Chiral Molecular Clusters And Single Molecule Magnets Studied By STM

The supramolecular pinwheel cluster is a unique chiral structure with evident handedness. Previous studies reveal that the chiral pinwheels are composed of chiral or achiral molecules with polar groups, which result in strong intermolecular interactions such as hydrogen-bonding or dipole interactions. Herein, it is shown that the simple linear aromatic molecule, pentacene, can be self-assembled into large chiral pinwheel clusters on the semimetal Bi(111) surface, due to enhanced intermolecular interactions. The pentacene pinwheels reveal two levels of organizational chirality:the chiral hexamers resulting from asymmetric shifting along the long molecular axis, and chiral arrangement of six hexamers with a rotor motif. Furthermore, a new relation between the local point chirality and organizational chirality is identified from the pinwheels:the former is not essential for the latter in2D pinwheel clusters of the pentacene molecule.In addition, we also find that, pentacene molecules exhibit three different kinds of adsorption orientation on the semi-metallic Bi(111) surface:flat-lying, side-lying and standing-up. With coverage increasing, small islands formed by flat-lying molecules, ID bands consisted of side-lying molecules and crystalline monolayer formed by standing-up molecules on the Bi(111) surface, respectively. The orientation transition of pentacene on Bi(111) can be attributed to the competition between the molecule-molecule interaction and molecule-substrate interaction.Single-molecule nanomagnets have unique quantum properties and their potential applications require characterization and accessibility of individual single-molecule magnets on various substrates. We develop a gentle tip-depositing method to bring individual manganese-12-acetate (Mil2:) molecules onto the semi-metallic Bi(lll) surface. Both the flat-lying and side-lying orientations of Mn12molecules have been identified with a low temperature scanning tunneling microscopy. Energy-resolved spectroscopic mapping enables the first observation of molecular orbitals of individual12molecules in real space, which is consistent with the density-functional theory calculations including spin-orbit coupling, Coulomb repulsion U, and dipole corrections. In spite of the reduction of HOMO-LUMO gap of Mn12molecules due to the charge transfer, the local lattices of Bi(111) covered with Mn12remain essentially intact, indicating a weak Mn12-Bi interaction. Our findings open an avenue to address directly the local structural and electronic properties of individual single molecule magnets on solid substrates.