A single crystal EPR investigation on (n-Bu4N)(2)[Cu(dmit)(2)] in the antiferro-magnetically coupled host lattice (n-Bu4N)(2)[(dmit)Cu(tto)Cu(dmit)]:A contribution to the nature of the so-called "paramagnetic impurities"

Single-crystal EPR investigations on the paramagnetic Cu-II impurity presen t in the binuclear anti ferromagnetically coupled complex (n-Bu4N)(2)[(dmit )Cu-II(tto)Cu-II (dmit)] (dmit = dimercaptoisotrithion, tto tetrathiooxalat e) identify the mononuclear S = 1/2 complex [Cu-II(dmit)(2)](2-) as being r esponsible for the observed EPR spectra. The Cu-63 hyperfine structure data as well as the data obtained from density functional theory (DFT) and exte nded Huckel theory molecular orbital (EHT-MO) calculations were used to cha racterize the spin-density distribution of the copper complex.