Structural Transformation of Two-Dimensional Metal–Organic Coordination Networks Driven by Intrinsic In-Plane Compression

Abstract

The coordination assembly of 1,3,5-trispyridylbenzene with Cu on a Au(111) surface has been investigated by scanning tunneling microscopy under ultrahigh vacuum conditions. An open two-dimensional (2D) metal-organic network of honeycomb structure is formed as the 2D network covers partial surface. Upon the 2D network coverage of the entire surface, further increment of molecular density on the surface results in a multistep nonreversible structural transformation in the self-assembly. The new phases consist of metal-organic networks of pentagonal, rhombic, zigzag, and eventually triangular structures. In addition to the structural change, the coordination configuration also undergoes a change from the two-fold Cu-pyridyl binding in the honeycomb, pentagonal, rhombic and zigzag structures to the three-fold Cu-pyridyl coordination in the triangular structure. As the increment of molecular packing density on the surface builds up intrinsic in-plane compression pressure in the 2D space, the transformation of the structure, as well as the coordination binding mode, is attributed to the in-plane compression pressure. The quantitative structural analysis of the various phases upon molecular density increment allows us to construct a phase diagram of network structures as a function of the in-plane compression.

Structure and Reactivity of Cu-doped Au(111) Surfaces

“…Copper and gold are known to be miscible already from room temperature [3], can form binary solid solutions across the full compositional range, and can also form ordered alloys in the bulk phase, most notably Cu 3 Au, CuAu and CuAu 3 . For the coppergold system different top layer structures have been proposed: segregation [7,30,35,36], complete encapsulation, whereby a single layer of copper is covered by a single layer of gold [32,[36][37][38] and intermixing [28,32,[36][37][38][39][40] have been considered. Often varying electronic contrast observed via STM when imaging an island has been considered as an indication that the top layer is of mixed (random) composition, as in surface solid solution [12,32,[41][42][43].…”

“…These networks show great structural flexibility as several phases of different geometry and/or coordination appeared upon varying the coverage in organic linker (and hence the stoichiometric ratio with copper, and the surface density) [7].…”

“…Nucleation of guest metals on Au(111) generally occurs via the place-exchange mechanism [5], which was initially ruled out for the adsorption of copper; however, it was later reported that the onset of copper adsorption does occur via a place-exchange mechanism, at specific sites identified as the narrowed regions within the highly reactive elbows of the Au(111)-(22× √ 3), irrespective of hcp or fcc stacking [1]. Other than for copper [6][7][8], this is also the case for other transition metals such as nickel [9][10][11][12], iron [13,14], and chromium [15,16], to name a few. Added clusters are regarded as a source of reactive metal atoms, over a surface commonly considered as a 2D inert support, opening up the possibility of modifying the reactivity of the Au(111) surface itself, via the formation of surface alloys, whereby both the added metal and gold are present in the top layer.…”

Cooperative Modulation of Electronic Structures of Aromatic Molecules Coupled to Multiple Metal Contacts

“…As shown in Fig. 1(a), molecules of 1,3,5-tris(pyridyl)benzene (TPyB) self-assemble into a honeycomb network structure, wherein the adjacent TPyB molecules are linked via pyridyl-Cu-pyridyl coordination bonds involving the molecules' N atoms [22,23]. In the interior of the network domains each molecule is laterally coupled through three coordination bonds while at the edge of the network domains each molecule is coupled through two coordination bonds.…”

Site-specific bonding of copper adatoms to pyridine end groups mediating the formation of two-dimensional coordination networks on metal surfaces

“…Self-assembled metal-organic networks consisting of molecular linkers and metal species provide longrange order [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and a programmable network architecture based on the interplay of the functionalized parts of the organic molecule and the metal species. With the choice of the symmetry and size of the organic linker, the geometry of the metal-organic network can be tuned [5,6].…”