A Conformational Study of 5,10,15,20-Tetraalkyl-22H+,24H+-porphyrindiium Salts (Dication Salts)
A Conformational Study of 5,10,15,20-Tetraalkyl-22H+,24H+-porphyrindiium Salts (Dication Salts)
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DOI：
10.1515/znb-2000-3-417
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发表时间：
2000
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影响因子：
--
通讯作者：
M. Senge
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文献类型：
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作者：
M. Senge
摘要5，10，15，20-四烷基卟啉与正丁基、异丁基、异丙基、1-乙丙基或叔丁基取代基的N-质子化反应，分别得到了具有高度非平面构象的22，24-二氢卟啉(22H~+，24H~+)。根据中位取代基的空间需求，游离碱卟啉具有平面到中度褶皱的大环(伯烷基或仲烷基残基)或严重褶皱的大环(叔烷基残基)。X-射线结晶学研究表明，卟啉与n-Bu(2)、i-Pr(3)或EtPr(4)取代基质子化导致了核心的空间堵塞，导致对称的、鞍形扭曲的大环，从平均平面的CB位置的平均位移从0.79到1.01？证明了这一点。观察到的这些卟啉二酸的结构与5，10，15，20-四芳基-22H+，24H+-卟啉盐和2，3，7，8，12，13，17，18-octaalkyl-5，10，15，20-tetraaryl-porphyrins.在扭曲方式和非平面度上非常相似相反，高度皱折的5，10，15，20-四(TEA-R-丁基)卟啉的质子化导致构象扭曲模式的切换。图6既显示了鞍形变形(CB位移-1.3？)，也显示了宏观周期的褶皱(约厘米位移。0.48？)。因此，需要在卟啉核心中容纳四个N-H单元及其相关的吡咯环的平面外倾斜和在介观碳原子处诱导的空间应变，从而导致具有混合扭曲模式的高度非平面的卟啉。
Abstract N-protonation of 5,10,15,20-tetraalkylporphyrins with n-butyl, isobutyl, isopropyl, 1-ethyl-propyl or tert-butyl substituents yields the respective 22,24-dihydroporphyrins (22H+,24H+-porphyrindiium salts) that exhibit highly nonplanar conformations. Depending on the steric demand of the meso substituents, the free base porphyrins have planar to moderately ruffled macrocycles (primary or secondary alkyl residues) or are severely ruffled (tertiary alkyl residues). X-ray crystallographic studies show that protonation of porphyrins with n-Bu (2), i-Pr (3) or EtPr (4) substituents leads to steric congestion of the core resulting in symmetric, saddle distorted macrocycles as evidenced by average displacements of the Cb positions from the mean plane ranging from 0.79 to 1.01 Å. The structures observed for these porphyrin diacids are very similar in distortion mode and degree of nonplanarity to 5,10,15,20-tetraaryl-22H+,24H+-porphyrindiium salts and to 2,3,7,8,12,13,17,18-octaalkyl-5,10,15,20-tetraaryl-porphyrins. In contrast, protonation of the highly ruffled 5,10,15,20-tetrakis(teA-r-butyl)porph-yrin results in a switch of the conformational distortion mode. The dication 6 shows both saddle distortion (Cb displacements -1.3 Å) and ruffling of the macrocycle (Cm displacements of approx. 0.48 Å). Thus, the need to accomodate four N-H units in the porphyrin core with its associated out-of-plane tilting of the pyrrole rings and the steric strain induced at the meso carbon atoms results in a highly nonplanar porphyrin with mixed distortion modes.