Editing Chlorin

{{distinguish|chlorine}}
{{Chembox
| Verifiedfields = changed
| Watchedfields  = changed
| verifiedrevid  = 445287858
| ImageFile      = Chlorin.svg
| ImageSize      = 
| IUPACName      = 2,3-Dihydroporphyrin<ref>https://iupac.qmul.ac.uk/tetrapyrrole/TP4.html</ref>
| OtherNames     = 2,3-Dihydroporphine
| Section1       = {{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 58616
| ChEBI_Ref = {{ebicite|changed|EBI}}
| ChEBI = 36303
| InChI = 1/C20H16N4/c1-2-14-10-16-5-6-18(23-16)12-20-8-7-19(24-20)11-17-4-3-15(22-17)9-13(1)21-14/h1-6,9-12,22-23H,7-8H2/b13-9-,14-10-,15-9-,16-10-,17-11-,18-12-,19-11-,20-12-
| InChIKey = UGADAJMDJZPKQX-CEVVSZFKBJ
| CASNo_Ref = {{cascite|correct|??}}
| CASNo=2683-84-3
| PubChem=65106
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C20H16N4/c1-2-14-10-16-5-6-18(23-16)12-20-8-7-19(24-20)11-17-4-3-15(22-17)9-13(1)21-14/h1-6,9-12,22-23H,7-8H2/b13-9-,14-10-,15-9-,16-10-,17-11-,18-12-,19-11-,20-12-
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = UGADAJMDJZPKQX-CEVVSZFKSA-N 
| SMILES = C(N1)(/C=C2N=C(C=C\2)/C=C3N/C(C=C\3)=C\4)=CC=C1/C=C5CCC4=N/5
}}
| Section2       = {{Chembox Properties
| Formula=C<sub>20</sub>H<sub>16</sub>N<sub>4</sub>
| MolarMass=312.36784
| Appearance=
| Density=
| MeltingPt=
| BoilingPt=
| Solubility=
  }}
| Section3       = {{Chembox Hazards
| MainHazards=
| FlashPt=
| AutoignitionPt =
  }}
}}

In [[organic chemistry]], '''chlorins''' are [[tetrapyrrole]] pigments that are partially [[hydrogenation|hydrogenated]] [[porphyrin]]s.<ref>{{cite journal|journal=European Journal of Biochemistry|year=1988|volume=178|issue=2|pages=277–328|title=Nomenclature of Tetrapyrroles. Recommendations 1986|author=Gerard P. Moss|doi=10.1111/j.1432-1033.1988.tb14453.x|pmid=3208761|doi-access=free}}</ref>  The parent chlorin is an unstable compound which undergoes air oxidation to [[porphine]].<ref>{{cite journal |doi=10.1039/b002635m|title=Tetrapyrroles: The pigments of life|year=2000|last1=Battersby|first1=Alan R.|journal=Natural Product Reports|volume=17|issue=6|pages=507–526|pmid=11152419}}</ref> The name chlorin derives from [[chlorophyll]]. Chlorophylls are magnesium-containing chlorins and occur as photosynthetic pigments in [[chloroplast]]s. 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 [[Temoporfin|m-tetrahydroxyphenylchlorin]] (mTHPC) and [[Talaporfin|mono-L-aspartyl chlorin e6]] are effectively employed in experimental [[photodynamic therapy]] as photosensitizer.<ref>{{cite journal|last1=Spikes|first1=John D.|title=New trends in photobiology|journal=Journal of Photochemistry and Photobiology B: Biology|date=July 1990|volume=6|issue=3|pages=259–274|doi=10.1016/1011-1344(90)85096-F|pmid=2120404}}</ref>

==Chlorophylls ==
The most abundant chlorin is the [[Photosynthesis|photosynthetic]] pigment [[chlorophyll]]. Chlorophylls have a fifth, ketone-containing ring unlike the chlorins.  Diverse chlorophylls exists, such as [[Chlorophyll a|chlorophyll ''a'']], [[Chlorophyll b|chlorophyll ''b'']], [[Chlorophyll d|chlorophyll ''d'']], chlorophyll ''e'', [[Chlorophyll f|chlorophyll ''f'']], and chlorophyll ''g''. Chlorophylls usually feature [[magnesium]] as a central metal atom, replacing the two N''H'' centers in the parent.<ref name="Hand">{{cite book |last1=K. Eszter |first1=Borbas |title=Handbook of Porphyrin Science: 181: Chlorins |publisher=worldscientific |doi=10.1142/9789813149564_0001 |isbn=9814322326 }}</ref>

== Variation ==
{{see also|Porphyrin#In nature}}
[[File:Porphyrin, chlorin, bacteriochlorins.png|class=skin-invert-image|440px|thumb|center|Structures comparing [[porphin]], chlorin, bacteriochlorin, and isobacteriochlorin]]

Microbes produce two reduced variants of chlorin, bacteriochlorins and isobacteriochlorins. Bacteriochlorins are found in some [[bacteriochlorophyll]]s; the ring structure is produced by  [[Chlorophyllide a reductase]] (COR) reducing a chlorin ring at the C7-8 double boud.<ref name=Maqueo>{{cite journal |doi=10.1146/annurev.micro.61.080706.093242 |title=Chlorophyll Biosynthesis in Bacteria: The Origins of Structural and Functional Diversity |year=2007 |last1=Chew |first1=Aline Gomez Maqueo |last2=Bryant |first2=Donald A. |journal=Annual Review of Microbiology |volume=61 |pages=113–129 |pmid=17506685 }}</ref> Isobacteriochlorins are found in nature mostly as [[sirohydrochlorin]], a biosynthetic intermediate of [[vitamin B12|vitamin B<sub>12</sub>]], produced without going through a chlorin. In living organisms, both are ultimately derived from [[uroporphyrinogen III]], a near-universal intermediate in tetrapyrrole biosynthesis.<ref>{{cite journal |doi=10.1039/B002635M |title=Tetrapyrroles: The pigments of life: A Millennium review |year=2000 |last1=Battersby |first1=Alan R. |journal=Natural Product Reports |volume=17 |issue=6 |pages=507–526 |pmid=11152419 }}</ref>

== Synthetic chlorins ==
Numerous synthetic chlorins with different functional groups and/or ring modifications have been examined.<ref>{{cite journal |doi=10.1021/acs.chemrev.5b00696|title=Synthetic Chlorins, Possible Surrogates for Chlorophylls, Prepared by Derivatization of Porphyrins|year=2017|last1=Taniguchi|first1=Masahiko|last2=Lindsey|first2=Jonathan S.|journal=Chemical Reviews|volume=117|issue=2|pages=344–535|pmid=27498781|osti=1534468}}</ref>

Contracted chlorins can be synthesised by reduction of B(III)subporphyrin or by oxidation of corresponding B(III)subbacteriochlorin.<ref>{{cite journal |last1=Osuka |first1=Atsuhiro |last2=Kim |first2=Dongho |title=Synthesis and Characterization of meso-Aryl-Substituted Subchlorins |journal=Journal of the American Chemical Society |year=2008 |volume=130 |issue=2 |pages=438–439 |doi=10.1021/ja078042b |pmid=18095693 |url=https://pubs.acs.org/doi/10.1021/ja078042b |archive-date=2021-08-05 |access-date=2021-08-05 |archive-url=https://web.archive.org/web/20210805193601/https://pubs.acs.org/doi/10.1021/ja078042b |url-status=live }}</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>{{cite journal |title=Meso-Free Boron(III)subchlorin and Its μ-Oxo Dimer with Interacting Chromophores |journal=Organic Letters |date=3 Dec 2020 |volume=22 |issue=24 |doi=10.1021/acs.orglett.0c03813 |url=https://pubs.acs.org/doi/full/10.1021/acs.orglett.0c03813|last1=Chandra |first1=Brijesh |last2=Soman |first2=Rahul |last3=Sathish Kumar |first3=B. |last4=Jose |first4=K. V. Jovan |last5=Panda |first5=Pradeepta K. |pages=9735–9739 |pmid=33270460 |s2cid=227282229 }}</ref><ref>{{cite journal |title=A2B- and A3-Type Boron(III)Subchlorins Derived from meso-Diethoxycarbonyltripyrrane: Synthesis and Photophysical Exploration |journal=The Journal of Organic Chemistry |date=15 Jul 2021 |doi=10.1021/acs.joc.1c01001 |url=https://pubs.acs.org/doi/10.1021/acs.joc.1c01001 |last1=Soman |first1=Rahul |last2=Chandra |first2=Brijesh |last3=Bhat |first3=Ishfaq A. |last4=Kumar |first4=B. Sathish |last5=Hossain |first5=Sk Saddam |last6=Nandy |first6=Sridatri |last7=Jose |first7=K. V. Jovan |last8=Panda |first8=Pradeepta K. |volume=86 |issue=15 |pages=10280–10287 |pmid=34264670 |s2cid=235959639 |archive-date=5 August 2021 |access-date=5 August 2021 |archive-url=https://web.archive.org/web/20210805193600/https://pubs.acs.org/doi/10.1021/acs.joc.1c01001 |url-status=live }}</ref>

==See also==
* [[Corrin]]
* [[Photodynamic therapy]]

==Further reading==
*{{cite journal|last1=Juse´lius|first1=Jonas|last2=Sundholm|first2=Dage|title=The aromatic pathways of porphins, chlorins and bacteriochlorins|journal=Physical Chemistry Chemical Physics|date=2000|volume=2|issue=10|pages=2145–2151|doi=10.1039/b000260g|url=https://zenodo.org/record/900813|bibcode=2000PCCP....2.2145J}}

==References==
{{reflist}}

{{tetrapyrroles}}{{Plant pigments}}
[[Category:Biomolecules]]
[[Category:Metabolism]]
[[Category:Tetrapyrroles]]