Spectrophotometric Determination of Formation Constants of Iron(III) Complexes with Several Ligands
Round 1
Reviewer 1 Report
Segoviano-Garfias et al. report on the spectrophotometric determination of formation constants of iron(III) complexes. The topic is important, but the methodology is not described. The manuscript is written in a confused style (language problem and content problem).
Are single species crystallised to obtain pure spectra? A lot of iron complexes can be isolated as tris(chelate) complexes and as bis(chelate) complexes. This information should be used to apply their spectra into the photometric models.
When all this information is added, it might become suitable for publication.
Author Response
Dear Reviewer:
Thank you for reviewing the manuscript “Spectrophotometric Determination of Formation Constants of Iron(III) Complexes with Several Ligands”. The Manuscript suffered a major editing of english languaje and style, hopefully this might help to clarify the methodology.
Also, the complexes were obtained in solid form, some of them in a form of needle-shaped, which cannot be used for x-ray diffraction. The purpose to obtain the complexes in solid form was to make sure that Fe-N bond was formed and discard a low energy interaction metal to ligand. Nevertheless, the complexes not were obtained in solid form to later studied in solution, considering that the equilibrium of solid complexes might to not be necessarily restored in solution (For example, DOI: 10.1016/j.jcrysgro.2019.03.026). On the other hand, the continuous variation method uses a gradual increase the concentration of metal or ligand in solution, maintaining one of them with a constant concentration.
Reviewer 2 Report
Dear authors
The study reported in this manuscript is novel and relevant.
But, I feel that the conclusions can be improved.
The reaction scheme of the synthesis of the complexes may be provided in section 3 where the details of the synthesis are discussed.
In future studies, youcould compare your results with computational chemistry UV spectral simulations.
Author Response
Dear Reviewer:
Thank you for reviewing the manuscript “Spectrophotometric Determination of Formation Constants of Iron(III) Complexes with Several Ligands”. The manuscript has suffered several changes: Scheme 1 in section 3 was added as suggested and conclusions were improved. Also, as future perspectives, was included the computational studies to obtain the theorical UV-vis spectra.
Reviewer 3 Report
The reviewed paper mainly describes the dependence of Fe3+ complexes formation on the concentration of various ligands with a broad study of their formation constants. Additionally, the calculated spectra of complexes studied have been presented to extend and support the discussion. The paper, in general, sounds good and presents a piece of interesting, well-prepared laboratory work with a comprehensive, well-written (except for some technical mistakes like typos, language mistakes, etc., which should be corrected) discussion. The only thing that makes the reviewer doubt is the correlation of the described results with the DSSCs. In the reviewer's opinion, it is redundant and seems to be put in the manuscript by force. In the reviewer's opinion, the conclusion about the spectral resemblance of Fe and Ru complexes is a little overinterpretation, especially since the analysis is made in the spectral range out of that, which is useful in DSSCs. DSSCs work mainly under the light with a wavelength over the 360 nm because the FTO substrates are cutting off the shortwave spectrum – see, e.g., Fig. 4 in the paper doi: 10.1155/2012/897595. The reviewer suggests skipping the forced connection of the presented results with DSSC and publishing the paper as just a well-prepared study of interesting effects of Fe3+ complexes formation.
To summarize, the minor revisions of the manuscript are suggested.
Author Response
Dear Reviewer:
Thank you for your kind comments and your reviewing on the manuscript “Spectrophotometric Determination of Formation Constants of Iron(III) Complexes with Several Ligands”. The manuscript has suffered several changes: a major editing of english language and style has been performed. Also the number of sentences about DSSCs and the emphasis on ruthenium complexes has been decreased
Reviewer 4 Report
The manuscript entitled “Spectrophotometric determination of formation constants of iron(III) complexes with several ligands” submitted by José J. N. Segoviano-Garfias and co-workers for consideration for publication in the MDPI journal Chemistry, presents the study of the singular spectrum analysis using the HypSpec software of the species of iron(III) with the ligands: 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 2,2’-bipyridyl, 5,5-dimethyl-2,2’-bipyridyl, 4,4’-di-tert-butyl-2,2’-bipyridyl, 1,10-phenanthroline or 3,4,7,8-tetramethyl-1,10-phenanthroline, in methanol solution. Moreover, the authors presented a spectral comparison of the complexes reported in the manuscript to ruthenium complexes cis-Ru(2,2’-bipyridyl-4-4’-dicarboxylate)2(SCN)2 and tris-(2,2'-bipyridyl)ruthenium(II). I do not understand the motivation for the presentation of these kinds of results as a scientific paper. More or less, this kind of investigation is typical for inorganic laboratory students at the bachelor's level of studies. The authors mentioned in the abstract about DSSCs and Ru-complexes, but their investigations are dedicated to Fe-complexes. The presentation of the results and their quality is really poor and insufficient to show the novelty of the results. The current version is only a simple protocol of applying the software HypSpec 2008, however, HypSpec 2014 has been established. Overall, there are editing mistakes, the language must be improved and polished. What is more, the name of all chemical compounds should be checked and revised according to IUPAC rules, such as 4,4’-di-tert-butyl-2,2’-bipyridyl, cis-Ru(2,2’-bipyridyl-4-4’-dicarboxylate)2(SCN)2 and many others. The Supporting Information must be revised. What is the motivation of the author to present this kind of result? I cannot recommend the revision and publication of the manuscript due to the lack of scientific novelty and potential application of the results, which are not as general as the authors claimed.
Author Response
Dear Reviewer:
Thank you for reviewing the manuscript “Spectrophotometric Determination of Formation Constants of Iron(III) Complexes with Several Ligands”. The manuscript suffered a major editing of English language, also was restructured by decreasing the emphasis on ruthenium complexes and DSSC.
Some of the motivation for this study is get an insight of the characteristics of the ligands and explore the generation an iron(III) complex with a higher molar absorbance at a wavelength in the vicinity of 360 nm (considering the light transmittance of FTO glass, please see Fig 4. in doi: 10.1155/2012/897595).
Is important to mention this class of experiments has not been implemented as laboratory practice for graduate or undergraduate students. Considering that a student requires an important dedication of time to learn how to use the software and developing the necessary skills to perform this class of experiments. In our experience, this requires several months.
According to the Hyperquad web page, the several versions of the Hypspec software are based in the same equations; the different versions have slightly differences in refinement speed and visual interfaces. The additional parameters that they mention can be manually charged.
The name or the ligands were taken directly from the canister label, in the case of the 4,4’-di-tert-butyl-2,2’-bipyridyl(also all the ligands) they can be checked for the Sigma-Aldrich web page: https://www.sigmaaldrich.com/MX/es/product/aldrich/515477
Also, the name of the cis-Ru(2,2’-bipyridyl-4-4’-dicarboxylate)2(SCN)2 was taken directly from the original reference: Grätzel, M., Photoelectrochemical cells. Nature 2001,414(6861), 338-344.
Thank you for sharing your scientific arguments about the manuscript.
kind regards
Round 2
Reviewer 1 Report
The revised version has gained in quality and is better readable! Thank you very much.
However, I still miss the usage of crystalline tris- and bischelate complexes and their UV as reference points for the titration analysis. The UV spectra of the clean compounds can serve as calibration for the method shown here. When this is added, the manuscript can be accepted.
Furthermore, still a lot of typos are present in the manuscript and the SI:
Examples: several times: metyl -> methyl
. Scheme 1. Procedure for the synthesis of the diferente iron(III) complexes.
-> Scheme 1. Procedure for the synthesis of the different iron(III) complexes.
Author Response
Dear Reviewer:
Thank you for reviewing the manuscript “Spectrophotometric Determination of Formation Constants of Iron(III) Complexes with Several Ligands”. The typos errors were corrected, also from the supplementary figures S21 to S37, were added the UV-vis spectrum in methanol of the complexes, which were obtained in solid phase.
Reviewer 4 Report
The revised manuscript entitled “Spectrophotometric determination of formation constants of iron(III) complexes with several ligands” resubmitted by José J. N. Segoviano-Garfias and co-workers for reconsideration for publication in the MDPI journal Chemistry presents definitely higher level than the first submission. The authors have constructively addressed the issues raised and modified the manuscript accordingly. My suggestion connected with the proper names of chemicals was about the presentation of the chemical names that should be written as italic (cis-, trans-, tert- and many others). I am afraid I have to disagree with the authors' answer that this class of experiments has not been implemented as laboratory practice for graduate or undergraduate students. This kind of investigation is the subject of study of students in the last year of first grade studies at my university, based on this kind of investigation, students gain experience, which is necessary in the future. I consider the revised manuscript is suitable for publication in the MDPI journal Chemistry.
I wish You all the best and the next good papers.
Author Response
Dear Reviewer:
Thank you for reviewing the manuscript “Spectrophotometric Determination of Formation Constants of Iron(III) Complexes with Several Ligands”. We perform a another check for the complexes and corrected the italics in the name of the complexes
kind regards
