Theoretical rationale for the role of the strong halogen bond in the design and synthesis of organic semiconductor materials

Abstract

The 1,8-naphthyridine and diiodine were selected as model molecules to investigate the possible effect of the strong N⋯I halogen bond on the electronic structures and properties of potential organic semiconductor building blocks. The N⋯I halogen bond in the crystal structure of the cocrystal formed between 1,8-naphthyridine and diiodine has an interaction energy of −21.41 kcal/mol. The cooperativity and anticooperativity between the strong halogen bond and other noncovalent interactions, including the hydrogen bond, tetrel bond and stacking interaction, were also studied in detail. The formation of the strong N⋯I halogen bond leads to the formation of the regularly layered structures of the cocrystal, which is a necessary condition for the organic semiconductor to conduct electrons or holes. On the other hand, the formation of the strong N⋯I halogen bond lowers both the energy of the lowest unoccupied molecular orbital of 1,8-naphthyridine and the energy gap of frontier molecular orbitals of 1,8-naphthyridine. These results clearly show that the strong halogen bond can be used as a cheap and effective tool for the design and synthesis of organic semiconductor materials.