High Thermally Stable n‑Type Semiconductor up to 850 K Based on Dianionic Naphthalenediimide Derivative

Electrostatic
cation–anion interaction is effective to form
a tightly bounded π-molecular assembly, which enhances the thermal
stability and carrier transport property. Dianionic bis­(benzenesulfonate)–naphthalenediimide
(BSNDI2–) formed simple
2:1 cation–anion pairs of (Na+)2(BSNDI2–) (1),
(K+)2(BSNDI2–) (2), and (NH4+)2(BSNDI2–) (3), and their redox behaviors, thermal stabilities, crystal structures,
electron transport properties, and dielectric constants were compared
to those of neutral bis­(phenyl)–naphthalenediimide (4). Crystals 1, 2, and 3 had
quite high thermal stabilities up to 850, 810, and 600 K, respectively,
even though organic molecules. A two-dimensional (2D) n-type electron
transport layer consisting of NDI π cores was sandwiched
between networks of highly polarized electrostatic cation–anion
pairs showing 2D herringbone (1), one-dimensional π-stacking
(2), and brickstone-like 2D π-stacking (3) interactions. The values of electron mobility in polycrystalline 1, 2, 3, and 4 reached
0.22, >0.0003, 0.036, and >0.028 cm2 V–1 s–1, respectively, according to flash-photolysis
time-resolved microwave conductivity measurements. The electron mobility
of crystal 1 was 1 order of magnitude higher than those
of crystals 2, 3, and 4 owing
to the tight intermolecular interactions within the 2D transport layer.
The real part dielectric constants of crystals 1, 2, 3, and 4 were ∼4, ∼50,
∼20, and ∼4 at 450 K, respectively, which affected the
electron transport property. The chemical design of highly polarized
electrostatic cation–anion pair formed the 2D transport layer
and also has high thermal stability up to ∼850 K in the ionic
n-type semiconducting materials.