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Published on: July 19, 2019
Meso-Strap Engineering of Aromaticity Redistribution in Porphyrinoids
Meng Ye1, Boyu Xiao1, Ling Xu1
1Key Laboratory of the Assembly and Application of Organic Functional Molecules of Hunan Province, College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha, China.
Meso-strap engineering in porphyrins can alter their aromaticity. Short straps collapse the [18]π circuit, while longer ones preserve it, offering control over aromaticity redistribution in macrocycles.
Area of Science:
- Organic Chemistry
- Supramolecular Chemistry
- Materials Science
Background:
- Porphyrins exhibit highly stable [18]π aromatic circuits, even when distorted.
- Maintaining aromaticity in complex porphyrin derivatives is a significant challenge.
Purpose of the Study:
- To investigate how meso-strap engineering influences aromaticity in porphyrinoids.
- To establish a predictive design principle for controlling aromaticity redistribution.
Main Methods:
- Systematic installation of various meso-straps (tripyrrin, dipyrrylcarbazole, tetrapyrrolic).
- Structural, spectroscopic, and computational analyses.
- Geometric strain and aromatic stabilization energy calculations.
Main Results:
- Short straps induce geometric strain, collapsing the central [18]π porphyrin aromatic circuit.
- Alternative aromatic subunits or nonaromatic cores are generated by short straps.
- Tetrapyrrolic straps preserve porphyrin aromaticity, even in doubly bridged systems.
Conclusions:
- Meso-strap length is critical in determining the fate of aromaticity in porphyrinoids.
- Strain energy versus aromatic stabilization governs conjugation.
- Meso-strap engineering provides a predictive method for controlling aromaticity in macrocycles.
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