organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J.; ...

, chlorins are

tetrapyrrole Tetrapyrroles are a class of chemical compounds that contain four pyrrole or pyrrole-like rings. The pyrrole/pyrrole derivatives are linked by ( =- or -- units), in either a linear or a cyclic fashion. Pyrroles are a five-atom ring with four car ...

pigments that are partially

hydrogenated Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic co ...

porphyrin Porphyrins ( ) are a group of heterocyclic macrocycle organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (=CH−). The parent of porphyrin is porphine, a rare chemical com ...

s. The parent chlorin is an unstable compound which undergoes air oxidation to

porphine Porphine or porphin is an organic chemical compound with formula . The molecule, which is flat, consists of four pyrrole-like rings joined by four methine (= C H−) groups to form a larger macrocycle ring, which makes it the simplest of the tetr ...

. The name chlorin derives from

chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...

. Chlorophylls are magnesium-containing chlorins and occur as photosynthetic pigments in

chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in ...

s. The reduced chlorin variants are present in

bacteriochlorophyll Bacteriochlorophylls (BChl) are photosynthetic pigments that occur in various phototrophic bacteria. They were discovered by C. B. van Niel in 1932. They are related to chlorophylls, which are the primary pigments in plants, algae, and cyanobact ...

s and are named ‘bacteriochlorins’ and ‘isobacteriochlorins’. Porphyrin, chlorin, bacteriochlorins

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 Photodynamic therapy (PDT) is a form of phototherapy involving light and a photosensitizing chemical substance, used in conjunction with molecular oxygen to elicit cell death (phototoxicity). PDT is popularly used in treating acne. It is used cl ...

as photosensitizer.

Chlorophylls

The most abundant chlorin is the

photosynthetic Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in c ...

pigment

. 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 Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

as a central metal atom, replacing the two N''H'' centers in the parent.

Synthetic chlorins

Numerous synthetic chlorins have been examined. Contracted chlorins can be synthesised by reduction of B(III)subporphyrin or by oxidation of corresponding B(III)subbacteriochlorin. 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

References

{{tetrapyrroles Biomolecules Metabolism Tetrapyrroles

Chlorophylls

Synthetic chlorins

See also

Further reading

References