Square Tiling by Square Macrocycles at the Liquid/Solid Interface: Co‐crystallisation with One‐ or Two‐Dimensional Order

We have systematically investigated the self‐assembled monolayers of seven bimolecular mixtures of square‐shaped pyridinophanes and cyclophanes bearing alkoxy or alkoxycarbonyl substituents in the presence of the tropylium ion as a marker of pyridinophanes at liquid/graphite interfaces by means of scanning tunnelling microscopy (STM). The purpose of this work was to elucidate the mixing behaviour of these macrocycles highlighting the formation of one‐ or two‐dimensionally ordered square tilings consisting of alternating alignments of different macrocycles as a result of attractive dipole–dipole or hydrogen‐bonding interactions; four co‐crystals differing in the dimensionality of the ordering of pyridinophane and cyclophane were observed. The different modes of interaction between the functional groups (ether or carbonyl group) in the side‐chains of the pyridinophanes and cyclophanes lead to the formation of co‐crystals with dimensionally different orderings of the two macrocycles. These observations revealed that a slight modification of the molecular structure may dramatically change the mixing behaviour and structures of the co‐crystals.