摘要
采用密度泛函方法在(U)B3LYP/6-31G(d,p)水平上对2,2,6,6-四甲基哌啶-1-氧自由基(TEMPO)及其衍生物共12个分子在真空与乙腈中失电子前后的属性进行了量化计算研究.结果表明:不同取代基对次高占据轨道与最低空轨道有明显影响,次高占据轨道的不同情形对分子单电子最高占据轨道(SOMO)中电子的失去与获得产生影响;但各物质的单电子最高占据轨道相似,失电子后这一轨道的组成仍基本保持不变.将自由基分子按取代基连接原子(即按O,N,C)的不同进行分组后,每组内随着取代基吸电子能力的降低:O1,N2上的自旋密度趋于一致,N2的正电荷布居增加,O1的负电荷布居增加,O1—N2键长呈增加趋势,SOMO能量呈升高趋势.失电子后O1—N2键长呈明显的双键特征,超过一半的正电荷增加在了O1,N2上.分析4个以TEMPO及其衍生物作还原介质的染料敏化太阳能电池的开路电压的实验数据发现:开路电压与SOMO能量和电离能呈很好的线性关系.
A theoretical study on the properties of 2,2,6,6-tetramethyl-l-piperidinyloxy （TEMPO） and its derivates and each molecule losing an electron in vacuum and in acetonitrile were carried out using the density functional theory （DFT） at the （U）B3LYP/6-31g（d,p） level. The computational results show that different substituents obviously influence the second highest occupied molecular orbitals and the lowestunoccupied molecular orbitals, but the singly occupied molecular orbitals （SOMO） are similar and keep almost unchanged after each molecule losing an electron. Grouping the derivates by the linking atoms（O,N, C） of substituents shows the orderliness： in each group, with the reduction of electron withdrawing ability, the difference of the spin densities on O1 and N2 decreases, while the positive charge population O2N2, the negative charge population of O1, bond length of O1--N2 and the energy of SOMO increase After losing an electron O1--N2 shows obvious double bond properties and above half positive char increases on O1 and N2. Through the analysis of the open-circuit voltage （Voc） of dye-sensitized solar cell, using the derivates as redox mediator, it was found that the Voc were in linear correlation with SOM（ levels and vertical ionization potentials.
基金
仲恺农业工程学院科研基金(No.G3072708)资助
