Electron acceptors of the fluorene series. Part 13. 9-(5-Nitrofuran-2-ylidene)- and 9-(5-nitro-2-thienylidene)-2,4,5,7-tetranitrofluorenes: novel π-extended electron acceptors. Synthesis, cyclic voltammetry and X-ray crystal structures for the acceptor and its 4,5-dimethyltetrathiafulvalene complex, and a theoretical study†
作者:Igor F. Perepichka、Dmitrii F. Perepichka、Svetlana B. Lyubchik、Martin R. Bryce、Andrei S. Batsanov、Judith A. K. Howard
DOI:10.1039/b103392c
日期:——
Two novel polynitrofluorene acceptors Ï-extended with 5-nitrofuran and 5-nitrothiophene moieties (2 and 3), have been synthesised. Cyclic voltammetry experiments show single electron reduction peaks at ca.
â0.66â0.67 V (vs. Fc/Fc+); however, this process (probably due to substantial changes in geometry of reduced species) is electrochemically irreversible and re-oxidation of the derived radical anions is observed at +0.05 and â0.04 V, for 2 and 3, respectively. Electronic absorption spectroscopy confirms charge transfer complexation of the studied acceptor with 4,5-dimethyltetrathiafulvalene (Me2TTF) in solution. The X-ray crystal structure of the 1Â â¶Â 1 charge transfer complex (CTC) of acceptor 2
with Me2TTF shows mixed Aâ¯Dâ¯Aâ¯D stacking, and its comparison with the structure of the acceptor itself indicates a neutral ground state of this CTC. Theoretical HF/6-31G(d) calculations for the acceptor 2 and its radical anion and dianion states are in agreement with this conclusion. Intramolecular hydrogen bonding in 2 between the oxygen of the furan ring and C(8)-H hydrogen of the fluorene moiety is observed in both solution (1H NMR) and solid state (X-ray) and also supported by theoretical calculations
合成了两种新型聚硝基氟烯受体,这些受体通过5-硝基呋喃和5-硝基噻吩基团进行π-延伸(2和3)。循环伏安实验显示,在约-0.66至-0.67 V(相对于Fc/Fc+)处有单电子还原峰。然而,该过程(可能由于还原物种几何形态的显著变化)是电化学不可逆的,2和3的衍生自由基阴离子的再氧化分别在+0.05 V和-0.04 V处被观察到。电子吸收光谱确认了所研究的受体与4,5-二甲基四硫富瓦烯(Me2TTF)在溶液中形成了电荷转移复合物。受体2与Me2TTF的1:1电荷转移复合物(CTC)的X射线晶体结构显示了混合的A⁻D⁻A⁻D堆叠,并且与受体本身的结构比较表明该CTC具有中性基态。对受体2及其自由基阴离子和二阴离子状态的理论HF/6-31G(d)计算与此结论一致。在2中,呋喃环的氧与氟烯部分的C(8)-H氢之间观察到分子内氢键,这一现象在溶液(1H NMR)和固态(X射线)中均有体现,并且得到了理论计算的支持。