Iron(III) Azadiphenolate Compounds in a New Family of Spin Crossover Iron(II)–Iron(III) Mixed-Valent Complexes
, David S. Macedo 1, Barnaby A. I. Lewis 1,2, Declan F. Wain 1 and Keith S. Murray 1,*Round 1
Reviewer 1 Report
In the manuscript entitled „Iron(III) azadiphenolate compounds in a new family of spin crossover iron(II)–iron(III) mixed-valent complexes” is presented synthesis and magnetic and single crystal X-ray diffraction studies of new family of mixed valence salts composed of cationic part comprising iron(II) complexed with tris-pyrazolylmethane (pz) or 2,3,5,6, tetrapyridylpyrazine (tppz) ligands and complex anion [FeIII(azp)2]-. Crystal structures of anionic and cationic precursors are precursors are presented too. It was found that Fe(II) ions in cationic parts of complexes 3-6 are not spin crossover active and remain in LS form in the investigated temperature range. In the complex 4 Fe(III) ions in [FeIII(azp)2]− moieties remain in HS form. For comparison in 5 and 6 there are two types of crystallographically independent Fe1 and Fe2 centers in [FeIII(azp)2]− anions. Results of single crystal X-ray diffraction studies revealed that in 5 and 6 Fe(III) ions (Fe1 site) remain in HS form in the range 100-300 K. In 5 and 6 Fe(III) ions, occupying second crystallographic site, are in LS form at 100 K. A comparison of Fe(II)-ligand distances with Fe(III)-ligand distances (site 2) in 6 indicates that upon heating to 300 K a greater elongation of Fe-ligand distances occurs for Fe(III) ions (site 2). According to results of magnetic studies, showing very gradual increasing of cMT value during heating from 300 to 360K, authors conclude that spin crossover occurs for Fe(III) ions occupying second crystallographic site.
The success of this work is preparation of Fe(II)/Fe(III) mixed valence salt 6 exhibiting spin crossover phenomenon. Studies were carried out with great care. Results are presented clear however many crystallographic details makes reading difficult. Below I have given some imperfections:
symbols of atoms or description of colors of elements on Figures S1-S6, S8 and S9 (SI) are required,
line 188. There is a lack of reference to Table 1 containing Crystallographic data and structure refinement for 4, 5 and 6.
In the experimental part it was mentioned that TGA measurements were performed however I cannot find these results. It could be valuable to place TGA results, in particular, taking into account presence of noncoordinated acetonitrile molecules in the crystal lattice of 6.
In my opinion this work deserve on publication in Magnetochemistry after minor revision.
Author Response
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Author Response.pdf
Reviewer 2 Report
This paper reports on the syntheses of a new family of Fe(III)-azadiphenolate complexes. The SCO magnetic behavior of one of Fe(II)-Fe(III) mixed-valence complex is also reported. Although the reports of such SCO compounds are interesting, the manuscript in its current form shows several weaknesses, see major points below. Authors should address following points before the manuscript be accepted by Magnetochemistry.
1. To add the definition of the octahedral distortion parameters in the manuscript was suggested, although it was mentioned in the refs. 34 and 35.
2. The authors mention that the Fe2 center in compounds 5 and 6 are LS Fe(III) center using the octahedral distortion parameters, which cited in refs. 34 and 35. However, these two references were reported on the studies octahedral distortion parameters for Fe(II)-N6 complexes was suggested.
3. P7, L221. The octahedral distortion parameters of Fe3 centers in complexes 5 and 6 should be discussed in the manuscript.
4. Complex 6 contains three solvated MeCN molecules. Are these three MeCN molecules losses at 360 K? To provide the TGA data was suggested.
5. To provide the CHN elemental analytical data to establish the purity of bulk sample of complex
Author Response
see attached word doc
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors have gone carefully through all remarks previously made by the referees and they have made corrections throughout the manuscript accordingly. It is therefore a pleasure for me to recommend the manuscript for publication in Magnetochemistry.
