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首页> 外文期刊>Inorganic Chemistry Communications >Substitution effects on the UV-vis and 1H NMR spectra of the dications of meso and/or β substituted porphyrins with trifluoroacetic acid: Electron-deficient porphyrins compared to the electron-rich ones
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Substitution effects on the UV-vis and 1H NMR spectra of the dications of meso and/or β substituted porphyrins with trifluoroacetic acid: Electron-deficient porphyrins compared to the electron-rich ones

机译：三氟乙酸对内消旋和/或β取代的卟啉指示剂的UV-vis和1H NMR谱的取代作用：与富电子的卟啉相比，缺电子的卟啉

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摘要

Spectral shifts upon core protonation of a series of electron-rich and electron-deficient porphyrins with five and six membered rings at the meso-positions have been studied by UV-vis and ~1H NMR spectroscopy. The direction of the shift of the Q(0,0) band of different porphyrins depends on the electron-donating or electron-withdrawing character of the meso-substituent and therefore it may be used to evaluate the relative electron donor ability of the substituents. Also, the shift of the Soret bands was found to be influenced to a lesser extent by the electron donor ability of substituted groups at the porphyrin periphery. Although, large red shifts of the Soret band of H4T(o-NO2)P~(2+), H4T(p-SCH3P)P~(2+) and H4T(p-N02P)P~(2+) indicate a significant out-of-plane deformation of porphyrin core, negligible upfield shifts of the p protons in their 'H NMR spectra show that the practice of using the change in the chemical shift of the β protons as an indicator of structurally induced changes in the porphyrin ring current should be approached with more caution. Interestingly, high level ab initio and DFT calculations demonstrate that in spite of the better electron donating ability of-OCH3 to benzene ring compared to that of-SCH3, meso-(p-SCH3)phenyl group is a deafly better electron donor to the porphyrin core than meso-(p-OCH3)phenyl one.
机译：通过紫外可见光谱和〜1H NMR光谱研究了一系列在中位具有五元和六元环的富电子和缺电子的卟啉的质子化过程中的光谱位移。不同卟啉的Q（0,0）带的移动方向取决于内取代基的给电子或吸电子特性，因此可用于评估取代基的相对给电子能力。而且，发现在卟啉外围的取代基团的电子供体能力在较小程度上影响了Soret带的移动。虽然，H4T（o-NO2）P〜（2 +），H4T（p-SCH3P）P〜（2+）和H4T（p-NO2P）P〜（2+）的Soret谱带出现大的红移表示卟啉核的明显平面外变形，p质子在其1H NMR光谱中的可忽略的高场位移表明，使用β质子化学位移的变化作为卟啉结构上诱导的变化的指标的实践环形电流应更加谨慎。有趣的是，高水平的从头算和DFT计算表明，尽管-OCH3对苯环的电子给体能力比-SCH3强，但内消旋-（p-SCH3）苯基对卟啉的电子给体要好得多核心比内消旋-（p-OCH3）苯基一。

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