Aurophilic Interactions of Dimeric Bisphosphine Gold(I) Complexes Pre-Organized by the Structure of the 1,5-Diaza-3,7-Diphosphacyclooctanes
, Elvira I. Musina 1,* and Andrey A. Karasik 1Round 1
Reviewer 1 Report
This paper of Dayanova et al. reports the synthesis and study of a couple (a chloride and an iodide derivative) of dimeric gold(I) complexes containing a cyclic bisphosphine similar to others previously employed by the authors. The main difference between these new complexes and those previously described is the substituent at the nitrogen atoms of the bisphosphine (alkyl instead of aryl groups), leading to shorter Au-Au distances in the metallic complexes, what is related to the conformation of the cyclic ligands.
In general, the aim of the manuscript is attractive, but, from my point of view, the paper contains very important inconsistences that invalidate the conclusions. First, the photophysical computational study is developed starting from optimized XRD structures of the complexes (solid state), but it is compared with the data obtained for 2 and 3 in DCM (solutions). For an acceptable comparison, both UV/vis spectra should be referred to the same state than that of the crystal structures (solid), so this comparison is wrong from its starting point.
Moreover, the optimized model of 2 employed in the theoretical study contains “one chlorine ion coordinated to Au(I) (which was applied for optimization according XRD structure) and the second one localized in outer sphere“. What the authors do not say is that the crystal structure of 2 contains two independent molecules in the asymmetric part, one of them displaying a Au···Cl interaction (not bond), while in the second one none of the chlorine atoms is in the vicinity of the metal centres. Both structural situations should be considered (one Au···Cl interaction in the dinuclear complex, and no interaction at all between Au and Cl atoms) for an adequate study. Otherwise, it is not valid.
Finally, the authors state that “The emission lifetimes with the values of ca. 0.35 (2) and
2.14 (3) microseconds indicates the phosphorescent origin of luminescence of complexes.” I strongly disagree with this assumption; from these emission lifetimes (one is six times larger than the other), and from their Stokes’ shifts (larger for the iodine derivative than for the chlorine one), I would say that only complex 3 is phosphorescent (microseconds regime vs. hundreds of nanoseconds). This is also in accordance with an increasing probability of finding phosphorescent emissions as the number of heavy atoms increases, that is, phosphorescence is more likely to be observed in 3 (with two iodine atoms) than in 2 (with lighter chlorine ones and one of them not coordinated).
Apart from these comments, some other corrections should be done:
- A throughout revision of the language is needed.
- The reagents for the synthesis of 2 and 3 in scheme 1 have been exchanged.
- The observation of a peak at m/z 1905 in the mass spectrum of 3 does not imply the presence of the [Au2L2]+ cation in solution. It only indicates its presence under the mass spectrum experimental conditions.
- Au-Au distances are mentioned only imprecisely, and neither Au-Cl nor Au-I distances are given. In this sense, the crystal structures are very roughly described. No comment about the environment of the gold centres is made.
- Reference dealing with the Van der Waals radium of gold ([31]) is quite old (1964). Is not difficult to find more recent references about Van der Waals radii (for example, those found in the webelements website: https://webelements.com, or Santiago Alvarez’s paper in Dalton Trans. published in 2013, DOI: 10.1039/c3dt50599e).
- The formula of complex 2 in Table 1 is wrong: there are 2 instead of 4 Cl atoms per molecule. This table also contains other typographical errors.
Therefore, and taking all the comments above, I consider that this paper does not merit publication in Inorganics, at least, in its actual form. Quite a lot of work is required before being suitable for publication.
Author Response
Dear reviewer,
Thank you for your high evaluation of the manuscript and for your useful questions and comments which allowed improving the quality of the manuscript. We have improved the manuscript, added the required experimental data to SI and answered the questions of the reviewers. All of the changes suggested by the reviewers have been inserted to the manuscript in the Track On mode. Please, find the step-by-step answers on the reviewers comments below. We hope that the answers will be satisfactory for you and for the reviewers, and you will find possible the publication of the manuscript in the “Inorganics”.
Reviewer 1
Comment 1. First, the photophysical computational study is developed starting from optimized XRD structures of the complexes (solid state), but it is compared with the data obtained for 2 and 3 in DCM (solutions). For an acceptable comparison, both UV/vis spectra should be referred to the same state than that of the crystal structures (solid), so this comparison is wrong from its starting point.
Moreover, the optimized model of 2 employed in the theoretical study contains “one chlorine ion coordinated to Au(I) (which was applied for optimization according XRD structure) and the second one localized in outer sphere“. What the authors do not say is that the crystal structure of 2 contains two independent molecules in the asymmetric part, one of them displaying a Au···Cl interaction (not bond), while in the second one none of the chlorine atoms is in the vicinity of the metal centres. Both structural situations should be considered (one Au···Cl interaction in the dinuclear complex, and no interaction at all between Au and Cl atoms) for an adequate study. Otherwise, it is not valid.
Answer. Indeed, data of X-Ray analysis of complexes 2 and 3 were used for quantum chemical computations. The vertical transitions were calculated for gas-phase optimized structures of 2 and 3. Obtained by these way geometries are expected to be closer to the existing in the solutions than to the packed in the crystal. Thus, simulated by this way spectra should be compared with the solution experiment.
Both crystal structure of 2 and 3 contains two independent molecules with slightly different geometry, but we agree with the suggestion that complex is able to exist in cationic and neutral forms, thus we added computations for dication and replaced corresponding paragraph in the manuscript (Figure S5).
“For the optimized structures received from the XRD data the computations predict T1-S0 transition at 649 nm, which does not meet the experimental observations. Therefore, quantum-chemically triplet states have been considered for other two possible structures: for dication of complex 2 without counterions (2a, Figure S5) and for the structure, obtained by the computational replacement of iodide anions in the optimized structure of 3 by chloride ions (2b, Figure S5). The computations predict T1-S0 transition at 462 nm for 2a and 513 nm for 2b. Experimentally observed emission at 505 nm is close to structure 2b however the existing of triplet state of 2a cannot be excluded. Analysis of frontier orbitals shows that model emission originates from 3(X+M)LCT for 2a transitions and from 3(M+X)C transitions for 2b (Figure S6).”
Solid-state UV/vis absorbance spectra have been added to the SI of the manuscript.
Comment 2. Finally, the authors state that “The emission lifetimes with the values of ca. 0.35 (2) and 2.14 (3) microseconds indicates the phosphorescent origin of luminescence of complexes.” I strongly disagree with this assumption; from these emission lifetimes (one is six times larger than the other), and from their Stokes’ shifts (larger for the iodine derivative than for the chlorine one), I would say that only complex 3 is phosphorescent (microseconds regime vs. hundreds of nanoseconds). This is also in accordance with an increasing probability of finding phosphorescent emissions as the number of heavy atoms increases, that is, phosphorescence is more likely to be observed in 3 (with two iodine atoms) than in 2 (with lighter chlorine ones and one of them not coordinated).
Answer. We agree with the suggestion regarding the dependence of the lifetime of emission on the changing of numbers of the heavy atoms. Despite of this, we suppose that the emission of gold(I) chloride complex is also phosphorescence. First, the Stokes shifts of the both complexes are rather large (ca. 6250 cm-1 for 3 and 5000 cm-1 for 2). It means if have a fluorescent origin of the emission, than some strong transformations of molecules should accompany the excitation and emission processes. It is possible if molecule has the opportunities for such transformation (e.g. proton transfer, excitation driven isomerization or other), but in the case of complex 2 the fluorescence can be caused by the π-π* transition of organic parts. These transitions cause the emission with very small Stokes shifts and shorter emission decay (ca. 0.01 µs). Moreover, there a lot of examples of gold(I) complexes with various ligands and structues, even with the dimeric structure like in complex 2, where the phosphorescence decay value is hundreds of nanoseconds [Inorg. Chem. 2016, 55, 4720−4732 DOI: 10.1021/acs.inorgchem.5b02722 Inorg.; Inorganic Chemistry, 2008, 47, 957 DOI: 10.1021/ic701763x; Appl. Phys. Lett., 1999, 74, 1361 DOI: 10.1063/1.123550].
We have added the corresponding sentence to the discussion part:
Notably, that gold(I) complexes often demonstrate a phosphorescence with the fast luminescence decay values of hundreds of nanoseconds.[5,33,34]
Comment 3. A throughout revision of the language is needed.
Answer. We have revised the language and made necessary corrections.
Comment 4. The reagents for the synthesis of 2 and 3 in scheme 1 have been exchanged.
Answer. Scheme 1 has been corrected.
Comment 5. The observation of a peak at m/z 1905 in the mass spectrum of 3 does not imply the presence of the [Au2L2]+ cation in solution. It only indicates its presence under the mass spectrum experimental conditions.
Answer. We have removed this statement
Comment 6. Au-Au distances are mentioned only imprecisely, and neither Au-Cl nor Au-I distances are given. In this sense, the crystal structures are very roughly described. No comment about the environment of the gold centres is made.
Answer. We have corrected and expanded the crystallographic part of the manuscript. We have added Table S1 with selected structure parameters.
Comment 7. Reference dealing with the Van der Waals radium of gold ([31]) is quite old (1964). Is not difficult to find more recent references about Van der Waals radii (for example, those found in the webelements website: https://webelements.com, or Santiago Alvarez’s paper in Dalton Trans. published in 2013, DOI: 10.1039/c3dt50599e).
Answer. The reference has been added.
Comment 8. The formula of complex 2 in Table 1 is wrong: there are 2 instead of 4 Cl atoms per molecule. This table also contains other typographical errors.
Answer. Table 2 (Table 1 in previous version) has been corrected.
Best regards,
Corresponding author
Prof. Dr. Elvira Musina
Author Response File: 
Author Response.docx
Reviewer 2 Report
The authors characterized two interesting phosphine gold(I) complexes using single crystal diffraction and studied their photophysics. The manuscript is interesting because of the two ligands and their phosphine gold(I) chloride and iodide structures. Here are some of the corrections:
1. Abstract: authors did X-ray single crystal diffraction (single crystal XRD) not XRD. It is confusing to just state XRD even though it is noticeably clear that the two structures were analyzed using a single crystal diffractometer. Please make it clear to the readers at least in the abstract.
2. Abstract: Which solvent(s) did you use to grow crystals?
3. Abstract: “…strong aurophilic interactions between two gold(I) cations…: please replace “cations” with “atoms.” Typically, we can not state that cations interact. See articles by Schmidbaur, Fackler, Balch, Vivian Yam, and others
4. Abstract: state the color and morphology of the complexes/crystals.
5. Abstract: at the start of the abstract authors stated the dinuclear compounds but later they stated the cluster. They are dinuclear not clusters. Please see “The cluster-centered origin of luminescence”
6. Keywords: phosphines must be replaced with bisphosphines as stated in the title.
7. Introduction: “Aurophilic interactions are still attractive phenomena actively studied” please change to “Aurophilic interactions are attractive phenomena actively studied” delete “still”
8. Please make sure the references in the introduction are related to the phosphine ligands, not NHC gold compounds. For example, reference “Barnard, P.J.; Wedlock, L.E.; Baker, M. V.; Berners-Price, S.J.; Joyce, D.A.; Skelton, B.W.; Steer, J.H. Luminescence Studies of the Intracellular Distribution of a Dinuclear Gold(I) N-Heterocyclic Carbene Complex. Angew. Chemie - Int. Ed. 2006, 45, 5966–5970, doi:10.1002/anie.200601526.” this is related to NHC and is outdated too. The same case in the following reference: “Si, X.; Zhang, L.; Wu, Z.; Rudolph, M.; Asiri, A.M.; Hashmi, A.S.K. Visible Light-Induced α-C(Sp3)-H Acetalization of Saturated Heterocycles Catalyzed by a Dimeric Gold Complex. Org. Lett. 2020, 22, 5844–5849, doi:10.1021/acs.orglett.0c01924.”
9. Why do you add copper references and the manuscript discusses gold in the introduction? “Grachova, E. V. Design of Supramolecular Cluster Compounds of Copper Subgroup Metals Based on Polydentate Phosphine 366 Ligands. Russ. J. Gen. Chem. 2019, 89, 1102–1114, doi:10.1134/S1070363219060045.”
10. Authors can add references focused on the chemistry related to their ligands. There are related papers by Fackler, Laguna, and Burini, for example. Overall, references must be checked carefully and updated.
11. Page 3, line 87: “The monocrystals of complexes 2 and 3 were obtained….” Why do you call the crystals “mono”? they are crystals of the complexes. Gold phosphine complexes are easy to grow crystals from and obtain good wR2.
12. Page 3, line 88: “mixture of dibutyl ether and dichloromethane (1:5 volume ratio)”. Please confirm if the two solvents were a mixture or two layers. Typically, the gold compounds are dissolved in dichloromethane and then the solution is layered with the ether solvent.
13. Did the author keep the crystallization vials in the fridge or at room temperature undisturbed?
14. Figure 2 is missing the halide atoms. Make figures 1 and 2 as similar as possible.
15. Authors must state similar examples from the literature in which this peculiar gold-halide bonding occurred.
16. Page 5, line 160: “The emission lifetimes with the values of ca. 0.35 (2) 160 and 2.14 (3) microseconds indicate the phosphorescent origin of luminescence of complexes.” Please relate the lifetimes to literature examples. Lifetime measurements must be included in the supporting information.
17. I understand that the luminescence studies were conducted in the solid state. It was not stated anywhere in the manuscript unless I missed if the data were collected at room temperature or 77K. Please include in the abstract, experimental, and discussion. From our experience, it is hard to collect good luminesce data for linear gold compounds at room temperature. Please clarify.
18. Throughout the manuscript, please avoid using “cluster.” Please read the definition of clusters by F.A. Cotton.
19. Figure 6. Solid state excitation and emission spectra of complexes 2 and 3. In the caption, please write a room temperature of 77K.
20. Page 6, line 188: …” whereas another chlorine counterion…” please change to “chloride”. Chlorine gas Cl2 but chloride anion Cl-.
21. Page 10, line 268: “….the resulting precipitate was isolated by filtration” what is the color of the precipitate?
22. Page 9, line 268-270: “Elemental analysis, calculated for C88H92N8P4Au2Cl2 [1850]: C 57.12, H 5.01, N 6.06, P 6.70, Au 21.29, Cl 3.83%.” Elemental analysis is used to calculate the percentage of carbon and hydrogen elements and most of the other elements can be estimated using other techniques. I wonder how the authors calculated the percentage for gold, for example?
23. Please be consistent and use complexes, as stated in the abstract throughout the manuscript. I see complexes, compounds (page 2, line 82), and clusters.
Author Response
Dear reviewer,
Thank you for your high evaluation of the manuscript and for your useful questions and comments which allowed improving the quality of the manuscript. We have improved the manuscript, added the required experimental data to SI and answered the questions of the reviewers. All of the changes suggested by the reviewers have been inserted to the manuscript in the Track On mode. Please, find the step-by-step answers on the reviewers comments below. We hope that the answers will be satisfactory for you and for the reviewers, and you will find possible the publication of the manuscript in the “Inorganics”.
Reviewer 2
Comment 1. Abstract: authors did X-ray single crystal diffraction (single crystal XRD) not XRD. It is confusing to just state XRD even though it is noticeably clear that the two structures were analyzed using a single crystal diffractometer. Please make it clear to the readers at least in the abstract.
Answer. Corrected.
Comment 2. Abstract: Which solvent(s) did you use to grow crystals?
Answer. We have corrected the part of discussion as follows:
Crystals of complex 2 were obtained at room temperature by the slow diffusion of dibutyl ether into a solution of the complex in dichloromethane, whereas crystals of complex 3 were obtained by recrystallization from dimethylformamide
Comment 3. Abstract: “…strong aurophilic interactions between two gold(I) cations…: please replace “cations” with “atoms.” Typically, we can not state that cations interact. See articles by Schmidbaur, Fackler, Balch, Vivian Yam, and others
Answer. Corrected
Comment 4. Abstract: state the color and morphology of the complexes/crystals.
Answer. We have added the following sentence to the abstract:
“The obtained complexes were isolated as white crystalline powders”
Comment 5. Abstract: at the start of the abstract authors stated the dinuclear compounds but later they stated the cluster. They are dinuclear not clusters. Please see “The cluster-centered origin of luminescence”
Answer. Corrected.
Comment 6. Keywords: phosphines must be replaced with bisphosphines as stated in the title.
Answer. Corrected.
Comment 7. Introduction: “Aurophilic interactions are still attractive phenomena actively studied” please change to “Aurophilic interactions are attractive phenomena actively studied” delete “still”
Answer. Corrected.
Comment 8. Please make sure the references in the introduction are related to the phosphine ligands, not NHC gold compounds. For example, reference “Barnard, P.J.; Wedlock, L.E.; Baker, M. V.; Berners-Price, S.J.; Joyce, D.A.; Skelton, B.W.; Steer, J.H. Luminescence Studies of the Intracellular Distribution of a Dinuclear Gold(I) N-Heterocyclic Carbene Complex. Angew. Chemie - Int. Ed. 2006, 45, 5966–5970, doi:10.1002/anie.200601526.” this is related to NHC and is outdated too. The same case in the following reference: “Si, X.; Zhang, L.; Wu, Z.; Rudolph, M.; Asiri, A.M.; Hashmi, A.S.K. Visible Light-Induced α-C(Sp3)-H Acetalization of Saturated Heterocycles Catalyzed by a Dimeric Gold Complex. Org. Lett. 2020, 22, 5844–5849, doi:10.1021/acs.orglett.0c01924.”
Answer. These articles have been cited due to these works observe the dimeric gold(I) compounds with application in biology or even medicine. They are cited in the part of introduction which discusses the application of gold(I) species without attention to the ligands applied. The gold(I) complexes with NHC-ligands are not too outdated due to the NHC-compounds are often observed as isolobal analogues of tertiary phosphines.
Comment 9. Why do you add copper references and the manuscript discusses gold in the introduction? “Grachova, E. V. Design of Supramolecular Cluster Compounds of Copper Subgroup Metals Based on Polydentate Phosphine 366 Ligands. Russ. J. Gen. Chem. 2019, 89, 1102–1114, doi:10.1134/S1070363219060045.”
Answer. This review observes complexes of copper subgroup metals: Cu, Ag, Au. Therefore, in this review there are a lot of examples of gold(I) complexes with polydentate phosphine ligands which are relevant to our research.
Comment 10. Authors can add references focused on the chemistry related to their ligands. There are related papers by Fackler, Laguna, and Burini, for example. Overall, references must be checked carefully and updated.
Answer. We have added several new references relevant to the chemistry of gold(I). It should be noted that the researches by Prof. Fackler and Prof. Laguna were mostly focused on the gold(I) clusters or on the chemistry of gold(I) with S- or N-ligands.
Van Zyl, W.E.; López-De-Luzuriaga, J.M.; Fackler, J.P. Luminescence Studies of Dinuclear Gold(I) Phosphor-1,1-Dithiolate Complexes. J. Mol. Struct. 2000, 516, 99–106, doi:10.1016/S0022-2860(99)00231-8.
Fackler, J.P.; Grant, T.A.; Hanson, B.E.; Staples, R. Characterization of the Luminescent, Homoleptic, Three-Coordinate, Water Soluble Au (I) Complex of Trisulfonated Triphenylphosphine (TPPTS) as the Cesium Salt, CS8[Au(TPPTS)3]·5.25 H20. Gold Bull. 1999, 32, 20–23.
Czerwieniec, R.; Hofbeck, T.; Crespo, O.; Laguna, A.; Concepción Gimeno, M.; Yersin, H. The Lowest Excited State of Brightly Emitting Gold(I) Triphosphine Complexes. Inorg. Chem. 2010, 49, 3764–3767, doi:10.1021/ic902325n.
Lim, S.H.; Schmitt, J.C.; Shearer, J.; Jia, J.H.; Olmstead, M.M.; Fettinger, J.C.; Balch, A.L. Crystallographic and Computational Studies of Luminescent, Binuclear Gold(I) Complexes, Au-2(I)(Ph2P(CH2)(n)PPh2)2I2 (N=3-6). Inorg. Chem. 2013, 52, 823–831.
Comment 11. Page 3, line 87: “The monocrystals of complexes 2 and 3 were obtained….” Why do you call the crystals “mono”? they are crystals of the complexes. Gold phosphine complexes are easy to grow crystals from and obtain good wR2.
Answer. We have removed mono and stated just “crystals”.
Comment 12. Page 3, line 88: “mixture of dibutyl ether and dichloromethane (1:5 volume ratio)”. Please confirm if the two solvents were a mixture or two layers. Typically, the gold compounds are dissolved in dichloromethane and then the solution is layered with the ether solvent.
Answer. We have corrected the description of the crystal growth. It was a layer of dibutyl ether covered a solution of complex 2 in DCM.
Crystals of complex 2 were obtained at room temperature by the slow diffusion of dibutyl ether into a solution of the complex in dichloromethane, whereas crystals of complex 3 were obtained by recrystallization from dimethylformamide
Comment 13. Did the author keep the crystallization vials in the fridge or at room temperature undisturbed?
Answer. Crystallization vials kept at room temperature
Comment 14. Figure 2 is missing the halide atoms. Make figures 1 and 2 as similar as possible.
Answer.
We have corrected Scheme 1 and Figure 2.
Scheme 1. The synthesis of complexes 2 and 3
Figure 2. Schematic illustration of structures of dimeric gold(I) complexes with N-alkyl and N-aryl substituted 1,5-diaza-3,7-diphosphacyclooctanes
Comment 15. Authors must state similar examples from the literature in which this peculiar gold-halide bonding occurred.
Answer. We have added the corresponding discussion with references to the text:
“Linear or T-shaped ligand environment is often observed for the gold(I) atoms in complexes with various ligands [21,34].”
Comment 16. Page 5, line 160: “The emission lifetimes with the values of ca. 0.35 (2) 160 and 2.14 (3) microseconds indicate the phosphorescent origin of luminescence of complexes.” Please relate the lifetimes to literature examples. Lifetime measurements must be included in the supporting information.
Answer. The figures of lifetime decays have been added to SI. We have added the citations of the articles discussing the fast luminescent decay as follow:
Notably, that gold(I) complexes often demonstrate a phosphorescence with the fast luminescence decay values of hundreds of nanoseconds.[5,33,34]
Comment 17. I understand that the luminescence studies were conducted in the solid state. It was not stated anywhere in the manuscript unless I missed if the data were collected at room temperature or 77K. Please include in the abstract, experimental, and discussion. From our experience, it is hard to collect good luminesce data for linear gold compounds at room temperature. Please clarify.
Answer. All photoluminescent measurement were carried out in solid state at room temperature on the Fluorolog 3 (Horiba). Complex 2 display a moderate emission at these conditions with the slits opened at 5 nm. Complex 3 display a stronger emission in the solid state at room temperature. there were no problems with the registering of the good quality emission spectra.
We have added comments to the discussion indicative the conditions of the measurements.
Page 1: The obtained complexes exhibit bluish-green phosphorescence (λem 505 (-Cl) and 530(-I)) in the solid state at room temperature originated by the metal-halide centered transitions, which was confirmed by TDDFT calculations.
Page 6: Dried powders of complexes 2 and 3 display a moderate emission in the solid state in the bluish-green region of the spectra at room temperature (Figure 6).
Comment 18. Throughout the manuscript, please avoid using “cluster.” Please read the definition of clusters by F.A. Cotton.
Answer. Corrected
Comment 19. Figure 6. Solid state excitation and emission spectra of complexes 2 and 3. In the caption, please write a room temperature of 77K.
Answer. Figure 6. Solid state excitation and emission spectra of complexes 2 and 3 at room temperature
Comment 20. Page 6, line 188: …” whereas another chlorine counterion…” please change to “chloride”. Chlorine gas Cl2 but chloride anion Cl-.
Answer. Corrected
Comment 21. Page 10, line 268: “….the resulting precipitate was isolated by filtration” what is the color of the precipitate?
Answer. The statement of precipitate color has been added to the experimental section
The reaction mixture was stirred at room temperature for 2 hours, the resulting white precipitate was isolated by filtration, washed with acetone and dried under reduced pressure.
Comment 22. Page 9, line 268-270: “Elemental analysis, calculated for C88H92N8P4Au2Cl2 [1850]: C 57.12, H 5.01, N 6.06, P 6.70, Au 21.29, Cl 3.83%.” Elemental analysis is used to calculate the percentage of carbon and hydrogen elements and most of the other elements can be estimated using other techniques. I wonder how the authors calculated the percentage for gold, for example?
Answer. The elemental analysis for metal traces and phosphorus was carried out by the gravimetric method of analysis (weight), which is based on the law of conservation of the mass of a substance during chemical transformations and consists in accurately measuring of the mass of the analyzed component of the sample, isolated in the form of a compound of known composition. The method consists in high-temperature combustion of the sample at 900°C in an oxygen flow (pyrolysis). In this case, non-volatile oxides (P2O5, MexOy) are formed, which are firmly held by quartz. Further, based on the measurements of the mass of the sample before and after combustion, the percentage of the element in the taken sample is calculated.
Elemental analysis on halogen was carried out by determination of the quantitative content of halogens according to Schöniger method. The method is based in a high-temperature (1200 °C) combustion of the sample in an oxygen atmosphere under the action of a catalyst (platinum), further formation of hydrohalic acid in the solution, and the measurement of a volume of 0.01 N solution of mercury nitrate, which was used for titration of the analyzed sample, and calculation of the percentage of halogen in the sample.
Corresponding description has been added to the experimental part.
Comment 23. Please be consistent and use complexes, as stated in the abstract throughout the manuscript. I see complexes, compounds (page 2, line 82), and clusters.
Answer. We have corrected clusters to complexes or to metal-halide-centered origin (3(M+X)C).
Best regards,
Corresponding author
Prof. Dr. Elvira Musina
Author Response File: Author Response.docx
Reviewer 3 Report
In this manuscript, Karasik et al. report new heteroleptic gold complexes bearing both cyclic phosphine ligands (chelate, can be regarded as macrocycles) and halide ligands. Due to the latter, the complexes are dimeric, and there are aurophilic interactions. Metallophilic contacts represent an intersting and rapidly growing area of supramolecular chemistry. In this work, it was demonstrated that there are correlations between the conformation of cyclic ligand and these interactions. Moreover, it was shown how abovementioned interactions affect the luminescence behavior of the complexes - it was studied by both experimental techniques and theoretical approaches, and results of the latter agree very well with experiment.
Characterization of the complexes was performed based on several techniques (single crystal XRD, multinuclear NMR, mass spectrometry), so that the authors can judge upon the nature of the products unequivocally. The style of the manuscript is good; no extensive corrections are needed.
Overall, this is a very nice contribution to the fields of coordination chemistry, and it will be also of interest for chemists dealing with supramolecular chemistry and chemistry of phosphorus. I do believe that the manuscript in current form is perfrctly suitable for publication in Inorganics. No corrections and/or additions are needed.
Author Response
Dear reviewer,
Thank you for your high evaluation of the manuscript and for your useful questions and comments which allowed improving the quality of the manuscript. We have improved the manuscript, added the required experimental data to SI and answered the questions of the reviewers. All of the changes suggested by the reviewers have been inserted to the manuscript in the Track On mode. We hope that the answers will be satisfactory for you and for the reviewers, and you will find possible the publication of the manuscript in the “Inorganics”.
Best regards,
Corresponding author
Prof. Dr. Elvira Musina
Round 2
Reviewer 1 Report
Comments for author File: 
Comments.pdf
Author Response
Dear editor and reviewer,
Thank you for your revision, which allowed to corrected the misprints and incorrections in the manuscript. We have made all required corrections in the TrackOn mode.
Hope that the new version of the manuscript is suitable for publishing in the Inorganics.
Reviewer 1.
Comment 1. In page 3, line 95, Figures 1 and S1 are cited, but Figure S2 should also had been mentioned.
Answer. Corrected
Comment 2. References should be carefully revised. At least, reference numbers 33 and 34 are wrong; they should be 35 and 36.
Answer. Corrected
Comment 3. Au-Au distances have been given with accuracy in this new version, but that corresponding to 3 (3.1680(5) Å) is different to that reported in the first version of the manuscript (3.09 Å) without any explanation. What is the reason for this change?
Answer. In the initial version the unrefined data were presented. Current value of the Au-Au distance is corrected according to the refined XRD data.
Comment 4. Regarding the theoretical calculations, the authors have added a paragraph in which the state: “Analysis of frontier orbitals shows that model emission originates from 3(X+M)LCT for 2a transitions and from 3(M+X)C transitions for 2b (Figure S6).” From Figure S6 I would not say so; on the contrary, I would assign 3L(X+M)CT transitions for 2a.
Answer. Corrected
Comment 5. A revision of subscripts, superscripts and special characters is needed in Table 1.
Answer. Corrected
Comment 6. Figure captions of Figures S7 and S8 are exactly the same.
Answer. Corrected
“Figure S8. UV/Vis absorbance spectra of complex 3 measured in solid state”
Author Response File: Author Response.docx
