Editing Porphyrin

{{Short description|Heterocyclic organic compound with four modified pyrrole subunits}}
{{Distinguish|Perforin|Porphyran}}
[[File:Porphyrin.svg|thumb|right|class=skin-invert-image|[[Porphine]], the parent of porphyrin]]
{{Use dmy dates|date=May 2022}}

'''Porphyrins''' ({{IPAc-en|ˈ|p|ɔːr|f|ər|ɪ|n|s}} {{respell|POR|fər|ins}}) are a group of [[heterocyclic compound|heterocyclic]], [[macrocyclic]], [[organic compound]]s, composed of four modified [[pyrrole]] subunits interconnected at their [[Alpha and beta carbon|α carbon]] atoms via [[methine]] bridges ({{chem2|\dCH\s}}). In [[vertebrate]]s, an essential member of the porphyrin group is [[heme]], which is a component of [[hemoprotein]]s, whose functions include carrying [[oxygen]] in the [[Circulatory system|bloodstream]]. In [[plants]], an essential porphyrin derivative is [[chlorophyll]], which is involved in [[light-harvesting complex|light harvesting]] and [[electron transfer]] in [[photosynthesis]].

The parent of porphyrins is [[porphine]], a rare chemical compound of exclusively theoretical interest. Substituted porphines are called porphyrins.<ref>{{cite journal |doi= 10.1021/acs.chemrev.6b00299|title= Energy-Related Small Molecule Activation Reactions: Oxygen Reduction and Hydrogen and Oxygen Evolution Reactions Catalyzed by Porphyrin- and Corrole-Based Systems|date= 2017|last1= Zhang|first1= Wei|last2= Lai|first2= Wenzhen|last3= Cao|first3= Rui|journal= Chemical Reviews|volume= 117|issue= 4|pages= 3717–3797|pmid= 28222601}}</ref> With a total of 26 π-electrons the porphyrin ring structure is often described as [[aromaticity|aromatic]].<ref>{{cite journal|author-link1=Timothy D. Lash | vauthors = Lash TD |journal= Journal of Porphyrins and Phthalocyanines |volume= 15 |issue= 11n12 |pages= 1093–1115 |year= 2011 |doi= 10.1142/S1088424611004063 |title= Origin of aromatic character in porphyrinoid systems }}</ref> One result of the large [[conjugated system]] is that porphyrins absorb strongly in the visible region of the electromagnetic spectrum, i.e. they are deeply colored. The name "porphyrin" derives {{ety|el|''πορφύρα'' (porphyra)|purple}}.<ref>{{cite web| vauthors = Harper D, Buglione DC |title=porphyria (n.)|url=http://www.etymonline.com/index.php?allowed_in_frame=0&search=porphyrin&searchmode=none|website=The Online Etymology Dictionary|access-date=14 September 2014}}</ref>

==Structure==

[[Porphyrin complexes]] consist of a square planar MN<sub>4</sub> core.  The periphery of the porphyrins, consisting of sp<sup>2</sup>-hybridized carbons, generally display small deviations from planarity.  "Ruffled" or saddle-shaped porphyrins is attributed to interactions of the system with its environment.<ref>{{cite journal | vauthors = Senge MO, MacGowan SA, O'Brien JM | title = Conformational control of cofactors in nature - the influence of protein-induced macrocycle distortion on the biological function of tetrapyrroles | journal = Chemical Communications | volume = 51 | issue = 96 | pages = 17031–17063 | date = December 2015 | pmid = 26482230 | doi = 10.1039/C5CC06254C | hdl-access = free | hdl = 2262/75305 }}</ref>  Additionally, the metal is often not centered in the N<sub>4</sub> plane.<ref>{{cite book |doi=10.1002/9781119951438.eibc0104 |chapter=Iron Porphyrin Chemistry |title=Encyclopedia of Inorganic and Bioinorganic Chemistry |year=2011 | vauthors = Walker FA, Simonis U |isbn=9781119951438 }}</ref>  For free porphyrins, the two pyrrole protons are mutually trans and project out of the N<sub>4</sub> plane.<ref> {{cite journal | vauthors = Jentzen W, Ma JG, Shelnutt JA | title = Conservation of the conformation of the porphyrin macrocycle in hemoproteins | journal = Biophysical Journal | volume = 74 | issue = 2 Pt 1 | pages = 753–763 | date = February 1998 | pmid = 9533688 | pmc = 1302556 | doi = 10.1016/S0006-3495(98)74000-7 | bibcode = 1998BpJ....74..753J }}</ref> These nonplanar distortions are associated with altered chemical and physical properties. [[Chlorophyll]]-rings are more distinctly nonplanar, but they are more saturated than porphyrins.<ref>{{Cite journal | vauthors = Senge MO, Ryan AA, Letchford KA, MacGowan SA, Mielke T | year = 2014 | title = Chlorophylls, Symmetry, Chirality, and Photosynthesis | journal = Symmetry | volume = 6 | issue = 3 | pages = 781–843 | doi = 10.3390/sym6030781 | bibcode = 2014Symm....6..781S | doi-access = free | hdl = 2262/73843 | hdl-access = free }}</ref>

==Complexes of porphyrins==
{{main|Transition metal porphyrin complexes}}
Concomitant with the displacement of two N-''H'' protons, porphyrins bind metal ions in the N4 "pocket". The metal [[ion]] usually has a charge of 2+ or 3+. A schematic equation for these syntheses is shown, where M = metal ion and L = a [[ligand]]:
:{{chem2|H2porphyrin + [ML_{''n''}](2+) -> M(porphyrinate)L_{''n''−4} + 4 L + 2 H+}}


<gallery class="skin-invert-image" caption="Representative porphyrins and derivatives" widths="140px" heights="140px">
File:PPIXtransH.png|Derivatives of [[protoporphyrin IX]] are common in nature, the precursor to [[heme]]s.
File:H2octaethylporphyrin.png |[[Octaethylporphyrin]] (H<sub>2</sub>OEP) is a synthetic analogue of protoporphyrin IX. Unlike the natural porphyrin ligands, OEP<sup>2−</sup> is highly symmetrical.
File:H2TPP.png|[[Tetraphenylporphyrin]] (H<sub>2</sub>TPP)is another synthetic analogue of protoporphyrin IX. Unlike the natural porphyrin ligands, TPP<sup>2−</sup> is highly symmetrical. Another difference is that its methyne centers are occupied by phenyl groups.
File:Heme B.svg|Simplified view of [[heme]], a complex of a protoporphyrin IX.
CP40model.png|A nanoring of 40 porphyrin molecules, model
CP40-STM.png|A nanoring of 40 porphyrin molecules, [[scanning tunneling microscope|STM image]]
</gallery>

==Ancient porphyrins==
A geoporphyrin, also known as a petroporphyrin, is a porphyrin of geologic origin.<ref name=handbook>{{cite book|title=The Porphyrin Handbook|publisher=[[Elsevier]]|isbn=9780123932006|url=https://books.google.com/books?id=Ci7rIe0Ohn8C&pg=PA381| veditors = Kadish KM |page=381|date=1999}}</ref> They can occur in [[crude oil]], [[oil shale]], coal, or sedimentary rocks.<ref name=handbook/><ref>{{cite journal| vauthors = Zhang B, Lash TD |title=Total synthesis of the porphyrin mineral abelsonite and related petroporphyrins with five-membered exocyclic rings|journal=Tetrahedron Letters|date=September 2003|volume=44|issue=39|page=7253|doi=10.1016/j.tetlet.2003.08.007}}</ref> [[Abelsonite]] is possibly the only geoporphyrin mineral, as it is rare for porphyrins to occur in isolation and form crystals.<ref>{{cite journal| vauthors = Mason GM, Trudell LG, Branthaver JF |title=Review of the stratigraphic distribution and diagenetic history of abelsonite|journal=Organic Geochemistry|year=1989|volume=14|issue=6|page=585|doi=10.1016/0146-6380(89)90038-7|bibcode=1989OrGeo..14..585M }}</ref>

The field of [[organic geochemistry]] had its origins in the isolation of porphyrins from petroleum.  These findings helped establish the biological origins of petroleum.<ref>Kvenvolden, Keith A. (2006). "Organic geochemistry – A retrospective of its first 70 years". Organic Geochemistry. 37: 1–11. doi:10.1016/j.orggeochem.2005.09.001</ref><ref>Treibs, A.E. (1936). "Chlorophyll- und Häminderivate in organischen Mineralstoffen". Angewandte Chemie. 49: 682–686. doi:10.1002/ange.19360493803</ref> Petroleum is sometimes "fingerprinted" by analysis of trace amounts of nickel and [[vanadyl]] porphyrins. Metalloporphyrins in general are highly stable organic compounds, and the detailed structures of the extracted derivatives made clear that they originated from chlorophyll.

==Biosynthesis==
In non-photosynthetic [[eukaryotes]] such as animals, insects, fungi, and [[protozoa]], as well as the α-proteobacteria group of bacteria, the [[committed step]] for porphyrin [[biosynthesis]] is the formation of [[Aminolevulinic acid|δ-aminolevulinic acid]] (δ-ALA, 5-ALA or dALA) by the reaction of the [[amino acid]] [[glycine]] with [[succinyl-CoA]] from the [[citric acid cycle]]. In [[plants]], [[algae]], [[bacteria]] (except for the α-proteobacteria group) and [[archaea]], it is produced from [[glutamic acid]] via glutamyl-tRNA and [[glutamate-1-semialdehyde]]. The enzymes involved in this pathway are [[Aminoacyl tRNA synthetases, class I|glutamyl-tRNA synthetase]], [[glutamyl-tRNA reductase]], and [[glutamate-1-semialdehyde 2,1-aminomutase]]. This pathway is known as the C5 or Beale pathway.

Two molecules of dALA are then combined by [[porphobilinogen synthase]] to give [[porphobilinogen]] (PBG), which contains a pyrrole ring. Four PBGs are then combined through [[deamination]] into [[hydroxymethyl bilane]] (HMB), which is [[hydrolysation|hydrolysed]] to form the circular tetrapyrrole [[uroporphyrinogen III]]. This molecule undergoes a number of further modifications. Intermediates are used in different species to form particular substances, but, in humans, the main end-product [[protoporphyrin IX]] is combined with iron to form heme. Bile pigments are the breakdown products of heme.

The following scheme summarizes the biosynthesis of porphyrins, with references by EC number and the [[OMIM]] database. The [[porphyria]] associated with the deficiency of each enzyme is also shown:

[[File:Heme-Synthesis-Chemical-Details-Mirror.svg|thumb|center|class=skin-invert-image|600 px|Heme B biosynthesis pathway and its modulators. Major enzyme deficiences are also shown.]]

{| class="wikitable"
!| [[Enzyme]]
!| Location
!| [[Substrate (biochemistry)|Substrate]]
!| Product
!| [[Chromosome]]
!| [[Enzyme Commission number|EC]]
!| [[OMIM]]
!| [[Disorder (medicine)|Disorder]]
|-
| [[ALA synthase]]
| Mitochondrion
| [[Glycine]], [[succinyl CoA]]
| δ-Aminolevulinic acid
| 3p21.1
| [http://www.expasy.org/cgi-bin/nicezyme.pl?2.3.1.37 2.3.1.37]
| [https://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=125290 125290]
| X-linked dominant protoporphyria, X-linked [[sideroblastic anemia]]
|-
| [[ALA dehydratase]]
| Cytosol
| [[Aminolevulinic acid|δ-Aminolevulinic acid]]
| Porphobilinogen
| 9q34
| [http://www.expasy.org/cgi-bin/nicezyme.pl?4.2.1.24 4.2.1.24]
| [https://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=125270 125270]
| [[aminolevulinic acid dehydratase deficiency porphyria]]
|-
| [[porphobilinogen deaminase|PBG deaminase]]
| Cytosol
| [[Porphobilinogen]]
| Hydroxymethyl bilane
| 11q23.3
| [http://www.expasy.org/cgi-bin/nicezyme.pl?2.5.1.61 2.5.1.61]
| [https://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=176000 176000]
| [[acute intermittent porphyria]]
|-
| [[Uroporphyrinogen III synthase]]
| Cytosol
| [[Hydroxymethyl bilane]]
| Uroporphyrinogen III
| 10q25.2-q26.3
| [http://www.expasy.org/cgi-bin/nicezyme.pl?4.2.1.75 4.2.1.75]
| [https://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=606938 606938]
| [[congenital erythropoietic porphyria]]
|-
| [[Uroporphyrinogen III decarboxylase]]
| Cytosol
| [[Uroporphyrinogen III]]
| Coproporphyrinogen III
| 1p34
| [http://www.expasy.org/cgi-bin/nicezyme.pl?4.1.1.37 4.1.1.37]
| [https://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=176100 176100]
| [[porphyria cutanea tarda]], [[hepatoerythropoietic porphyria]]
|-
| [[Coproporphyrinogen III oxidase]]
| Mitochondrion
| [[Coproporphyrinogen III]]
| Protoporphyrinogen IX
| 3q12
| [http://www.expasy.org/cgi-bin/nicezyme.pl?1.3.3.3 1.3.3.3]
| [https://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=121300 121300]
| [[hereditary coproporphyria]]
|-
| [[Protoporphyrinogen oxidase]]
| Mitochondrion
| [[Protoporphyrinogen IX]]
| Protoporphyrin IX
| 1q22
| [http://www.expasy.org/cgi-bin/nicezyme.pl?1.3.3.4 1.3.3.4]
| [https://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=600923 600923]
| [[variegate porphyria]]
|-
| [[Ferrochelatase]]
| Mitochondrion
| [[Protoporphyrin IX]]
| Heme
| 18q21.3
| [http://www.expasy.org/cgi-bin/nicezyme.pl?4.99.1.1 4.99.1.1]
| [https://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=177000 177000]
| [[erythropoietic protoporphyria]]
|}

==Laboratory synthesis==
{{main|Rothemund reaction}}
[[Image:Tetratolylporphyrin.jpg|thumb|right|Brilliant crystals of ''meso''-tetratolylporphyrin, prepared from [[4-methylbenzaldehyde]] and pyrrole in refluxing [[propionic acid]]]]
A common synthesis for porphyrins is the [[Rothemund reaction]], first reported in 1936,<ref>{{cite journal | vauthors = Rothemund P | title = A New Porphyrin Synthesis. The Synthesis of Porphin | year = 1936 | journal = [[J. Am. Chem. Soc.]] | volume = 58 | issue = 4 | pages = 625–627 | doi = 10.1021/ja01295a027| bibcode = 1936JAChS..58..625R }}</ref><ref>{{cite journal | vauthors = Rothemund P | title = Formation of Porphyrins from Pyrrole and Aldehydes | year = 1935 | journal = J. Am. Chem. Soc. | volume = 57 | issue = 10 | pages = 2010–2011 | doi=10.1021/ja01313a510| bibcode = 1935JAChS..57.2010R }}</ref> which is also the basis for more recent methods described by Adler and Longo.<ref>{{cite journal | vauthors = Adler AD, Longo FR, Finarelli JD, Goldmacher J, Assour J, Korsakoff L | title = A simplified synthesis for ''meso''-tetraphenylporphine | year = 1967 | journal = [[J. Org. Chem.]] | volume = 32 | issue = 2 | pages = 476 | doi = 10.1021/jo01288a053}}</ref> The general scheme is a [[condensation reaction|condensation]] and [[organic oxidation reaction|oxidation]] process starting with pyrrole and an [[aldehyde]].

:[[Image:H2TPPsyn.png|class=skin-invert-image|400px]]

{{-}}

==Potential applications==
===Photodynamic therapy===
Porphyrins have been evaluated in the context of [[photodynamic therapy]] (PDT) since they strongly absorb light, which is then converted to heat in the illuminated areas.<ref>{{cite encyclopedia|title=Porphyrin conjugates for cancer therapy| vauthors = Giuntini F, Boyle R, Sibrian-Vazquez M, Vicente MG | veditors = Kadish KM, Smith KM, Guilard R |encyclopedia=Handbook of Porphyrin Science|year=2014|volume=27|pages=303–416}}</ref> This technique has been applied in [[macular degeneration]] using [[verteporfin]].<ref name="pmid17636693">{{cite journal | vauthors = Wormald R, Evans J, Smeeth L, Henshaw K | title = Photodynamic therapy for neovascular age-related macular degeneration | journal = The Cochrane Database of Systematic Reviews | issue = 3 | pages = CD002030 | date = July 2007 | pmid = 17636693 | doi = 10.1002/14651858.CD002030.pub3 | url = https://researchonline.lshtm.ac.uk/id/eprint/6367/1/Wormald_et_al-2007-The_Cochrane_library.pdf }}</ref>

PDT is considered a noninvasive cancer treatment, involving the interaction between light of a determined frequency, a photo-sensitizer, and oxygen. This interaction produces the formation of a highly reactive oxygen species (ROS), usually singlet oxygen, as well as superoxide anion, free hydroxyl radical, or hydrogen peroxide.<ref>{{cite journal | vauthors = Price M, Terlecky SR, Kessel D | title = A role for hydrogen peroxide in the pro-apoptotic effects of photodynamic therapy | journal = Photochemistry and Photobiology | volume = 85 | issue = 6 | pages = 1491–1496 | year = 2009 | pmid = 19659920 | pmc = 2783742 | doi = 10.1111/j.1751-1097.2009.00589.x }}</ref> These high reactive oxygen species react with susceptible cellular organic biomolecules such as; lipids, aromatic amino acids, and nucleic acid heterocyclic bases, to produce oxidative radicals that damage the cell, possibly inducing apoptosis or even necrosis.<ref>{{cite journal | vauthors = Singh S, Aggarwal A, Bhupathiraju NV, Arianna G, Tiwari K, Drain CM | title = Glycosylated Porphyrins, Phthalocyanines, and Other Porphyrinoids for Diagnostics and Therapeutics | journal = Chemical Reviews | volume = 115 | issue = 18 | pages = 10261–10306 | date = September 2015 | pmid = 26317756 | pmc = 6011754 | doi = 10.1021/acs.chemrev.5b00244 }}</ref>

===Molecular electronics and sensors===
Porphyrin-based compounds are of interest as possible components of [[molecular electronics]] and photonics.<ref>{{cite journal | vauthors = Lewtak JP, Gryko DT | title = Synthesis of π-extended porphyrins via intramolecular oxidative coupling | journal = Chemical Communications | volume = 48 | issue = 81 | pages = 10069–10086 | date = October 2012 | pmid = 22649792 | doi = 10.1039/c2cc31279d }}</ref> Synthetic porphyrin dyes have been incorporated in prototype [[dye-sensitized solar cells]].<ref>{{cite journal | journal = [[Journal of Porphyrins and Phthalocyanines]] | year = 2010 | volume = 14 | pages = 759–792 | doi= 10.1142/S1088424610002689 | title = Porphyrins and phthalocyanines in solar photovoltaic cells | vauthors = Walter MG, Rudine AB, Wamser CC | issue = 9}}</ref><ref>{{cite journal | vauthors = Yella A, Lee HW, Tsao HN, Yi C, Chandiran AK, Nazeeruddin MK, Diau EW, Yeh CY, Zakeeruddin SM, Grätzel M | display-authors = 6 | title = Porphyrin-sensitized solar cells with cobalt (II/III)-based redox electrolyte exceed 12 percent efficiency | journal = Science | volume = 334 | issue = 6056 | pages = 629–634 | date = November 2011 | pmid = 22053043 | doi = 10.1126/science.1209688 | bibcode = 2011Sci...334..629Y | s2cid = 28058582 }}</ref>

=== Biological applications ===
Porphyrins have been investigated as possible anti-inflammatory agents<ref>{{cite journal | vauthors = Alonso-Castro AJ, Zapata-Morales JR, Hernández-Munive A, Campos-Xolalpa N, Pérez-Gutiérrez S, Pérez-González C | title = Synthesis, antinociceptive and anti-inflammatory effects of porphyrins | journal = Bioorganic & Medicinal Chemistry | volume = 23 | issue = 10 | pages = 2529–2537 | date = May 2015 | pmid = 25863493 | doi = 10.1016/j.bmc.2015.03.043 }}</ref> and evaluated on their anti-cancer and anti-oxidant activity.<ref>{{cite journal | vauthors = Bajju GD, Ahmed A, Devi G | title = Synthesis and bioactivity of oxovanadium(IV)tetra(4-methoxyphenyl)porphyrinsalicylates | journal = BMC Chemistry | volume = 13 | issue = 1 | pages = 15 | date = December 2019 | pmid = 31384764 | pmc = 6661832 | doi = 10.1186/s13065-019-0523-9 | doi-access = free }}</ref> Several porphyrin-peptide conjugates were found to have antiviral activity against HIV ''in vitro''.<ref>{{cite journal | vauthors = Mendonça DA, Bakker M, Cruz-Oliveira C, Neves V, Jiménez MA, Defaus S, Cavaco M, Veiga AS, Cadima-Couto I, Castanho MA, Andreu D, Todorovski T | display-authors = 6 | title = Penetrating the Blood-Brain Barrier with New Peptide-Porphyrin Conjugates Having anti-HIV Activity | journal = Bioconjugate Chemistry | volume = 32 | issue = 6 | pages = 1067–1077 | date = June 2021 | pmid = 34033716 | pmc = 8485325 | doi = 10.1021/acs.bioconjchem.1c00123 }}</ref>

=== Toxicology ===
Heme biosynthesis is used as [[biomarker]] in environmental toxicology studies. While excess production of porphyrins indicate [[organochlorine]] exposure, [[lead]] inhibits [[ALA dehydratase]] enzyme.<ref>{{Cite book|title=Principles of Ecotoxicology| vauthors = Walker CH, Silby RM, Hopkin SP, Peakall DB |publisher=CRC Press|year=2012|isbn=978-1-4665-0260-4|location=Boca Raton, FL|pages=182}}</ref>

==Gallery==
<gallery class="skin-invert-image">
File:H2TPP.png|Lewis structure for ''meso''-tetraphenylporphyrin
File:Meso-tetraphenylporphyrin UV-vis.JPG|[[Ultraviolet–visible spectroscopy|UV–vis]] readout for ''meso''-tetraphenylporphyrin
File:Porfirina activada con la luz.svg|Light-activated porphyrin. Monatomic oxygen. Cellular aging
</gallery>

{{-}}

==Related species==
===In nature===

Several heterocycles related to porphyrins are found in nature, almost always bound to metal ions. These include
{| class="wikitable"
! N4-macrocycle !! Cofactor name!! metal!! comment
|-
|[[chlorin]]|| chlorophyll || magnesium||several versions of chlorophyll exist (sidechain; exception being [[chlorophyll c]])
|-
|bacteriochlorin|| [[bacteriochlorophyll]] (in part) || magnesium|||several versions of bacteriochlorophyll exist (sidechain; some use a usual chlorin ring)
|-
| rowspan="2" | [[sirohydrochlorin]] (an isobacteriochlorin)||[[siroheme]]||iron||Important cofactor in sulfur assimilation
|-
|
|
|biosynthetic intermediate en route to cofactor F430 and B12
|-
| [[corrin]] || vitamin B12 || cobalt||several variants of B12 exist (sidechain)
|-
| corphin || [[Cofactor F430]] || nickel||highly reduced macrocycle
|}

===Synthetic===
A '''benzoporphyrin''' is a porphyrin with a benzene ring fused to one of the pyrrole units. e.g. [[verteporfin]] is a benzoporphyrin derivative.<ref name=Scott2000>{{cite journal | vauthors = Scott LJ, Goa KL | title = Verteporfin | journal = Drugs & Aging | volume = 16 | issue = 2 | pages = 139–146; discussion 146–8 | date = February 2000 | pmid = 10755329 | doi = 10.2165/00002512-200016020-00005 | s2cid = 260491296 }}</ref>

====Non-natural porphyrin isomers====
[[File:First Porphycene synthesis.tif|thumb|class=skin-invert-image|Porphycene, first porphyrin isomer, synthesised from bipyrrole dialdehyde through [[McMurry reaction|McMurry coupling reaction]]]]

The first synthetic porphyrin [[isomer]] was reported by Emanual Vogel and coworkers in 1986.<ref>{{cite journal | vauthors = Vogel E, Köcher M |title=Porphycene—a Novel Porphin Isomer |journal=Angewandte Chemie |date=March 1986 |volume=25 |issue=3 |page=257 |doi=10.1002/anie.198602571 }}</ref>  This isomer [18]porphyrin-(2.0.2.0) is named as '''porphycene''', and the central N<sub>4</sub> Cavity forms a [[rectangle]] shape as shown in figure.<ref>{{cite journal | vauthors = Nagamaiah J, Dutta A, Pati NN, Sahoo S, Soman R, Panda PK |title=3,6,13,16-Tetrapropylporphycene: Rational Synthesis, Complexation, and Halogenation |journal=The Journal of Organic Chemistry |date=March 2022 |volume=87 |issue=5 |pages=2721–2729 |doi=10.1021/acs.joc.1c02652 |pmid=35061396 |s2cid=246165814 }}</ref> Porphycenes showed interesting [[Photochemistry|photophysical]] behavior and found versatile compound towards the [[photodynamic therapy]].<ref>{{cite journal | vauthors =  Dougherty TJ |title=Basic principles of photodynamic therapy |journal=Journal of Porphyrins and Phthalocyanines  |date=2001 |volume=5 |issue=2 |page=105 |doi=10.1002/jpp.328 }}</ref> This result was followed by the preparation of [18]porphyrin-(2.1.0.1), named it as '''corrphycene''' or '''porphycerin'''.<ref>{{cite journal | vauthors = Vogel E, Guilard R |title=New Porphycene Ligands: Octaethyl- and Etioporphycene (OEPc and EtioPc)—Tetra- and Pentacoordinated Zinc Complexes of OEPc |journal=Angewandte Chemie International Edition |date=November 1993 |volume=32 |issue=11 |page=1600 |doi=10.1002/anie.199316001 }}</ref> Other non-natural porphyrins include [18]porphyrin-(2.1.1.0) and  [18]porphyrin-(3.0.1.0) or '''isoporphycene'''.<ref>{{cite journal | vauthors = Vogel E, Scholz P, Demuth R, Erben C, Bröring M, Schmickler H, Lex J, Hohlneicher G, Bremm D, Wu YD | display-authors = 6 | title = Isoporphycene: The Fourth Constitutional Isomer of Porphyrin with an N(4) Core-Occurrence of E/Z Isomerism | journal = Angewandte Chemie | volume = 38 | issue = 19 | pages = 2919–2923 | date = October 1999 | pmid = 10540393 | doi = 10.1002/(SICI)1521-3773(19991004)38:19<2919::AID-ANIE2919>3.0.CO;2-W }}</ref> The '''N-confused porphyrins''' feature one of the pyrrolic subunits with the nitrogen atoms facing outwards from the core of the macrocycle.<ref>{{cite journal | vauthors = Hiroyuki F |title="N-Confused Porphyrin": A New Isomer of Tetraphenylporphyrin |journal=J. Am. Chem. Soc. |year=1994 |volume=116 |issue=2 |page=767 |doi=10.1021/ja00081a047 |bibcode=1994JAChS.116..767F }}</ref><ref>{{cite journal | vauthors = Chmielewski PJ, Latos-Grażyński L, Rachlewicz K, Glowiak T |title=Tetra-p-tolylporphyrin with an Inverted Pyrrole Ring: A Novel Isomer of Porphyrin |journal=Angewandte Chemie International Edition |date=18 April 1994 |volume=33 |issue=7 |page=779 |doi=10.1002/anie.199407791 }}</ref> 
[[File:Isomers of porphyrins soman.jpg|500 px|thumb|center|class=skin-invert-image|Various reported Isomers of porphyrin]]

== See also ==
* A porphyrin-related disease: [[porphyria]]
* Porphyrin coordinated to iron: [[heme]]
* A heme-containing group of enzymes: [[Cytochrome P450]]
* Porphyrin coordinated to magnesium: [[chlorophyll]]
* The one-carbon-shorter analogues: [[corrole]]s, including [[Vitamin B12|vitamin B<sub>12</sub>]], which is coordinated to a cobalt
* Corphins, the highly reduced porphyrin coordinated to nickel that binds the [[Cofactor F430]] active site in [[methyl coenzyme M reductase]] (MCR)
* Nitrogen-substituted porphyrins: [[phthalocyanine]], [[tetrapyrazinoporphyrazine]]

== References ==
{{reflist}}

== External links ==
{{Commons category|Porphyrins}}
* [http://www.worldscinet.com/jpp/ Journal of Porphyrins and Phthalocyanines]
* [https://web.archive.org/web/20100331125114/http://www.worldscibooks.com/chemistry/7376.html Handbook of Porphyrin Science]
* [https://web.archive.org/web/20180709131903/http://www.porphyrin.net/ Porphynet – an informative site about porphyrins and related structures]
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[[Category:Biomolecules]]
[[Category:Metabolism]]
[[Category:Photosynthetic pigments]]
[[Category:Chelating agents]]
[[Category:Porphyrins| ]]