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

• Main Authors: Linda Laflör, Michael Reichling, Philipp Rahe
• Format: Article
• Language: English
• Published: Beilstein-Institut 2020-09-01
• Series: Beilstein Journal of Nanotechnology
• Subjects: calcium fluoride (caf2); ferrocene; functionalised tips; high-resolution imaging; non-contact atomic force microscopy
• Online Access: https://doi.org/10.3762/bjnano.11.127

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.