Corroles

Abstract

This article covers the chemistry of corroles, tetrapyrrole macrocycles having relevance with biologically relevant corrin ring of vitamin B12. Corroles are 18π electron aromatic systems like porphyrin. Despite few similarities, corroles have some major differences with porphyrin. Unlike porphyrin, which is dianionic in nature, the inner N4 coordination core of corroles consists of three amino nitrogens and one imino nitrogen, and thus corroles act as trianionic chelating ligands. Corroles are more acidic than porphyrin. As the corrole core is more compressed than porphyrin, the inner π system is more electron rich. Thus, it can stabilize higher oxidation states of metals. Various interesting spectroscopic properties and wide range of applications make corrole one of the most intriguing macrocycles in the porphyrinoid chemistry.

Photocatalytic C–H Thiocyanation of Corroles: Development of Near-Infrared (NIR)-Emissive Dyes

“…Important crystallographic parameters for 2 are summarized in Table S1. Bond angles and distances of 2 tally well with the previously reported other FB corrole derivatives . The pyrrolic nitrogen atoms deviate from the 19-carbon atom mean corrole plane by distances ranging from 0.189 to (−0.149) Å in 2 .…”

“…However, to our ultimate surprise, we have observed that the photophysical properties are drastically altered in the case of tetrathiocyanatocorroles in comparison to dithiocyanatocorroles. In general, 18 π-electron systems like porphyrins and corroles have strong absorption in the 400–450 nm region, and also, they have much weaker absorption at around 500–650 nm (Q peaks). , However, in the case of tetrathiocyanatocorroles, we have observed strong absorption in the whole visible region of the spectrum with a high molar absorption coefficient. To generalize this photochemical thiocyanation reaction, the substituents at the meso -phenyl rings of corroles are varied from electron-withdrawing groups (−CN [ 2A ], −NO 2 [ 3A ], −F [ 4A ], and −Br [ 5A ]) to electron-donating groups (−OMe [ 6A ]) including the unsubstituted phenyl ring (−H [ 1A ]).…”

“…The obtained fluorescence quantum yields of 1 – 6 were estimated to be 0.07 for 1 , 0.08 for 2 , 0.11 for 4 , 0.10 for 5 , and 0.15 for 6 , respectively. The low-lying singlet excited states of 1 – 6 are responsible for the origin of these kinds of emissive properties …”

“…Porphyrinoids, which will absorb the whole UV–vis region of the spectrum, will have great potential in this regard. Corrole, a contracted version of porphyrin having 18 π-electrons has many similarities with porphyrins . The spectroscopic properties of corroles are similar to those of porphyrin in many aspects. − The triplet state lifetime of corroles is in the range of 10 –4 to 10 –5 s .…”

“…Corrole, a contracted version of porphyrin having 18 π-electrons has many similarities with porphyrins . The spectroscopic properties of corroles are similar to those of porphyrin in many aspects. − The triplet state lifetime of corroles is in the range of 10 –4 to 10 –5 s . Similar to porphyrin, corroles also act as a photosensitizer. , Although there are few examples of porphyrin in photoredox catalysis, similar studies in corroles are still rare.…”