Engineering Periodic Dinuclear Lanthanide‐Directed Networks Featuring Tunable Energy Level Alignment and Magnetic Anisotropy by Metal Exchange

Abstract

The design of lanthanide multinuclear networks is an emerging field of research due to the potential of such materials for nanomagnetism, spintronics, and quantum information. Therefore, controlling their electronic and magnetic properties is of paramount importance to tailor the envisioned functionalities. In this work, a multidisciplinary study is presented combining scanning tunneling microscopy, scanning tunneling spectroscopy, X‐ray absorption spectroscopy, X‐ray linear dichroism, X‐ray magnetic circular dichroism, density functional theory, and multiplet calculations, about the supramolecular assembly, electronic and magnetic properties of periodic dinuclear 2D networks based on lanthanide‐pyridyl interactions on Au(111). Er‐ and Dy‐directed assemblies feature identical structural architectures stabilized by metal–organic coordination. Notably, despite exhibiting the same +3 oxidation state, there is a shift of the energy level alignment of the unoccupied molecular orbitals between Er‐ and Dy‐directed networks. In addition, there is a reorientation of the easy axis of magnetization and an increment of the magnetic anisotropy when the metallic center is changed from Er to Dy. Thus, the results show that it is feasible to tune the energy level alignment and magnetic anisotropy of a lanthanide‐based metal‐organic architecture by metal exchange, while preserving the network design.

Lanthanide metal–organic network featuring strong perpendicular magnetic anisotropy

“…[14][15][16][17][18] However, the investigation of the magnetism of lanthanides embedded in metalorganic networks remains underexplored. 19,20 This is surprising since the engineering of 2D metal-organic networks exploiting lanthanides as single atom magnets, [4][5][6] represents a promising path to design nanoarchitectures for information storage at the smallest scale.…”

“…According to previous results for Dy-directed networks, the oblate charge of Dy 3+ ions is associated with close to in-plane magnetic anisotropy. 19,20 In the case of Er 3+ ions the prolate charge density can be related to an out-ofplane orientation of the magnetic anisotropy. 20 Accordingly, for the case of Er-TDA network the multiplet calculations indicate that the magnetic anisotropy is uniaxial and totally out-of-plane with a maximum J z as expected for prolate Er 3+ ions, 3 which is further confirmed by the sum rule analysis.…”

“…A resonance at approximately the same energy was observed in the Er-DBDP case. 20 In order to interrogate the nature of the bonds and the plausible emergence of a delocalized band (not expected) we performed angle-resolved photoemission spectroscopy (ARPES) on this sample (see ESI †). Our results only indicate the confinement of the surface state, with no fingerprint of the presence of a band that could be assigned to the network.…”

“…More recently, we have inspected the magnetism of a different molecular linker, [1,4-bis(4-pyridyl)-biphenyl] (DPBP), coordinated with Dy and Er on Au(111). 20 Dy- and Er-DPBP molecular networks present the same structure with dinuclear metallic centers, but there is a significant change in the electronic and magnetic properties. While Dy-DPBP has close to in-plane anisotropy, Er-DPBP presents a tilted magnetization easy axis.…”

Construction and Structural Transformation of Metal–Organic Nanostructures Induced by Alkali Metals and Alkali Metal Salts

“…Metal–organic nanostructures, consisting of metal nodes and organic ligands, make up a class of structurally diverse and functionally tunable materials , and have proven to be versatile platforms in a wide range of scientific fields, including biomedicine, energy harvesting, and catalysis. , In an effort to achieve tailored properties and the desired performance, different types of metals have been integrated to regulate fundamental chemical interactions within building blocks, which range from transition metals to alkali and alkaline earth metals. − It has also aroused considerable interest in the surface science community; meanwhile, surface science techniques allow direct visualization of metal–organic nanostructures supported by solid surfaces in real space and determination of the intermolecular interactions involved. Tremendous effort has been devoted to the engineering of low-dimensional metal–organic architectures on surfaces mainly based on directional coordination bonds with d-block transition metals embedded, − as well as flexible coordination provided by f-block lanthanides. − Recently, alkali metals derived from either pure alkali metals − or alkali halides (e.g., NaCl and KBr) − have been introduced to interact with organic molecules on surfaces via isotropic electrostatic ionic bonding, enabling the structural diversity of metal–organic nanostructures. , In these cases, both pure alkali metals and alkali metal salts are applied to provide metal centers. However, their differences in the construction of alkali-based metal–organic nanostructures as alkali metal providers have been less discussed, and the corresponding influence on the structural diversity remains elusive.…”