Organobismuth Molecular Crystals for Organic Topological Insulators

Abstract

Three different types of large and high-quality organobismuth molecular crystals were grown by a physical vapor transport process. The target organobismuth molecules that have similar molecular structures, except for the type and position of the functional group, were crystallized into colorless and wire-shaped crystals having lengths at the centimeter scale with uniform flat surface. The crystal-packing structures of the organobismuth crystals were determined by single-crystal X-ray diffraction. The results show that the molecular packing can be controlled by a slight change of the functional group due to their different intermolecular interactions. Especially, the Bi-Bi distance was successfully controlled to vary from 5.11(1) to 5.71(3) and 5.18(2) A for triphenylbismuth (TPB), tri-p-tolylbismuthine (p-TTB), and tri-o-tolylbismuthine (o-TTB), respectively. The different crystal structures and Bi-Bi distances can affect the topological behavior of the materials. Moreover, the electrical and optical properties of the target organobismuth crystals were confirmed through the I-V characteristics, density functional theory calculation, and photoluminescence spectroscopy. These findings potentially offer a new route and strategy for the development of organic topological insulators.