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.
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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.
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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.
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Cisplatin
Cisplatin is a square planar complex.
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/4979856/341165_250241.png)
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
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/4979856/818668_145322.png)
Tollen's reagent
In Tollen's reagent, the solution is linear complex ion diammine silver(I) [Ag(NH3)2]+.
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The Ag is reduced when the complex ion reacts with an aldehyde.
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/4979856/410243_84563.jpeg)
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