Neutral Organic Radical Formation by Chemisorption on Metal Surfaces

Abstract

Organic radical monolayers (r-MLs) bonded to metal surfaces are potential materials for the development of molecular (spin)electronics. Typically, stable radicals bearing surface anchoring groups are used to generate r-MLs. Following a recent theoretical proposal based on a model system, we report the first experimental realization of a metal surface-induced r-ML, where a rationally chosen closed-shell precursor 3,5-dichloro-4-[bis(2,4,6-trichlorophenyl)methylen]cyclohexa-2,5-dien-1one (1) transforms into a stable neutral open-shell species (1 • ) via chemisorption on the Ag(111) surface. X-ray photoelectron spectroscopy reveals that the >CO group of 1 reacts with the surface, forming a C−O−Ag linkage that induces an electronic rearrangement that transforms 1 to 1 • . We further show that surface reactivity is an important factor in this process whereby Au( 111) is inert towards 1, whereas the Cu(111) surface leads to dehalogenation reactions. The radical nature of the Ag(111)-bound monolayer was further confirmed by angle-resolved photoelectron spectroscopy and electronic structure calculations, which provide evidence of the emergence of the singly occupied molecular orbital (SOMO) of 1 • .

Electrochemical Control of Charge Current Flow in Nanoporous Graphene

“…This result is in agreement with other studies which have reported spin polarization (open‐shell character) of quinoidal derivatives by means of N‐doping, [ 47–49 ] electrochemical reduction, [ 50 ] and surface chemisorption. [ 51 ] The magnetic coupling between the spin‐polarized quinone units is rather weak both along the x and y directions, as shown with the nearly energetic degeneracy between the ferromagnetic solution with other antiferromagnetic spin configurations (see Figure S5, Supporting Information). This is typical for paramagnetic ground states, however, in such situations, the application of moderate magnetic fields, as regularly done for graphene, [ 52 ] may easily populate the ferromagnetic state of the material (Figure 4b), which is the most promising one for spintronic applications.…”

Tethered Blatter Radical for Molecular Grafting: Synthesis of 6-Hydroxyhexyloxy, Hydroxymethyl, and Bis(hydroxymethyl) Derivatives and Their Functionalization

“…Functionalization of flat surfaces [1][2][3][4][5][6][7][8][9], polymers [10][11][12][13][14], well-defined macromolecules (dendrimers [15][16][17][18], cyclodextrins [19][20][21][22], fullerene [23], and nanotubes [24]), and nanoparticles [25][26][27][28][29][30] with stable radicals is becoming an important avenue for obtaining materials [31,32] for advanced technologies [33], which include organic electronics [11,34], spintronics [1, 3,6], contrast agents in bioimaging [15,35,36], and energy storage [12,[37][38][39]. This effort has concentrated mainly on the traditional stable radicals, such as nitroxides [6,[14][15][16]…”

Hybridization-Induced Inversion of Spin Polarization at Rubrene/Ferromagnetic Cobalt Interface

“…22 Recently, a switchable spinterface was realized by controllable chemisorbed and physisorbed states of organic molecules on ferromagnetic metal surfaces. 23,24 With the help of spin-resolved PES, the spin-dependent hybrid interface states at the spinterface can be directly detected and characterized in the frame of the energy-level alignment. 13,16,25,26 Rubrene is a π-conjugated molecular semiconductor possessing high carrier mobility (∼20 cm 2 /V•s).…”

“…For example, a high spin injection efficiency for hot electrons and a spin diffusion length as long as 12.6 ± 3.4 nm at the CuPc/Co(001) interface were determined by spin-resolved two-photon photoemission spectroscopy (2PPE) . Recently, a switchable spinterface was realized by controllable chemisorbed and physisorbed states of organic molecules on ferromagnetic metal surfaces. , With the help of spin-resolved PES, the spin-dependent hybrid interface states at the spinterface can be directly detected and characterized in the frame of the energy-level alignment. ,,, …”