Synthesis, Properties and Applications of Lanthanide and Actinide Molecular Compounds

Lanthanides and actinides have unique physical and chemical properties, and their compounds continue to be extensively studied on a fundamental level during the search for applications that range from energy production and related environmental issues to the life sciences [1,2,3,4,5,6]. This Special Issue aimed to collect contributions focused on recent results on the synthesis, reactivity, properties and applications of lanthanide and actinide molecular compounds. It followed a previous Inorganics Special Issue devoted to “Rare Earth and Actinide Complexes” that featured Stephen Mansell and Stephen Liddle as Guest Editors [7]. The five- to eight-year period between them witnessed significant advancements that relied on the exceptional optical and magnetic properties of the lanthanides [8,9,10,11] and on exploring and enlightening the properties of less-studied actinides, particularly heavier ones [12,13]. Therefore, this Special Issue, provides a small but significant sample of the current research in f-element coordination chemistry, comprising seven contributions involving the lanthanides and two focusing on omnipresent uranyl.

Evans and co-workers [14], as well as Reinfandt and Roesky [15], reported interesting examples of the widely studied but still fascinating organometallic chemistry of samarium, involving vintage, but ever-present, cyclopentadienyl ligands. Vostrikova and co-workers, in two contributions [16,17], examined the structure and magnetic properties of new lanthanide complexes comprising tripodal ligands. Vostrikova [18] also contributed a review on this topic of lanthanide complexes with tripodal ligands, particularly air-stable ones, and their usage in magnetism studies. Lanthanide complexes can be the building blocks of more extended structures that can tune luminescence and/or magnetic properties. Ivanova et al. [19] evaluated the photoluminescence of lanthanide(III) coordination polymers with a triazolyl methane linker, while Liu et al. [20] examined the properties of oligomeric Gd compounds as possible magnetic refrigerants. For the actinides, Tsantis et al. [21] provided a study of selected amidoxime ligands as models for understanding the selective extraction of uranyl ions from seawater, employing structural and spectroscopic analyses. Maria and Marçalo [22] contributed a review on a long-running topic in actinide chemistry concerning the challenges associated with the formation of uranyl analog complexes.

We hope that this Special Issue has contributed to highlighting the scope and distinctiveness of f-element chemistry. Owing to the unique properties of lanthanide ions, the potential utility of molecular lanthanide compounds in biosensing and bioimaging continues to increase. The search for new bonding motifs in molecular actinide compounds is ongoing and key to the development of separation strategies for spent nuclear fuel and the processing of radioactive waste.