Functionalized Trigonal Lanthanide Complexes: A New Family of 4f Single-Ion Magnets

Abstract

We report the synthesis, characterization, and magnetic properties of eight neutral functionalized trigonal lanthanide coordination complexes LnL with Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5), Tm (6), Yb (7), Lu (8). These were prepared through a one-pot synthesis where, first, the ligand H3L was synthesized in situ through a Schiff base reaction of tris­(2-aminoethyl)­amine with 2,6-diformyl-p-cresol. Following addition of Ln­(OTf)3·xH2O and base, LnL was obtained. Powder X-ray diffraction confirms that all complexes are isostructural. LnL contain pendant, noncoordinating carbonyl functions that are reactive and represent direct anchoring points to appropriately functionalized surfaces. Furthermore, these reactive carbonyl functions can be used to postfunctionalize LnL: for example, with aromatic π systems. We present herein the Schiff base condensation of 7 with benzylamine to yield 9 as well as the characterization and magnetic properties of 9. Our study establishes LnL as a truly versatile module for the surface deposition of Ln-based single-ion magnets.

Mononuclear Dysprosium Alkoxide and Aryloxide Single‐Molecule Magnets

“…The most recent Yb III SMMs containing functionalised trensal ligands were reported by Buch et al. in 2020 [133, 152] . In one study, Buch et al.…”

“…There has been no Tb alkoxide or aryloxide SMM with CN <6 in the literature to date. Tb SMMs with higher CNs with mainly multi‐dentate chelating aryloxide ligands have been investigated [85, 95, 131–133] . However, they do not show a remarkable improvement over their Dy and Pc counterparts [130, 133] …”

“…Despite being a Kramers ion, there are only a few Yb III SMMs in the literature compared to Dy III , Er III and even non‐Kramers Tb III ions [27, 142] . Almost all the Yb III SMMs require an external magnetic field to show slow magnetic relaxation [85, 103, 108, 133, 142, 143] . Owing to the possibility of ferromagnetic exchange interactions, the vast majority of Yb III SMMs are either homometallic dimers or heterometallic 3d‐4f mixed multinuclear complexes, which have been discussed in detail elsewhere [142] .…”

Design of pure heterodinuclear lanthanoid cryptate complexes

“…[78][79][80][81][82] We have previously presented the synthesis, magnetic and spectroscopic properties of LnL 1 and LnL. 83,84 Both these families of complexes have merits on their own and should not simply be regarded as mere intermediate compounds in the synthesis of our targeted heterodinuclear complexes. LnL 1 contains pendant, reactive carbonyl functions that can be used as anchoring points for surface deposition protocols.…”

“…These same functionalities can also be exploited in post-synthetic reaction schemes making them truly versatile modules for deposition on various surfaces. 84 LnL have previously been considered as targets for the development of novel MRI contrast agents. 83…”