Heteroleptic Samarium(III) Chalcogenide Complexes: Opportunities for Giant Exchange Coupling in Bridging σ- and π-Radical Lanthanide Dichalcogenides

Conrad A. P. Goodwin, Benjamin L. L. Réant, Gianni F. Vettese, Jon G. C. Kragskow, Marcus J. Giansiracusa, Ida M. Dimucci, Kyle M. Lancaster, David P. Mills, Stephen Sproules

Research output: Contribution to journalArticlepeer-review

15 Citations (SciVal)

Abstract

The introduction of (N2)3–• radicals into multinuclear lanthanide molecular magnets raised hysteresis temperatures by stimulating strong exchange coupling between spin centers. Radical ligands with larger donor atoms could promote more efficient magnetic coupling between lanthanides to provide superior magnetic properties. Here, we show that heavy chalcogens (S, Se, Te) are primed to fulfill these criteria. The moderately reducing Sm(II) complex, [Sm(N††)2], where N†† is the bulky bis(triisopropylsilyl)amide ligand, can be oxidized (i) by diphenyldichalcogenides E2Ph2 (E = S, Se, Te) to form the mononuclear series [Sm(N††)2(EPh)] (E = S, 1-S; Se, 1-Se, Te, 1-Te); (ii) S8 or Se8 to give dinuclear [{Sm(N††)2}2(μ-η2:η2-E2)] (E = S, 2-S2; Se, 2-Se2); or (iii) with Te═PEt3 to yield [{Sm(N††)2}(μ-Te)] (3). These complexes have been characterized by single crystal X-ray diffraction, multinuclear NMR, FTIR, and electronic spectroscopy; the steric bulk of N†† dictates the formation of mononuclear complexes with chalcogenate ligands and dinuclear species with the chalcogenides. The Lα1 fluorescence-detected X-ray absorption spectra at the Sm L3-edge yielded resolved pre-edge and white-line peaks for 1-S and 2-E2, which served to calibrate our computational protocol in the successful reproduction of the spectral features. This method was employed to elucidate the ground state electronic structures for proposed oxidized and reduced variants of 2-E2. Reactivity is ligand-based, forming species with bridging superchalcogenide (E2)−• and subchalcogenide (E2)3–• radical ligands. The extraordinarily large exchange couplings provided by these dichalcogenide radicals reveal their suitability as potential successors to the benchmark (N2)3–• complexes in molecular magnets.
Original languageEnglish
Pages (from-to)7571-7583
Number of pages13
JournalInorganic Chemistry
Volume59
Issue number11
Early online date18 May 2020
DOIs
Publication statusPublished - 1 Jun 2020
Externally publishedYes

Bibliographical note

D.P.M. thanks the EPSRC (Doctoral Prize Fellowship to C.A.P.G., EP/P002560/1 and EP/K039547/1), the ERC (CoG 816268 for M.J.G.), the EPSRC UK National EPR Service for access to the SQUID magnetometer an the University of Manchester for a Ph.D. studentship for B.L.L.R., a work experience bursary for J.G.C.K., and access to the Computational Shared Facility. S.S. thanks the Scottish Funding Council for a Postgraduate and Early Career Researcher Exchange grant. K.M.L. thanks the National Science Foundation (CHE-1454455) and A. P. Sloan Foundation for financial support. We thank Dr. Pieter Glatzel (ESRF) for kindly providing Si(422) analyzer crystals for use in the data collection and Dr. Nicholas Chilton (Manchester) for insightful discussions. This work is based upon research conducted at the Cornell High Energy Synchrotron Source (CHESS), which is supported by the National Science Foundation and the National Institutes of Health/National Institute of General Medical Sciences under NSF award DMR-0936384, using the Macromolecular Diffraction at CHESS (MacCHESS) facility, which is supported by award GM-103485 from the NIH/NIGMS.

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