Nucleobase-Functionalized
1,6-Dithiapyrene-Type Electron-Donors:
Supramolecular Assemblies by Complementary Hydrogen-Bonds and π‑Stacks
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Abstract
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 CH<sub>2</sub>Cl<sub>2</sub> 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<sup>–6</sup> to 10<sup>–7</sup> S cm<sup>–1</sup>