Zhu Chongwei, Poater Albert, Duhayon Carine, Kauffmann Brice, Saquet Alix, Maraval Valérie, Chauvin Remi
CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne, BP44099, 31077, Toulouse Cedex 4, France.
Université de Toulouse, UPS, ICT-FR 2599, 31062, Toulouse Cedex 9, France.
Angew Chem Int Ed Engl. 2018 May 14;57(20):5640-5644. doi: 10.1002/anie.201713411. Epub 2018 Apr 23.
Ring carbo-mers of oligo(phenylene ethynylene)s (OPEn, n=0-2), made of C -catenated C carbo-benzene rings, have been synthesized and characterized by NMR and UV-vis spectroscopy, crystallography and voltammetry. Analyses of crystal and DFT-optimized structures show that the C rings preserve their individual aromatic character according to structural and magnetic criteria (NICS indices). Carbo-terphenyls (n=2) are reversibly reduced at ca. -0.42 V/SCE, i.e. 0.41 V more readily than the corresponding carbo-benzene (-0.83 V/SCE), thus revealing efficient inter-ring π-conjugation. An accurate linear fit of E vs. the DFT LUMO energy suggests a notably higher value (-0.30 V/SCE) for a carbo-quaterphenyl congener (n=3). Increase with n of the effective π-conjugation is also evidenced by a red shift of two of the three main visible light absorption bands, all being assigned to TDDFT-calculated excited states, one of them restricting to a HOMO→LUMO main one-electron transition.
由C连接的C碳苯环构成的低聚苯撑乙炔（OPEn，n = 0 - 2）的环状碳聚物已通过核磁共振、紫外可见光谱、晶体学和伏安法进行了合成与表征。晶体结构和密度泛函理论（DFT）优化结构的分析表明，根据结构和磁性标准（核独立化学位移指数），C环保留了其各自的芳香特性。碳代三联苯（n = 2）在约-0.42 V/SCE处可被可逆还原，即比相应的碳苯（-0.83 V/SCE）更容易0.41 V，从而揭示了有效的环间π共轭。E与DFT最低未占分子轨道（LUMO）能量的精确线性拟合表明，碳代四联苯同系物（n = 3）的值明显更高（-0.30 V/SCE）。三个主要可见光吸收带中的两个出现红移也证明了有效π共轭随n的增加，所有这些吸收带都被指定为含时密度泛函理论（TDDFT）计算的激发态，其中一个仅限于HOMO→LUMO主要的单电子跃迁。
