Layered Hybrid iron Fluorides

Round 1

Reviewer 1 Report

The manuscript is well written and well organized.

The procedures are well done and the reported new structures are new and interesting.

 

The main problem is reproducibility:

 

"The PXRD data of 1 and 2 were not characterized due to the low yield. Unfortunately, further exploratory reactions

46 failed to produce purer samples of 1 and 2."

 

The manuscript may not be accepted until the synthesis of the 1 and 2 compounds are completely under control and the whole synthesis may be reproducible and the products 1 and 2 are probed to be pure.

Author Response

As we have stated, we DID make several further attempts to improve the purity of phases 1 and 2. Unfortunately, it has not proved possible to prepare pure samples. Nevertheless, we do not believe this issue detracts from the overall quality and significance of the work: indeed, it is quite a common problem in exploratory chemistry of this type. We also note that neither of the other referees require phase purity. It’s not possible to conduct further experimental work at this stage, as Dr Li has now left the lab, and Prof Lightfoot is winding down his research activities prior to retirement this Xmas. We hope the referee and Editor will therefore accept this work as it stands. No doubt future work from other groups will provide purer samples suitable for probing of physical properties of these, and related, compounds. The key point of the present paper is merely to demonstrate that such phases exist, and to encourage further work in the field.

Reviewer 2 Report

 The manuscript presents the hydrothermal synthesis of two types hybrid iron fluorides, and the crystalline structure is analyzed in detail. The work is well organized and written, and can be accepted by Crystals after a minor revision. Other suggestions are listed in the following.

---considering the potential applications of these materials as Li-ion battery cathodes, I suggest the authors cite some relevant Refs, e.g., J Mater Chem A 2015, 3, 19832-19841.

---some relevant reports of hybrid iron fluorides with [FeF6] coordination, e.g., Solid State Sci 2009, 11, 1631-1638; Dalton Trans 2013, 42, 15748-15755; J Solid State Chem 2018, 262, 343-350 are needed to cover.

Author Response

We thank the referee for their further suggestions of further citations. We have added two of these (new refs 8 and 17), and one other (new ref 18) to the Introduction. We note that we have not incorporated the other two references suggested, as they are not strictly isolated [FeF6] octahedra, but are of the ‘mixed ligand’ type, which we have cited as the original reference 15 (now ref 16).

Reviewer 3 Report

This work entitled “Layered hybrid iron fluorides” shows some interesting results. I would recommend minor revisions for the following comments.

1.       What is the main reason for synthesizing these compounds (1, 2, and 3)?

2.       What could be the potential applications for these layered hybrid iron fluorides?

 

3.       The layered structure is a quite interesting structure. Is it possible to grow a 2-D structure for these layered hybrid iron fluorides? And how?

Author Response

Point 1: Exploratory work is very important in chemistry. As stated in the Introduction, the present work is purely exploratory – the field of hybrid fluorides is severely underexplored, and recent work in hybrid compound of the heavier halogens has revealed a remarkably diverse chemistry, with many important functional materials having been discovered by using ‘exploratory’ synthetic methods. Such advances in ‘new materials’ would not be possible without exploratory work of this type. No further changes have been made to the MS.

 

Point 2: Of course, exploratory work always has potential functionalities in mind. In this case, the most likely properties of interest will be magnetic or electrochemical properties (batteries). We have added in the first paragraph of the Introduction.

 

Point 3: We haven’t tried to deposit thin films of these materials, mainly due to the problem of phase purity. Such work would certainly be of interest in the future. No changes have been made to the MS.

Round 2

Reviewer 1 Report

I understand the difficulties to synthesise separated pure phases in amounts
sufficient to perform bulk solid state XRPD.

As the single crystal samples are well characterised it is worth to publish the
structural results as compounds found along the synthetic processes.
I will be more confortable if this fact is clearly stated in the Abstract, modifying
the abstract by inserting the suggested text:

 Abstract: The first examples of layered hybrid iron fluorides are reported. - to insert - In the reactions carried out, compound (H2pipz)FeF5·H2O, 

always occurs as the main phase, with compounds (H2pipz)3Fe4F18·2H2O,
and (H2pipz)2Fe3F13·H2O, being isolated from some reactions as major
impurities. - end inserted text -
The two new compounds, (H2pipz)3Fe4F18·2H2O and (H2pipz)2Fe3F13·H2O
feature two-dimensional sheets of corner-and edge-shared FeIIIF6 octahedra,
resulting in two distinct layer architectures. A further compound
(H2pipz)FeF5·H2O, isolated from the same reactions, crystallises with
a one-dimensional structure exhibiting zig-zag [FeF5]∞ chains.
This work opens up the potential for a much wider family of layered hybrid
transition-metal fluorides. 
In conclusions:
Please check whether the formulae is correct.

.... compound 3, (H2pipzH2)FeF5·H2O ... 

I see also a contradiction (please, explain and clarify)
In Abstract:

 A further compound (H2pipz)FeF5·H2O, isolated from the same reactions ... 

In Conclusions:

In the reactions carried out so far, compound 3, (H2pipzH2)FeF5·H2O, always occurs as the main phase, with compounds 1, (H2pipz)3Fe4F18·2H2O, and 2, (H2pipz)2Fe3F13·H2O, being isolated from some reactions as major impurities. 

When these minor changes and clarifications are satisfactorily solved I shall be in favor of accepting this manuscript for publication.

 

Author Response

Many thanks for the further comments. We fully agree with the referee's suggested changes, which do indeed clarify better the nature of our reactions and their products. We have made the further change to the Abstract, and slightly reworded the rest of the Abstract for further clarification, and to avoid any apparent contradiction. We have also corrected the error to the formula in the Conclusions section.

Author Response File: Author Response.docx