Submitted by MurphysLab t3_11m6wec in science
Previously, aromatic hexazine, [N₆]⁴⁻, was a hypothetical chemical structure which would follows Hückel rule for aromaticity: a planar ring molecule will have aromatic properties if it has 4n + 2 π electrons, where n is a non-negative integer.
Compounds with a high proportion of nitrogen tend to exhibit explosive properties, given the relative stability of molecular nitrogen (N₂ gas) (see: The Explosive Chemistry of Nitrogen: A Fascinating Journey From 9th Century to the Present), making their synthesis both difficult and risky, hence why a synthesis for [N₆]⁴⁻ has been so long in coming and why it would need to be performed at high pressure.
Prior to this, all-nitrogen aromaticity, had restricted to the [N₅]⁻ pentazolate anion. A similar synthesis reported in 2022 produced the anti-aromatic [N₆]²⁻, starting from potassium azide (KN₃).
The results are published in Nature Chemistry:
Dominique Laniel et al.: Aromatic hexazine [N₆]⁴⁻ anion featured in complex structure of the high-pressure potassium nitrogen compound K₉N₅₆. Nature Chemistry (2023). DOI: https://doi.org/10.1038/s41557-023-01148-7
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Beautiful and also would you mind sharing why this is important in basic terms? I respect science enthusiasms but have no expertise
The article states that hopefully they "can stimulate further exploration of nitrogen chemistry in the search of novel nitrogen-based technological materials."
So it looks like nothing super specific here, but it's yet another building block for the advancement of chemistry and nano technology. Now that [ N6]4- can be synthesized, it now can be studied off of paper.
Let's say we find out that cute ring is fantastic at shuttling around an ion? What if it's great at temporarily holding ions or creates a bed of electrons, similar to how precious metals work in the catalytic converter of your car. Nitrogen makes up the majority of the air we breathe, so it's dirt cheap. If it could be converted to a highly usefully ring for cheap? That'd be fantastic!
It also might be useful for synthesizing other compounds. Boron chemistry is an entire sub field because boron doesn't follow the octet rule, so it does cool things. Way beyond the scope of this response but instead of directly reacting in the reaction, it'll form intermediate complexes, or hold a temporary structure so that the reaction you want to happen can take place at all, or maybe significantly faster than without.
Edit: I'd like to add that rings, especially complex rings can be a huge pain to form. Vitamin B-12 synthesis took an obscene amount of manpower with many, many teams running concurrent studies to create parts of the vitamin, then the end goal was to link those pieces together, which took more research.
What are the applications of this molecule?
I’m hoping to help the nitrogen cycle and food, but I’m guessing not.
Molecules with lots of nitrogens tend to be… explodey
There are no applications. It's just a theoretical exercise.
I wouldn't expect this compound to be directly useful for anything, given that it's unstable at all but the most extreme pressures. It's more of a theoretical demonstration.
True, I got so excited about the ring I glossed over the ridiculous environmental constraints. But I was also thinking it might be a high energy step in the process of synthesizing something else or possibly stabilized as part of a larger carrying unit, sort of like hemoglobin. I have no proof but I like to dream.
/u/BiochemistChef's response is great, so I'll try not to repeat.
Instead, I'll highlight another aspect: A ring containing 6 nitrogen atoms and 6 electrons in pi-orbitals is something which theory has predicted could exist for a long time and which we might make. But while theory is good, reality is always more interesting. Reality often functions as the measuring stick by which we can see if our theories are correct or not. That's the fundamental nature of science.
Consider those physicists who keep on proving Einstein right again and again: They're checking to see if reality looks the same as our theoretical understanding.
Another aspect of why this was published in a prominent chemistry journal (and why I'm rather enthused about the result) is that benzene has very interesting chemistry which is the result of the special arrangement of electrons which it possesses. It's the foundation of huge swaths of chemistry. And so chemists have seen how we might modify it so it's not just 6 carbon atoms in a ring.
Chemists wonder "What happens if we start swapping out some of the 6 carbon atoms in a benzene ring for different atoms?" Those molecules are termed heterocyclic compounds.
https://i0.wp.com/www.compoundchem.com/wp-content/uploads/2014/07/Heterocycles-graphic.png?ssl=1
What happens if you swap 1 carbon atom with a nitrogen atom? Pyridine is just that and it's a motif which appears frequently. The nitrogen allows chemists to use it as a ligand for metal atoms.
What if we replace 2 carbon atoms with nitrogen atoms? We've done that. It give you pyrimidine, pyrazine, and pyridazine, each with different chemical properties.
You'll note that the series doesn't stop with just 1 or 2 nitrogen atoms substituted. We can imagine a complete series:
Using series of molecules like that, we can better understand why they have the properties that we observe and how we might plan to change the properties of other similar heterocyclic molecules.
I'd add that many of those N-heterocycle motifs turn up in really useful molecules. For a munch of my PhD, I worked with plastics containing polyvinylpyridine to make cool nano patterns.
Those nitrogen containing aromatic molecules also turn up in pharmaceuticals:
Many of those need the nitrogen(s) in the ring for efficacy, so it's also worth exploring new synthetic methods for making nitrogen heterocycles. They aren't typically using lasers and diamond anvil cells, but the future might hold some surprises.
Thank you so very much for this. Beyond the pure beauty of it, the “what happens?”, I had no idea about the medical application and now can reverse engineer my knowledge of that field a little.
Fascinating to see the intersection, and I am grateful for you all for taking the time to show me.
Stay safe all of you, just watched the fairly inaccurate Radioactive movie about M Curie and don’t want any of you sleeping with glowing heterocyclic vials on your pillows!
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These molecules help chemists to understand the properties of aromatic molecules. Think of it as a single data point, but the most difficult data point for the experiment; one which no one has ever been able to get before. But that data point answers questions about the nature of several other chemical compounds.
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