Mesoionic

Mesoionic

Mesoionic refers to heterocyclic systems that have chains of odd-numbered V-type atoms separated by X and/or Z-type atoms. These compounds are characterized by their 1,3 dipolar nature and undergo cycloaddition reactions with unsaturated compounds. This term is an alternative definition to the usual one, which was first devised for sydnones.From: Chemical Graph Theory [2019], One-pot synthesis of novel fused mesoionic compounds: 1-substituted-5-thioxo-5,6-dihydro-[1,2,4]triazolo[1,5-c]quinazolin-1-ium-2-thiolates [2020]

Fe Complexes as Photosensitizers for Dye-Sensitized Solar Cells

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Published in Carlito S. Ponseca, Emerging Photovoltaic Technologies, 2019

Yizhu Liu, Kenneth Wärnmark

Compared to normal NHCs, mesoionic NHCs such as 1,2,3-triazolylidene (tz) are more σ-donating due to the compulsory formal negative charge on the ylidene carbon atom in its various resonance structures (Fig. 5.9) as well as a fewer number of inductively electron-withdrawing N atoms immediately surrounding the carbene carbon atom [128, 129]. In addition, less π-stabilization from the adjacent N atoms into the empty pz orbital of the ylidene carbon atom also renders it a better π-acceptor compared to normal NHCs. Both aspects are shown to be beneficial for improving the photophysical properties of FeIIL6 complexes for use as PSs.

One-pot synthesis of novel fused mesoionic compounds: 1-substituted-5-thioxo-5,6-dihydro-[1,2,4]triazolo[1,5-c]quinazolin-1-ium-2-thiolates

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Published in Journal of Sulfur Chemistry, 2020

Sergiy M. Kovalenko, Oleksandr G. Drushlyak, Illia O. Mariutsa

Mesoionic compounds are of interest primarily as synthons for various heterocyclic compound syntheses [41]. Due to their 1,3 dipolar nature, mesoionic compounds undergo cycloaddition reactions with unsaturated compounds. The five-membered ring can be cleaved both hydrolytically and upon the action of nucleophilic reagents [41]. In addition, the sulfur atom can be easily alkylated by the action of alkyl halides [42,43]. However, the chemical behavior of fused mesoionic compounds, especially triazolo[3,2-c]quinazolinium derivatives, is poorly described. The biological activity of fused mesoionic compounds has also not been adequately investigated.

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Fe Complexes as Photosensitizers for Dye-Sensitized Solar Cells

One-pot synthesis of novel fused mesoionic compounds: 1-substituted-5-thioxo-5,6-dihydro-[1,2,4]triazolo[1,5-c]quinazolin-1-ium-2-thiolates