Like penguins on ice, buckybowl molecules move closer together when cooled on a copper surface (see model of a corannulene molecule adsorbed on Cu(111)). Upon heating, the molecules spread out into the original crystal phase again. The lower density at room temperature can be explained by the increase in entropy owing to the excitation of bowl vibrations at the surface.

Concepts of close packing in monolayers of 5-fold-symmetric buckybowls are discussed. When the symmetry of lattice and molecular building blocks are incompatible, new strategies evolve. Corannulene forms a hexagonal lattice on Cu(111) by tilting away from the C(5) symmetry and aligning one hexagonal ring parallel to the surface. The chiral 5-fold-substituted chloro and methyl derivatives do not show this tilt and maintain the 5-fold symmetry as adsorbates. Consequently, a nonperfect tiling is observed. Their lattices are quasi-hexagonal: one in an antiparallel fashion with almost pm symmetry and the other with azimuthal and positional disorder on the hexagonal grid. Our results are in remarkable agreement with computational and mechanical modeling experiments of close packing of hard pentagonal discs in macroscopic two-dimensional systems and prove the validity of such modeling strategies.

Self-assembled monolayers of [Ru(terpy)(terpy-py)]2+ and [Os(terpy)(terpy-py)]2+ salts (terpy is 2,2‘:6‘,2‘ ‘-terpyridine and terpy-py is 4‘-(4-pyridyl)-2,2‘:6‘,2‘ ‘-terpyridine) on platinum were investigated by means of STM and electrochemistry. The STM experiments reveal that the species within the monolayer are ordered in a hexagonal array. This information was utilized together with the scan rate dependency of the peak current density (j p) of potential sweep experiments to calculate interaction energies within the monolayer. Significantly, the repulsive interactions within the monolayers of 2,2‘:6‘,2‘ ‘-terpyridine complex are greater than those observed with analogous 2,2‘-bipyridine species. This results in a lower overall surface coverage, an ordered structure where each particle has 6 closest neighbors, and a shift of the redox potentials toward more positive values with the terpy complexes. Also, a correlation between the solvent dielectric constant and the interaction energies could be established, reflecting the different ability of the solvent to screen charges depending upon its polarity.

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