Effect of functional group (fluorine) of aromatic thiols on electron transfer at the molecule-metal interface

Abstract

Electron transferal the molecule-metal interface of self-assembled monolayers of 1,1′;4′,1″-terphenyl-4″-thiol (BBB) and its partially fluorinated counterpart (BFF: p-thiophenyl-nonafluorobiphenyl) on Au(111) is investigated by core-hole clock spectroscopy. Ultrafast electron transfer at the BBB/Au(111) interface in the low-femtosecond regime (on the same time scale as the C 1s core-hole lifetime, ∼6 fs) was observed. In contrast, for BFF/Au(111), the interface electron transfer was forbidden during the core-hole decay. This strongly suggests that fluorination of phenyl rings significantly enhances the localization of the excited electrons in the LUMO. © 2006 American Chemical Society.