Molecular Nanowire Bonding to Epitaxial Single‐Layer MoS₂ by an On‐Surface Ullmann Coupling Reaction

Abstract

Lateral heterostructures consisting of 2D transition metal dichalcogenides (TMDCs) directly interfaced with molecular networks or nanowires can be used to construct new hybrid materials with interesting electronic and spintronic properties. However, chemical methods for selective and controllable bond formation between 2D materials and organic molecular networks need to be developed. As a demonstration of a self‐assembled organic nanowire‐TMDC system, a method to link and interconnect epitaxial single‐layer MoS2 flakes with organic molecules is demonstrated. Whereas pristine epitaxial single‐layer MoS2 has no affinity for molecular attachment, it is found that single‐layer MoS2 will selectively bind the organic molecule 2,8‐dibromodibenzothiophene (DBDBT) in a surface‐assisted Ullmann coupling reaction when the MoS2 has been activated by pre‐exposing it to hydrogen. Atom‐resolved scanning tunneling microscopy (STM) imaging is used to analyze the bonding of the nanowires, and thereby it is revealed that selective bonding takes place on a specific S atom at the corner site between the two types of zig‐zag edges available in a hexagonal single layer MoS2 sheet. The method reported here successfully combining synthesis of epitaxial TMDCs and Ullmann coupling reactions on surfaces may open up new synthesis routes for 2D organic‐TMDC hybrid materials.

Lateral Interfaces between Monolayer MoS2 Edges and Armchair Graphene Nanoribbons on Au(111)

“…The formation of a covalent C–S br bond is considered to be initiated by an elimination of Br from the organobromine group (Br–C) of the precursor, which subsequently binds the C to a S br on the MoS 2 edge. A similar process was recently observed for another MoS 2 edge-bonded network structure system using 2,8-dibromo­dibenzothiophene undergoing Ullmann-like coupling . In support of this, we could observe in rare cases the initial edge-on attachment of a still hydrogenated PPA wire segment in low temperature STM images (see figure S4).…”

“…We can therefore discriminate the edge type (i.e., Mo-edge or S-edge) alone based on the morphology, which is used in our subsequent analysis of GNR bonding to edge types. Fully sulfided edges covered with S 2 -dimers (100% S coverage) resulting from sulfidation alone are rather inert toward edge bonding, so the postreduction step in H 2 applied here serves to reduce the edge coverage of S and thus promote the reaction between the terminal edge S br atoms and the GNRs . In this context, we note that the position of the terminal edge S br is different for the S-edge and Mo-edge relative to the basal plane lattice, with the S br on the longer Mo edges being out of registry with the basal plane lattice.…”

Interface-Driven Assembly of Pentacene/MoS2 Lateral Heterostructures

“…Addressing these issues requires the controlled synthesis of model heterostructures under ideal conditions, e.g., using ultrahigh vacuum (UHV) growth approaches, and their in situ nanoscale characterization by high-resolution techniques, such as scanning tunneling microscopy (STM) and spectroscopy (STS). This experimental approach has recently led to the study of lateral heterostructures between molecules and 2D materials, such as graphene, 7 MoS 2 , 8 and borophene. 9 In this work, we focus on the combination of MoS 2 and pentacenewhich is presently the most performing molecule in organic electronicsin a mixed-dimensional lateral heterostructure.…”

“…In parallel to the development of vertical mixed-dimensional vdWHs, the possibility to fabricate lateral (i.e., in-plane) hybrid heterostructures has been recently demonstrated. − Lateral vdWHs can form one-dimensional heterojunctions, enabling the development of atomically thin circuitry. However, the nanoscale assembly of low-dimensional materials into a functional lateral heterostructure poses important challenges, such as (i) the development of bottom-up synthesis methods providing molecular-scale control of the assembly structure and (ii) the detailed investigation of the lateral heterointerface at the molecular level.…”

Enabling room-temperature reductive C–N coupling of nitroarenes: combining homogeneous and heterogeneous synergetic catalyses mediated by light

“…Chief among them include homogeneous catalysis, such as the palladium-catalyzed Buchwald-Hartwig reaction, which enables the net redoxneutral nucleophilic substitution of an aryl halide with N-nucleophiles via Pd(0)/Pd(II) activation by oxidative addition. [3][4][5][6][7] In alternative strategies, the copper-catalyzed Ullmann reaction [8][9][10][11][12] and the Chan-Lam reaction [13][14][15] have been established for the construction of the C-N bond in an oxidative manner by the reaction of N-nucleophiles with aryl boron reagents under aerobic copper catalysis (Scheme 1A). However, all well-known strategies adopt primary amines as nitrogen sources, which are always derived from nitroarenes by stoichiometric reduction.…”