A charge transfer salt consisted of bis(maleonitriledithiolato)zincate dianion and 1,1'-didecyl-4,4'-bipyridinium exhibiting uncommon nematic mesophase behavior

An ionic metal–dithiolene complex, 1,1'-didecyl-4,4'-bipyridinium bis(maleonitriledithiolato)zincate(II) ([Zn(mnt)2]2−), was synthesized and characterized by elemental analysis, infrared spectroscopy and crystal structure. In the [Zn(mnt)2]2− moiety, the complex shows distorted tetrahedral geometry with Zn2+ coordinated to four S-atoms from two mnt2− ligands, and its long molecular axis adopts a similar orientation with 1,1'-didecyl-4,4'-bipyridinium. Two distinguishable redox processes occur in the voltage region of − 1.0 to 1.0 V, with the irreversible and reversible redox couples corresponding to [Zn(mnt)2]2−/[Zn(mnt)2]− and 1,1'-didecyl-4,4'-bipyridinium+/1,1'-didecyl-4,4'-bipyridinium2+, respectively. An uncommon nematic mesophase behavior in this complex was confirmed by polarized-light optical microscopy (POM) and differential scanning calorimetry (DSC) measurements.

Graphical abstractAn uncommon nematic mesophase behavior was observed in a charge transfer salt consisted of bis(maleonitriledithiolato)zincate dianion with 1,1'-didecyl-4,4'-bipyridiniumFigure optionsDownload full-size imageDownload as PowerPoint slideResearch Highlights► A viologen derivative, 1,1'-didecyl-4,4'-bipyridinium, as liquid crystal architecture. ► A charge-transfer-salt-type ionic liquid crystal. ► Ionic liquid crystal shows nematic mesophase. ► Formation of mesophase arises from the hydrocarbon chain melting.