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-BSNDI2–) forms various types of single-crystal (M+)2(m-BSNDI2–)·n(guest) with a combination of M+ = Na+, K+, Rb+, and guest = H2O, CH3OH. Four crystals of (K+)2(m-BSNDI2–)·n(H2O), (K+)2(m-BSNDI2–)·n(CH3OH), α-(K+)2(m-BSNDI2–), and β-(K+)2(m-BSNDI2–) were transformable using the guest adsorption–desorption cycle. Two kinds of single-crystal (K+)2(m-BSNDI2–)·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-BSNDI2–)·n(H2O). Systematic change of the ionic radii in (M+)2(m-BSNDI2–) modified the crystal lattice flexibility for the guest adsorption–desorption cycles.