TEMPERATURE-DEPENDENT ELECTRONIC ABSORPTION-SPECTRUM OF K(TCNQ), BA(TCNQ)2, CA(TCNQ)2 AND PERYLENE-TCNQ

The absorption spectrum of D-TCNQ (D is potassium, barium, calcium and perylene) has been studied between 3100 Å and 24000 Å and from 10 K to room temperature. In the metal compounds, the locally excited ultraviolet and visible bands sharpened considerably at lower temperatures revealing vibronic structure, while the charge transfer bands in the infrared remained relatively broad and temperature independent. In these compounds the TCNQ's stack on top of each other. We have also observed the monomer spectrum in Ba(TCNQ)2, indicating incomplete charge transfer. In the perylene- TCNQ compounds, we have observed at lower temperatures vibronic structure in the locally excited ultraviolet bands but not in the charge transfer intrared bands. We have also observed the monomer spectrum in the perylene-TCNQ compounds. © 1979.