First charge-transfer complexes between tetrathiafulvalene and 1,2,5-chalcogenadiazole derivatives: Design, synthesis, crystal structures, electronic and electrical properties

The first charge-transfer complexes of tetrathiafulvalene (1) with 1,2,5-chalcogenadiazole derivatives, i.e. with [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (2) and 3,4-dicyano-1,2,5-telluradiazole (3), were designed, prepared in the form of air and thermally stable single crystals and structurally defined by X-ray diffraction as 1·2 and 1·32, respectively. Starting compound 2 (effective electron acceptor with potentially broad application in the field) was synthesized by a new efficient one-pot method from 3,4-diamino-1,2,5-oxadiazole and disulfur dichloride. The electronic structure of complexes 1·2 and 1·32 and thermodynamics of their formation were studied by means of DFT and QTAIM calculations and UV–Vis spectroscopy. The electrical properties of single crystals of the complexes were investigated revealing semiconductor properties with an activation energy of 0.34 eV for 1·2 and 0.40 eV for 1·32. Polycrystalline films of the complexes displayed photoconductive effects with increased conductivity under white-light illumination.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The first CT complexes of TTF with 1,2,5-chalcogenadiazoles are designed. ► These complexes were synthesized and characterized by single-crystal XRD. ► Their properties were studied using DFT calculations and UV–Vis spectroscopy. ► The single crystals of the complexes revealed low band-gap semiconductor properties. ► Polycrystalline films of the complexes displayed increased conductivity under white-light illumination.