Journal article
Fluoride Bridges as Structure-Directing Motifs in 3d-4f Cluster Chemistry
The use of kinetically robust chromium(III) fluorido complexes as synthons for mixed 3d-4f clusters is reported. The tendency toward linear {CrIII–F–LnIII} units dictates the cluster topology. Specifically, we show that reaction of cis-[CrIIIF2(NN)2]NO3 (NN = 1,10-phenanthroline (“phen”) or 2,2′-bipyridine (“bpy”)) with Ln(NO3)3·xH2O produces isostructural series of molecular {Ln2Cr2} squares (1–9) with linear fluoride bridges.
In a parallel fashion, fac-[CrIIIF3L], where L = N,N′,N″-trimethyl-1,4,7-triazacyclononane (“Me3tacn”), reacts with Nd(NO3)3·6H2O to form a fluoride-centered penta-nuclear complex and fac-[CrIIIF3L′], with L′ = 1,1,1-tris-((methylamino)methylethane) (“Me3tame”), reacts with [Ln(hfac)3(H2O)2] (hfacH = 1,1,1,5,5,5-hexafluoroacetylacetone) to yield an isostructural series of {Ln3Cr2} (10–14) trigonal bipyramids with no central ligand.
The formation of the latter is accompanied by a partial solvolysis of the Cr(III) precursor but without formation of insoluble LnF3. The magnetic properties of the gadolinium containing clusters allow quantification of fluoride-mediated, antiferromagnetic Gd–Cr exchange interactions of magnitude between 0.14 cm–1 and 0.71 cm–1 (Ĥ = J12Ŝ1·Ŝ2 formalism) and vanishingly small JGd–Gd of 0.06(0) cm–1.
The large spin and small anisotropy together with weak exchange interactions in the {Gd3Cr2} (11) cluster give rise to a very large magneto-caloric effect of −ΔSm = 28.7 J kg–1 K–1 (μ0H = 90 to 0 kOe).
Language: | English |
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Publisher: | American Chemical Society (ACS) |
Year: | 2012 |
Pages: | 5435-5443 |
ISSN: | 1520510x and 00201669 |
Types: | Journal article |
DOI: | 10.1021/ic300421x |
ORCIDs: | Mossin, Susanne , 0000-0002-4011-6476 , 0000-0001-6194-1486 and 0000-0003-1255-2868 |