New semiconducting naphthalene bisimides N-substituted with alkoxyphenyl groups: spectroscopic, electrochemical, structural and electrical properties

Three new naphthalene bisimides with alkoxyphenyl N-substituents (abbreviated as NBI-4-n-ORPhs, where R = butyl, hexyl or octyl group) were synthesized as well as spectroscopically, electrochemically and structurally characterized. DFT calculations predicted a high value of the electron affinity (EA) and a low lying LUMO level for these compounds. These findings were corroborated by cyclic voltammetry which yielded the experimental |EA| values of ca. of 4.11–4.12 eV and the ionization potential (IP) values in the range of 6.33–6.37 eV. When solution processed, the investigated semiconductors formed highly ordered and oriented layers, whose supramolecular organizations were derived from the structures determined for the corresponding single crystals. In particular π-stacked molecules formed molecular rows with stacking direction parallel to the substrate on which the films were deposited. As determined by X-ray diffraction studies, zone-casting technique turned out to be especially suitable for depositing layers of very good structural homogeneity, desired orientation of the molecules and high coherence length. High |EA| values of NBI-4-n-ORPhs together with their ordered supramolecular organization in zone-cast layers made these new semiconductors very good candidates for fabrication of n-channel field effect transistors (FETs). The devices with the Parylene C dielectric reached an electron mobility up to 0.05 cm2 V−1 s−1 in air operating conditions.