1,2,3-Triazolate-bridged tetradecametallic transition metal clusters [M14(L)6O6(OMe)18X6] (M = FeIII, CrIII and VIII/IV) and related compounds: Ground-state spins ranging from S = 0 to S = 25 and spin-enhanced magnetocaloric effect

Research output: Contribution to journalArticle

  • External authors:
  • 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 Affronte
  • David Collison
  • Euan K. Brechin

Abstract

We report the synthesis, by solvothermal methods, of the tetradecametallic cluster complexes [M14(L)6O6(OMe) 18-Cl6] (M = FeIII, CrIII) and [V14(L)6O6(OMe)18Cl 6-xOx] (L = anion of 1,2,3-triazole or derivative). Crystal structure data are reported for the {M14} complexes [Fe 14(C2H2N3)6O 6(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, the remainder are disordered between {VIII-CI}2+ and {V IV=O}2+] and for the distorted [FeIII 14O9(OH)(OMe)8(bta)7-(MeOH) 5(H2O)Cl8] structure that results from non-solvothermal synthetic methods, highlighting the importance of temperature regime in cluster synthesis. Magnetic studies reveal the {Fe14} complexes to have ground state electronic spins of S ≤ 25, among the highest known, while in contrast the {Cr14} complex has an S = 0 ground state despite having a very similar structure and all complexes being dominated by intramolecular antiferromagnetic exchange interactions. The {Fe14} complexes undergo a magnetic phase transition to long-range ordering at relatively high temperatures for molecular species, which are governed by the steric bulk of the triazole (TN = 1.8 and 3.4 K for L = bta - and H2C2N3-, respectively). The huge spins of the {Fe14} complexes lead to very large magnetocaloric effects (MCE) - the largest known for any material below 10 K - which is further enhanced by spin frustration within the molecules due to the competing antiferromagnetic interactions. The largest MCE is found for [Fe14-(C2H2N3)6O 6(OMe)18Cl6] with an isothermal magnetic entropy change -ΔSm of 20.3 J kg-1 K-1 at 6 K for an applied magnetic field change of 0-7 T. © 2007 American Chemical Society.

Bibliographical metadata

Original languageEnglish
Pages (from-to)4968-4978
Number of pages10
JournalInorganic Chemistry: including bioinorganic chemistry
Volume46
Issue number12
DOIs
Publication statusPublished - 11 Jun 2007

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