期刊
ACS NANO
卷 15, 期 3, 页码 4937-4946出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.0c09756
关键词
on-surface synthesis; alkyne coupling reactions; conjugation; HOMO-LUMO gap; scanning probe microscopy
类别
资金
- European Union [635919, 863098]
- Spanish Agencia Estatal de Investigacion [PID2019-107338RB-C62, PID2019-107338RB-C63]
- Xunta de Galicia (Centro singular de investigacion de Galicia) [ED431G 2019/03]
- European Regional Development Fund-ERDF
This study investigates the reaction pathways and product structures on an Au(111) surface using a pyrene-based precursor with alkyne and halogen functional groups, revealing the relationship between reaction activity and product structures through scanning tunneling spectroscopy.
The combination of alkyne and halogen functional groups in the same molecule allows for the possibility of many different reactions when utilized in on-surface synthesis. Here, we use a pyrene-based precursor with both functionalities to examine the preferential reaction pathway when it is heated on an Au(111) surface. Using high-resolution bond-resolving scanning tunneling microscopy, we identify multiple stable intermediates along the prevailing reaction pathway that initiate with a clearly dominant Glaser coupling, together with a multitude of other side products. Importantly, control experiments with reactants lacking the halogen functionalization reveal the Glaser coupling to be absent and instead show the prevalence of non-dehydrogenative head-to-head alkyne coupling. We perform scanning tunneling spectroscopy on a rich variety of the product structures obtained in these experiments, providing key insights into the strong dependence of their HOMO-LUMO gaps on the nature of the intramolecular coupling. A clear trend is found of a decreasing gap that is correlated with the conversion of triple bonds to double bonds via hydrogenation and to higher levels of cyclization, particularly with nonbenzenoid product structures. We rationalize each of the studied cases.
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