On-Surface Synthesis of Sandwich Molecular Nanowires on Graphene

Abstract

We demonstrate a new synthesis route for the growth of organometallic sandwich molecular nanowires, taking the example of Eu-cyclooctatetraene (EuCot), a predicted ferromagnetic semiconductor. We employ simultaneous exposure of Cot molecules and Eu vapor in ultrahigh vacuum to an inert substrate, such as graphene. Using a Cot excess under temperature conditions of a finite residence time of the molecule, the reactand diffusion confined to two dimensions results in a clean product of ultralong wires. In situ scanning tunneling microscopy reveals not only their molecular structure but also a rich and intriguing growth morphology. The new on-surface synthesis permits experimental access to a largely unexplored class of one-dimensional organometallic systems with potential for exciting electronic and magnetic properties.

Single-crystal graphene on Ir(110)

“…In DFT calcuations naphthalene is used as a paradigm for an aromatic molecule to explore the anisotropic energy landscape of physisorption induced by the wave pattern. Based on these insights, unaxial alignment of sandwich-molecular wires during organometallic on-surface synthesis [8,38] is experimentally demonstrated. Inert single-crystal substrates are rare, but attractive for the growth of quasifreestanding 2D layers.…”

“…Due to its inertness, Gr is also well suited as substrate when investigating the properties of molecular layers in the absence of strong molecule-substrate hybridization [6,7]. Similarly, its inertness makes it an ideal substrate for organometallic chemistry with the function to confine the reactand diffusion to two dimensions [8]. In case of Gr forming a moiré with its growth substrate, also templating of molecular layers [9] and of atom or cluster superlattices has been reported [10,11].…”

1D Coordination π–d Conjugated Polymers with Distinct Structures Defined by the Choice of the Transition Metal: Towards a New Class of Antiaromatic Macrocycles

“…Pure organic 1D materials can be obtained through catalyzed C−C coupling reactions on surface from halogenated precursors [7, 8] . Alternatively, 1D coordination‐polymers (CPs) can be isolated through coordination chemistry, the covalent bond formation resulting from on‐surface reactions between metal atoms and suitable linker groups [9–14] . One major advantage of this approach is the possibility to tune the properties of the wires by changing the nature of the metal and/or the ligand.…”

“…[7,8] Alternatively,1 D coordination-polymers (CPs) can be isolated through coordination chemistry,the covalent bond formation resulting from on-surface reactions between metal atoms and suitable linker groups. [9][10][11][12][13][14] One major advantage of this approach is the possibility to tune the properties of the wires by changing the nature of the metal and/or the ligand. In this strategy,t he ligand design is crucial since maximizing the conjugation through coordination requires keeping the p-d systems as coplanar as possible.Previous studies reported that low-lying p*o rbitals of quinoidal ligands can mix extensively with the valence d-orbitals of am etal center, yielding complexes in which the electrons could be delocalized over both the metal and the ligand.…”

Prediction of a Nine−Membered Aromatic Heterocyclic 1,4,7−triazacyclononatetraenyl anion and its Sandwich Complexes with Divalent Lanthanides

“…[1−4] Besides, metallocenes play an important role in the development of new class of materials, associated with intriguing electronic and magnetic properties Recently a new surface−supported one−dimensional organometallic sandwich molecular nanowires associated with ferromagnetic insulator properties has been synthesized . Discovery of the first sandwich complex, viz., biscyclopentadienyl Iron [Fe(C 5 H 5 ) 2 ] (ferrocene) has provided an extensive series of breakthroughs in the field of organometallic chemistry …”