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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 16, Number 3
BKCSDE 16(3)
March 20, 1995 

Single Crystal EPR Spectra of K12[As2W18O66Cu3(H2O)2]·11H2O, a Copper(Ⅱ) Trimer
Young Hwan Cho, Hyunsoo So*
Single crystal EPR spectra of K12[As2W18O66Cu3(H2O)2]·11H2O exhibit an orientation-dependent fine structure of an S = 3/2 system which is accounted for by the exchange and magnetic dipole interactions among the three Cu2+ ions. The hyperfine structure and the lines from the S = 1/2 manifolds have not been observed. The isotropic exchange parameters determined from the magnetic susceptibility data at 5-300 K are J1 = J2 =-7.8 cm-1. The magnitude of J values suggests that the unpaired electrons on three Cu2+ ions interact through a sequence of six bonds involving two tungsten atoms and three oxygen atoms. The Cu-Cu distance, 4.37 Å, determined from the EPR spectra is considerably smaller than the value from the X-ray crystal structure determination, 4.76 ± 0.03 Å, indicating that the point-dipole model underestimates the dipolar interaction.
243 - 247
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