jp9b05602_si_001.pdf (1.89 MB)
On the Impact of Geometrical Factors on Hot Electron-Induced Tautomerization
journal contribution
posted on 2019-06-13, 00:00 authored by Jens Kügel, Tim Zenger, Markus Leisegang, Matthias BodeThe ability to controllably switch
molecules, for example, by the
application of external stimuli, such as charge carriers or photons,
has fascinated the scientific community since the advent of nanoscience.
A prominent example is isomerization, that is, the transformation
of a molecule with a given shape into another atomic arrangement without
changing the chemical formula. This rearrangement often only involves
a small subunit of the molecule, the active part, whereas the inactive
part remains unchanged. Here, we present a systematic low-temperature
scanning tunneling microscopy investigation of the influence the inactive
part has on hot electron-induced tautomerization processes. In our
study, we investigate crosslike molecules, namely, deprotonated phthalocyanine
and naphthalocyanine molecules, which exhibit the same central active
unit but possess molecule arms of different lengths. If deposited
on a sixfold symmetric Ag(111) surface, the four molecule arms loose
degeneracy, resulting in two pairs of opposing arms with different
tautomerization efficiencies. Our data reveal that the electron yield
changes significantly depending on the specific molecular arm the
charge carriers reach after injection into the Ag(111) surface state.
To partially separate the fraction of hot electrons reaching the different
arms, we performed distance- and angle-dependent molecular nanoprobe
measurements. The experimental results are interpreted within a very
simple geometrical model assuming rectangular shaped molecular arms,
which nicely explains the effects observed for phthalocyanine and
naphthalocyanine molecules.