Taming salophen in rare earth metallocene chemistry

Abstract

A series of multinuclear metallocenes composed of a ^tBusalophen dianion bound to two rare earth metal ions, where each is encased in a bis-pentamethylcyclopentadienyl scaffold, was realized. The isolated molecules (Cp*₂RE)₂(μ-^tBusalophen), where RE = Gd (1), Dy (2), and Y (3), constitute the first salophen-bridged metallocene complexes for any metal ion. 1–3 were characterised by X-ray crystallography, cyclic voltammetry, IR, NMR, and UV-Vis-NIR spectroscopy. Cyclic voltammograms of 1–3 excitingly exhibit quasi-reversable features attributed to the (^tBusalophen²⁻/^tBusalophen³⁻˙) redox couple. DFT calculations on 3 uncovered the highest occupied molecular orbital to be primarily localized on the metallocene and phenolate moieties of the ^tBusalophen ligand. Furthermore, the nuclear spin I = ½ for yttrium allowed the collection of ⁸⁹Y NMR spectra for 3. Magnetic studies revealed slow magnetic relaxation, placing 2 among dysprosocenium-based single-molecule magnets containing a doubly anionic ligand in the equatorial plane.