We present here the synthesis, characterization, and thin film transistor performance of six semiconducting materials by alkyl substitution on the N-positions of tetrachlorinated di(perylene bisimide) (4CldiPBI). Although the different alkyl chain substituents have a negligible effect on the absorption maximum and energy gap, the DSC thermal behaviour and electron performance are sensitive to the length of the alkyl chains. Substitution with the longer alkyl chains produced higher electron mobilities in air. C18-4CldiPBI (6), which exhibited the best solubility in common organic solvents, has demonstrated excellent thin film electron performance in air with the mobility as high as 0.70 cm2 V−1 s−1 and a high on/off ratio of 4 × 107. Furthermore, the device performance showed good stability in air for months without apparent degradation.