Lanthanide-Directed Assembly of Interfacial Coordination Architectures–From Complex Networks to Functional Nanosystems

Abstract

Metallo-supramolecular engineering on surfaces provides a powerful strategy toward low-dimensional coordination architectures with prospects for several application fields. To date, most efforts have relied on transition metal centers, and only recently did we pioneer lanthanide-directed assembly. Coordination spheres and motifs with rare-earth elements generally display distinct properties and structural features. The size of the cations and shielding role of the 4f orbitals induces high coordination numbers, frequently entailing flexible coordination geometries. Following Pearson's hard and soft acid-base theory, lanthanide cations are hard Lewis acids and thus feature strong affinity for nitrile, terpyridine, and carboxylate donor moieties. The prevailing oxidation state is +3, although in certain compounds stable +2 or +4 cations occur. The chemistry of rare-earth elements is currently receiving widespread attention, as they are key ingredients for established and emerging 21st century science and technology with relevance for energy conversion, sensing, catalysis, magnetism, photonics, telecommunications, superconductivity, biomedicine, and quantum engineering. In this Account, we review recent advances toward the design of interfacial supramolecular nanoarchitectures incorporating lanthanide centers. We apply controlled ultrahigh vacuum conditions whereby atomistically clean substrates are prepared and exposed to ultrapure atomic and molecular beams of the chosen sublimable constituents. We focus on direct molecular-level investigations and in situ assembly operative close to equilibrium conditions. Our scanning probe microscopy techniques provide atomistic insights regarding the formation, stability, and manipulability of metal-organic compounds and networks. In order to gain deeper insights into the experimental findings, complementary computational analysis of bond characteristics, electronic properties, and coordination motifs has been performed for several case studies. Exemplary elements under consideration include cerium, gadolinium, dysprosium, and europium. By the use of ditopic molecular linkers equipped with carbonitrile moieties, adaptive coordination spheres are unveiled, yielding vertices with two- to sixfold symmetry. The respective coordination nodes underlie the expression of complex networks, such as semiregular Archimedean tessellations for cerium- or gadolinium-directed assemblies and random-tiling quasicrystalline characteristics for europium. Tunability via constituent stoichiometry regulation is revealed for bimolecular arrangements embedding europium centers, simultaneously connecting to carbonitrile and terypyridine ligands. Ditopic carboxylate linkers yield robust reticular networks based on a lateral coordination number of 8 for either gadolinium or dysprosium complexation, featuring a prevalent ionic nature of the coordination bond. Orthogonal insertion protocols give rise to d-f reticular architectures exploiting macrocyclic tetradentate cobalt complexation and peripheral carbon...

Rare earth element alcohol dehydrogenases widely occur among globally distributed, numerically abundant and environmentally important microbes

“…These include Na, K, Mg, Ca, Fe, Zn, Mn, Cu, Co and Mo [1]. At the same time, some metals, such as rare earth elements (REEs), while revealing attractive catalytic properties in in vitro manipulations, leading to their wide use in industrial and medical applications [2][3][4], have been assumed biologically inert [5]. This assumption has been dramatically reversed recently with the demonstration of the activity of REEs lanthanides (Ln 3+ ) as cofactors of methanol dehydrogenases (MDH), enzymes essential in metabolism of single-carbon compounds such as methane and methanol [6][7][8][9][10][11][12][13][14].…”

Diarylphosphate as a New Route for Design of Highly Luminescent Ln Complexes

“…The development of highly luminescent compounds that are potentially applicable in modern optical materials is still a great challenge due to the rapidly evolving requirements of practical life [ 1 , 2 ]. In coordination chemistry of lanthanide elements, the key role among organic ligands has always belonged to carboxylates [ 3 , 4 ]. Meanwhile, related organophosphorus ligands (phosphonates, phosphinates, and phosphoric esters), which can coordinate a Ln 3+ cation as mono- and polydentate ligands, also have great potential for the formation of complexes with 4f elements.…”

Template-controlled on-surface synthesis of a lanthanide supernaphthalocyanine and its open-chain polycyanine counterpart

“…The small Fe atom has four in-plane coordination sites for -C≡N groups 40 and pyrrole ligands 40 , which is consistent with the formation of a tetramer macrocycle. Using a much larger rare-earth metal, gadolinium, which allows for five in-plane coordination sites for -C≡N groups 43–45 , enables the on-surface synthesis of the Gd-SNPc pentamer macrocycle, as indicated by the five-lobed pentamer structures in Fig. 2e.…”

“…The general concept behind this approach is illustrated in Fig. 1b: the small (Fe 40 ), large (Gd 41–43 ), and the infinite (silver surface) templates coordinate different numbers (four, five, and infinite) of building blocks that become eventually covalently connected. The benefits of the on-surface approach are apparent: the two-dimensional (2D) confinement posed by the surface allows only in-plane coordination of ligands with the metal.…”