Organic field-effect transistor based on paramagnetic Cu(II) neutral complexes coordinated by Schiff base-type TTF ligands

Article abstract of DOI:10.1016/j.poly.2017.03.006

We have succeeded in preparation of novel paramagnetic Cu(II) complexes composed of tetrathiafulvalene (TTF)-based ligands as electrical conducting units, [Cu^II(Bz-OMe-^tBu-sae-TTF)₂], [Cu^II(EDT-bissae-TTF)] and [Cu^II(Bz-bis(OMe-^tBu-sae)-TTF)]. Electrochemical measurements of these neutral complexes revealed that they exhibited two pairs of redox waves attributed to the oxidation of TTF moieties. Among the newly synthesized TTF complexes, only [Cu^II(EDT-bissae-TTF)] gave a radical salt by electrochemical crystallization, but its resistive behavior was insulating. Field-effect transistors (FET) were fabricated with spin-coated films of [Cu^II(Bz-OMe-^tBu-sae-TTF)₂] and [Cu^II(EDT-bissae-TTF)], and their FET performances were very low compared with the conventional organic thin film transistors (OTFT) based on TTF derivatives. Atomic force microscopy (AFM) images of the spin-coated films indicated the non-uniform film surfaces with many small grains leading to the large grain boundaries, which probably causes the low carrier mobility of the FET devices.