chemistry

Tetraphenylporphyrin

Tetraphenylporphyrin is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tetraphenylporphyrin rather than just read about it. In short: Tetraphenylporphyrin, abbreviated TPP or 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.

Key takeaways

Tetraphenylporphyrin belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tetraphenylporphyrin to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tetraphenylporphyrin from memory before moving on to harder problems.

Reference excerpt

Tetraphenylporphyrin, abbreviated TPP or 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 dark purple solid that dissolves in nonpolar organic solvents such as chloroform and benzene.

Synthesis and structure 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. 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:

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. 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. The conjugate base of the porphyrin, TPP2−, belongs to the symmetry group D4h while its hydrogenated counterpart H2(TPP) is D2h. 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.

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

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) Zn(TPP)Lx VO(TPP) Fe(TPP)Cl Co(TPP) Ni(TPP)

Optical properties

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%. 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.

Applications

H2TPP is a photosensitizer for the production of singlet oxygen. Its molecules have potential applications in single-molecule electronics, as they show diode-like behavior that can be altered for each individual molecule.

References

Illustrations

Worked examples

Example 1 — a first encounter with Tetraphenylporphyrin

Start with the simplest possible case. Write down what Tetraphenylporphyrin claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tetraphenylporphyrin before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tetraphenylporphyrin ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tetraphenylporphyrin

In research: Tetraphenylporphyrin appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tetraphenylporphyrin in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tetraphenylporphyrin is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chelating agents, Macrocycles, Phenyl compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Tetraphenylporphyrin outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Tetraphenylporphyrin in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tetraphenylporphyrin means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tetraphenylporphyrin out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tetraphenylporphyrin in simple terms?

Why does Tetraphenylporphyrin matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tetraphenylporphyrin?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tetraphenylporphyrin.