tetraphenylporphyrin

Tetraphenylporphyrin was first synthesized in 1935 by Rothemund, who caused benzaldehyde and pyrrole to react in a sealed bomb at 150 °C for 24 h.{{cite journal | author = P. Rothemund | 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 }} Adler and Longo modified the Rothemund method by allowing benzaldehyde and pyrrole to react for 30 min in refluxing propionic acid (141 °C) open to the air:{{cite journal | author = A. D. Adler, F. R. Longo, J. D. Finarelli, J. Goldmacher, J. Assour and L. Korsakoff | title = A simplified synthesis for meso-tetraphenylporphine | year = 1967 | journal = J. Org. Chem. | volume = 32 | issue = 2 | pages = 476 | doi = 10.1021/jo01288a053 }}

:8 C₄H₄NH + 8 C₆H₅CHO + 3 O₂ → 2 (C₆H₅C)₄(C₄H₂N)₂(C₄H₂NH)₂ + 14 H₂O

Despite its modest yields, the synthesis of H₂TPP is a common experiment in university teaching labs.{{cite journal | title = Microscale Synthesis and ¹H NMR Analysis of Tetraphenylporphyrins |author1=Falvo, RaeAnne E. |author2=Mink, Larry M. |author3=Marsh, Diane F. | journal = J. Chem. Educ. | volume = 1999 | issue = 76 | pages = 237 | doi=10.1021/ed076p237| year = 1999 |bibcode=1999JChEd..76..237M }}G. S. Girolami, T. B. Rauchfuss and R. J. Angelici (1999) Synthesis and Technique in Inorganic Chemistry, University Science Books: Mill Valley, CA.{{ISBN|0935702482}} Highly efficient routes to H₂TPP and many analogues involve the air-free condensation of the pyrrole and aldehyde to give the porphyrinogen. In this so-called Lindsey synthesis of meso-substituted porphyrins, the porphyrinogen is subsequently oxidized to deliver the porphyrin.{{cite encyclopedia|editor1= Kadish, Karl M. |editor2=Smith, Kevin M. |editor3=Guilard, Roger|title=Synthesis of meso-substituted porphyrins|author= Lindsey, Jonathan S.|encyclopedia=Porphyrin Handbook|year=2000|volume=1|pages=45–118|isbn=0-12-393200-9}}

The conjugate base of the porphyrin, TPP²⁻, belongs to the symmetry group D_4h while its hydrogenated counterpart H₂(TPP) is D_2h.{{Cn|date=February 2022}} Unlike natural porphyrins, H₂TPP is substituted at the oxidatively sensitive "meso" carbon positions, and hence the compound is sometimes called meso-tetraphenylporphyrin. Another synthetic porphyrin, octaethylporphyrin (H₂OEP) does have a substitution pattern that is biomimetic. Many derivatives of TPP and OEP are known, including those prepared from substituted benzaldehydes. One of the first functional analogues of myoglobin was the ferrous derivative of the "picket fence porphyrin," which is structurally related to Fe(TPP), being derived via the condensation of 2-nitrobenzaldehyde and pyrrole.

File:PicketFenceGenericRevised.png|A picket-fence porphyrin complex of Fe, with axial coordination sites occupied by methylimidazole (green) and dioxygen (R = amide groups).S. J. Lippard, J. M. Berg “Principles of Bioinorganic Chemistry” University Science Books: Mill Valley, CA; 1994. {{ISBN|0-935702-73-3}}.

File:FeTPP(CCl2)Mansuy.png|Structure of Fe(TPP)CC(C₆H₄Cl)₂, one of several iron carbenoid complexes reported by Daniel Mansuy.{{cite journal|doi=10.1021/ic00279a023|title=Nature of the complexes derived from the reaction of 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT) with iron porphyrins: Crystal and molecular structure of the vinylidene carbene complex Fe(TPP)(C:C(p-ClC6H4)2)|journal=Inorganic Chemistry|volume=27|issue=6|pages=1052–1056|year=1988|last1=Mansuy|first1=Daniel|last2=Battioni|first2=Jean Paul|last3=Lavallee|first3=David K.|last4=Fischer|first4=Jean|last5=Weiss|first5=Raymond}}

Sulfonated derivatives of TPP are also well known to give water-soluble derivatives, e.g. tetraphenylporphine sulfonate:

:4 SO₃ + (C₆H₅C)₄(C₄H₂N)₂(C₄H₂NH)₂

→ (HO₃SC₆H₄C)₄(C₄H₂N)₂(C₄H₂NH)₂ + 4 H₂O

{{main|Transition metal porphyrin complexes}}

Complexation can be thought of as proceeding via the conversion of H₂TPP to TPP²⁻, with 4-fold symmetry. The metal insertion process proceeds via several steps, not via the dianion. Representative complexes:

• Cu(TPP){{cite journal | author = R. F. Pasternack, G. C. Vogel, C. A. Skowronek, R. K. Harries and J. G. Miller| title = Copper(II) Incorporation into Teteraphenylporphine in Dimethyl Sulfoxide| year = 1981 | journal = Inorg. Chem. | volume = 20 | issue = 11 | pages = 3763–3765 | doi = 10.1021/ic50225a038}}
• Zn(TPP)L_x{{cite journal | author = G. C. Vogel and J. R. Stahlbush| title = Thermodynamic Study of the Adduct Formation of Zinc Tetraphenylporphine with Several Neutral Donors in Cyclohexane| year = 1976 | journal = Inorg. Chem. | volume = 16 | issue = 4 | pages = 950–953 | doi = 10.1021/ic50170a049}}
• VO(TPP)F. A. Walker, E. Hui, and J. M. Walker (1975) the Journal of The American Chemical Society, 87, 2375
• Fe(TPP)Cl

File:TPP.tif

Tetraphenylporphyrin has a strong absorption band with maximum at 419 nm (so called Soret band) and four weak bands with maxima at 515, 550, 593 and 649 nm (so called Q-bands). It shows red fluorescence with maxima at 649 and 717 nm. The quantum yield is 11%.{{cite journal | author = J. B. Kim, J. J. Leonard and F. R. Longo | title = A mechanistic study of the synthesis and spectral properties of meso-tetraphenylporphyrin. | year = 1972 | journal = J. Am. Chem. Soc. | volume = 94 | issue = 11 | pages = 3986–3992 | doi = 10.1021/ja00766a056 | pmid = 5037983 }}

Soret red shifts for Zn(TTP)-Donor systems relative to the Soret band at 416.2 nm for Zn(TTP) in cyclohexane have been measured.

File:Dehydrogenation of H2TPP by STM.jpg (a); this removal alters the I-V curves of TPP from diode like (red curve in b) to resistor like (green curve). Image (c) shows a row of TPP, H₂TPP and TPP molecules. While scanning image (d), excess voltage was applied to H₂TPP at the black dot, which instantly removed hydrogen, as shown in the bottom part of (d) and in the re-scan image (e).]]

H₂TPP is a photosensitizer for the production of singlet oxygen.Karl-Heinz Pfoertner (2002) "Photochemistry" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a19_573}} Its molecules have potential applications in single-molecule electronics, as they show diode-like behavior that can be altered for each individual molecule.{{cite journal|doi=10.1038/srep08350|pmid=25666850|pmc=4322354|title=N and p type character of single molecule diodes|journal=Scientific Reports|volume=5|pages=8350|year=2015|author=Vinícius Claudio Zoldan, Ricardo Faccio and André Avelino Pasa|bibcode= }}

{{Reflist}}

Category:Chelating agents

Category:Tetrapyrroles

Category:Macrocycles

Category:Phenyl compounds