Surface-Confined Self-Assembly of Di-carbonitrile Polyphenyls

This Feature Article reports on the controlled formation and structure-functionality aspects of vacuum-deposited self-assembled organic and metal-organic networks at metal surfaces using ditopic linear and nonlinear molecular bricks, namely di-carbonitrile polyphenyls. Surface confined supramolecular organization of linear aromatic molecules leads to a fascinating variety of open networks. Moreover, cobalt-directed assembly of the same linear linkers reveals highly regular, open honeycomb networks with tunable pore sizes representing versatile templates for the organization of molecular guests or metal clusters and the control of supramolecular dynamers. In addition, the 2D nanopore organic networks act as arrays of quantum corrals exhibiting confinement of the surface-electronic states of the metallic substrate. A reduction of the linker symmetry leads to the formation of disordered, glassy coordination networks, which represent a structural model for amorphous materials

Hierarchically organized bimolecular ladder network exhibiting guided one-dimensional diffusion

The assembly and dynamics of a hierarchical, bimolecular network of sexiphenyl dicarbonitrile and N,N'-diphenyl oxalic amide molecules on the Ag(111) surface are studied by scanning tunneling microscopy at controlled temperature. The network formation is governed by a two-step protocol involving hierarchic interactions, including a novel carbonitrile-oxalic amide bonding motif. For temperatures exceeding similar to 70 K, more weakly bound sexiphenyl dicarbonitrile molecules carry out one-dimensional diffusion guided by the more stable substructure of the network held together by the carbonitrile-oxalic amide bonding motif. A theoretical investigation at the ab initio level confirms the different binding energies of the two coupling motifs and rationalizes the network formation and the diffusion pathway

Positioning of Single Co Atoms Steered by a Self-Assembled Organic Molecular Template

The bonding and organization of cobalt atoms on a self-assembled organic molecular template are investigated by low-temperature scanning tunneling microscopy. In a first step, <i>N</i>,<i>N</i>′-diphenyl oxalic amide is deposited on the Ag(111) surface with submonolayer and monolayer coverage, leading to the formation of supramolecular nanogratings and a dense-packed layer, respectively. These templates are exposed to evaporated cobalt at different substrate temperatures in the range of 110 to 240 K. We find that Co always binds on top of the phenyl rings, and thus the realization of Co–phenyl complexes is preferred over metal cluster growth on the bare Ag(111) surface. In the case of the dense-packed template, a large fraction of the provided Co is engaged in the formation of well-defined, uniform monomeric Co-half-sandwich structures. At optimal temperatures in the 180–200 K range, the fraction of monomeric Co species on the template exceeds 80% of the total amount of Co deposited. The temperature-dependent adsorption behavior and monomer fraction are compared with calculations, simulating the site-selective positioning in the diffusionless limit by a hit-and-stick adsorption model. This analysis indicates that the organic template suppresses the clustering tendency inherent to diffusing Co atoms and allows the production of a monomer fraction as high as that for statistical growth in the low-coverage regime

Hierarchically Organized Bimolecular Ladder Network Exhibiting Guided One-Dimensional Diffusion

The assembly and dynamics of a hierarchical, bimolecular network of sexiphenyl dicarbonitrile and <i>N</i>,<i>N</i>′-diphenyl oxalic amide molecules on the Ag(111) surface are studied by scanning tunneling microscopy at controlled temperature. The network formation is governed by a two-step protocol involving hierarchic interactions, including a novel carbonitrile–oxalic amide bonding motif. For temperatures exceeding ∼70 K, more weakly bound sexiphenyl dicarbonitrile molecules carry out one-dimensional diffusion guided by the more stable substructure of the network held together by the carbonitrile–oxalic amide bonding motif. A theoretical investigation at the <i>ab initio</i> level confirms the different binding energies of the two coupling motifs and rationalizes the network formation and the diffusion pathway

Hierarchically Organized Bimolecular Ladder Network Exhibiting Guided One-Dimensional Diffusion

The assembly and dynamics of a hierarchical, bimolecular network of sexiphenyl dicarbonitrile and <i>N</i>,<i>N</i>′-diphenyl oxalic amide molecules on the Ag(111) surface are studied by scanning tunneling microscopy at controlled temperature. The network formation is governed by a two-step protocol involving hierarchic interactions, including a novel carbonitrile–oxalic amide bonding motif. For temperatures exceeding ∼70 K, more weakly bound sexiphenyl dicarbonitrile molecules carry out one-dimensional diffusion guided by the more stable substructure of the network held together by the carbonitrile–oxalic amide bonding motif. A theoretical investigation at the <i>ab initio</i> level confirms the different binding energies of the two coupling motifs and rationalizes the network formation and the diffusion pathway