Single Crystal EPR Spectra of $K_{12}[As_2W_18O_{66}Cu_3(H_2O)_2]{\cdot}11H_2O$, a Copper(II) Trimer

• Published in: Bulletin of the Korean Chemical Society 1995, Vol.16 (3), p.243-248
• Main Authors: 조영환, 소현수, Jo, Yeong Hwan, So, Hyeon Su
• Format: Article
• Language: Korean
• ISSN: 0253-2964; 1229-5949

Single crystal EPR spectra of K12[As2W18O66Cu3(H2O)2]${\cdot}$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 $\AA$, determined from the EPR spectra is considerably smaller than the value from the X-ray crystal structure determination, 4.76 $\pm$ 0.03 $\AA$, indicating that the point-dipole model underestimates the dipolar interaction.