The polymethine concept is known to rationalize a plethora of spectroscopic issues, thus finding wide applications in modern color theory. This approach was questioned by the arguments in the relevant “dye” literature. Based on the critical analysis of these arguments, the errors are clarified and the superiority of the polymethine concept above other attempts to qualitatively explain color and constitution relationships is exemplified at relevant dye molecules absorbing in the visible and near-infrared spectral region. The classical chromophore theory, topological approaches, different-level semiempirical techniques, and DFT/ab initio methods are comparatively analyzed to interpret the optical effects of structural modifications in conjugated compounds regarded as polymethine derivatives.

中文翻译：

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可见光/近红外发色团的聚次甲基性质

众所周知，聚次甲基概念可以合理化大量的光谱问题，从而在现代色彩理论中得到广泛的应用。这种方法受到了相关“染料”文献中论点的质疑。基于对这些论点的批判性分析，澄清了错误，并且在相关染料分子在可见光和近红外光谱区域吸收时，聚次甲基概念相对于定性解释颜色和构成关系的其他尝试的优越性得到了例证。对经典发色团理论、拓扑方法、不同水平的半经验技术和DFT/从头计算方法进行比较分析，以解释作为聚次甲基衍生物的共轭化合物的结构修饰的光学效应。