Knowledge Bank

Nuclear quadrupole resonances for both $\mathrm{<mrow\; data-mjx-texclass="ORD">63</mrow>}Cu$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">65</mrow>}Cu$ have been observed in $Cu(etu)2Br$, $Cu(etu)2Cl$ and $Cu2(etu)4SO4$. (etu=ethylene thiourea). The $\mathrm{<mrow\; data-mjx-texclass="ORD">63</mrow>}Cu$ resonances are in the region of 29 33 MHz. Resonances for $\mathrm{<mrow\; data-mjx-texclass="ORD">79</mrow>}Br$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">81</mrow>}Br$ have been observed in $Cu(etu)2Br$ at 38.824 and 46.588 MHz. All resonances were observed using a noise controlled super-regenerative spectrometer and frequency measurements were made by means of a spectrum analyzer and digital counter. The studies were made at room temperature. The observed magnitude of the Br resonances leads one to conclude that the Br in this compound is essentially ionic. Reported crystal structure analysis on similar type compounds shows that the Cu is generally in a tetrahedral environment of bonded sulfur atoms and anions. Both structural and NQR data regarding compounds is very limited, so one can only generalize regarding the magnitude of the Cu resoances. They do, however, lie close to that reported for $KCu(CN)2$. Both $sp2$ and $sp2$ bonding schemes for the copper atom will be employed to rationalize the changes in frequency with anion substitution. A direct calculation of the electric field gradient tensor components will be discussed and a comparison of the calculated and experimental values will be presented.