3 research outputs found
Interactions and Self-Assembly of Stable Hydrocarbon Radicals on a Metal Support
Stable hydrocarbon radicals are able to withstand ambient
conditions.
Their combination with a supporting surface is a promising route toward
novel functionalities or carbon-based magnetic systems. This will
remain elusive until the interplay of radical–radical interactions
and interface effects is fundamentally explored. We employ the tip
of a low-temperature scanning tunneling microscope as a local probe
in combination with density functional theory calculations to investigate
with atomic precision the electronic and geometric effects of a weakly
interacting metal support on an archetypal hydrocarbon radical model
system, i.e., the exceptionally stable spin-1/2 radical α,γ-bisdiphenylene-β-phenylallyl
(BDPA). Our study demonstrates the self-assembly of stable and regular
one- and two-dimensional radical clusters on the Au(111) surface.
Different types of geometric configurations are found to result from
the interplay between the highly anisotropic radical–radical
interactions and interface effects. We investigate the interaction
mechanisms underlying the self-assembly processes and utilize the
different configurations as a geometric design parameter to demonstrate
energy shifts of up to 0.6 eV of the radicals’ frontier molecular
orbitals responsible for their electronic, magnetic, and chemical
properties
Spectroscopic Scanning Tunneling Microscopy Studies of Single Surface-Supported Free-Base Corroles
Corroles are versatile chemically active agents in solution.
Expanding
their applications toward surface-supported systems requires a fundamental
knowledge of corrole–surface interactions. We employed the
tip of a low-temperature scanning tunneling microscope as local probe
to investigate at the single-molecule level the electronic and geometric
properties of surface-supported free-base corrole molecules. To provide
a suitable reference for other corrole-based systems on surfaces,
we chose the archetypal 5,10,15-trisÂ(pentafluorophenyl)Âcorrole [H<sub>3</sub>(TpFPC)] as model system, weakly adsorbed on two surfaces
with different interaction strengths. We demonstrate the nondissociative
adsorption of H<sub>3</sub>(TpFPC) on pristine Au(111) and on an intermediate
organic layer that provides sufficient electronic decoupling to investigate
geometric and frontier orbital electronic properties of almost undisturbed
H<sub>3</sub>(TpFPC) molecules at the submolecular level. We identify
a deviating adsorption behavior of H<sub>3</sub>(TpFPC) compared to
structurally similar porphyrins, characterized by a chiral pair of
molecule–substrate configurations
Bilayer of Terbium Double-Decker Single-Molecule Magnets
We report a low-temperature scanning
tunneling microscopy and spectroscopy
study of the structural and electronic properties of a bilayer of
terbium double-decker (bisÂ(phthalocyaninato)ÂterbiumÂ(III), TbPc<sub>2</sub>) molecules on Au(111) at 5 K. The TbPc<sub>2</sub> molecules
are found to adsorb flat on top of a first compact TbPc<sub>2</sub> monolayer on Au(111), forming a square-like packing similar to the
underlying first layer. Their frontier-orbital electronic structure,
measured by tunneling conductance spectroscopy, clearly differs from
that of the underlying first monolayer. Our results of second-layer
molecules indicate the absence of, both, hybrid molecule–substrate
electronic states close to the Fermi level and a zero-bias Kondo resonance.
We attribute these findings to a decreased electronic coupling with
the Au(111) substrate