Expanding the Polymethine Paradigm: Evidence for the Contribution of a Bis-Dipolar Electronic Structure
Expanding the Polymethine Paradigm: Evidence for the Contribution of a Bis-Dipolar Electronic Structure
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DOI：
10.1021/jp501358q
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发表时间：
2014-06-12
影响因子：
2.9
通讯作者：
Maury, Olivier
中科院分区：
文献类型：
--
作者：
Pascal, Simon;Haefele, Alexandre;Maury, Olivier
尽管在少数情况下报道了菁染料的光谱性质强烈地依赖于其中心碳原子的化学取代的性质，但到目前为止还没有任何专门旨在使这一行为合理化的系统研究。本文对中心碳上带有不同取代基的17种多亚胺染料进行了系统的研究，其中一些是为本研究而专门合成的，有些与以前报道的化合物相似，以便于比较。它们的吸收性能分布在整个可见光到近红外光谱范围内，被认为与这种中心取代基的给电子特性有很大关系。通过将这一行为与核磁共振光谱和(振动)TD-DFT计算相关联，我们表明这是由于基态电子构型的深刻改变，即随着中心取代基的供电子性质的增加，中心碳上的阳离子电荷逐渐局域化。
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.