Electron spin resonance and relaxation of tetrahedrally coordinated copper(11) in some complex halides

Abstract

AbstractElectron spin resonance and relaxation measurements are reported for some copper salts in which the Cu2+ ion has tetrahedral coordination. For the CuCl42− ion in Cs2CuCl4, the results are in some respects at variance with those previously reported [1]. The crystallographic cell parameters for [(C4H9)4N]2CuBr4 have been measured, and in this material a single broad asymmetric ESR line is reported, about 145 G wide at X‐band, having principal g‐values of 2.068, 2.053, and 2.220. Spin‐lattice relaxation times measured by both pulse and continuous saturation methods yielded values of T1 in the range 60 μs at 4.2 K to 140 μs at 1.7 K. These are compared with the much larger values predicted for copper in other tetrahedrally coordinated materials [2]. The ESR spectra of CuCl42− and CuBr42− ion adsorbed on an ion exchange resin are compared with those from powdered samples of the above two complexes. Measurements of T1 for the CuBr42− ion on the resin yielded values of 100 μs at 4.2 K and 280 μs at 1.86 K. It is concluded that the complex halides are not a suitable system in which to study relaxation behaviour of Cu2+ in a tetrahedral crystal field.