1,2,3-Triazolate-Bridged Tetradecametallic Transition Metal Clusters [M14(L)6O6(OMe)18X6] (M = FeIII, CrIII and VIII&#
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- 作者：Rachel Shaw ; Rebecca H. Laye ; Leigh F. Jones ; David M. Low ; Caytie Talbot-Eeckelaers ; Qiang Wei ; Constantinos J. Milios ; Simon Teat ; Madeleine Helliwell ; James Raftery ; Marco Evangelisti ; Marco Affron
- 刊名：Inorganic Chemistry
- 出版年：2007
- 出版时间：June 11, 2007
- 年：2007
- 卷：46
- 期：12
- 页码：4968 - 4978
- 全文大小：369K
- 年卷期：v.46,no.12(June 11, 2007)
- ISSN：1520-510X
文摘
We report the synthesis, by solvothermal methods, of the tetradecametallic cluster complexes [M14(L)6O6(OMe)18Cl6] (M = FeIII, CrIII) and [V14(L)6O6(OMe)18Cl6-xOx] (L = anion of 1,2,3-triazole or derivative). Crystal structuredata are reported for the {M14} complexes [Fe14(C2H2N3)6O6(OMe)18Cl6], [Cr14(bta)6O6(OMe)18Cl6] (btaH =benzotriazole), [V14O6(Me2bta)6(OMe)18Cl6-xOx] [Me2btaH = 5,6-Me2-benzotriazole; eight metal sites are VIII, theremainder are disordered between {VIII-Cl}2+ and {VIV=O}2+] and for the distorted [FeIII14O9(OH)(OMe)8(bta)7(MeOH)5(H2O)Cl8] structure that results from non-solvothermal synthetic methods, highlighting the importance oftemperature regime in cluster synthesis. Magnetic studies reveal the {Fe14} complexes to have ground state electronicspins of S 
25, among the highest known, while in contrast the {Cr14} complex has an S = 0 ground statedespite having a very similar structure and all complexes being dominated by intramolecular antiferromagneticexchange interactions. The {Fe14} complexes undergo a magnetic phase transition to long-range ordering at relativelyhigh temperatures for molecular species, which are governed by the steric bulk of the triazole (TN = 1.8 and 3.4K for L = bta- and H2C2N3-, respectively). The huge spins of the {Fe14} complexes lead to very large magnetocaloriceffects (MCE)-the largest known for any material below 10 K-which is further enhanced by spin frustration withinthe molecules due to the competing antiferromagnetic interactions. The largest MCE is found for [Fe14(C2H2N3)6O6(OMe)18Cl6] with an isothermal magnetic entropy change -
Sm of 20.3 J kg-1 K-1 at 6 K for anapplied magnetic field change of 0-7 T.
25, among the highest known, while in contrast the {Cr14} complex has an S = 0 ground statedespite having a very similar structure and all complexes being dominated by intramolecular antiferromagneticexchange interactions. The {Fe14} complexes undergo a magnetic phase transition to long-range ordering at relativelyhigh temperatures for molecular species, which are governed by the steric bulk of the triazole (TN = 1.8 and 3.4K for L = bta- and H2C2N3-, respectively). The huge spins of the {Fe14} complexes lead to very large magnetocaloriceffects (MCE)-the largest known for any material below 10 K-which is further enhanced by spin frustration withinthe molecules due to the competing antiferromagnetic interactions. The largest MCE is found for [Fe14(C2H2N3)6O6(OMe)18Cl6] with an isothermal magnetic entropy change -Sm of 20.3 J kg-1 K-1 at 6 K for anapplied magnetic field change of 0-7 T.