On-Surface Debromination of C<sub>6</sub>Br<sub>6</sub>: C<sub>6</sub> Ring versus C<sub>6</sub> Chain.
basic_science · Level V
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- Record sourced from PubMed, PMID 35377612.
- Also identified by DOI 10.1021/acsnano.2c00945.
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Abstract
Carbon allotropes comprising sp-hybridized carbon atoms have been investigated for decades for their molecular structure. One of the unsolved mysteries is whether they should take a linear or cyclic configuration in condensed phases due to the lack of atomistic characterizations. Herein, we designed a molecule with a C<sub>6</sub> skeleton as a model system to address this issue, which was achieved by eliminating Br atoms from hexabromobenzene (C<sub>6</sub>Br<sub>6</sub>) molecule on the Ag(111) substrate via thermal treatment. It is found that the C<sub>6</sub> ring intermediate resulting from complete debromination is energetically unstable at room temperature based on theoretical calculations. It subsequently transforms into the C<sub>6</sub> polyynic chain via a ring-opening process and ultimately polymerizes into the organometallic polyyne, whose triyne structural unit is revealed by bond-resolved noncontact atomic force microscopy. Theoretical calculations demonstrated an energetically favorable pathway in which the ring-opening process occurs after complete debromination of C<sub>6</sub>Br<sub>6</sub>. Our study provides a platform for the synthesis of elusive carbon-rich materials.