Ferromagnetic exchange interactions for Cu 6 12+ and Mn 6 12+ hexagons sandwiched by two B-α-[XW 9O 33] 9- (X = As III and Sb III) ligands in D 3d-symmetric polyoxotungstates

Toshihiro Yamase, Keisuke Fukaya, Hiroyuki Nojiri, Yuhgo Ohshima

Research output: Contribution to journalArticle

135 Citations (Scopus)

Abstract

Two novel Cu 6 and Mn 6 hexagon sandwiched polyoxometalates, [(CuCl) 6(AsW 9O 33) 2] 12- (1a) and [(MnCl) 6(SbW 9O 33) 2] 12- (2a), have been synthesized and characterized by X-ray single-crystal analysis and magnetic measurements. These complexes are D 3d symmetric and were isolated as [n-BuNH 3] + salts from aqueous solutions: (n-BuNH3)12[(CuCl) 6-(AsW 9O 33) 2]·6H 2O (1), rhombohedral, R3, a = 20.33(1) Å, c = 26.35(2) Å, Z = 3 and (n-BuNH 3) 12[(MnCl) 6-(SbW 9O 33) 2]·6H 2O (2). Six Cu (or Mn) atoms, each of which shows 5-fold coordination, make an approximately equatorial hexagon with a first-neighboring Cu⋯Cu (Mn⋯Mn) distance of 2.913(2) Å (3.248(1) Å) and a Cu-O-Cu (Mn-O-Mn) bond angle of 94.5(2)° (100.4(2)°). The magnetic behavior investigated by magnetic susceptibility measurements shows the ferromagnetic exchange interactions with J/k = +12.7 K (J/hc = +8.82 cm -1) and a S = 3 ground state for 1 and J/k = +0.20 K (J/hc = +0.14 cm -1) and a S = 15 ground state for 2, when only J refers to the isotropic magnetic-exchange interactions for first-neighbor atoms of the approximately equilateral Cu 6 12+ and Mn 6 12+ hexagons. The single-crystal ESR spectroscopy of 1 under the orientation of the magnetic field along a Cu 6 hexagon's nearly 6-fold axis equal to the c axis on the variation of temperature supports the S = 3 ground state and allows an estimate of the zero-field (fine-structure) energy separation between S z = O and S z = ±1 of D = -0.182 K to be obtained.

Original languageEnglish
Pages (from-to)7698-7704
Number of pages7
JournalInorganic Chemistry
Volume45
Issue number19
DOIs
Publication statusPublished - 2006 Sep 18

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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