Structural Transformable Coulomb Lattice of n-Type Semiconductors for Guest Sorption

In recent years, highly designable organic porous materials have attracted considerable attention in the development of new types of molecular adsorption-desorption materials. The adsorption-desorption process also changes the electronic structure via the existence of guest molecules. Therefore, it is possible to change the physical property during the guest adsorption-desorption cycle using an appropriate chemical design of the host crystal lattice. As the development of n-type organic semiconductors has been limited, we focused on designing an n-type organic semiconductor material to control the host crystal lattice, electronic dimensionality, chemical stability, and high electron mobility using an ionic naphthalenediimide (NDI) derivative. Low symmetrical dianionic bis(benzene-m-sulfonate)-naphthalenediimide (m-BSNDI) forms various types of single-crystal (M⁺)₂(m-BSNDI)·n(guest) with a combination of M⁺ = Na⁺, K⁺, Rb⁺, and guest = H₂O, CH₃OH. Four crystals of (K⁺)₂(m-BSNDI)·n(H₂O), (K⁺)₂(m-BSNDI)·n(CH₃OH), α-(K⁺)₂(m-BSNDI), and β-(K⁺)₂(m-BSNDI) were transformable using the guest adsorption-desorption cycle. Two kinds of single-crystal (K⁺)₂(m-BSNDI)·n(CH₃OH) with n = 0 and 2.0 showed a single-crystal to single-crystal (SCSC) transformation through CH₃OH desorption. On the contrary, five kinds of single crystals with n = 0, 3.0, 3.3, 4.75, and 5.5 were identified in the single-crystal X-ray structural analyses of (K⁺)₂(m-BSNDI)·n(H₂O). Systematic change of the ionic radii in (M⁺)₂(m-BSNDI) modified the crystal lattice flexibility for the guest adsorption-desorption cycles.