Contrasted behaviours of methylthiolated perylene and pyrene as organic semiconductors: implications of molecular electronic structure and crystal structure

Abstract

Following the ultrahigh mobility of 1,3,6,8-tetrakis(methylthio)pyrene (MT-pyrene)-based single-crystal transistors (SC-FETs), we have synthesized and characterized its closely related compound, 2,5,8,11-tetrakis(methythio)perylene (MT-perylene). Like parent pyrene and perylene with similar sandwich herringbone structures, MT-perylene crystallizes into a brickwork structure as MT-pyrene does. However, the transport properties of MT-perylene evaluated by SC-FETs were far inferior to those of MT-pyrene: about 0.2 cm² V⁻¹ s⁻¹ for the former, whereas 32 cm² V⁻¹ s⁻¹ for the latter. Such marked differences can be ascribed to the solid-state electronic structures, which are the outcome of both the molecular electronic structure and crystal structure in the solid state. This indicates the importance of choosing molecules that can realize an appropriate combination of molecular orbitals and solid-state structure so that the solid-state electronic structure is suitable for efficient carrier transport.