Self-Terminating Protocol for an Interfacial Complexation Reaction in Vacuo by Metal–Organic Chemical Vapor Deposition

Abstract

The fabrication and control of coordination compounds or architectures at well-defined interfaces is a thriving research domain with promise for various research areas, including single-site catalysis, molecular magnetism, light-harvesting, and molecular rotors and machines. To date, such systems have been realized either by grafting or depositing prefabricated metal-organic complexes or by protocols combining molecular linkers and single metal atoms at the interface. Here we report a different pathway employing metal-organic chemical vapor deposition, as exemplified by the reaction of meso-tetraphenylporphyrin derivatives on atomistically clean Ag(111) with a metal carbonyl precursor (Ru3(CO)12) under vacuum conditions. Scanning tunneling microscopy and X-ray spectroscopy reveal the formation of a meso-tetraphenylporphyrin cyclodehydrogenation product that readily undergoes metalation after exposure to the Ru-carbonyl precursor vapor and thermal treatment. The self-terminating porphyrin metalation protocol proceeds without additional surface-bound byproducts, yielding a single and thermally robust layer of Ru metalloporphyrins. The introduced fabrication scheme presents a new approach toward the realization of complex metal-organic interfaces incorporating metal centers in unique coordination environments.

Surface chemistry of porphyrins and phthalocyanines

“…The interaction of RuTPP with a Ag(1 1 1) surface reduces the oxidation state of the metal center to Ru(0), as was shown by XPS [482].…”

“…The planar, partially dehydrogenated 2HTPP derivative described above was shown to react with co-adsorbed Fe [377], Co [372] and Ru atoms [482], resulting in the formation of the respective metal complexes (cf. Section 6).…”

“…on Ag(1 1 1). After adsorption of the carbonyl at room temperature, the reaction was induced by heating to 550 K [482]. The reaction of 2HTPP films with diethylzinc, Zn(C 2 H 5 ) 2 , resulted in the formation of ZnTPP [705].…”

“…The resulting formation of intramolecular C-C bonds between the 2-positions of the peripheral phenyl rings and adjacent positions at the porphyrin core led to a flat geometry of the product molecule [372,373,377]. This flat species was then metalated with post-deposited Fe atoms [377], Co atoms [372], or Ru from a Ru 3 (CO) 12 precursor [482]. Interestingly, CoTPP on Ag(1 1 1) was found to be less prone to dehydrogenation; even heating to 575 K left the structure intact [372].…”

Orthogonal Insertion of Lanthanide and Transition‐Metal Atoms in Metal–Organic Networks on Surfaces

“…[14,21] Thea ssembly procedure was directly investigated at the molecular level by using low-temperature scanning tunneling microscopy (STM), which reveals subtle details of the resulting arrangements.A sa ne xample,w ee ngineered hybrid lanthanide/transition-metal-organic coordination networks on an atomistically clean Ag(111) metal support (see the Supporting Information for the experimental procedures). Thee mployed free-base tetra[(4-cyanophenyl)phen-4-yl]porphyrin (2H-TPCN,F igure 2a and see the Supporting Information for the molecular synthesis) is equipped with four meso-4-cyanobiphenylene ligands.T he deposition of Gd atoms onto ap reassembled 2H-TPCN array gives rise to an anoporous metal-organic layer with the cyano groups engaged in fourfold Gd···NC coordination nodes.Subsequent exposure to ab eam of Co atoms [19,20,22] under appropriate conditions results in selective metalation of the tetrapyrrolic macrocycles,while preserving the reticulating Gd···NC motifs, ultimately leading to ah ybrid array with the topology of an alternating bimetallic square grid. Importantly,t he sequence of metal exposure is ad ecisive parameter for the successful expression of abimetallic network capitalizing on orthogonal coordinative interactions.…”