anion and the ethanol molecule(s). This might also be a cause in the different slow relaxation of the magnetization between 2 and 1. Furthermore, are there 1.5 EtOH and 1 H2O molecules in the crystal lattice? This should be clearly stated in the text. The elemental analysis reports only 0.5 EtOH and 0.5 H2O: were the magnetic measurements performend on which sample?
2 - I do not really get the reason why the theoretical calculations on compound 1 were performed without considering the anion NO3 (m1 is then only the cation [DyL(NO3)2]+, while this has been done for 2 and 3 (m2 and m3 are [DyL(A)](CF3SO3)). Conclusions drawn by the help of these non-equivalent calculations might be then dangerous. I would suggest to withdraw this theoretical paragraph from this paper, which does not add any foundamental information from my point of view, also in the light of the fact that Authors are planning to further study their complexes with this regard.
Just few other small points:
- I personally prefer mononuclear without the separation mono-nuclear
- line 31: charactherized by slow relaxation of magnetization
- line 104: acetylacetonate (o missing)
- line 166: I would substitute 'confirmed' with 'analyzed'
After Authors have properly replied to these points and consequently modified the manuscript, the paper is suitable for publication on Magnetochemistry, since it will be of sure interest for the scientific community working on lanthanide-based SMMs.
Author Response
Comment 1: Regarding the compound 2, there is no mention of the solvent molecule(s) present in the crystal structure, and the hydrogen bonds present between the coordinated AcO anion and the ethanol molecule(s). This might also be a cause in the different slow relaxation of the magnetization between 2 and 1. Furthermore, are there 1.5 EtOH and 1 H2O molecules in the crystal lattice? This should be clearly stated in the text. The elemental analysis reports only 0.5 EtOH and 0.5 H2O: were the magnetic measurements performend on which sample?
Answer 1: Thank you for your precise comments and we apologize for your confusion. Although we have collected X-ray data very carefully with the wide data range of 2θ up to 65 degrees, solvent molecule showed heavy disordering and they were hard to assign. On the bases of the elemental analyses, we found that the compound involves both EtOH and H2O molecule as solvent molecules, and we have assigned the differential peaks to two EtOH and one H2O with the occupancies of 50%, 25%, and 50%, which leads to the composition of 0.75 EtOH and 0.5 H2O. Elemental data were re-calculated along this results, which showed better agreement with the observation.
As was pointed out, EtOH and H2O were closely located to O3 of acetate ligand with the distances around 2.85 A. We have confirmed that the presence of solvent molecules did not affect on the electronic distribution of pi-conjugate system on acetate ligand: pi electron is symmetrically delocalized both on O3 and O4 which give the same bonding distances of O3-C22 = 1.263(3) and O4-C22 = 1.265(3) angstroms, and hence the hydrogen bonding did not affect on the negative charge distributions of O3 and O4.
We added the short explanations above in the main text.
Comment 2: I do not really get the reason why the theoretical calculations on compound 1 were performed without considering the anion NO3 (m1 is then only the cation [DyL(NO3)2]+, while this has been done for 2 and 3 (m2 and m3 are [DyL(A)](CF3SO3)). Conclusions drawn by the help of these non-equivalent calculations might be then dangerous. I would suggest to withdraw this theoretical paragraph from this paper, which does not add any foundamental information from my point of view, also in the light of the fact that Authors are planning to further study their complexes with this regard.
Answer 2: We are very sorry for incomplete calculations in the previous manuscript. According to reviewers’ comments, we have carried out a DFT calculation on the complete model of 1, which involves counter anion, and the results were replaced. Fortunately, the new model gives a result being very similar with the older one, and the discussions were not changed.
Comment 3: Just few other small points:
- I personally prefer mononuclear without the separation mono-nuclear
- line 31: charactherized by slow relaxation of magnetization
- line 104: acetylacetonate (o missing)
- line 166: I would substitute 'confirmed' with 'analyzed'
Answer 3: Thank you for pointing out. We have collected the manuscript.
Reviewer 2 Report
The article by Kajiwara et al. reports the synthesis and magnetostructural correlation of a new family of Dy(III) mononuclear complexes based on Schiff base N5 ligands. The article is well written and the purpose of the work is explained in a broader context. The results are well exposed and the conclusions are supported by appropriate data. The citations are appropriate. I therefore recommend its publication without any modification.
Author Response
Answer to reviewer: Thank you for your kind comments.
Reviewer 3 Report
In this work, three Dy(III) complexes presenting the same equatorial N5 ligand and two different O2 ligands, namely NO3-, AcO and acac are synthesised, characterized and their magnetic properties are studied both experimentally (DC and AC magnetic susceptibilities) and theoretically (DFT).
The huge barrier height difference between the three complexes is attributed both to changes of the structure of the coordination sphere of the Dy(III) and to a difference in the Dy(III)-axial ligands interactions. This last point is based on DFT calculations.
Nevertheless, I question the choice of the 3 models m1-m3 on which DFT is performed. Indeed, m1 positively charged whereas m2 and m3 are neutral since counter-cations are considered. Then, I am not sure that the difference in f-orbitals delocalization over the ligands and then the spin density of Dy(III) are not artefactual and that the conclusions are correct.
This point must be clarified.
Nevertheless, this work is interesting and should be published once this point has been addressed.
Author Response
Comment: Nevertheless, I question the choice of the 3 models m1-m3 on which DFT is performed. Indeed, m1 positively charged whereas m2 and m3 are neutral since counter-cations are considered. Then, I am not sure that the difference in f-orbitals delocalization over the ligands and then the spin density of Dy(III) are not artefactual and that the conclusions are correct.
This point must be clarified.
Answer: We are very sorry for making you confused. According to reviewers’ comments, we have carried out a DFT calculation on the complete model of 1, which involves a counter anion, and the results were replaced. Fortunately, the new model gives a result being very similar with the older one, and the discussions were not changed.
Round 2
Reviewer 3 Report
Corrections are OK
