Scanning Tunneling Microscopy Study of a Phenalenyl-Based Singlet Biradical on Graphite
Author(s):
Kai Iketaki, Kaname Kanai, Akihiro Shimizu, Takashi Kubo, Zhi-Hong Wang, Yukio Ouchi, Yasushi Morita, Kazuhiro Nakasuji, Kazuhiko Seki
Journal:
The Journal of Physical Chemistry C
Year:
2009
Volume:
113
Pages
1515-1519
DOI:
10.1021/jp808686v
Abstract:
The adsorption of a phenalenyl-based singlet biradical, 8,16-diphenyl-s-indaceno[1,2,3-cd:5,6,7-c′d′]diphenalene
(Ph2-IDPL), on a highly oriented pyrolytic graphite surface has been studied using scanning tunneling
microscopy (STM), tunneling spectroscopy, and ultraviolet photoelectron spectroscopy (UPS) under ultrahigh-
vacuum conditions. Ph2-IDPL molecules form a highly ordered monolayer on the graphite surface. The
STM images of Ph2-IDPL monolayers show a strong bias-dependence in the range from -1.8 to +1.6 V.
The observed image contrast may be associated with the distortion of the adsorption configuration or structural
deformation of the molecules. UPS and tunneling spectroscopy reveal the electronic structure of Ph2-IDPL.
The energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular
orbital (LUMO) was determined to be 2.7 eV from the measured peak-to-peak energy difference between the
HOMO and LUMO in the tunneling spectrum.