A Theoretical Design of Chiral Molecules through Conformational Lock towards Circularly Polarized Luminescence

Round 1

Reviewer 1 Report

I am happy to recommend thix paper for publication in Photonics.

Author Response

Thanks for the positive comments. 

Reviewer 2 Report

It is an interesting and relevant paper for the community of Biophysics and Neurosciences. The Introduction gives a clear presentation of the motivations and sets up the relevance of the contribution in the context of the area of the article. The technical developments for the attainment of the results are clean and presented with details in a very balanced way. Conclusions, insights and perspectives are also discussed with a great deal of information. The paper has a high quality and I hereby accept it in its present form.

Author Response

Many thanks. We hope this method can be seen by more researchers. 

Reviewer 3 Report

The manuscript “A theoretical design of chiral molecules through conformational lock towards circularly polarized luminescence”, by Lewen Wang, Tengfei He, Hailiang Liao, Yige Luo, Wen Ou, Yinye Yu, Wan Yue, Guankui Long, Xingzhan Wei and Yecheng Zhou, highlights the possibility to obtain an advanced method for circularly polarized light emission materials, by changing chirality through alkyl chains. The manuscript respects the journal template; the results are clear presented. The Manuscript can be considered for publication after minor changes.

1.       Please insert a section where are defined the used/ purchased materials (name of the composite, name of the supplier, chemical composition, etc), how the materials were prepared, the used instruments for analyzing the materials (name, measurement parameters, etc).

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 4 Report

The authors promote an interesting idea of constructing molecules capable of strongly chiral photoluminescence by combining achiral constituents in chiral configurations. In this way, they consider molecules formed by achiral light-emitting diketopyrrolopyrrole units connected to achiral alkyl chains. The connection areas attain chirality due to a conformational lock. As the chiral parts of the molecule are adjacent to the light emitting center, they affect the corresponding electronic states and induce the chirality of various optical properties. The mechanism is thoroughly studied by the density functional theory simulations using commercial Gaussian software. Spectra of absorption and electronic circular dichroism as well as emission intensity and dissymmetry spectra are evaluated for the molecules of the opposite handedness and having alkyl chains of different lengths. The electronic structure of the ground and excited states is analyzed with special attention paid to the chiral connection areas. Finally, the substances are synthesized and their absorption and circular dichroism spectra are measured to verify the theoretical predictions.

The presented research is very timely: materials for emission and detection of chiral light indeed receive increasing attention. The research design in general is appropriate. The main results and conclusions are supported by the data. I propose to publish after the following issues are fixed/clarified:

1. Following the logic of the authors, the chiral connection areas in R and S conformations depicted in Fig.2c) have to be exact mirror images of each other. Now it is hard to see this.

2. The authors present spectra of various quantities for the RR and SS molecules stating that they are identical up to the change of sign. In fact, the spectra for (R, R)-CDPP-11 molecules and (S, S)-CDPP-11 in Fig. 4b) as well as their parameters in Table 1 only approximately fulfill this rule. Also, the spectra in Fig S1b) are not exactly inverted compared to those in Fig 3b). Does this indicate insufficient simulation accuracy?

3. It is impossible to assess the electronic density in the chiral parts of the molecule in Figs. 3c), 3d),  4c), and 4d). Important conclusions like “These results indicate that the chiral center is indeed involved in the light absorption” (lines 136,137) remain vaguely supported.

4. The experimental optical data looks somewhat fragmented. First, the measured circular dichroism and absorption spectra in Fig 6 are given for different wavelength ranges. Second, the emission spectrum is given in supplementary Fig. S2, while the emission polarization remains unresolved. The latter is the key characteristic of molecules designed for “circularly polarized luminescence” (paper title)!

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 4 Report

The authors have nicely clarified all indicated issues and added important data. The paper is ready for publication.