Buckybowls at surfaces: Polymorphism, phase transitions and symmetry mismatch in 2D crystals

Abstract

The two-dimensional (2D) self-assembly into supramolecular structures has been employed effectively to study more fundamental processes such as polymorphism, phase transitions, molecular recognition and crystallization. The condensation into denser phases leads to low-density areas at the surface containing disordered glassy 2D structures with semi-ordered motifs. The molecules must move around in order to become arranged into the new lattice. It is possible due to the low-density areas that are also present on the surface. The filling of these areas with additional molecules should therefore suppress molecular movement and the transition. Adsorbing more corannulene at the temperature where the intermediate phase exists, leads to a completely (40, 37)-covered surface. The local adsorbate geometry of corannulene (COR) is such that a hexagonal ring is oriented parallel to the surface plane and the C 5 axis of molecule is tilted with respect to the surface normal.