Analysis of Local and Global Aromaticity in Si₃C₅ and Si₄C₈ Clusters. Aromatic Species Containing Planar Tetracoordinate Carbon

Round 1

Reviewer 1 Report

This is  an informative article that contributes the minimum energy structures of the C-Si clusters in planar and planar tetracoordinate carbons, and gives a new concepting method. The research strategy, the methodology, and the results as well all are innovative  and inspiring for these materials analysis and fabrication. The strategy is beneficial for both research and design of C-Si compound. 

So I suggest its publishing with a minor revision at the conclusion's form: seperate the all text into several pargraphs with numbers, to show clearer.

Author Response

We thank the reviewer for her/his positive feedback on our work. In addition, following her/his recommendation, we have separated the different conclusions into paragraphs.

Conclusions :

The global (p) and local (s) aromaticity of Si₃C₅ and Si₄C₈ clusters has been reviewed employing an orbital localization method (ELF-LOC) and magnetically induced current density analysis.

The ELF-LOC investigation leads to bond descriptions like those reported previously based on the adaptive natural partitioning analysis (AdNDP) method. These systems show  s- and  p-delocalization in agreement with Hückel's rule of 4n+2 electrons.

 The induced current density analysis identifies global and local aromatic current circuits. In the case of Si₃C₅, a local paratropic current (of moderate-intensity, RCS=-8.1 nA T^-1) is detected inside the C₅ ring. However, a diatropic current of higher intensity (RCS=12.16 nA T^-1) is also present, which provides a global aromatic character to this species. A local s-diatropic current involving the Si-ptC-Si fragment is also identified, with moderate intensity (RCS=5.2 nA T^-1). These results highlight the double aromatic character of this species. In the case of Si₄C₈, a weak global paratropic current (RCS=-1.5 nA T^-1) and an intense global diatropic current (RCS=10.4 nA T^-1) are identified. In addition, two local diatropic currents around the Si-ptC-Si rings (RCS=5.8 nA T^-1) are also identified. This study highlights the double aromatic character of these clusters and the importance of this delocalization pattern in the stabilization of these species.

Reviewer 2 Report

The Authors have approach to the analysis of local and global aromaticity in Si₃C₅ and Si₄C₈ clusters. For this purpose, Authors use an orbital localization method based on the partitioning of the molecular space according to the topology of the electronic localization function (LOC-ELF). Also the magnetically induced current density was analyzed. The LOC-ELF-based analysis coincides with the AdNDP study (double aromaticity, global and local).

The manuscript deserves to publish in Chemistry after a minor correction. I would like to suggest introducing changes before publishing in Chemistry.

The authors should revise in the manuscript as the following points:

1. Why the Authors used B3LYP/6-311+G* method? Whether another method was taken into account? Are there any links to the previous experimental data?
2. Please complete conclusions to combine theoretical work with future or proven experimental work.

Author Response

We thank the reviewer for her/his positive feedback on our work. Additionally, we have included changes to address questions or recommendations:

reviewer:

1. Why the Authors used B3LYP/6-311+G* method? Whether another method was taken into account? Are there any links to the previous experimental data?

Response:

The used methodologies are little dependent on the method or basis set used in the wave function calculations. Thus, it was explicitly noted in the revised version:

It is essential to mention that both the ring currents analysis[77] and the ELF analysis [86,87] are not very dependent on the method or the basis set used in their calculation.

77. Jusélius, J.; Sundholm, D.; Gauss, J. Calculation of current densities using gauge-including atomic orbitals. J. Chem. Phys. 2004, 121, 3952–3963, doi:10.1063/1.1773136.

86. Llusar, R.; Beltrán, A.; Andrés, J.; Noury, S.; Silvi, B. Topological analysis of electron density in depleted homopolar chemical bonds. J. Comput. Chem. 1999, 20, 1517–1526.

87. Silvi, B.; Savin, A. Classification of chemical bonds based on topological analysis of electron localization functions. Nature 1994, 371, 683–686.

reviewer:

1. Please complete conclusions to combine theoretical work with future or proven experimental work.

Response:

We have added one conclusion in the revised version of the manuscript:

"The ptC structures of the Si3C5 and Si4C8 clusters correspond to the global minima, together with their double aromatic character, suggest that gas-phase experiments could detect these species."