On‐Surface Hydrogen/Deuterium Isotope Exchange in Polycyclic Aromatic Hydrocarbons

Abstract

Hydrogen plays important roles in the on-surface synthesis of carbon-based materials in ultra-high vacuum. The complex interplay between hydrogen and surface-adsorbed polycyclic aromatic hydrocarbons (PAHs) is tracked by in situ time-of-flight secondary ion mass spectrometry (ToF-SIMS) combined with isotope labeling. In situ deuterium labeling of prototypical PAHs, coronene (CR) and 7-armchair graphene nanoribbons (GNRs), on Au(111) is achieved by annealing either in D 2 gas or in the vapor of perdeuterio-acenaphthene. By following the mass spectra of in situ deuterated CR mixed with hydrogen-CR, it is demonstrated that PAHs adsorbed at hot Au(111) surfaces continuously exchange hydrogen atoms. Also, D 2 present during the Ullmann coupling step leads to incorporation of deuterium and to shorter GNRs. Scheme 1. PAHs used for on-surface isotope exchange.

On-surface cyclodehydrogenation reaction pathway determined by selective molecular deuterations

“…These reaction conditions are different from the recently reported H/D isotope exchange for PAHs on Au(111) in the presence of D 2 gas of various partial pressures (10 −5 to 10 −1 torr). 45 The D 2 molecules present in the gas phase can shift the physisorption toward chemisorption giving dissociated D atoms on the Au(111) surface to facilitate the H/D isotope exchange (Fig. S14 † ).…”

“…54,55 This study also opens an avenue to achieving designer deuteration patterns in atomically precise GNRs and other large graphitic scaffolds, offering an isotopic labeling strategy to examine the dynamics of neutron scattering and nuclear magnetic resonance scattering. 45,56,57 Author contributions…”