Interactions and Self-Assembly of Stable Hydrocarbon Radicals on a Metal Support

Abstract

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.

Surface-Supported Hydrocarbon π Radicals Show Kondo Behavior

“…Single isolated BDPA monomers are rarely observed on the sample surface due to an increased surface mobility. Dimers are more stable due to pinning at surface defect sites 19 and constitute the smallest BDPA clusters. Larger clusters are 1-D chains up to several nanometers long that start to grow at trimers with a characteristic three-fold symmetric arrangement acting as nucleation centers for the chain growth.…”

“…This interpretation is supported by density functional theory calculations of BDPA in the gas phase performed previously by our group. 19 The vertical bars in the top part of Figure 2a mark the calculated energies of collective backbone vibrations; they are symmetrically aligned above and below the Kondo minimum of the dimer (marked by dashed line). Indeed, a number of calculated energies lie within the broad symmetric shoulders of the spectrum.…”

“…(a) DFT-calculated isodensity representation of the singly occupied molecular orbital (SOMO) of the stable π radical BDPA (C 33 H 21 ) from ref (19). (b) STM topographic image of 0.2 monolayers of BDPA grown at 300 K on the Au(111) surface (+0.5 V, 50 pA, 7 K); scale bar = 1 nm.…”

Selective adsorption of metal-phthalocyanine on Au(111) surface with hydrogen atoms

“…24,25,[27][28][29] Thus, adsorption behavior of H-MnPc molecules with hcp regions as their preferential sites after the full decoration of pointed elbows is very interesting, especially for the skeleton of MnPc and H-MnPc is the same. Our calculation shows that the density of states (DOS) of adsorbates around the Fermi level is different: there are d z 2 states in MnPc, while they are nearly absent in H-MnPc.…”

Organic Light‐Emitting Diodes Using a Neutral π Radical as Emitter: The Emission from a Doublet

“…However, the EL Band is red-shifted and broader compared to the counterpart of PL spectrum, probably due to the formation of dimers and trimer of BDPA. [15] Fig. 4 (a) shows the photographs of BDPA-based OLEDs at luminance of 10, 100, and 1000 cd/m 2 , respectively.…”