Cooperative Action for Molecular Debromination Reaction on Cu(110)

Abstract

Copper is the paradigmatic catalyzer of the Ullmann cross-coupling reaction. Despite this, its role in the reaction is still under debate. Here, we shed light on the mechanistic steps of debromination, characterizing a prototypical molecule, namely 4,7-dibromobenzo[c]-1,2,5-thiadiazole (2Br-BTD), deposited on a Cu(110) surface. By means of scanning probe techniques and first principle calculations, we demonstrate the oxidative addition of Cu atoms leading to a −C−Cu−Br metal− organic complex. The scission of the strongly bound bromine atoms requires the cooperative action of neighboring complexes resulting in the formation of Cucoordinated BTD structures.

Anisotropic Electron Conductance Driven by Reaction Byproducts on a Porous Network of Dibromobenzothiadiazole on Cu(110)

“…BTD molecules are a prototypical compound widely used in electronics and photovoltaics due to the electronic structure and the capability to form donor‐acceptor units . The assembly of these molecules on the Cu surface leads to the spontaneous chemical‐reaction of the two Br terminations, which detach, transmetalating the molecules with Cu adatoms, according to the Ullmann redox‐reaction on copper surfaces …”

“…As a necessary condition for the electron backscattering and the consequent quantum confinement is a variation of the surface potential, Δ Φ , we have locally probed its spatial dependence along the molecular structures focusing on the differences between isolated dimer units and the molecular assembly . Specifically, we aimed to identify modifications of the local electrostatic potential induced by the detachment of the Br atoms, which occurs upon self‐assembly, as previously reported . The electrophilic character and high polarizability of the Br atoms is indeed expected to result into a local surface dipole, which acts as repulsive potential promoting the surface state confinement …”

“…[11][12][13][14] The assembly of these molecules on the Cu surface leads to the spontaneous chemical-reaction of the two Br terminations, which detach, transmetalating the molecules with Cu adatoms, according to the Ullmann redox-reaction on copper surfaces. [15,16] A prototypical image showing the molecular self-assembly on the Cu(110) surface after a mild post-deposition annealing at 400 K is shown in Figure 1. Self-assembled BTD dimers pile-up into parallel rail-lines along the 1 " 10 Â Ã crystallographic direction.…”

“…[22] Specifically, we aimed to identify modifications of the local electrostatic potential induced by the detachment of the Br atoms, which occurs upon self-assembly, as previously reported. [16] The electrophilic character and high polarizability of the Br atoms is indeed expected to result into a local surface dipole, [23] which acts as repulsive potential promoting the surface state confinement. [19][20][21] The potential, measured along the main axis of the isolated dimer adsorbed on Cu(110) shown in Figure 3 with a blue line, is characterized by a sharp peak at the center and by two maxima at the hetero-organic groups of each of the BTD units.…”

Kinetically Controlled Synthesis of Four‐ and Six‐Member Cyclic Products via Sequential Aryl‐Aryl Coupling on a Au(111) Surface

“…5b. Similar phenomenon of insertion of a metal atom to form a metal‐organic complex consisting of C‐metal‐Br moiety was also reported recently . We propose that C1 is stabilized by a C 2 ‐Au‐Br 2 moiety: two HBTP monomers are linked via an aryl‐aryl bond to form an organo‐gold complex consisting of two aryl‐gold bonds, as illustrated in the model shown in Figure e.…”