Porous Organic Frameworks Utilizing Halogen···Halogen Interactions of X4-tetra[2,3]Thienylene (X = Br, I): Guest Dynamics and Dielectric Response.

X4-tetrabromo[2,3]thienylene (1, Br4-tetra[2,3]thienylene) and X4-tetraiodotetra[2,3]thienylene (2, I4-tetra[2,3]thienylene) were used to investigate the formation of various guest inclusion crystals through intermolecular halogen···halogen (X···X) interactions and the dynamics of guest molecules. 1 and 2 formed host-guest crystals with aromatic molecules such as benzene (Bz), toluene (Tol), anisole (An), and chlorobenzene (ClBz). X-ray crystal structure analysis revealed the formation of a channel structure where 1D chains formed by intermolecular X···X interactions were arranged in a grid pattern. Host lattices of 1 and 2 were capable of reversibly adsorbing and desorbing Tol molecules while maintaining crystallinity. Dielectric measurements showed dielectric relaxation due to molecular motion of polar guest molecules (Tol and ClBz) in the host lattice formed by molecule 2. In particular, crystals containing ClBz exhibited rotational dynamics of guest molecules with increasing temperature. These results provide important insights for the design of flexible porous materials using halogen···halogen interactions and the creation of dielectric materials based on guest molecule dynamics.