Molecular Lanthanide Switches for Magnetism and Photoluminescence

Abstract

Solvation of [(CNT)Ln(η8‐COT)] (Ln=La, Ce, Nd, Tb, Er; CNT=cyclononatetraenyl, i.e., C9H9−; COT=cyclooctatetraendiid, i.e., C8H82−) complexes with tetrahydrofuran (THF) gives rise to neutral [(η4‐CNT)Ln(thf)2(η8‐COT)] (Ln=La, Ce) and ionic [Ln(thf)x(η8‐COT)][CNT] (x=4 (Ce, Nd, Tb), 3 (Er)) species in a solid‐to‐solid transformation. Due to the severe distortion of the ligand sphere upon solvation, these species act as switchable luminophores and single‐molecule magnets. The desolvation of the coordinated solvents can be triggered by applying a dynamic vacuum, as well as a temperature gradient stimulus. Raman spectroscopic investigations revealed fast and fully reversible solvation and desolvation processes. Moreover, we also show that a Nd:YAG laser can induce the necessary temperature gradient for a self‐sufficient switching process of the Ce(III) analogue in a spatially resolved manner.

Mono-cyclononatetraenyl lanthanide complexes

“…In particular, the Ln-Cnt vibrational bands are clearly observable (see above). As seen for [( η 9 -CNT)Ln III ( η 8 -COT)] (Ln = Ce, Nd, Tb, Er), 16 this effect offers some potential with respect to switchable materials.…”

“…The resulting compounds act as switchable luminophores and single-molecule magnets. 16 Nocton and co-workers also reported on the tris(cyclononatetraenyl) rare earth complexes [Ln III (Cnt) 3 ] (Ln = Y, Gd, Tb, Dy, Ho, Er, Tm). 17 These compounds were obtained by salt metathesis form LnI 3 and [K(Cnt)].…”

“…21 A similar displacement of the Cnt ligand by THF was observed for the sandwich complexes [(Cnt)Ln III ( η 8 -COT)] (Ln = Ce, Nd, Tb, Er) with THF. 16 Among others the ionic species [Ln III (thf) x ( η 8 -COT)][Cnt] ( x = 4 (Ce, Nd, Tb), 3 (Er)) with a non-coordinated Cnt anion were isolated. This clearly shows that the Cnt anion is significantly weaker bound to the lanthanide ions than the smaller cyclopentadienyl ligand.…”

“…Since the related full displacement of the Cnt ring with THF in the ionic compounds [Ln III (thf) x ( η 8 -COT)][CNT] ( x = 4 (Ce, Nd, Tb), 3 (Er)) is fully reversible, 16 we were interested to study the back reaction of 3 and 4 to compounds 1 and 2 . After drying the crystals of the THF adducts 3 and 4 in high vacuum, Raman spectra of the isolated solids were obtained analogous to those of the unsolvated compounds 1 and 2 .…”

Cryptands on a Solid Support for the Separation of Europium from Gadolinium

“…The unique properties of rare-earth elements in magnetic, optical, and catalytic applications make them essential elements in green-energy technologies. − Europium (Eu) is one of the main elements used in energy-efficient phosphors in televisions, mobile phones, and computer displays due to its unique luminescence properties. Furthermore, Eu is categorized as a critical material by the U.S. Department of Energy .…”