We have learn that transition metal ions form complexes and let's see how they are utilised in A-Level Chemistry!
The haem group
The haem group in a haemoglobin molecule is a multidentate ligand surrounding a central Fe2+ ion. Each of the four polypeptide subunits of the haemoglobin contains one of this prosthetic group.
The shape of the complex ions is similar to a dome. When oxygen binds to form oxyhaemoglobin, the complex ion becomes more planar - a conformational change which makes it easier for the haemoglobin to pick up two more oxygen molecules. The affinity for the fourth oxygen decreases after the haemoglobin has three oxygen molecules.
The O2 molecules actually bind to the Fe, forming a 6th bond. Carbon monoxide has a higher affinity for haemoglobin than oxygen and forms carboxyhaemoglobin. As a result, the haemoglobin is unable to carry oxygen around the body, leading to death. The gas is colourless, odorless and tasteless.
Cisplatin
Cisplatin is a square planar complex.
It is an anticancer drug. It binds to the DNA bases (particularly guanine) and forms cross-links, which damages the DNA in cancer cells. This elicits DNA repair mechanisms, which in turn activitate apoptosis when this proves impossible. Side effects include:
- Nephrotoxicity (kidneys) and neurotoxicity (nerves)
- Nausea and vomiting
- Hearing loss
Tollen's reagent
In Tollen's reagent, the solution is linear complex ion diammine silver(I) [Ag(NH3)2]+.
The Ag is reduced when the complex ion reacts with an aldehyde.
Drafted by Eunice (Chemistry)
References
https://blog.ekincare.com/2016/07/20/hemoglobin-levels-and-its-significance/
https://labpedia.net/carboxyhemoglobin-cohb-carbon-monoxide-co-poisoning/
https://www.researchgate.net/figure/The-platinum-atom-of-cisplatin-binds-covalently-to-the-N7-position-of-purines-to-form_fig2_221920821