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.