Temperature and Orientation Dependence of Electron-Spin Relaxation Rates for Bis(diethyldithiocarbamato)copper(II)

Abstract

Spin–lattice relaxation rates were measured by saturation recovery for bis(diethyldithiocarbamato)copper(II), Cu(dtc)2, dissolved in glassy 2:1 toluene:chloroform between 25 and 140 K and doped into Ni(dtc)2between 25 and 298 K. The temperature dependence is consistent with that expected for a two-phonon Raman process. For Cu(dtc)2in glassy solution and doped into Ni(dtc)2, 1/T1at 50 or 100 K is greater when the magnetic field is in the molecular plane than when it is perpendicular to the molecular plane, which is attributed to orientation dependence of intramolecular vibrations. The smaller orientation dependence of 1/T1for Cu(dtc)2doped into Zn(dtc)2than into Ni(dtc)2is attributed to the lower symmetry of the Cu(II) center in the Zn(dtc)2host. The phase-memory relaxation rate, 1/Tm, measured by electron spin echoes, exhibits a temperature dependence near 100 K that is characteristic of a dynamic process. This is attributed to rotation of the ligand methyl groups. The orientation dependence of 1/Tmat 50 K in glassy solution is that expected for low-amplitude molecular motion. Faster relaxation is observed for orientations at which the resonance field is more strongly dependent on small changes in molecular orientation.