ESR Study of Morpholinium TCNQ Complexes

Electron paramagnetic resonance studies have been carried out on three morpholinium–TCNQ charge resonance salts of varying stoichiometry. The three salts which have been studied include the previously known 1:1 and 2:3 complexes as well as a new, relatively unstable salt believed to be a 3:4 complex. All three materials exhibit resonance behavior similar to that found in other triplet-exciton-containing systems. A phase transition in the 1:1 salt has been discovered at 151°C which is accompanied by only minor changes in the zero-field splitting tensor parameters and principal axes. The morpholinium salts are characterized by an anomolous “impurity” resonance which occurs along with the zero-field doublet(s). The behavior of this “impurity” signal as a function of temperature suggests that it may be a characteristic property of the system.