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.
Highlights
The concept of Hard and Soft Acids and Bases (HSAB) presents a challenge for synthetic chemists aiming to bind heavy chalcogens to f-elements, as there is a dichotomy between large and diffuse soft Lewis bases and highly electropositive hard f-block ions.1 For this reason, the chemistry of the f-block with sulfur, selenium, and tellurium has lagged behind that of their more congenial partner oxygen
The exchange interaction in Ln systems was often ignored until the arrival of a series of dilanthanide complexes bearing a highly reduced (N2)3− radical ligand that produced record high exchange couplings with exceptional magnetic performance to match,9−11 promoting a re-evaluation of magnetic exchange mechanisms in molecular magnets and materials for related emergent technologies
Dialkylavailable sources and diarylof ER as the E−E bond can be homolytically cleaved by two single electron transfer (SET) events, i.e., two Sm(II) ions can be oxidized to each gain a coordinated ER− unit
Summary
The concept of Hard and Soft Acids and Bases (HSAB) presents a challenge for synthetic chemists aiming to bind heavy chalcogens to f-elements, as there is a dichotomy between large and diffuse soft Lewis bases and highly electropositive hard f-block ions. For this reason, the chemistry of the f-block with sulfur, selenium, and tellurium has lagged behind that of their more congenial partner oxygen. The concept of Hard and Soft Acids and Bases (HSAB) presents a challenge for synthetic chemists aiming to bind heavy chalcogens to f-elements, as there is a dichotomy between large and diffuse soft Lewis bases and highly electropositive hard f-block ions.. The concept of Hard and Soft Acids and Bases (HSAB) presents a challenge for synthetic chemists aiming to bind heavy chalcogens to f-elements, as there is a dichotomy between large and diffuse soft Lewis bases and highly electropositive hard f-block ions.1 For this reason, the chemistry of the f-block with sulfur, selenium, and tellurium has lagged behind that of their more congenial partner oxygen. The exchange interaction in Ln systems was often ignored until the arrival of a series of dilanthanide complexes bearing a highly reduced (N2)3− radical ligand that produced record high exchange couplings with exceptional magnetic performance to match,− promoting a re-evaluation of magnetic exchange mechanisms in molecular magnets and materials for related emergent technologies.. Importance of the coligand in the design of new radical-bridged complexes with f elements
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