Global versus Local Aromaticity in Porphyrinoid Macrocycles: Experimental and Theoretical Study of “Imidacene”, an Imidazole-Containing Analogue of Porphycene
作者:Andrew L. Sargent、Ian C. Hawkins、William E. Allen、Hong Liu、Jonathan L. Sessler、Christopher J. Fowler
DOI:10.1002/chem.200204694
日期:2003.7.7
The synthesis, spectroscopic properties, and computational analysis of an imidazole-based analogue of porphycene are described. The macrocycle, given the trivial name "imidacene", was prepared by reductive coupling of a diformyl-substituted 2,2'-biimidazole using low-valent titanium, followed by treatment with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. Imidacene displays a porphyrin-like electronic
描述了基于咪唑的卟啉类似物的合成、光谱特性和计算分析。大环,俗称“咪并苯”,是通过使用低价钛还原偶联二甲酰基取代的 2,2'-联咪唑,然后用 2,3-dichloro-5,6-dicyano-1 处理来制备的,4-苯醌。根据其 1 H NMR、 1 3 C NMR 和 UV/Vis 光谱特性判断,咪并苯显示出类似卟啉的电子结构。尽管存在环状 18 π 电子通路,但发现咪并苯的二氯甲烷或乙酸乙酯溶液即使在没有光和空气的情况下也会快速分解。进行了一系列高级理论计算,以探究这种不稳定性的根源,揭示了在咪并苯和卟啉中存在离域的 18 n 电子途径比在其还原对应物中的局部芳族 6 n 电子杂环提供更少的芳族稳定能量。咪并苯的还原发生在周边氮原子上,使其能够保持其平面性和两个稳定的分子内氢键,从而将其与卟啉区分开来,更一般地说,与卟啉区分开来。尽管在平面还原形式的咪并苯中同时存在 18 个 π 和 22
Self-Assembled Helices from 2,2′-Biimidazoles
作者:William E. Allen、Christopher J. Fowler、Vincent M. Lynch、Jonathan L. Sessler
2,2'-Biimidazoles were synthesized by palladium(0)-catalyzed coupling of 2-iodoimidazoles bearing an alkyl and an ester group at the 4- and 5-positions, respectively. The products were found to be fluorescent and moderately soluble in organic solvents. Three biimidazoles were subjected to single crystal X-ray diffraction analysis. In all three instances, adjacent molecules were found to be bound together