Dielectric relaxation in 2 : 1 charge-transfer complexes of 2,3,7,8-tetramethoxychalcogenanthrenes and tetracyanoethene

Abstract

The dielectric behaviour of 2 : 1 charge-transfer complexes of the 2,3,7,8-tetramethoxychalcogenanthenes (5,10-dichalcogenacyclodiveratrylenes) Vn₂EE′(E = E′= S, Se; E = S, E′= Se) with tetracyanoethene (TCNE) is studied by conventional a.c. measurements and by the thermostimulated depolarization current (TSCD) technique as an alternative experimental method. In the low-frequency side of the dielectric loss curves (ε″vs. frequency plots) the relaxation peaks of the compounds are hidden by a continuous increase in dielectric loss. By a transformation of complex permittivity ε*=ε′–ε″ into complex polarizability α*=α′– iα″ the loss peaks can be seen in the α″vs. frequency plots. The existence of these relaxations is confirmed by TSDC measurements.