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.

本研究针对以核碱基（尿嘧啶（uracil）、胞嘧啶（cytosine）与腺嘌呤（adenine））修饰的1,6-二硫杂芘（1,6-dithiapyrene, DTPY）型电子给体的合成、晶体结构及氧化还原性质展开了探究。电化学测试结果表明，尿嘧啶取代的衍生物相较于纯DTPY，其给电子能力略强；而胞嘧啶与腺嘌呤的取代则会小幅削弱该类化合物的给电子性能。在晶体结构层面，DTPY-核碱基衍生物通过其核碱基基团上的互补氢键、DTPY骨架上的π堆积与S···S相互作用，构建出多维组装体。其中尿嘧啶修饰的衍生物可形成两种具有不同氢键模式的氢键对（沃森-克里克（Watson–Crick）型与反向沃森-克里克（reverse Watson–Crick）型），二者进一步通过DTPY骨架上的π堆积连接，形成一维交替柱结构。在二氯甲烷（CH2Cl2）溶剂化晶体中，该尿嘧啶衍生物借助互补氢键与π堆积构筑出二维π层结构。对于胞嘧啶修饰的衍生物，其互补氢键对通过DTPY骨架的π堆积与S···S相互作用进行组装，进而形成二维网络结构。腺嘌呤修饰的衍生物则通过互补氢键对的一维π堆积形成通道结构，其中包埋有类梯形氢键链的结晶水分子。DTPY-核碱基衍生物与四氰基对醌二甲烷（tetracyanoquinodimethane）形成的电荷转移复合物呈现中性基态，并表现出半导体特性，其室温电导率介于10⁻⁶至10⁻⁷ S·cm⁻¹之间。