Introduction
Benzylic amide [2] catenanes are novel supramolecular species which are versatile prototype for multifunctional materials. [1] A catenane (Fig. 1) consists of 2 interlocked amide macrocycles assembled by hydrogen bonds. The supramolecule in Fig. 1 is termed CAT1.
The conformation of the macrocyclic rings and their rotation depend on the chemical substitution, the solvent, the oxidation state, and the excitated states. [2] Most of the existing studies concern solutions of CAT1 while little is cnown on their behaviour on surfaces, on the formation of aggregates in a condensed phase and thin films which might be relevant to potential applications.
* corresponding author: fabio@ism.bo.cnr.it
Here we report a preliminary investigation of catenanes by means of scanning tunneling microscopy (STM). Our aim is to explore the behaviour of individual catenane molecules on surfaces.
Experimental
CAT1 has been deposited from a 20 gl drop of methanol solution (=1×10-4 M) onto freshly cleaved highly oriented pyrolitic graphite (HOPG). This amount corresponds roughly to 1 monolayer coverage on a 1 cm2 surface. Ambient STM has been used to image the surface at high resolution after the solvent has dried out at RT. Etched tungsten tips have been used and typical imaging conditions were 0.3 nA setpoint current, 0.5 V sample bias, and 1 Hz scan rates. The solution was added only after steps on HOPG were resolved on the submicron scan range without exhibiting either decoration by impurities or extensive defects.
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Stm investigation of flexible supramolecules: Benzilic amide catenanes