Fluoride-bridged {Ln2Cr2} polynuclear complexes from semi-labile mer-[CrF3(py)3] and [Ln(hfac)3(H2O)2]

TY - JOUR

T1 - Fluoride-bridged {Ln2Cr2} polynuclear complexes from semi-labile mer-[CrF3(py)3] and [Ln(hfac)3(H2O)2]

AU - Thuesen, Christian Aagaard

AU - Pedersen, Kasper Steen

AU - Schau-Magnussen, Magnus

AU - Evangelisti, Marco

AU - Vibenholt, Johan Elias

AU - Piligkos, Stergios

AU - Weihe, Høgni

AU - Bendix, Jesper

PY - 2012

Y1 - 2012

N2 - The trifluorido complex mer-[CrF3(py)3] (py = pyridine) reacts with 1 equiv. of [Ln(hfac)3(H2O) 2] and depending on the solvent forms the tetranuclear clusters [Cr2Ln2(μ-F)4(μ-OH)2(py) 4(hfac)6], 1Ln, and [Cr2Ln2(μ-F) 4F2(py)6(hfac)6], 2Ln, in acetonitrile and 1,2-dichloroethane, respectively (Ln = Y, Gd, Tb, Dy, Ho, and Er; hfacH = 1,1,1,5,5,5-hexafluoroacetylacetone). Reaction with [Dy(hfac) 3(H2O)2] in dichloromethane produces the dinuclear cluster [CrDy(μ-F)F(OH2)(py)3(hfac) 4], 3Dy. All the clusters feature fluoride bridges between the chromium(iii) and lanthanide(iii) centres. Fits of susceptibility data for 1Gd and 2Gd reveal the fluoride-mediated chromium(iii)-lanthanide(iii) exchange interactions to be 0.43(5) cm-1 and 0.57(7) cm-1, respectively (in the convention). Heat capacity measurements on 2Gd reveal a moderate magneto-caloric effect (MCE) reaching -ΔSm(T) = 11.4 J kg-1 K-1 for ΔB0 = 9 T → 0 T at T = 4.1 K. Out-of-phase alternating-current susceptibility (χ′′) signals are observed for 1Dy, 2Dy and 2Tb, demonstrating slow relaxation of the magnetization.

AB - The trifluorido complex mer-[CrF3(py)3] (py = pyridine) reacts with 1 equiv. of [Ln(hfac)3(H2O) 2] and depending on the solvent forms the tetranuclear clusters [Cr2Ln2(μ-F)4(μ-OH)2(py) 4(hfac)6], 1Ln, and [Cr2Ln2(μ-F) 4F2(py)6(hfac)6], 2Ln, in acetonitrile and 1,2-dichloroethane, respectively (Ln = Y, Gd, Tb, Dy, Ho, and Er; hfacH = 1,1,1,5,5,5-hexafluoroacetylacetone). Reaction with [Dy(hfac) 3(H2O)2] in dichloromethane produces the dinuclear cluster [CrDy(μ-F)F(OH2)(py)3(hfac) 4], 3Dy. All the clusters feature fluoride bridges between the chromium(iii) and lanthanide(iii) centres. Fits of susceptibility data for 1Gd and 2Gd reveal the fluoride-mediated chromium(iii)-lanthanide(iii) exchange interactions to be 0.43(5) cm-1 and 0.57(7) cm-1, respectively (in the convention). Heat capacity measurements on 2Gd reveal a moderate magneto-caloric effect (MCE) reaching -ΔSm(T) = 11.4 J kg-1 K-1 for ΔB0 = 9 T → 0 T at T = 4.1 K. Out-of-phase alternating-current susceptibility (χ′′) signals are observed for 1Dy, 2Dy and 2Tb, demonstrating slow relaxation of the magnetization.

U2 - 10.1039/c2dt31302b

DO - 10.1039/c2dt31302b

M3 - Journal article

SN - 1477-9226

VL - 41

SP - 11284

EP - 11292

JO - Dalton Transactions (Print Edition)

JF - Dalton Transactions (Print Edition)

IS - 37

ER -