Temperature-controlled metal/ligand stoichiometric ratio in Ag-TCNE coordination networks

Abstract

The deposition of tetracyanoethylene (TCNE) on Ag(111), both at Room Temperature (RT, 300 K) and low temperatures (150 K), leads to the formation of coordination networks involving silver adatoms, as revealed by Variable-Temperature Scanning Tunneling Microscopy. Our results indicate that TCNE molecules etch away material from the step edges and possibly also from the terraces, which facilitates the formation of the observed coordination networks. Moreover, such process is temperature dependent, which allows for different stoichiometric ratios between Ag and TCNE just by adjusting the deposition temperature. X-ray Photoelectron Spectroscopy and Density Functional Theory calculations reveal that charge-transfer from the surface to the molecule and the concomitant geometrical distortions at both sides of the organic/inorganic interface might facilitate the extraction of silver atoms from the step-edges and, thus, its incorporation into the observed TCNE coordination networks. C 2015 AIP Publishing LLC. [http://dx

Deposition Order Controls the First Stages of a Metal–Organic Coordination Network on an Insulator Surface

“…This suggests that the nodes contain more than one metal atom, but probably not more than a dozen: the physical size of clusters much larger than this would not be able to accommodate the observed elongation along the [010] surface direction. Along the [- [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] direction, the BPDCA molecule and the metal cluster are not able to form a structure with a matching lattice periodicity (see Figure 8b). Energetically this complex is more than 2 eV less favorable than the structure along the [010] direction.…”

Breaking time-reversal symmetry at the topological insulator surface by metal-organic coordination networks

“…The mismatch obtained can to some extent be accommodated with the bending of the MOCN units. Indeed, the conformational freedom of the organic acceptor increases upon the uptake of electrons and the cyano groups are then able to bend [63,84]. According to the results of a recent theoretical study [64], there is a significant charge transfer (between 1 and 2 e − ) from the Ni and Mn atoms to the TCNQ lowest unoccupied molecular orbital (LUMO).…”

“…Namely, to achieve the long-range FM order in the system of adatoms at the TI surface one has to organize their ordered arrays [14,34,35] and prevent them from diffusion [44,47] or intercalation inside the bulk or the van der Waals gaps [34,[51][52][53][54]. Lately, a type of system which may provide these conditions were successfully grown on metallic substrates-selfassembled metal-organic coordination networks (MOCNs) [55][56][57][58][59][60][61][62][63][64]. In such experiments, strong electron acceptors like tetracyanoethylene (TCNE, C 6 H 4 ), tetracyanobenzene (TCNB, C 10 H 2 N 4 ), and tetracyanoquinodimethane (TCNQ, C 12 H 4 N 4 ) are the most frequently used molecules.…”

Structure Prediction for Surface-Induced Phases of Organic Monolayers: Overcoming the Combinatorial Bottleneck

“…As mentioned in the introduction, TCNE forms very different surface-induced phases on various metallic substrates. 24−26 In the specific case of Au(111), STM experiments performed at low temperature ( T = 7 K, see Supporting Information, Methods) reveal a triangular pattern in a nonorthogonal unit cell containing three TCNE molecules, as shown in Figure 2b. (Note that these structures have already previously been reported in ref (24). )…”

“…Interfacing SAMPLE with dispersion-corrected density functional theory (DFT), we demonstrate the power and efficiency of our algorithm by application to the strong electron-accepting molecule tetracyanoethylene (TCNE) adsorbed on the Au(111) surface. TCNE is particularly interesting for computational structure search studies, as it forms very different surface-induced phases on various metallic substrates 24−26 with structures that are markedly different to those observed in the bulk. 27,28 Employing the SAMPLE approach to TCNE/Au(111) we find that a “naïve” evaluation of the structure on the basis of the scanning tunneling microscopy (STM) image does not yield the global minimum geometry, and we provide an alternative interpretation that cannot be inferred from experimental data alone.…”