Initial Coupling and Reaction Progression of Directly Deposited Biradical Graphene Nanoribbon Monomers on Iodine-Passivated Versus Pristine Ag(111)

Round 1

Reviewer 1 Report

The paper is nice and well written and should be published, but needs some minor changes:

I believe a D is missing in the initial word of affiliation a)

line 71, authors should explain what Ullmann coupling limits are.

Figure 1 caption should be improved. Please put a legend with the atoms colour, explaining what they are

Author Response

-The missing "D" has been added to the first affiliation

-A brief explanation why metal surfaces are necessary for Ullmann coupling has been added

-We have added a legend to Figure 1 explaining the atom color code

Reviewer 2 Report

The authors explored the conditions for synthesizing GNRs on inert surfaces. They systematically examined whether the products changed depending on annealing temperatures, surface passivity, and the presence or absence of halogen atoms of the precursor. With STM, the authors clarified that GNRs form by depositing the pre-radicalized precursor on the iodine-covered Ag surface and annealing the sample; however, the issue is that the iodine film was removed by the post-annealing process.
The manuscript is well written and this finding is useful in the search for the ideal synthetic method of GNRs.
The manuscript should be published if the authors can address the following points.

1) Page 2, Line 60. The authors state that reactive metal support is required for the first reaction step (i.e., dehalogenation), but the metal contribution should be rather important for the second step (CDH). Indeed this is mentioned by the authors on Page 2, Lines 70-72.

2）Page 3. The authors propose a structural model of DITTP/Ag(111) and describe in detail possible intermolecular interactions (such as halogen-halogen interactions). However, for me, the model in Fig. 1b is suspicious. In Fig. 1a, the protrusion is assigned to the phenanthrene group, which is not consistent with the steric geometry of the molecule. In fact, the phenyl groups appear as a bright spot in the chain (Fig. 1c). Can the authors show additional data to support this structural model?　Otherwise, the intermolecular interaction claim should be toned down because this is off the main topic of the manuscript. 

3) Page 6, Line 221. Is there any evidence of the iodine film remaining on the surface even in solution?

4) Figure 3. This figure layout is misleading: Fig. 3a and c show chains on Ag(111), whereas Fig. 3b shows chains on I-Ag(111). For example, putting a label of the sample on top of each image makes it easier to understand.

5) Figure 3b and c. The chain width looks to be different between the two samples. In other words, the vertical distance of the alternating bright spots of the chain in Fig. 3b looks shorter than that in Fig. 3c. Can the authors mention the possible reason for this?

6) Figure S5. The axis labels are too small to see.

Author Response

1) No action required

2) We agree with reviewer 2 and have moved the detailed discussion of the self-assembled structure of intact DITTP and the corresponding model from the main manuscript to the Supporting Information. However, we think that the contrast of the still iodinated DITTP precursor molecule and the covalent chains obtained by dehalogenative coupling cannot be directly compared. The bulky iodine substituents definitely have an influence on the adsorption height, which again will affect the appearance of the phenyl substituents in STM. We also explain in the Supporting Information how we allocated individual DITTP molecules in the self-assembled structure, using the bright contrast of the iodine substituents as hallmark. But we also agree with reviewer 2 that a definitive assignment is not possible based on the presented STM data. Accordingly, we toned down our statements.

3) We do not have clear evidence that the iodine monolayer still remains intact after the solution processing. We have added a respective comment

4) We have added a label to Fig. 3 to make the assignment easier

5) Very good point. Our hypothesis is that both the increased repeat distance in the organometallic chains and the stronger molecule-surface interactions on pristine Ag(111) as compared to I-Ag(111) result in a more planar adsorption of the phenyl substituents. This would also affect their STM appearance and the width of the chains. A brief comment has been added.

6) We have increased the font size of the axis labels

Reviewer 3 Report

As entitled, this paper investigates the surface-confined formation of graphene nanoribbons (GNRs). The authors investigated the formation of these GNRs by using an original method, RaDes, on Ag(111) and on Ag(111)-I surfaces. The experimental part of this manuscript is very-well written and detailed. The manuscript of Galeotti et al. is certainly of sufficient importance and high quality to be acceptable for Chemistry. The topic is of great current interest. The described results are very important. The assertions of the paper are tested experimentally by surface science tools. The presentation of the results is generally clear and concise and the text is well written.

I have one minor comment:

• Figure 1c. The formation of polymer is visible but there are two other features (up left, and middle right). What are these features?

Author Response

Also these features with a different STM contrast consistently show an internal periodicity (repeat distance) of 1.7 nm. So we likewise assign them to covalent chains despite their slightly different appearance in STM. We no longer observed such pronounced contrast variations for the longer chains obtained after mild annealing. So maybe this is related to the inferior stability of shorter chains and the associated difficulties in STM imaging. We added a brief comment.