Tetraphenylporphyrin
| Tetraphenylporphyrin | |
|---|---|
| File:H2TPP.png | |
| Other names 5,10,15,20-Tetraphenylporphin, H2TPP | |
| style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers | |
| CAS number | 917-23-7 
|
| style="background: #F8EABA; text-align: center;" colspan="2" | Properties | |
| Molecular formula | C44H30N4 |
| Molar mass | 614.74 g/mol |
| Appearance | dark purple solid liquid |
| Density | 1.27 g/cm3 |
| Solubility in water | insoluble in water |
 (what is this?) (verify)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
| Infobox references | |
Tetraphenylporphyrin, abbreviated H2TPP, is a synthetic heterocyclic compound that resembles naturally occurring porphyrins. Porphyrins are dyes and cofactors found in hemoglobin and cytochromes and are related to chlorophyll and vitamin B12. The study of naturally-occurring porphyrins is complicated by their low symmetry and the presence of polar substituents. Tetraphenylporphyrin is hydrophobic, symmetrically substituted, and easily synthesized. The compound is a deep blue solid that dissolves in nonpolar organic solvents such as chloroform and benzene.
Synthesis and structure
Tetraphenylporphyrin is prepared by the reaction of benzaldehyde and pyrrole in refluxing propanoic acid, the so-called Rothemund method:[1]
- 8 C4H4NH + 8 C6H5CHO + 3 O2 → 2 (C6H5C)4(C4H2N)2(C4H2NH)2 + 14 H2O
Despite low yields, the synthesis of H2TPP is a common experiment in university teaching labs.[2][3]
The porphyrin belongs to the symmetry group C2h, the low symmetry being due to the orientation of the two N-H bonds, which project out of the plane of the four pyrrole rings. 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 tetraphenylporphyrin 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 H2TPP, being derived via the condenation 2-nitrobenzaldehyde and pyrrole. H2TPP can be sulfonated 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
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 step, not via the dianion. The resulting complexes are symmetrical with simple NMR or EPR spectra. For example, Cu(TPP) has D4h symmetry. The corresponding iron complexes are more complex owing to variable oxidation states and coordination numbers. Well-studied derivatives include the ferric compounds, e.g. Fe(TPP)Cl and the oxide [Fe(TPP)]2O, and ferrous compounds, e.g. Fe(TPP)CO(L) (L = imidazole, pyridine).
Applications
H2TPP is a photosensitizer for the production of singlet oxygen.[4]
References
- ↑ A. D. Adler, F. R. Longo, J. D. Finarelli, J. Goldmacher, J. Assour and L. Korsakoff (1967). "A simplified synthesis for meso-tetraphenylporphine". J. Org. Chem. 32 (2): 476–476. doi:10.1021/jo01288a053.
- ↑ Falvo, RaeAnne E.; Mink, Larry M.; Marsh, Diane F. "Microscale Synthesis and 1H NMR Analysis of Tetraphenylporphyrins". J. Chem. Educ. 1999 (76): 237.
- ↑ Girolami, G. S.; Rauchfuss, T. B.; Angelici, R. J., Synthesis and Technique in Inorganic Chemistry, University Science Books: Mill Valley, CA, 1999.ISBN 0935702482
- ↑ Karl-Heinz Pfoertner "Photochemistry" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. doi:10.1002/14356007.a19_573
