The Effect of Pressure on the Electronic Absorpion Spectra of TCNQ Ion Radical Salts

Abstract

Abstract The effect of pressure up to 7 kbar on the electronic absorption spectra of the crystalline TCNQ anion radical salts and Li(TCNQ) in PVA has been studied. For simple TCNQ salts such as Li(TCNQ), a blue shift with an increase in the pressure has been observed in the absorption band associated with the intramolecular transition. The magnitude of the blue shift is between 45 and 86 cm−1/kbar. The observed shift has been discussed in terms of the crystal-field effect of the cations. For N-MePhe(TCNQ) and M(TCNQ)2, composed of the formally-neutral TCNQ and its anion radical such as TEA(TCNQ)2, a pressure-induced absorption band has been observed at around 20 kK; it may be assigned to the charge-transfer band between the anion radicals.