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

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-E 2 , 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-E 2 . 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.

Structural Diversity and Multielectron Reduction Reactivity of Samarium(II) Iodido-β-diketiminate Complexes Dependent on Tetrahydrofuran Content

“…Here, we consider that the μ 2 -I positions in this molecule cannot be occupied by Te 2− because the Sm−μ 2 -I bond lengths in this complex (3.14 and 3.17 Å) are well comparable with the analogous bond lengths in all of the other complexes under the current study. On the contrary, in the only two structurally characterized molecular Ln complexes with a bridging telluride, [{SmCp* 2 (thf)} 2 (μ-Te)] 61 and [{Sm(N(Si i Pr 3 ) 2 )} 2 (μ-Te)], 62 the Sm−Te bonds are by ca. 0.2 Å shorter (2.99 or 2.95 Å, respectively).…”

Studies on the structural and optical properties of samarium β‐diketonate complex incorporated electrospun poly(methylmethacrylate) nanofibres with different architectures

“…[18,20] The spectra peaks were shifted to lower wavelengths with lesser intensity after incorporation of the prepared samarium β-diketonate complexes into these nanofibres; this was in agreement with recently published results. [33] Surface-modified PMMA showed absorption across the entire visible region, but less absorption. Pure PMMA showed absorption over a narrow range in the visible region with greater absorption compared with surface-modified PMMA, while coaxial hollow PMMA nanofibres showed the greatest absorption with the least broadening among the three samples, before and after incorporation of the complex into the fibre.…”

Recent progress in rare-earth metal-catalyzed sp2 and sp3 C–H functionalization to construct C–C and C–heteroelement bonds

“…In 2013, Pan and Chen disclosed the samarium-catalyzed synthesis of indolizine derivatives via the intermolecular cyclization of propargyl alcohols with 2-alkylpyridines via benzylic C–H activation of the latter component (Scheme 23A). 123 The underlying chemistry is based on the realization of strong nitrophilicity and π-electron affinity in the Sm 3+ centre 124 through its high charge density and hard Lewis acid character, in conjunction with the similar features of other rare-earth metal ions. 31,53 b ,54 In a series of tested rare-earth metal, transition-metal and post-transition-metal-catalysts, 10 mol% Sm(OTf) 3 gave the best result and obviated any additional co-catalyst/activator or ligand.…”