Stabilization of exotic minority phases in a multicomponent self-assembled molecularnetwork

Abstract

Trimesic acid (TMA) and alcohols were recently shown to self-assemble into a stable,two-component linear pattern at the solution/highly oriented pyrolytic graphite (HOPG)interface. Away from equilibrium, the TMA/alcohol self-assembled molecular network (SAMN)can coexist with pure-TMA networks. Here, we report on some novel characteristics of thesenon-equilibrium TMA structures, investigated by scanning tunneling microscopy (STM).We observe that both the chicken-wire and flower-structure TMA phases can host ‘guest’C60 moleculeswithin their pores, whereas the TMA/alcohol SAMN does not offer any stable adsorption sites for theC60 molecules. Thepresence of the C60 molecules at the solution/solid interface was found to improve the STM image quality. Wehave taken advantage of the high-quality imaging conditions to observe unusual TMAbonding geometries at domain boundaries in the TMA/alcohol SAMN. Boundaries betweenaligned TMA/alcohol domains can give rise to doubled TMA dimer rows in twodifferent configurations, as well as a tripled-TMA row. The boundaries createdbetween non-aligned domains can create geometries that stabilize TMA bondingconfigurations not observed on surfaces without TMA/alcohol SAMNs, includingsmall regions of the previously predicted ‘super flower’ TMA bonding geometryand a tertiary structure related to the known TMA phases. These structures areidentified as part of a homologic class of TMA bonding motifs, and we exploresome of the reasons for the stabilization of these phases in our multicomponentsystem.