Chlorin
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In organic chemistry, chlorins are tetrapyrrole pigments that are partially hydrogenated porphyrins.<ref>Template:Cite journal</ref> The parent chlorin is an unstable compound which undergoes air oxidation to porphine.<ref>Template:Cite journal</ref> 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.
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.<ref>Template:Cite journal</ref>
ChlorophyllsEdit
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.<ref name="Hand">Template:Cite book</ref>
VariationEdit
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.<ref name=Maqueo>Template:Cite journal</ref> 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.<ref>Template:Cite journal</ref>
Synthetic chlorinsEdit
Numerous synthetic chlorins with different functional groups and/or ring modifications have been examined.<ref>Template:Cite journal</ref>
Contracted chlorins can be synthesised by reduction of B(III)subporphyrin or by oxidation of corresponding B(III)subbacteriochlorin.<ref>Template:Cite journal</ref> 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<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>