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首页> 外文期刊>RSC Advances >The influence of protonation on the structure and spectral properties of porphine: UV-vis, H-1 NMR and ab initio studies
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The influence of protonation on the structure and spectral properties of porphine: UV-vis, H-1 NMR and ab initio studies

机译：质子化对卟啉结构和光谱特性的影响：UV-Vis，H-1 NMR和AB Initio研究

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摘要

In this study, protonation of porphine (H2P) with a range of weak and strong acids was investigated. The dication of H2P was water soluble and therefore UV-vis and H-1 NMR studies were performed in water and D2O as well as in dichloromethane and dimethylformamide. In contrast to the dication of other porphyrins, protonated species of H2P were completely decomposed upon evaporation of solvent at room temperature and therefore were studied in solution. Also, high level ab initio calculations were used to predict the structure, frontier molecular orbitals and transition energies of H2P dication. The Soret band of H2P was only slightly shifted to longer or shorter wavelengths in reaction with weak and strong acids, respectively. The results show that the presence of aryl or at least alkyl substituents at the meso positions of porphyrin macrocycle is necessary for the observation of significant red shifts of the Soret band. In the case of the Q(0,0) band, large blue shifts of the band were observed for the dications that correlate with the absence of any pi electron-donating group at the meso position. In H-1 NMR spectra, signals for both the beta and meso protons were shifted downfield, which shows the negligible decrease in the porphine ring current caused by the out-of-plane distortion of the macrocycle. While ab initio calculations show a saddle shaped conformation for [H4P](2+), H4P(CF3COO)(2) was found to adopt an unusual wave conformation that clearly differs from that of previously characterized dications of mesotetra(aryl)-and meso-tetra(alkyl) porphyrins. Also, the calculations on monoprotonated species show that [H3P](+) and H3P(CF3COO) adopt a nearly saddle type and dome shaped conformation, respectively. On the other hand, the energies of absorption bands of H4P(CF3COO)(2) calculated at the TD-B3LYP/cc-pVDZ level of theory predicted the red shift of the Soret band and the blue shift of the Q(0,0) bands that are in accord with the results of UV-vis studies. The results revealed the role played by the acid molecules on the blue shift of the Q(0,0) band of the diprotonated species. Furthermore, the calculated changes in the bond lengths and bond angles show that the involvement of in-plane nuclear reorganization (IPNR) in the observed red shifts of the Soret and Q(0,0) bands cannot be excluded.
机译：在该研究中，研究了具有一系列弱和强酸的卟啉（H2P）的质子化。 H 2P的溶剂是水溶性的，因此在水和D2O以及二氯甲烷和二甲基甲酰胺中进行UV-Vis和H-1 NMR研究。与其他卟啉的二滴定相反，在室温下蒸发溶剂时，对H2P的质子化物种完全分解，因此在溶液中进行了研究。此外，使用高级别AB初始计算来预测H2P DIPT的结构，前沿分子轨道和转变能量。 H2P的SORET带分别仅略微移位到与弱和强酸反应的更长或更短的波长。结果表明，在卟啉宏循环的中间位置处存在芳基或至少烷基取代基对于观察Soret带的显着红色偏移是必要的。在Q（0,0）带的情况下，对于在MESO位置不存在任何PI电子给予基团的情况下，观察到带的大的蓝色偏移。在H-1 NMR光谱中，β和Meso质子的信号移位下场，其表示由宏循环的面外变形引起的卟啉环电流的可忽略不计。虽然AB初始计算显示[H4P]（2+）的鞍形构象，但发现H4P（CF3COO）（2）被发现采用异常的波形构象，从而清楚地不同于先前表征的Mesotetro（芳基） - 和Meso的标准-tetra（烷基）卟啉。此外，对单议议性物种的计算表明，[H3P]（+）和H3P（CF3COO）分别采用了几乎鞍型和圆顶形构象。另一方面，在TD-B3LYP / CC-PVDZ理论下计算的H4P（CF3COO）（2）的吸收带的能量预测了SORET带的红色偏移和Q的蓝色偏移（0,0 ）符合UV-VIS研究结果的乐队。结果表明，酸分子在曲调物种Q（0,0）带的蓝色偏移上的作用。此外，键合长度和键角的计算变化表明，不能排除在观察到的索引和Q（0,0）带的观察到的红色移位中的面内核重组（IPNR）的参与。

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  • 来源
    《RSC Advances》 |2016年第85期|共8页
  • 作者

    Zakavi Saeed; Omidyan Reza; Talebzadeh Sadegh;

  • 作者单位

    Inst Adv Studies Basic Sci Dept Chem Zanjan 4513766731 Iran;

    Univ Isfahan Dept Chem Esfahan 8174673441 Iran;

    Inst Adv Studies Basic Sci Dept Chem Zanjan 4513766731 Iran;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 化学;
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