Quinoidal oligothiophenes: towards biradical ground-state species.
Quinoidal oligothiophenes: towards biradical ground-state species.
复制标题
醌型低聚噻吩：朝向双自由基基态物种。
作者：
Rocío Ponce Ortiz;J. Casado;Sandra Rodríguez González;V. Hernández;J. T. López Navarrete;P. Viruela;E. Ortí;K. Takimiya;T. Otsubo
通过电子和振动光谱、电化学测量和密度泛函计算，广泛地研究了具有稠合双（丁氧基甲基）环戊烷基团的从二聚体到六聚体的醌型寡聚噻吩家族。后者预测，电子基态总是对应于一个单重态，并且，对于最长的低聚物，这种状态具有双自由基的字符，随着低聚物长度的增加而增加。最短的低聚物显示出闭壳层醌型结构。计算还预测存在可以在室温下填充的非常低能量的激发三重态。共轭碳骨架的芳构化是决定基态的双自由基特征增加和低三重态出现的驱动力。紫外/维斯，拉曼，红外光谱和电化学实验支持预测的最长的低聚物的基态的芳香族双自由基的结构，并揭示了人口的低洼三重态占这些化合物所显示的磁性活动。
A family of quinoidal oligothiophenes, from the dimer to the hexamer, with fused bis(butoxymethyl)cyclopentane groups has been extensively investigated by means of electronic and vibrational spectroscopy, electrochemical measurements, and density functional calculations. The latter predict that the electronic ground state always corresponds to a singlet state and that, for the longest oligomers, this state has biradical character that increases with increasing oligomer length. The shortest oligomers display closed-shell quinoidal structures. Calculations also predict the existence of very low energy excited triplet states that can be populated at room temperature. Aromatization of the conjugated carbon backbone is the driving force that determines the increasing biradical character of the ground state and the appearance of low-lying triplet states. UV/Vis, Raman, IR, and electrochemical experiments support the aromatic biradical structures predicted for the ground state of the longest oligomers and reveal that population of the low-lying triplet state accounts for the magnetic activity displayed by these compounds.