Crystal Lattice Design of HO-Tolerant n-Type Semiconducting Dianionic Naphthalenediimide Derivatives.

Dianionic bis(propionate)-naphthalenediimide () formed simple 2:1 cation-anion salts of (M)()·(HO) (M = Li, Na, K, Rb, and Cs), which exhibited reversible HO adsorption-desorption behavior because of the presence of their electrostatically binding crystal lattices. The maximum HO adsorption amounts () for M = Li, Na, K, Rb, and Cs were 0.25, 6.0, 4.0, 6.0, and 2.0, respectively, whereas the reversible gate-opening (gate-closing) HO adsorption-desorption isotherms were observed at 273 and 298 K, except for M = Li. High ionic conductivities of around 10-10 S cm were observed in M = Na and K salts, whereas short-range thermal fluctuations occurred in large cations of M = Rb and Cs. The change in the electrostatic lattice energy for M = Na and K salts during the HO adsorption-desorption cycles was significantly larger than those for M = Rb and Cs. Therefore, the Na and K salts had a considerably flexible electrostatic crystal lattice with a large amplitude of lattice modulation during the HO sorption cycle. In contrast, the lattice modulation for M = Rb and Cs salts involved a low magnitude of ion displacements, forming a relatively rigid cation-anion electrostatic crystal lattice. The flash-photolysis time-resolved microwave conductivity and transition absorption spectroscopy results revealed the high electron mobility of HO-adsorbed thin films, wherein the crystallized HO molecules did not act as electron-trapping sites. The values of electron mobility increased in the order of Cs ≈ Rb > K > Na > Li.