Electric field effect of positive and negative charges of substituents on electronic structure and reactivity of oxoiron(IV) porphyrin pi-cation radical complex
Electric field effect of positive and negative charges of substituents on electronic structure and reactivity of oxoiron(IV) porphyrin pi-cation radical complex
复制标题
取代基正负电荷电场对氧代铁(IV)卟啉阳离子自由基配合物电子结构和反应活性的影响
DOI：
10.1016/j.jinorgbio.2023.112208
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Hiroshi Fujii
中科院分区：
文献类型：
--
作者：
Kanae Yanai;Masahiko Hada;Hiroshi Fujii
活性中心附近的正负变化产生的电场效应是控制金属酶活性的重要因素。在此之前，我们曾报道，由于化合物I中具有吸引电子的库仑相互作用，当时-甲基-2-吡啶阳离子的正电荷增加了氧铁(IV)卟啉阳离子自由基络合物(化合物I)的反应活性。为了进一步研究电场效应，我们用meso-tetrakis(2，4，6-trimethyl-3-sulfonatophenyl)porphyrin的化合物I(π-I)研究了磺酸基的负电荷对电子结构和反应活性的影响。尽管化合物I被认为是一个非常不稳定的络合物，但TMPS-I在0.1M醋酸盐缓冲液中非常稳定，在pH=6.6时，TMPS-I的半衰期估计为6.9×10~3s，是已报道的化合物I中最长的。在pH=0.10的磷酸盐缓冲溶液中，TMPS-I的氧化还原电位为0.76×10~(-1)vsSCE。停流动力学分析表明，TMPS-I的氧化还原活性低于文献报道的化合物I。然而，TMPS-I的~1H核磁共振和EPR谱与我以前报道的化合物非常接近。密度泛函理论计算表明，邻苯基上的正电荷和负电荷使化合物I的轨道能量发生了很大的变化，表明存在电场效应。化合物I的反应性差异可以用正负电荷的分子内电场效应引起的轨道能变化来解释。
Electric field effect by the positive and negative changes near the active site is an important factor for controlling the reactivity of metalloenzymes. Previously, we reported that the positive charge of theN-methyl-2-pyridinium cation increases the reactivity of oxoiron(IV) porphyrin π-cation radical complex (Compound I), due to the attractive Coulomb interaction with electrons in Compound I. To further investigate the electric field effect, we study here the effect of the negative charge of the sulfonate group on the electronic structure and reactivity using Compound I of meso-tetrakis(2,4,6-trimethyl-3-sulfonatophenyl)porphyrin (TMPS-I). Although Compound I has been known as a very unstable complex, TMPS-I is very stable in 0.1 M acetate buffer at pH = 6. The half-life of TMPS-I is estimated to be 6.9 × 103s, which is the longest in Compound I previously reported. The redox potential of TMPS-I is estimated to be 0.76 V vs SCE in phosphate buffer, pH = 10. Kinetic analysis with stopped-flow technique indicates TMPS-I is less reactive than Compounds I reported previously. However,1H NMR and EPR spectra of TMPS-I are very close to those of Compounds I reported previously. The DFT calculations show that the orbital energy of Compound I is drastically altered by the positive and negative charges on themeso-phenyl group, suggesting the electric field effect. The difference of the reactivity of Compound I can be rationalized with the change of the orbital energy caused by the intramolecular electric field effect of the positive and negative charges.