Tetraphenylporphyrin

• 5,10,15,20 - tetraphenylporphyrin
• TPP
• H2TPP

Purple solid

1.244 g/cm3

449-451 ° C

Insoluble in water

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Tetraphenylporphyrin, TPP or abbreviated H2TPP, is a synthetic heterocyclic material that resembles naturally occurring porphyrins. Porphyrins are dyes and cofactors that are present in hemoglobin and cytochromes and similar chlorophyll and vitamin B12. Tetraphenylporphyrin is a hydrophobic purple solid which was substituted symmetrical, easy to synthesize and in non-polar organic solvents such as chloroform and benzene is soluble.

Synthesis and Structure

Tetraphenylporphyrin was first synthesized in 1935 by Rothemund by letting pyrrole react with benzaldehyde in a sealed tube at 150 ° C. The reaction time in this case was 24 h and the yield was never higher than about 10%. 1967 Adler and Longo developed an effective synthesis, in that they caused to react as solvents pyrrole and benzaldehyde in propionic acid. Here, the reaction time was about 30 min and it was above 20% yields are obtained:

Despite the low yield of this synthesis is often performed for teaching purposes in universities.

TPP belongs to the symmetry group C2h. The low symmetry is caused by the out of the plane of the pyrrole N-H bonds. Unlike natural porphyrins H2TPP is present in the oxidation-sensitive " meso " shape and is therefore sometimes referred to as meso- tetraphenyl porphyrin. H2TPP can be sulfonated in order to obtain water- soluble derivatives:

Optical Properties

Tetraphenylporphyrin has a strong absorption maximum at 419 nm ( the so-called Soret band ), and four minor peaks at 515 nm, 550 nm, 593 nm and 649 nm is a red fluorescence with a maximum at 649 nm and 717 nm, the quantum efficiency is 11%.

Applications

Tetraphenylporphyrin and its derivatives can act as ligands for heavy metal cations. The complexes prepared in this way have some interesting properties and can be used for example as a colorant in histology. Tetraphenylporphyrin itself can be used as a photosensitizer in the preparation of singlet oxygen. It can be used as a moisture indicator and instead of the carcinogenic cobalt (II ) chloride in combination with magnesium chloride, and silica gel.