Two Morphologies of Stable, Highly Ordered Assemblies of a Long‐Chain‐Substituted [2 × 2]‐Grid‐Type FeII Complex Adsorbed on HOPG

The programmed self‐assembly of a multimetallic grid‐type supramolecular architecture and its hierarchical organization on graphite are described. The doubly functionalized 4,6‐bis(2,2'‐bipyridyl‐6‐yl)‐2‐phenylpyrimidine derivative 1, equipped with CH2OC16H33 moieties at the terminal pyridine rings, was designed as a new bis(tridentate) ligand and synthesized using Stille‐type coupling reactions. Treatment of ligand 1 with Fe(BF4)2·6H2O in CHCl3/CH3CN led to the spontaneous formation of a [2 × 2]‐grid‐type FeII complex 2 in quantitative yield. The self‐assembled tetranuclear complex 2 was adsorbed onto highly oriented pyrolytic graphite (HOPG) and studied by scanning tunneling microscopy (STM), which showed two morphologies of highly ordered two‐dimensional arrays of the metallo‐supramolecular architectures. The resulting monolayers of the grid‐type complex 2 are much more stable than that obtained from the corresponding unsubstituted grid‐type complex owing to the additional attractive forces between the hexadecyl moieties in 2 and the HOPG surface. Moreover, the reproducibility of the STM images of the hexadecyl‐substituted grid 2 was strongly improved compared to the unsubstituted one. These results suggest that the introduction of long alkyl chains into metallo‐supramolecular architectures would have general advantages for their organization and STM investigation on HOPG. Details of the preparation and the STM investigation of ligand 1 are also presented. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)