New routes to polymetallic clusters: Fluoride-based tri-, deca-, and hexaicosametallic Mn clusters and their magnetic properties

L.F. Jones, G. Rajaraman, J. Raftery, E.K. Brechin, D. Collison, J. Brockman, M. Murugesu, E.C. San̂udo, G. Christou, W. Wernsdorfer, S.J. Teat

Research output: Contribution to journalArticlepeer-review

Abstract

The syntheses, structures and magnetic properties of three new Mn-III clusters, [Mn26O17(OH)(8)(OMe)(4)F-10(bta)(22)(MeOH)(14)(H2O)(2)] (1), [Mn10O6(OH)(2)(bta)(8)(py)(8)F-8] (2) and [NHEt3](2)[Mn3O(bta)(6)F-3] (3), are reported (bta anion of benzotriazole), thereby demonstrating the utility of MnF3 as a new synthon in Mn cluster chemistry. The "melt" reaction (100 degreesC) between MnF3 and benzotriazole (btaH, C6H5N3) under an inert atmosphere, followed by dissolution in MeOH produces the cluster [Mn26O17(OH)(8)(OMe)(4)F-10(bta)(22)(MeOH)(14)(H2O)(2)] (1) after two weeks. Complex 1 crystallizes in the triclinic space group P!, and consists of a complicated array of metal tetrahedra linked by mu(3)-O2- ions, mu(3)- and mu(2)-OH- ions, mu(2)-MeO- ions and mu(2)-bta(-) ligands. The "simpler" reaction between MnF3 and btaH in boiling MeOH (50 degreesC) also produces complex 1. If this reaction is repeated in the presence of pyridine, the decametallic complex [Mn10O6(OH)(2)(bta)(8)(py)(8)F-8] (2) is produced. Complex 2 crystallizes in the triclinic space group Pi and consists of a "supertetrahedral" [Mn-10(III)] core bridged by six mu(3)-O2- ions, two mu(3)-OH- ions, four mu(2)-F- ions and eight mu(2)-bta(-) ions. The replacement of pyridine by triethylamine in the same reaction scheme produces the trimetallic species [NHEt3](2)[Mn3O(bta)(6)F-3] (3). Complex 3 crystallises in the monoclinic space group P2(1)/c and has a structure analogous to that of the basic metal carboxylates of general formula [M3O(RCO2)(6)L-3](0/+), which consists of an oxo-centred metal triangle with mu(2)-bta(-) ligands bridging each edge of the triangle and the fluoride ions acting as the terminal ligands. DC magnetic susceptibility measurements in the 300-1.8 K and 0.1-7 T ranges were investigated for all three complexes. For each, the value of chi(M)T decreases with decreasing temperatures; this indicates the presence of dominant antiferromagnetic exchange interactions in 1-3. For complex 1, the low-temperature value of chi(M)T is 10 cm(3) Kmol(-1) and fitting of the magnetisation data gives S=4, g=2.0 and D=-0.90cm(-1). For complex 2, the value of chi(M)T falls to a value of approximately 5.0 cm(3) K mol(-1) at 1.8 K, which is consistent with a small spin ground state. For the triangular complex 3, the best fit to the experimental chi(M)T versus T data was obtained for the following parameters: J(a)=-5.01cm(-1), J(b)=+9.16cm(-1) and g=2.00, resulting in an S=2 spin ground state. DFT calculations on 3, however, suggest an S=1 or S=0 ground state with J(a) = -2.95 cm(-1) and J(b) = -2.12 cm(-1). AC susceptibility measurements performed on 1 in the 1.8-4.00 K range show the presence of out-of-phase AC susceptibility signals, but no peaks.

Low-temperature single-crystal studies performed on 1 on an array of micro-SQUIDS show the time- and temperature-dependent hysteresis loops indicative of single-molecule magnetism behaviour.

Original languageEnglish
Pages (from-to)5180-5194
Number of pages15
JournalChemistry - A European Journal
Volume10
Issue number20
DOIs
Publication statusPublished - 11 Oct 2004

Keywords

  • cluster compounds
  • density functional calculations
  • fluorides
  • magnetic properties
  • manganese
  • N ligands
  • SINGLE-MOLECULE MAGNETS
  • TRANSITION-METAL-COMPLEXES
  • PHOTOSYNTHETIC WATER OXIDATION
  • EXCHANGE COUPLING-CONSTANTS
  • MANGANESE COMPLEXES
  • CRYSTAL-STRUCTURES
  • GROUND-STATE
  • REACTIVITY
  • LIGAND
  • CAGES

Fingerprint

Dive into the research topics of 'New routes to polymetallic clusters: Fluoride-based tri-, deca-, and hexaicosametallic Mn clusters and their magnetic properties'. Together they form a unique fingerprint.

Cite this