Protruding hydrogen atoms as markers for the molecular orientation of a metallocene.

Linda Laflör,Michael Reichling,Philipp Rahe

doi:10.3762/bjnano.11.127

Linda Laflör, Michael Reichling + Show 1 more

Open Access

https://doi.org/10.3762/bjnano.11.127

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Abstract

A distinct dumbbell shape is observed as the dominant contrast feature in the experimental data when imaging 1,1’-ferrocene dicarboxylic acid (FDCA) molecules on bulk and thin film CaF2(111) surfaces with non-contact atomic force microscopy (NC-AFM). We use NC-AFM image calculations with the probe particle model to interpret this distinct shape by repulsive interactions between the NC-AFM tip and the top hydrogen atoms of the cyclopentadienyl (Cp) rings. Simulated NC-AFM images show an excellent agreement with experimental constant-height NC-AFM data of FDCA molecules at several tip–sample distances. By measuring this distinct dumbbell shape together with the molecular orientation, a strategy is proposed to determine the conformation of the ferrocene moiety, herein on CaF2(111) surfaces, by using the protruding hydrogen atoms as markers.

Highlights

It is still a challenge to determine the precise adsorption geometry of three-dimensional (3D) molecules on surfaces
Barrier values of up to 0.7 eV are measured [17,18] and for ionised derivates calculations yielded rotational barrier values of up to 1.4 eV [19]. From this class of molecules we investigate the ferrocene derivate 1,1’-ferrocene dicarboxylic acid (FDCA), a ferrocene functionalised with two carboxylic acid moieties
Data were acquired above a region where several FDCA molecules were arranged along the direction, with a molecular separation determined by the

Summary

Introduction

It is still a challenge to determine the precise adsorption geometry of three-dimensional (3D) molecules on surfaces. A distinct dumbbell shape is observed as the dominant contrast feature in the experimental data when imaging 1,1’-ferrocene dicarboxylic acid (FDCA) molecules on bulk and thin film CaF2(111) surfaces with non-contact atomic force microscopy (NC-AFM). We use NC-AFM image calculations with the probe particle model to interpret this distinct shape by repulsive interactions between the NC-AFM tip and the top hydrogen atoms of the cyclopentadienyl (Cp) rings.

Results

Conclusion