Coordination number 12 in praseodymium and 11 in neodymium complexes with organofluorotitanate ligands

Pevec, Andrej; Mrak, Maja; Demšar, Alojz; Petriček, Saša; Roesky, Herbert W.

doi:10.1016/s0277-5387(02)01419-5

Cited by 23 publications

(8 citation statements)

References 16 publications

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“…Nevertheless a few examples of fluoride-bridged 3d-4f clusters incorporating diamagnetic Ti IV have been prepared by serendipitous approaches. The scarce examples include only [La{(C 5 Me 4 Et) 2 Ti 2 F 7 } 3 ] and [Ln{(C 5 Me 5 ) 2 Ti 2 F 7 } 3 ] (Ln ¼ Pr, Nd) 17,18 in which the 12-coordinate lanthanide ion is exclusively surrounded by fluoride ions. Recently the first clusters incorporating {Cr III -F-Ln III } linking units were reported by Winpenny and co-workers.…”

Section: Introductionmentioning

confidence: 99%

Direct observation of a ferri-to-ferromagnetic transition in a fluoride-bridged 3d–4f molecular cluster

et al. 2012

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We report on the synthesis, crystal structure and magnetic characterisation of the trinuclear, fluoridebridged, molecular nanomagnet [Dy(hfac) 3 (H 2 O)-CrF 2 (py) 4 -Dy(hfac) 3 (NO 3 )] (1) (hfacH ¼ 1,1,1,5,5,5-hexafluoroacetylacetone, py ¼ pyridine) and a closely related dinuclear species [Dy(hfac) 4 -CrF 2 (py) 4 ]$ 1 / 2 CHCl 3 (2). Element-specific magnetisation curves obtained on 1 by X-ray magnetic circular dichroism (XMCD) allow us to directly observe the field-induced transition from a ferrimagnetic to a ferromagnetic arrangement of the Dy and Cr magnetic moments. By fitting a spinHamiltonian model to the XMCD data we extract a weak antiferromagnetic exchange coupling of j ¼ À0.18 cm À1 between the Dy III and Cr III ions. The value found from XMCD is consistent with SQUID magnetometry and inelastic neutron scattering measurements. Furthermore, alternating current susceptibility and muon-spin relaxation measurements reveal that 1 shows thermally activated relaxation of magnetisation with a small effective barrier for magnetisation reversal of D eff ¼ 3 cm À1 . Density-functional theory calculations show that the Dy-Cr couplings originate from superexchange via the fluoride bridges.

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Section: Introductionmentioning

confidence: 99%

Direct observation of a ferri-to-ferromagnetic transition in a fluoride-bridged 3d–4f molecular cluster

et al. 2012

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“…Compounds 2 and 3 add to the tiny family of fourth row/transition element-lanthanide, fluoride-bridged systems, which, in addition to the Cr III systems, [3,4] only encompasses [La{(C 5 Me 4 Et) 2 Ti 2 F 7 } 3 ] and [Ln{(C 5 Me 5 ) 2 Ti 2 F 7 } 3 ] (Ln = Pr, Nd). [6] These latter systems, however, rely on the pronounced "hard" metal ions Ti IV and Ln III , which compete efficiently for fluoride abstraction. Neither Fe III nor Ga III are as hard as Ti IV or kinetically robust as Cr III , but, surprisingly, exhibit similar reactivity towards Gd III .…”

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confidence: 99%

Fluoride‐Bridged {Gd^III₃M^III₂} (M=Cr, Fe, Ga) Molecular Magnetic Refrigerants

et al. 2014

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The reaction of fac-[M(III)F3(Me3tacn)]⋅x H2O with Gd(NO3)3⋅5H2O affords a series of fluoride-bridged, trigonal bipyramidal {Gd(III)3M(III)2} (M = Cr (1), Fe (2), Ga (3)) complexes without signs of concomitant GdF3 formation, thereby demonstrating the applicability even of labile fluoride-complexes as precursors for 3d-4f systems. Molecular geometry enforces weak exchange interactions, which is rationalized computationally. This, in conjunction with a lightweight ligand sphere, gives rise to large magnetic entropy changes of 38.3 J kg(-1) K(-1) (1) and 33.1 J kg(-1) K(-1) (2) for the field change 7 T→0 T. Interestingly, the entropy change, and the magnetocaloric effect, are smaller in 2 than in 1 despite the larger spin ground state of the former secured by intramolecular Fe-Gd ferromagnetic interactions. This observation underlines the necessity of controlling not only the ground state but also close-lying excited states for successful design of molecular refrigerants.

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“…For related structures of second sphere interactions with robust chromium(III) fluoride complexes, see: Birk et al (2010); Terasaki et al (1999); Kaizaki & Takemoto (1990). For other examples of fluoride bridges between 3d and 4f metal atoms, see: Pevec et al (2003); McRobbie et al (2011). For the structure of the cationic chromium precursor complex, see: Birk et al (2008).…”

Section: Related Literaturementioning

confidence: 99%

“…2).Studies of the magnetic properties of this system and the possible generalization of this route to fluoride-bridged systems are currently being undertaken.Related structures of second sphere interactions with robust chromium(III) fluoride complexes were presented byBirk et al (2010);Terasaki et al (1999);Kaizaki & Takemoto (1990). For other examples of fluoride bridges between 3d and 4f metal atoms, see:Pevec et al (2003).Acta Cryst. (2011).…”

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confidence: 95%

cyclo-Tetra-μ-fluorido-1:2κ²F;2:3κ²F;3:4κ²F;1:4κ²F-octanitrato-1κ⁸O,O′;3κ⁸O,O′-tetrakis(1,10-phenanthroline)-2κ⁴N,N′;4κ⁴N,N′-2,4-dichromium(III)-1,3-dineodymium(III) methanol tetrasolvate monohydrate

et al. 2011

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In the title compound, [Cr2Nd2F4(NO2)8(C12H8N2)4]·4CH3OH·H2O, two cis-difluoridobis(1,10-phenanthroline)chromium(III) fragments containing octahedrally coordinated chromium(III) bridge via fluoride ions to two tetranitratoneodymate(III) fragments, forming an uncharged tetranuclear square-like core. The fluoride bridges are fairly linear, with Cr—F—Nd angles of 168.74 (8)°. Cr—F bond lengths are 1.8815 (15) Å, slightly elongated compared to those of the parent chromium(III) complex, which has bond lengths ranging from 1.8444 (10) to 1.8621 (10) Å. The tetranuclear complex is centered at a fourfold rotoinversion axis, with the Cr and Nd atoms situated on two perpendicular twofold rotation axes. The uncoordinated water molecule resides on a fourfold rotation axis. The four methanol solvent molecules are located around this axis, forming a cyclic hydrogen-bonded arrangement. The title compound is the first structurally characterized example of unsupported fluoride bridges between lanthanide and transition metal ions.

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Coordination number 12 in praseodymium and 11 in neodymium complexes with organofluorotitanate ligands

Cited by 23 publications

References 16 publications

Direct observation of a ferri-to-ferromagnetic transition in a fluoride-bridged 3d–4f molecular cluster

Direct observation of a ferri-to-ferromagnetic transition in a fluoride-bridged 3d–4f molecular cluster

Fluoride‐Bridged {Gd^III₃M^III₂} (M=Cr, Fe, Ga) Molecular Magnetic Refrigerants

cyclo-Tetra-μ-fluorido-1:2κ²F;2:3κ²F;3:4κ²F;1:4κ²F-octanitrato-1κ⁸O,O′;3κ⁸O,O′-tetrakis(1,10-phenanthroline)-2κ⁴N,N′;4κ⁴N,N′-2,4-dichromium(III)-1,3-dineodymium(III) methanol tetrasolvate monohydrate

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Coordination number 12 in praseodymium and 11 in neodymium complexes with organofluorotitanate ligands

Cited by 23 publications

References 16 publications

Direct observation of a ferri-to-ferromagnetic transition in a fluoride-bridged 3d–4f molecular cluster

Direct observation of a ferri-to-ferromagnetic transition in a fluoride-bridged 3d–4f molecular cluster

Fluoride‐Bridged {GdIII3MIII2} (M=Cr, Fe, Ga) Molecular Magnetic Refrigerants

cyclo-Tetra-μ-fluorido-1:2κ2F;2:3κ2F;3:4κ2F;1:4κ2F-octanitrato-1κ8O,O′;3κ8O,O′-tetrakis(1,10-phenanthroline)-2κ4N,N′;4κ4N,N′-2,4-dichromium(III)-1,3-dineodymium(III) methanol tetrasolvate monohydrate

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Fluoride‐Bridged {Gd^III₃M^III₂} (M=Cr, Fe, Ga) Molecular Magnetic Refrigerants

cyclo-Tetra-μ-fluorido-1:2κ²F;2:3κ²F;3:4κ²F;1:4κ²F-octanitrato-1κ⁸O,O′;3κ⁸O,O′-tetrakis(1,10-phenanthroline)-2κ⁴N,N′;4κ⁴N,N′-2,4-dichromium(III)-1,3-dineodymium(III) methanol tetrasolvate monohydrate