Effects of aldehyde or dipyrromethane substituents on the reaction course leading to meso-substituted porphyrins
摘要:
To better understand the effects of diverse substituents on reactions leading to porphyrins, pyrrole + aldehyde condensations and related reactions of dipyrromethanes were examined. The course of pyrrole + aldehyde condensations was investigated by monitoring the yield of porphyrin (by UV-Vis spectroscopy), reaction of aldehyde (by TLC), and changes in the composition of oligomers (by laser desorption mass spectrometry). Reaction reversibility was examined via exchange experiments. Reversibility of reactions leading to porphyrin was further probed with studies of dipyrromethanes. The reaction course was found to depend on the nature of the substituent and the acid catalyst. Alkyl or electron-donating substituents displayed levels of reversibility (exchange/scrambling) on par or greater than that of the pbenyl substituent, whereas electron-withdrawing or sterically bulky substituents exhibited little to no reversibility. The results obtained provide insight into the electronic and steric effects of different substituents and should facilitate the design of synthetic plans for preparing porphyrinic macrocycles. (C) 2004 Elsevier Ltd. All rights reserved.
efficient synthetic route to unsymmetrically substituted dihydropyridine scaffolds via dehydrative [4 + 2] cycloaddition of N-tosylated α,β-unsaturated imines with aldehydes has been developed. This transformation is enabled by (i) the remarkable catalytic ability of the cationic Ru(IV) porphyrin complex to activate both the imino and carbonyl groups and (ii) the hydrophobic nature of the porphyrin ligand,
that metal-free porphyrins host delocalized pi-electron magnetism as revealed by scanning probe microscopy and different level of theory calculations. Our results demonstrate that engineering of -electron topologies introduces spin polarized singlet state and delocalized net spins in metal-free porphyrins. In addition, the pi-electron magnetism can be switched on/off via STM manipulation by tunning
卟啉大环可以稳定一组磁性金属离子,从而在中心附近引入局部净自旋。然而,在具有广泛意义的卟啉中引入离域自旋仍然是难以捉摸但最理想的,例如,用于构建相关的量子自旋。在这里,我们证明了无金属卟啉承载离域 pi 电子磁性,如扫描探针显微镜和不同水平的理论计算所揭示的。我们的结果表明,π 电子拓扑的工程在无金属卟啉中引入了自旋极化单线态和离域净自旋。此外,可以通过 STM 操作通过调整界面电荷转移来打开/关闭 pi 电子磁性。我们的结果为精确控制无金属卟啉中的π电子磁性提供了一种有效的方法,
Molecular Engineering of Co
<sup>II</sup>
Porphyrins with Asymmetric Architecture for Improved Electrochemical CO
<sub>2</sub>
Reduction
Beauty in balanced asymmetry: An asymmetric CoII porphyrin (as-PorCo) is constructed with a substituent of 2,6-dimethylbenzene to enhance the charge transfer capability from carbon nanotubes to as-PorCo, resulting in large partial current density of 8 mA cm−2 and high turnover frequency of 5656 h−1 at −0.7 V vs. reversible hydrogen electrode in aqueous solution. The present study provides the new insight
平衡不对称之美:不对称Co II卟啉(as -PorCo)由2,6-二甲苯取代基构成,以增强从碳纳米管到as -PorCo的电荷转移能力,产生8 mA cm的大部分电流密度-2和 5656 h -1的高周转频率在 -0.7 V 与水溶液中的可逆氢电极。本研究为高效电化学CO 2还原催化剂的分子设计提供了新的见解。
Improved method for synthesis of substituted tetraphenylporphins