Highly Ordered, Self‐Assembled Monolayers of a Spin‐Crossover Complex with In‐Plane Interactions

Abstract

For the technological integration of molecular switches in electronic devices, self‐assembling nanomaterials of such switches are highly sought after. The syntheses of a new tetrapyridyl ligand bearing a C12 alkyl chain and two N−H bridges (compound 1) and of its iron(II) complex [Fe(1)(NCS)2] (compound 2), are described. Magnetic susceptibility data for bulk samples of 2 confirmed their gradual spin‐crossover properties. The self‐assembly of 1 and 2 on highly ordered pyrolytic graphite surfaces (HOPG) was investigated by Scanning Tunneling Microscopy (STM). Both compounds 1 and 2 formed ordered monolayers after deposition by drop casting. The patterns of the two compounds are very different, which is attributed to the fundamentally different hydrogen bonding networks before and after coordination of Fe(NCS)2 to the tetradentate chelate. Two possible models for the self‐assembly of 1 and 2 are provided. This work suggests that it is possible to design molecular switches that self‐assemble on surfaces in highly ordered monolayer films. This is a significant step in the development of spin‐switching materials, which may streamline the integration of molecular switches in for example memory and sensing devices.