PNNL

Abstract

The rare- earths are comprised of scandium, yttrium, and the lanthanides (atomic numbers 21, 39 and 57-71).1 While these elements are essential to modern life, they were historically characterized as simple, perhaps dull, compared to the rich multi-electron chemistry of d-block metals in catalysts and enzymes. These descriptions were quite fair and largely true at the time these elements were discovered and the first compounds containing them were synthesized, though much progress has been made to overturn this view of the rare- earths. Similarly, discussions about actinide chemistry are sometimes limited to research pertinent to the nuclear industry, which, while comprising technologies vital to modern society, does not celebrate the fascinating chemical space that much of the actinide series occupies. These historic characterizations of most of the rare- earth and actinide elements persist in some textbooks, and we acknowledge it is a helpful place to start; but, together, these series comprise 32 elements—27% of the 118 known by 2024—and we suggest it would be an unfortunate twist of physics if such a large proportion of the Periodic Table were genuinely dull. Indeed, as this Inorganic Chemistry Special Issue highlights, the chemistry—let alone the physics, that is spectroscopy and magnetism—of these elements, is rich and depends on ligands!