Tuning the Crystal Packing and Semiconductor Electronic Properties of 7,7′-Diazaisoindigo by Side-Chain Length and Halogenation

Abstract

In the last years, 7,7′-diazaisoindigo has emerged as a promising building block for semiconductor materials. In this work, we have studied different electronic properties, which can be related to the semiconducting character of a family of 7,7′-diazaisoindigo derivatives. Concretely, we have analyzed the role of halogen substituents and different side-chain lengths on these properties calculated by means of the density functional theory. In total, 16 halogenated and nonhalogenated diazaisoindigo derivatives were investigated. Four of these compounds were also synthetized, and their X-ray structures were employed as starting points for the calculation of the crystal structure of the rest of the novel compounds. In general, high electron-transfer rate constants and electron mobilities were calculated for the studied 7,7′-diazaisoindigo derivatives, especially for bromine derivatives and compounds with long side chains. The origin of these high rate constants mainly resides in the strong electronic couplings found for diazaisoindigo crystals in the π-stacking direction.