Development of Molecular Switches Based on Molecular Recognition of Organic Dianions

用电化学和光谱电化学结合从头算方法研究了有机π-二价阴离子分子识别的电荷转移络合物形成过程。对氢键系统的循环伏安和光谱行为的详细分析表明，对苯醌二价阴离子（PQ^<2->）形成1：2络合物和1：4络合物在高浓度下通过强的n-σ型CT相互作用形成。HF/6- 31 G（d）计算结果表明，PQ^的结构<2->特征是C=O键的延长和苯环的存在.总之，生物醌的不同功能和性质是通过二价阴离子与其蛋白质环境的氢键作用的n-σ CT相互作用赋予的。基于电生二价阴离子形成π-π型电荷转移络合物的分子间相互作用，对联苯（BP）与氧化还原活性有机分子如四氯苯醌（CL）和TCNE组成的络合物形成体系进行了实验和理论研究。结果表明，BP与TCNE和CL形成氧化还原介导的络合物，其特征为几何构型的改变和颜色的变化。通过氧化还原控制分子间HOMO-LUMO相互作用，调节系统中的相互转换，中性络合物形成，阴离子自由基生成和二价阴离子络合物形成产生三色变化。这是一种利用有机二价阴离子性质的氧化还原介导的络合物形成的原始方法。该结论对于进一步探讨电生π-二价阴离子参与的高度设计的氧化还原介导的识别系统以及利用该识别的分子器件的设计具有重要意义。

Charge-transfer (CT) complex formation based on molecular recognition of organic π-dianions has been investigated by electrochemistry and spectroelectrochemistry combined with ab initio MO calculations. Detailed analyses of the cyclic voltammetric and spectral behaviors for the hydrogen-bonding systems reveal that para-quinone dianions (PQ^<2->) form the 1 : 2 complexes at low concentrations of MeOH and the 1 : 4 complexes at high concentrations by the hydrogen bonding involving strong n-σ type CT interaction. The HF/6-31G (d) calculation results show that the structure of PQ^<2-> is characterized by a lengthening of the C=O bonds and a benzenoid ring. In conclusion, the differing functions and properties of biological quinones are conferred by the n-σ CT interaction through hydrogen bonding of the dianions with their protein environment. The bistable complex formation systems consisting of biphenylene (BP) and redox-active organic molecules such as chloranil (CL) and TCNE have been experimentally and theoretically investigated, based on an intermolecular interaction which characteristically occurs in the electrogenerated dianions forming a π-π type charge-transfer complex. It has been found that BP forms the redox-mediated bistable complexes with TCNE and CL, characterized by the geometrical alteration and the chromatic change. The interconversion in the systems is modulated through redox control of the intermolecular HOMO-LUMO interaction, with trichromic change arising from the neutral complex formation, the anion radical generation, and the dianion complex formation. This is an original approach to the redox-mediated bistable complex formation in terms of use of the properties of organic dianions. The present conclusion is important for extended discussion on generation of highly designed, redox-mediated recognition systems involving the electrogenerated π-dianions and the design of molecular devices utilizing the recognition.