Effect of backbone aspect ratio on the surface-confined self-assembly of tetratopic molecular building blocks

Abstract

Tetratopic organic molecules have been recently used for the construction of diverse ordered supramolecular networks adsorbed on solid substrates. In this works, using computer simulations, we demonstrate how the structure of such low-dimensional molecular architectures can be predicted based on individual properties of a tetrapod building block at play. Specifically, we study the on-surface self-assembly of model organic molecules consisting of a linear core and four equal arms equipped with terminal interaction centres. The molecules are assumed to comprise discrete segments representing, for example, phenyl rings which are interconnected to form the tetrapod units. Our main focus is on the effect of core/arm length ratio on the morphology of the resulting networks formed on a (111) crystalline surface. It is shown that a suitable manipulation of this structural descriptor allows for directing the self-assembly towards porous networks with diverse periodicity and range of order. In particular, our Monte Carlo calculations predicted the formation of Kagome, brickwall and honeycomb networks with morphologies similar to the corresponding experimental counterparts. Moreover, glassy structures with aperiodic distribution of intermolecular bonds were observed and the associated structural (core/arm ratio) condition was provided. The effect of surface corrugation on the creation of these networks was also examined. The results of our theoretical investigations can be helpful in designing and fabrication of low-dimensional openwork structures sustained by weak intermolecular forces as well as by covalent bonds.