Inorganic chemistry, chlorins are tetrapyrrole pigments that are partially hydrogenated porphyrins.[1] The parent chlorin is an unstable compound which undergoes air oxidation to porphine.[2] The name chlorin derives from chlorophyll. Chlorophylls are magnesium-containing chlorins and occur as photosynthetic pigments in chloroplasts. The term "chlorin" strictly speaking refers to only compounds with the same ring oxidation state as chlorophyll.
| |
| Names | |
|---|---|
| Other names
2,3-Dihydroporphine | |
| Identifiers | |
3D model (JSmol) |
|
| ChEBI | |
| ChemSpider |
|
PubChem CID |
|
CompTox Dashboard (EPA) |
|
| |
| |
| Properties | |
| C20H16N4 | |
| Molar mass | 312.36784 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
Chlorins are excellent photosensitizing agents. Various synthetic chlorins analogues such as m-tetrahydroxyphenylchlorin (mTHPC) and mono-L-aspartyl chlorin e6 are effectively employed in experimental photodynamic therapy as photosensitizer.[3]
The most abundant chlorin is the photosynthetic pigment chlorophyll. Chlorophylls have a fifth, ketone-containing ring unlike the chlorins. Diverse chlorophylls exists, such as chlorophyll a, chlorophyll b, chlorophyll d, chlorophyll e, chlorophyll f, and chlorophyll g. Chlorophylls usually feature magnesium as a central metal atom, replacing the two NH centers in the parent.[4]
Microbes produce two reduced variants of chlorin, bacteriochlorins and isobacteriochlorins. Bacteriochlorins are found in some bacteriochlorophylls; the ring structure is produced by Chlorophyllide a reductase (COR) reducing a chlorin ring at the C7-8 double boud.[5] Isobacteriochlorins are found in nature mostly as sirohydrochlorin, a biosynthetic intermediate of vitamin B12, produced without going through a chlorin. In living organisms, both are ultimately derived from uroporphyrinogen III, a near-universal intermediate in tetrapyrrole biosynthesis.[6]
Numerous synthetic chlorins with different functional groups and/or ring modifications have been examined.[7]
Contracted chlorins can be synthesised by reduction of B(III)subporphyrin or by oxidation of corresponding B(III)subbacteriochlorin.[8] The B(III)subchlorins were directly synthesized as meso-ester B(III)subchlorin from meso-diester tripyrromethane, these class of compound showed very good fluorescence quantum yield and singlet oxygen producing efficiency[9][10]
