Laboratoire de caractérisation photophysique des matériaux conjugués, Département de Chimie, Université de Montréal , CP 6128, Centre-ville Montreal, QC H3C 3J7, Canada.
J Org Chem. 2013 Sep 20;78(18):9258-69. doi: 10.1021/jo401497z. Epub 2013 Aug 28.
A series of azomethine and vinylene dyad and triad analogues were prepared. Their absorbance, fluorescence, and redox properties were examined experimentally and theoretically using density functional theory (DFT) calculations. These measurements were done to determine the effect of the heteroatom of the azomethine relative to its all-carbon counterpart and to assess the isoelectronic character of the two bonds. The orientation of the azomethine was found to have little effect on the absorbance, fluorescence, and electrochemical properties. In contrast, the spectral and electrochemical properties were highly contingent on the electronic groups and degree of conjugation. The spectral properties could be tuned 200 nm across the visible region. More importantly, the heteroatom in the conjugated bond was found to give rise to only a 20 nm bathochromic shift in the absorbance and fluorescence spectra. The fluorescence quantum yield (ΦFl) of the vinylene derivatives varied between 5% and 20% with fluorescence quenching occurring by photoisomerization from the E to Z isomers. In contrast, the fluorescence of the analogous azomethine derivatives was completely quenched. The collective spectroscopic and electrochemical ab initio DFT data additionally confirmed that the azomethine and its analogous vinylene are isoelectronic. It was also found that a conjugated thiophene vinylene dyad with primary amines in the α,α'-positions could be prepared and isolated. The compound was stable under aerobic conditions providing electron withdrawing (either ester or nitrile) groups were located in the adjacent positions.
一系列的亚甲胺和乙烯基偶联和三联体类似物被制备。使用密度泛函理论（DFT）计算实验和理论上检查了它们的吸收、荧光和氧化还原性质。这些测量是为了确定相对于其全碳对应物的亚甲胺杂原子的影响，并评估两个键的等电子特性。发现亚甲胺的取向对吸收、荧光和电化学性质几乎没有影响。相比之下，光谱和电化学性质高度依赖于电子基团和共轭程度。光谱性质可以在可见区域内调谐 200nm。更重要的是，共轭键中的杂原子仅导致吸收和荧光光谱的红移 20nm。乙烯基衍生物的荧光量子产率（ΦFl）在 5%到 20%之间变化，荧光猝灭是通过从 E 到 Z 异构体的光异构化发生的。相比之下，类似的亚甲胺衍生物的荧光完全猝灭。集体光谱和电化学从头算 DFT 数据还证实，亚甲胺及其类似的乙烯基是等电子的。还发现，在α，α'-位具有伯胺的共轭噻吩乙烯基偶联物可以制备和分离。在相邻位置存在吸电子（酯或腈）基团的情况下，该化合物在有氧条件下稳定。
