Dielectric relaxation peaks in the low-frequency/high-temperature range of the loss permittivity curve studied by the thermostimulated depolarization current (TSDC) technique in 2,3,7,8-tetramethoxychalcogenanthrenes–TCNQ charge-transfer complexes

Abstract

The dielectric behaviour of the 1 : 1 charge-transfer complexes of the 2,3,7,8-tetramethoxychalcogenanthrenes (5,10-dichalcogena-cyclo-diveratrylenes) Vn2EE′(E = E′= S, Se; E = S, E′= Se) with 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) is studied by the thermostimulated depolarization current (TSDC) technique as an alternative experimental method to the more conventional a.c. measurements. In the low-frequency side of the dielectric loss curves (Iµ″vs. frequency plots) the relaxation peaks of the compounds are hidden by a continous increase in dielectric loss. By a transformation of complex permittivity Iµ*=Iµ′–iIµ″ into complex polarizability α*=α′–iα″ loss peaks can be observed in the α″vs. frequency plots (E. Sanchez Martinez, R. Diaz Calleja, P. Berges, J. Kudning and G. Klar, Synth. Met., 1989, 30, 67). The existence of these relaxations is now proven by the TSDC method.