Solution-processable molecules based on 1,4,5,8-naphthalenetetracarboxylic diimide (NTCDI, 1), which constitutes the central unit, have been synthesized with thiophene substituents of varying chain length attached to the naphthalene core. In this paper, the synthetic route to this new class of star-shaped NTCDI derivatives are given. Cyclovoltammetric, UV spectroscopic, photoelectron spectroscopy, and field effect transistor measurements are performed to characterize the electronic and optical properties of the new materials. The relationship between the donor–acceptor structure and the electronic and optical properties is thus shown in detail. Organic field-effect transistor devices have been built from this series of molecules and the results clearly describe the transfer from n-type to an ambipolar character depending on the structural components, i.e., naphthalene, diimide, and thiophene, of the molecules.