No abstract

The temperature dependences of copper (II) EPR and 17 0 NMR spectra are analyzed in terms of a tetragonally distorted Cu(H20)e2+ ionic species in which only the equatorial water molecules form strong (1' bonds to copper (II). By reconstructing the EPR spectra at temperatures in the range _10° to 100°C the contributions to the linewidth from spin-lattice relaxation, tumbling of an ionic complex having an aclsotropic g factor and an anisotropic hyperfine coupling constant, and from isotropic hyperfine splitting, are separated. It is found that the spin-lattice relaxation time Tlo has components from both spin-rotational and Van Vleck processes. The 17 0 NMR linewidth is due to scalar hyperfine interaction with the copper (n) electron spin, and the spin-exchange correlation time T. for this mechanism is determined over the same temperature range. While Tlo and T. have similar temperature dependences, T. is 6-8 times smaller than T1., suggesting that it may be related to inversion of tetragonal distortion in the complex rather than to electron relaxation.'

At liquid-nitrogen temperature, crystalline carbonyl sulfide has been reported 1 to have the space group C3• 5 with one molecule per unit cell. The infrared spectra of the intramolecular vibrations 2 and of the lattice modes 3

No abstract

In an aqueous solution of a paramagnetic ion which exchanges water rapidly between its first coordination sphere and the solvent, a single oxygen-17 NMR signal is observed shifted from its normal position in pure H20. The magnitude of the shift is a measure of the ratio of the paramagnetic ion concentration to total (labile) water in the system. If a second ion for which the first coordination sphere water is sufficiently nonlabi!e ~T>"'1O-4 sec) is adde~ to t~e system, the decrease in the water available to interact with paramagnetic Ions due to water retamed m the nonlabile environment will produce an increase in the shift in the labile H2 17 0 resonance by the paramagnetic ion. The application of this "molal shift" method to the determination of the hydration numbers of certain diamagnetic and paramagnetic cations in aqueous solutions is demonstrated and discussed.