Bilayer of Terbium Double-Decker Single-Molecule Magnets.

Giulia Serrano,Svetlana Klyatskaya,Mario Ruben,Stefan Müllegger,Stefano Tebi,Reinhold Koch,Stefan Wiespointner-Baumgarthuber

doi:10.1021/acs.jpcc.6b03676

Abstract

We report a low-temperature scanning tunneling microscopy and spectroscopy study of the structural and electronic properties of a bilayer of terbium double-decker (bis(phthalocyaninato)terbium(III), TbPc2) molecules on Au(111) at 5 K. The TbPc2 molecules are found to adsorb flat on top of a first compact TbPc2 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.

Highlights

The lanthanide double-decker molecules, and in particular the terbium double-decker molecule (bis(phthalocyaninato)terbium(III), TbPc2, Figure 1), have attracted great interest due to their single-molecule magnet behavior.[1]
The TbPc2 molecule is a double-decker complex, where a single Tb3+ ion is sandwiched by two phthalocyanine ligands; the two ligands are oppositely domed and rotated by 45° with respect to each other (Figure 1).[20]
To investigate the electronic coupling, we have studied the frontier-orbital related electronic properties of first- and second-layer TbPc2 molecules by spatially resolved scanning tunneling spectroscopy

Summary

Introduction

The lanthanide double-decker molecules, and in particular the terbium double-decker molecule (bis(phthalocyaninato)terbium(III), TbPc2, Figure 1), have attracted great interest due to their single-molecule magnet behavior.[1]. Recent successful experiments to switch the electronic and nuclear spin state at the level of single individual TbPc2 molecules adsorbed on surfaces[2,11,12] have fueled attempts to enhance the magnetic bistability of surface-adsorbed TbPc2 molecules by tailoring the molecule−substrate interaction. While lattice formation of TbPc2 on Au(111) was found to weaken the molecule−substrate interaction,[13] a significant enhancement of the magnetic bistability has been recently achieved by chemical grafting of TbPc2 derivatives on doped semiconductor surfaces.[5] Previous attempts to electronically decouple similar functional molecules from the substrate include thin oxide[14] or cloride[15] layers, which have been found to lower the electronic interaction between molecules and metal substrates. Decreased electronic coupling of molecules and substrates has been reported for multilayer coverages of (metal−)organic functional molecules such as porphyrins,[16] phthalocyanines,[17] and C6018 on different surfaces

Methods

Results

Conclusion