Pascal Simon, Haefele Alexandre, Monnereau Cyrille, Charaf-Eddin Azzam, Jacquemin Denis, Le Guennic Boris, Andraud Chantal, Maury Olivier
Laboratoire de Chimie, UMR 5182, CNRS, ENS Lyon, Université Lyon 1, 46 Allée d'Italie, 69364 Lyon Cedex 07, France.
J Phys Chem A. 2014 Jun 12;118(23):4038-47. doi: 10.1021/jp501358q. Epub 2014 Jun 2.
Although it has been reported in a few instances that the spectroscopic properties of cyanine dyes were strongly dependent on the nature of the chemical substitution of their central carbon atom, there has not been to date any systematic study specifically aimed at rationalizing this behavior. In this article, such a systematic study is carried out on an extended family of 17 polymethine dyes carrying different substituents on their central carbon, some of those being specifically synthesized for this study, some of those similar to previously reported compounds, for the sake of comparison. Their absorption properties, which spread over the whole visible to near-infrared spectral range, are seen to be dramatically dependent on the electron-donating character of this central substituent. By correlating this behavior to NMR spectroscopy and (vibronic) TD-DFT calculations, we show that it results from a profound modification of the ground state electronic configuration, namely, a progressive localization of the cationic charge on the central carbon as the electron-donating nature of the central substituent is increased.
尽管在少数情况下有报道称，花菁染料的光谱性质强烈依赖于其中心碳原子的化学取代性质，但迄今为止，尚未有专门旨在合理解释这种行为的系统研究。在本文中，针对一个由17种聚甲炔染料组成的扩展系列进行了这样一项系统研究，这些染料在其中心碳原子上带有不同的取代基，其中一些是专门为该研究合成的，一些与先前报道的化合物相似，以便进行比较。它们的吸收特性覆盖了整个可见光到近红外光谱范围，结果发现其极大地依赖于该中心取代基的给电子特性。通过将这种行为与核磁共振光谱和（振子）含时密度泛函理论计算相关联，我们表明这是由于基态电子构型的深刻改变导致的，即随着中心取代基给电子性质的增加，阳离子电荷在中心碳原子上逐渐定位。
