Miloslav Šorm

A photochemical synthesis of bis(ethylenedithiolo)tetrathiafulvalene

Bis(ethylenedithiolo)tetrathiafulvalene was prepared by a photochemical desulphurization of 4,5-ethylenedithiolo-1,3-dithiole-2-thione (1), and the effect of the type of solvent, nucleophilic agent and its concentration, and temperature on the yield of the reaction is discussed.

Organic semiconductors: optical magnetic and electrical properties of 1-methyl-3-propylimidazolium 7,7,8,8-tetracyano-p-quinodimethane

Abstract Electrical conductivity and spectral properties (UV VIS absorption and especially the temperature dependence of IR absorption) are studied for the simple salt 1-methyl-3-propyl-imidazolium 7,7,8,8-tetracyano-p-quinodimethane (MPI+ TCNQ− . The temperature dependence of the IR absorption coefficient for the bands due to activation of the mode Ag is discussed in terms of changes in energy level population, geometry, and electron interactions. The temperature dependence of the absolute number of the TCNQ dimers in the triplet state is measured independently using the EPR method. The temperature dependences of the ground (singlet) state population of the TCNQ dimers and of the singlet—triplet energy separation J(T) = [(0.18 ± 0.01)-(2.5 ± 0.5) × 10−4 T] eV were determined from this measurement. These values lead to an unrealistically large value of the linear temperature expansion coefficient within the framework of the simple isolated model of dimers. Therefore, the weakly interacting model of dimers should be preferred. The activation energy of the triplet state exchange frequency. EW = 0.27 eV, and the room temperature jumping frequency of the exciton along the TCNQ stacks, νj = 5 × 1010 s−1, were determined from EPR measurements of the width of triplet lines.

Crystalline domains as trapping states in amorphous materials

SummaryThe photoconductivity and thermostimulated currents were measured on amorphous and spherulitic layers of oligo(ethyleneoxy) 2,5-di(anilino)terephthalate. The crystalline domains in the amorphous phase form new traps, c. 0,6 eV deep.