Infrared properties of the organic semiconductor MEM(TCNQ)2 in its high-temperature phase

The infrared spectrum of N-methyl-N-ethylmorpholinium tetra-cyanoquinodimethane, MEM(TCNQ)2, at temperatures above the phase transition at T=335 K is reported. The oscillator strength associated with chargetransfer processes is shifted down in frequency as compared to the room-temperature phase. The sharp vibrational structure observed at 300 K is considerably broadened. The derived linear electron-molecular-vibration coupling constants are almost unchanged from those obtained at 300 K, thus confirming the theoretical framework used.