Thermodynamics and Photodynamics of a Monoprotonated Porphyrin Directly Stabilized by Hydrogen Bonding with Polar Protic Solvents
Thermodynamics and Photodynamics of a Monoprotonated Porphyrin Directly Stabilized by Hydrogen Bonding with Polar Protic Solvents
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极性质子溶剂氢键直接稳定的单质子化卟啉的热力学和光力学
DOI：
10.1002/chem.201606012
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发表时间：
2017
影响因子：
4.3
通讯作者：
T. Kojima
中科院分区：
文献类型：
--
作者：
W. Suzuki;H. Kotani;T. Ishizuka;K. Ohkubo;Y. Shiota;K. Yoshizawa;S. Fukuzumi;T. Kojima
在10%MeOH（v/v）的存在下，向含有十二苯基卟啉（H2 DPP）的丙酮溶液中加入1当量的TFA，导致选择性地形成单质子化形式（H3 DPP+），这与在不存在MeOH的情况下在丙酮中H2 DPP的质子化直接提供双质子化形式（H4 DPP 2+）形成鲜明对比。MeOH对于选择性H3 DPP+形成的关键作用被解释为H3 DPP+的氢键稳定，因为发现MeOH分子与晶体中H3 DPP+的NH质子形成氢键。通过H3 DPP+的形成产率来评价H3 DPP+形成的选择性，当升高MeOH在丙酮中的部分（0- 10%）时，H3 DPP+的形成产率增加，具有饱和行为，表明H3 DPP+甚至在溶液中通过与MeOH的氢键结合而稳定，连同由基于光谱滴定的范特霍夫图确定的热力学参数。飞秒和纳秒激光闪光光解使我们能够阐明H3 DPP+在分子间光诱导电子转移（ET）中的光动力学，从作为单电子供体的二茂铁衍生物到作为电子受体的H3 DPP+的三重激发态。根据Marcus ET理论评估ET反应的二级速率常数。ET的重组能被确定为1.87 eV，这略大于H4 DPP 2+在乙腈中的重组能（1.69 eV），这是由于ET时的结构变化大于H4 DPP 2+。
Addition of 1 equiv of TFA to an acetone solution containing dodecaphenylporphyrin (H2DPP) in the presence of 10 % MeOH (v/v) resulted in selective formation of a monoprotonated form (H3DPP+), in sharp contrast to protonation of H2DPP directly affording a diprotonated form (H4DPP2+) in acetone in the absence of MeOH. The crucial role of MeOH for selective H3DPP+formation was interpreted as hydrogen‐bonding stabilization of H3DPP+, since a MeOH molecule was found to form hydrogen bonds with an NH proton of H3DPP+in the crystal. The selectivity of H3DPP+formation was evaluated by the formation yield of H3DPP+, which increased when elevating the portion of MeOH (0–10 %) in acetone with saturation behavior, suggesting that H3DPP+is stabilized by hydrogen bonding with MeOH even in solution, together with the thermodynamic parameters determined from a van't Hoff plot based on the spectroscopic titration. Femto‐ and nanosecond laser flash photolysis allowed us to elucidate the photodynamics of H3DPP+in intermolecular photoinduced electron transfer (ET) from ferrocene derivatives as one‐electron donors to the triplet excited state of H3DPP+as an electron acceptor. The second‐order rate constants of the ET reactions were evaluated in light of the Marcus theory of ET. The reorganization energy of ET was determined to be 1.87 eV, which is slightly larger than that of H4DPP2+in acetonitrile (1.69 eV), due to larger structural change upon ET than that of H4DPP2+.