Electronic effects of peripheral substituents at porphyrin meso positions

Yaoqiu Zhu, Richard B. Silverman*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

Porphyrins are stable molecules with a macrocyclic conjugated system and often peripheral substituents. This unique structure makes the electronic properties of the four meso-carbons (the methine bridges) nearly identical. Replacement of the weakly electron-polarizing 2,4-vinyl groups of protoporphyrin IX with strongly electron-polarizing acetyl groups not only leads to much lower meso-carbon reactivities toward electrophilic aromatic substitution but also results in a significant meso-selectivity (the β- and γ-meso- positions become much more nucleophilic (basic) than the α- and δ-meso-positions). To further investigate the relationship between the porphyrin meso-carbon reactivities and the peripheral substituents, two monoacetylporphyrin analogues also were synthesized. This investigation not only leads to empirical rules for predicting porphyrin meso-carbon selectivities but also provides important models for theoretical calculations of porphyrin aromaticity.

Original languageEnglish (US)
Pages (from-to)233-239
Number of pages7
JournalJournal of Organic Chemistry
Volume72
Issue number1
DOIs
StatePublished - Jan 5 2007

ASJC Scopus subject areas

  • Organic Chemistry

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