Constitutional Dynamics of Metal–Organic Motifs on a Au(111) Surface

Abstract

Constitutional dynamic chemistry (CDC), including both dynamic covalent chemistry and dynamic noncovalent chemistry, relies on reversible formation and breakage of bonds to achieve continuous changes in constitution by reorganization of components. In this regard, CDC is considered to be an efficient and appealing strategy for selective fabrication of surface nanostructures by virtue of dynamic diversity. Although constitutional dynamics of monolayered structures has been recently demonstrated at liquid/solid interfaces, most of molecular reorganization/reaction processes were thought to be irreversible under ultrahigh vacuum (UHV) conditions where CDC is therefore a challenge to be achieved. Here, we have successfully constructed a system that presents constitutional dynamics on a solid surface based on dynamic coordination chemistry, in which selective formation of metal-organic motifs is achieved under UHV conditions. The key to making this reversible switching successful is the molecule-substrate interaction as revealed by DFT calculations.

Structural Transformation and Stabilization of Metal–Organic Motifs Induced by Halogen Doping

“…4:1) on Au(111) at room temperature (RT) and further annealing at 390 Kf or 10 min results in the formation of ar homboid network structure as shown in Figure 1a.F rom the close-up STM image ( Figure 1b), we identify that the network structure is composed of two kinds of elementary motifs (that is,the trimeric and the dimeric ones as indicated by the corresponding contours). Tw oe nantiomers of the trimeric motif are also observed as indicated by green and blue trimeric contours where the individual molecular chiralities are denoted by Ra nd L. As experienced with coordination schemes between DNAb ases and transition metals, [7,9,[26][27][28] after extensive structural search, we assign this trimeric motif to aG 3 Ni 1 metal-organic structure as highlighted in Figure 1c.F rom the DFT-optimized model superimposed on the corresponding STM image,w ed istinguish that it is formed by three Gm olecules (with different chiralities) coordinating with one Ni atom via one N7 site and two O6 sites,and the intermolecular NH···O and NH···N hydrogen bonds further stabilize the structure.T he dimeric structure (depicted by the white contour in Figure 1b)i s assigned to ah ydrogen-bonded dimer according to the morphology and the well-established NH···O hydrogen bonds involved. These two elementary structural motifs are also linked together via hydrogen bonds.…”

“…Again, based on DFT calculations,w ea ssign the dimeric motif in blue contour to aG 2 Ni 2 metal-organic structure as highlighted in Figure 1f.F rom the DFT-optimized model superimposed on the corresponding STM image,w ed istinguish that it is formed by two homochiral Gm olecules coordinating with two Ni atoms via both N7 and O6 sites.The other dimeric structure (white contour) is the same hydrogenbonded dimer as the one discussed above.T hese two elementary structural motifs are also linked together via hydrogen bonds.Itisworth noting that the formation of such hybrid structures involving alternating metal-organic motifs and hydrogen-bonded dimers may be originated from the registry between metal-organic motifs with respect to the substrate lattice as reported previously. [9] Furthermore,o wing to the dynamic characteristics of coordination bonds,w eh ave achieved reversible structural transformations between the above mentioned G 2 Ni 2 and G 3 Ni 1 motifs on Au(111) as shown in the Supporting Information, Figure S1 by adding Gm olecules or Ni atoms followed by annealing at 390 Kf or 10 min. Note that in the structural transformation processes we do not observe the formation of any other typical metal-organic motifs by changing either the G/Ni ratios or the post annealing temperatures.F urthermore,b ased on at horough inspection of the obtained G 3 Ni 1 and G 2 Ni 2 structures,w ef ind that the Au herringbone reconstruction remains intact indicating aw eak interaction between metal-organic structures and surface (compare with the Supporting Information, Figure S2a).…”

Structural Transformation and Stabilization of Metal–Organic Motifs Induced by Halogen Doping

“…From the close‐up STM image (Figure b), we identify that the network structure is composed of two kinds of elementary motifs (that is, the trimeric and the dimeric ones as indicated by the corresponding contours). Two enantiomers of the trimeric motif are also observed as indicated by green and blue trimeric contours where the individual molecular chiralities are denoted by R and L. As experienced with coordination schemes between DNA bases and transition metals, after extensive structural search, we assign this trimeric motif to a G 3 Ni 1 metal–organic structure as highlighted in Figure c. From the DFT‐optimized model superimposed on the corresponding STM image, we distinguish that it is formed by three G molecules (with different chiralities) coordinating with one Ni atom via one N7 site and two O6 sites, and the intermolecular NH⋅⋅⋅O and NH⋅⋅⋅N hydrogen bonds further stabilize the structure. The dimeric structure (depicted by the white contour in Figure b) is assigned to a hydrogen‐bonded dimer according to the morphology and the well‐established NH⋅⋅⋅O hydrogen bonds involved.…”

“…Owing to the advantage of dynamic characteristics of non‐covalent interactions, the transformation of supramolecular nanostructures with constitutional diversity and adaptability would be of fundamental importance for potential applications in molecular switching devices . Among others, by virtue of coordination selectivity and diversity with respect to different metals, various static metal–organic structures can be fabricated on the surface, and furthermore these structures could be responsive to metal/molecule stoichiometric ratios, coverage, and/or temperatures resulting in structural transformations via dynamic coordination chemistry . In addition to the abovementioned intrinsic regulation factors (that is, constituent molecules and metals), the introduction of a third agent may offer another train of thought to obtain structural transformations .…”

On‐Surface Synthesis of Adenine Oligomers via Ullmann Reaction

“…[4,[7][8][9][10] Previously,s elf-assembly of DNA bases and derivatives have been widely studied on different surfaces where non-covalent interactions are mostly considered. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Meanwhile, DNA macromolecules have also been introduced onto surfaces by using pulse-injection deposition methodt oa lleviate the difficulties in vacuum sublimation method. [4, 8-10, 28, 29] Althougha dvanced deposition strategies have been successfully employed, it is nevertheless of general interest to explore comparatively simple routes toward in situ synthesis of DNA macromolecules on surfaces.…”