Effect of multiple interactions on face-on vs edge-on configurations of butadiyne-bridged octadehydrodibenzo[12]annulene derivatives at the liquid/graphite interface

We investigated the self-assembled monolayers of octadehydrodibenzo[12]annulene (DBA) derivatives to see the effect of multiple intermolecular interactions on the formation of face-on vs edge-on configurations of planar compounds having weak core to core interactions at the liquid/graphite interfaces by means of scanning tunneling microscopy (STM). A DBA derivative having an N-dodecylamide chain at each end of the π-core formed face-on mode self-assemblies at the interfaces of both 1-phenyloctane (PO) and 1-octanoic acid (OA) and graphite. On the other hand, another DBA having both N-dodecylamide chains and methoxymethyl groups formed an edge-on mode self-assembly at the PO/graphite interface. However, at the OA/graphite interface, it formed a face-on mode self-assembly due to the solvent-molecule hydrogen bonds which suppress the intermolecular interactions. These results indicate that by multiple interactions between substituents the edge-on mode of self-assembly can be stabilized, rendering the otherwise unfavorable pattern be formed preferentially.