chemistry

Transition metal amino acid complexes

Transition metal amino acid complexes 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 Transition metal amino acid complexes rather than just read about it. In short: Transition metal amino acid complexes are a large family of coordination complexes containing the conjugate bases of the amino acids, the 2-aminocarboxylates. Amino acids are prevalent in nature, and all of them function as ligands toward the transition metals.

Key takeaways

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

Reference excerpt

Transition metal amino acid complexes are a large family of coordination complexes containing the conjugate bases of the amino acids, the 2-aminocarboxylates. Amino acids are prevalent in nature, and all of them function as ligands toward the transition metals. Not emphasized in this article are complexes of amino acid amides (including peptide) and ester derivatives of amino acids.

Binding modes

Commonly, amino acids coordinate to metal ions as N,O bidentate ligands, utilizing the amino group and the carboxylate. A five-membered chelate ring (NCCCOM) is formed. The chelate ring is only slightly ruffled at the sp3-hybridized carbon and nitrogen centers. N,O bidentate amino carboxylates are "L-X" ligands in the Covalent bond classification method. With respect to HSAB theory, N,O bidentate amino carboxylate is a pair of hard ligands. For those amino acids containing coordinating substituents, the resulting complexes are more structurally diverse since these substituents can coordinate. Histidine, aspartic acid, and methionine sometimes function as tridentate N,N,O-, N,O,O-, and S,N,O-ligands, respectively. Doubly deprotonated cysteine is often an N,S-bidentate ligand, with a non-coordinated carboxylate. Using kinetically inert metal ions, complexes containing monodentate amino acids have been characterized. These complexes exist in either the N or the O linkage isomers.

Stoichiometry and structure

Homoleptic complexes (only amino acid ligands) Mixing simple metal salts with solutions of amino acids near neutral or elevated pH often affords bis- or tris complexes. For metal ions that prefer octahedral coordination, these complexes often adopt the stoichiometry M(aa)3 (aa = amino carboxylate, such as glycinate, H2NCH2CO2−). Complexes of the 3:1 stoichiometry have the formula [M(O2CC(R)HNH2)3]z. Such complexes adopt octahedral coordination geometry. These complexes can exist in facial and meridional isomers, both of which are chiral. The stereochemical possibilities increase when the amino acid ligands are not homochiral. Both the violet meridional and red-pink facial isomers of tris(glycinato)cobalt(III) have been characterized With L-alanine, L-leucine, and other amino acids, one obtains four stereoisomers. With cysteine, the amino acid binds through N and thiolate. Complexes with the 2:1 stoichiometry are illustrated by copper(II) glycinate [Cu(O2CC(R)HNH2)2], which akso exists as a pentacoordinate monohydrate. When the metal is square planar, these complexes can exist as cis and trans isomers. The stereochemical possibilities increase when the amino acid ligands are not homochiral. Homoleptic complexes are also known where the amino carboxylate is tridentate amino acids. One such complex is Ni(κ3-histidinate)2.

Peptides and proteins In addition to the amino acids, peptides and proteins bind metal cofactors through their side chains. For the most part, the α-amino and carboxylate groups are unavailable for binding as they are otherwise engaged in the peptide bond. The situation is more complicated for the N-terminal and C-terminal residues where the carboxylate groups and α-amino are unavailable, respectively. Ignoring the N-and C-terminal sites, side chains of the individual residues function as ligands, e.g., histidine (imidazole), cysteine (thiolate), and methionine (thioether).

Heteroleptic complexes (amino acids plus other ligands)

Mixed ligand complexes are common for amino acids. Well known examples include [Co(en)2(glycinate)]2+, where en (ethylenediamine) is a spectator ligand. In the area of organometallic complexes, one example is the half-sandwich complex Cp*Ir(κ3-methionine).

Synthesis and reactions

A well studied complex is tris(glycinato)cobalt(III). It is produced by the reaction of glycine with sodium tris(carbonato)cobalt(III). Similar synthetic methods apply to the preparation of tris(chelates) of other amino acids. Commonly amino acid complexes are prepared by ligand displacement reactions of metal aquo complexes and the conjugate bases of amino acids:

[PtCl4]2- + 2 H2NCH(R)CO2− → [Pt(H2NCH(R)CO2)2] + 4 Cl− Relevant to bioinorganic chemistry, amino acid complexes can be generated by the hydrolysis of amino acid esters and amides (en = ethylenediamine):

[(en)2CoOH(κ1N-H2NCH(R)CO2Et)]2+ → [(en)2CoOH(κ2NO-H2NCH(R)CO2)]2+ + EtOH Because their 5-membered MNC2O chelate ring is rather stable, amino acid complexes represent protecting groups for amino acids, allowing diverse reactions of the side chains.

Aminocarboxylate complexes

Organic compounds featuring two or more 2- and 3-aminocarboxylate groups are ligands of extensive use in nature, industry, and research. Famous examples include EDTA and NTA.

References

Illustrations

Worked examples

Example 1 — a first encounter with Transition metal amino acid complexes

Start with the simplest possible case. Write down what Transition metal amino acid complexes 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 Transition metal amino acid complexes 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 Transition metal amino acid complexes 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 Transition metal amino acid complexes

In research: Transition metal amino acid complexes 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 Transition metal amino acid complexes 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: Transition metal amino acid complexes is common in secondary-school and first-year university syllabi. It links to neighbouring topics Coordination complexes, Metal-amino acid complexes, so understanding it makes those chapters shorter.
In everyday life: Look for Transition metal amino acid complexes 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.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Transition metal amino acid complexes” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Transition metal amino acid complexes in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Transition metal amino acid complexes 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 Transition metal amino acid complexes out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Transition metal amino acid complexes in simple terms?

Why does Transition metal amino acid complexes 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 Transition metal amino acid complexes?

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 Transition metal amino acid complexes.