Nucleobase-Functionalized 1,6-Dithiapyrene-Type Electron-Donors: Supramolecular Assemblies by Complementary Hydrogen-Bonds and π‑Stacks

Synthesis, crystal structures and redox properties of 1,6-dithiapyrene (DTPY)-type electron-donors functionalized with nucleobases (uracil, cytosine and adenine) were investigated. The electrochemical measurements showed that the uracil-substituted derivatives were slightly stronger electron-donors than DTPY, and the cytosine- and adenine-substitution caused a slight weakening of the electron-donating ability. In the crystal structures, DTPY-nucleobases constructed multidimensional assemblies by complementary hydrogen-bonds on the nucleobase moieties and π-stacks and S···S interactions on the DTPY skeleton. The uracil derivative formed two kinds of hydrogen-bonded pairs with different H-bonding modes (Watson–Crick and reverse Watson–Crick types), both of which were further linked through π-stacks on the DTPY skeleton to construct one-dimensional alternating columns. In the CH₂Cl₂ solvated crystal, the uracil derivative built up a two-dimensional π-layer by the complementary hydrogen-bonds and π-stacks. In the cytosine derivative, the complementary hydrogen-bonded pair assembled by the π-stacks and S···S interactions of the DTPY skeleton constructed a two-dimensional network. The adenine derivative formed a channel structure by the one-dimensional π-stack of complementary hydrogen-bonded pairs, where crystalline water molecules with a ladder-like hydrogen-bonded chain were included. Charge-transfer complexes of DTPY-nucleobases with tetracyanoquinodimethane possessed a neutral ground state and exhibited semiconductive behaviors with room temperature conductivities of 10^–6 to 10^–7 S cm^–1.