EFFECT OF MOLECULAR-MOTION ON ELECTRON-SPIN PHASE MEMORY TIMES FOR COPPER(II) COMPLEXES IN DOPED SOLIDS

Electron spin phase memory times, T(m), as a function of temperature were measured for Cu(II) bis(diethyldithiocarbamate), Cu(Et2dtc)2; Cu(II) bis(diethyldithiophosphate), Cu(Et2dtp)2; Cu(II) bis(diphenyldithiophosphate), Cu(Ph,dtp)2; Cu(II) tetratolylporphyrin, CuTTP; vanadyl 5-(4-carboxyphenyl)-10,15,20-tritolylporphyrin, VOTTP-COOH; and Ag(II) tetratolylporphyrin, AgTTP, doped into powdered samples of closely-related dimagnetic hosts. For the three metalloporphyrins, the electron spin relaxation rate (1/T(m)) increased monotonically with increasing temperature. However the temperature dependence of the relaxation rate was not monotonic for the three other Cu(II) complexes. For Cu(Et2dtc)2 and Cu(Et,dtp)2 the temperature dependence of 1/T(m) between about 85 and 130 K is attributed to the effects of methyl rotation, with activation energies of 1.0 kcal/mole. Between 120 and 250 K the 1/T(m), data for Cu(Ph,dtp)2, exhibit effects that are attributed to motion of the phenyl rings.