What is quasi-aromaticity?

During my study of aromaticity, I came through this topic of *quasi-aromaticity*. Can you please elaborate what Quasi aromatic compounds are and how are they designated?




In general, we can describe a quasi aromatic compound as a compound, which is ionic in nature with a counter ion, and the $\pi$ electrons in such compounds follow Huckel's rule ($4n+2$).


In other words, quasi aromatic compounds are those in which the charges present on the molecule are a part of aromaticity of the compound. A few examples of such compounds are depicted in the diagram:


[![QuasiAromatic](https://i.stack.imgur.com/QxzQR.jpg)](https://i.stack.imgur.com/QxzQR.jpg)


However, it has a deeper and broader meaning. For a more in-depth explanation, please read the given references.




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**References:**


1. T. M. Krygowski, B. Bankiewicz, Z. Czarnocki, M. Palusiak, “Quasi-aromaticity—what does it mean?” *Tetrahedron* **2015**, *71(30)*, 4895–4908 (<https://doi.org/10.1016/j.tet.2015.05.074>).
2. E. Kleinpeter, A. Koch, “Characterization and quantification of *quasi-aromaticity* by spatial magnetic properties (TSNMRS),” *Tetrahedron* **2015**, *71(33)*, 5275–5284 (<https://doi.org/10.1016/j.tet.2015.06.019>).


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