Mastodawn

SellaTheChemist Jun 18

Holy moley! Careful oxidation of an azide at very low temps gives rise to an absolutely bonkers bonkers bonkers molecule: N6!!
An allotrope of nitrogen! And it seems to be stable at liquid nitrogen temperature, 77 K. Look at the isotopic signature in the infrared spectra. Spectacular fundamental science.

In case you're wondering, the starting material, silver azide is terrifyingly explosive. This is chemistry at the absolute absolute limit of the possible. Chapeau

https://www.nature.com/articles/s41586-025-09032-9

ChookMother 🇦🇺🦘Jun 19

@sellathechemist I'd like to get excited but absolutely no idea what this means.

Теодор Златанов / Ted Zlatanov Jun 21

SellaTheChemist

@anne_twain Good question. Let me try to explain. The element nitrogen just happens to form very strong bonds with itself. It's the coincidence of the size of the atoms, the charge on the nucleus and the number of electrons, but the result is that nitrogen forms a diatomic (two-atom) molecule, dinitrogen, that has one of the strongest bonds that we know of.
If you add in the fact that it is symmetrical, it means the molecule is particularly unreactive. It's "stable" and difficult to attack. 1/n

SellaTheChemist Jun 19

@anne_twain This means that on the one hand, dinitrogen is very "stable" - it sits at the bottom of a deep energy valley and pretty well everything you might wnat to do to it means going uphill. And the symmetry of it makes it difficult for an attacking molecule to get hold of it. This makes dinitrogen an interesting challenge - biology needs to do a process called nitrogen fixation to convert N2 into something usable. There are bacteria with an enzyme called nitrogenase that make ammonia. 2/n

SellaTheChemist Jun 19

@anne_twain This is a process that has long been a mystery, and a target for chemists since nitrogen is one of the limiting nutrients for agriculture. The famous Haber-Bosch process combines dintrogen and dihydrogen into ammonia, but it requires high temperatures, pressures in a real heat-and-beat type of process.
It is the one of the ultimate essential uses of hydrogen itself and one of the few thigns that sits at the top of Michael Liebreich's hydrogen ladder. 3/n

SellaTheChemist Jun 19

@anne_twain I mention all that to emphasize that nitrogen is a kind rock and the end product of a lot of chemistry. it's much harder to go the other way.
In fact, it turns out that nitrogen compounds are often rather unstable. Most of the explosive used in warfare and in mining are nitrogen-based. The point is that in an explosive you make a molecule which is a kind of accident waiting to happen - fuel and oxidizer in one molecule - and when they go, they make this super-stable N2 molecule. 4/n

SellaTheChemist Jun 19

@anne_twain What is more, N2 is a gas down to -196 ˚C at normal pressure. So not only do you make this very stable bond (that will release energy to everything else around it) but also you make a gas that expands. And if you start from a solid, you know that when you convert it to gas, it will expand 1000-ish times.
This might start making you feel nervous, because any molecule that already has some kind of N–N link will be naturally predisposed or even primed to potentially turn into N2 5/n

SellaTheChemist Jun 19

@anne_twain Among common chemical 'salts' that contain such N–N bonds are the azides, compounds that contain some kind of metal (sodium, or lead or silver or many others) and a N3 unit. The metal is +1 and the N3 is –1. A salt.
Some of these salts are pretty touchy. while potassium azide is fairly well-behaved the lead and silver salts are brutally unstable and have long been notorious for being shock, static electricity and friction sensitive. They go bang very very easily. 6/n

SellaTheChemist Jun 19

@anne_twain And that means that they've been used for little bangers and poppers for a very long time. I've made silver azide and it gives me the heebies. Why? Remember what I said about N2 sitting at the bottom of an energy valley. Certain azides sit on a cliff edge above that valley. While some have a nice little railing that keeps them from falling over the edge, lead and silver azides have almost no lip. And it is that that makes them so scary - they are just waiting to fall apart. 7/n

SellaTheChemist Jun 19

@anne_twain So now I will get to the point. These german chemists have done something really special. They have used the exceptionally unstable silver azide and cooled it down - cooling it down is important because the molecules slow down and are less likely to do the unexpected. They dissolved them up, which keeps them apart - again, that's smart because you don't want a crowd of them decomposing at the same time.
And then they added an oxidizing agent - Cl2 or Br2. Again diatomics. 8/n

SellaTheChemist Jun 19

@anne_twain Now the beauty here is that either of these molecules will want to grab an electron from the N3– (the azide anion). You get chloride (the stuff you have in everyday salt) and you get N3dot - that's chemistry parlance for azide with an unpaired electron. Electrons tend to pair up when they can. So N3dot meets dotN3 and they presto you have N3–N3 - in other words you have a molecule with six nitrogens in a row formed from two of those rather unstable azides. 9/n

SellaTheChemist Jun 19

@anne_twain Now that is utterly unprecedented. People have made rings with 5 nitrogens in them (pentazoles) which aren't exactly the most stable things but still quite manageable.
N6 is really quite astonishing to a chemist. And it is an accident waiting to happen. That's why they say that they wear ear protection, face shields, and leather under and overpants. 🤣 These are molecules that teeter on the edge of stability, a bit like trying to balance a sharp knife on its tip. 10/n

SellaTheChemist Jun 19

@anne_twain So why in heaven's name, you might ask, would anyone try that? The answer is both childish and quite profound. As Mallory said "Because it's there". Because you want to see where the limits are. Because you want to explore the limits of the possible. In doing so you can gain further understanding of how the bonding between the atoms is. And because in the end, like the Red Queen, you want to imagine impossible things before breakfast. Much basic research can be like that. 11/n

SellaTheChemist Jun 19

@anne_twain It is "pointless" in that there is no obvious application for it. But by extending the methods for making such weird chemical species and by showing that they exist, you give your colleagues other further ideas to push the envelope of our understanding. And of that envelope pushing turns out to have important applications.
I should just mention one example. Azides sound like accidents waiting to happen. But organic compounds with azide groups can be made, carefully, but easily. 12/n

SellaTheChemist Jun 19

@anne_twain These azides are v useful because you can use them in something called "click chemistry" where the N3 reacts with a C-C triple bond to make a nice 5-atom ring. This is a really simple and broadly usable way to build biocompatible molecules to explore cellular processes, put in labels, deliver drugs and more. Carolyn Bertozzi, Morten Meldal and Barry Sharpless won the Nobel for developing these methods. So you push the envelope and someone mashes together the ideas into the new. 13/n

SellaTheChemist Jun 19

@anne_twain And it's just a reminder that creativity is not something restricted to the arts. The same creative impulse to try something different and see what happens - something with very dangerous results - but more often not, is the thing that drives forward our understanding the the richness of a our world in new ways. /ends

(and thanks for the observation)

Marcos Dione Jun 20

@sellathechemist @anne_twain Wow, this is awesome, thanks. I still can't read the graph, tho :-P

SellaTheChemist Jun 20

@mdione @anne_twain Meh. Not essential. The whole thing is a landscape. Lower is more stable. And getting from one place to another often involves getting over railings - easier/faster at higher temperature tham at lower. So you can "trap" highly unstable things if you can keep them behind the railing by cooling the thing down to liquid nitrogen temperatures or lower.

Vassil Nikolov Jun 21

@sellathechemist

A beautiful, clear exposition!

As to creativity, most definitely so.
Like Hilbert said about a student of his, "He became a poet: didn't have enough imagination for a mathematician."

Laberpferd Jun 19

@sellathechemist
you might be interested to read up about the molecule C2N14

F4GRX SÃ©bastien Jun 19

@Laberpferd @sellathechemist @anne_twain aaah, azidoazide azide! Love it, just for the name!

WHERE IS TOM FFS get him out of twitter and discord! We need yellow chemistry in the fediverse!

SellaTheChemist Jun 19

@Laberpferd @anne_twain Bloody hell. Yes. You’re absolutely right. I’d forgotten about that. Another amazing molecule and remarkably stable in an unstable sort of way.

Bob McMeeking Jun 21

@Laberpferd @sellathechemist @anne_twain

Made by the Klapötke group, who even determined the crystal structure. Judging by the unit cell given here it looks like even some of the constituent molecules are trying to make a run for it..

SellaTheChemist Jun 21

@luddchem @Laberpferd @anne_twain Ah yes. Lovely!

Bob McMeeking Jun 21

@Laberpferd @sellathechemist @anne_twain

Here is a link to the related papers using CrystalWorks. You can display the structures interactively using the JSmol structure display application. Please note the second paper is open access.

So you can sit in a pub with your tablet and a cooling beer

https://cds.dl.ac.uk/cgi-bin/rfm/crystalworks_trawl_new?2353_2261_2174

CrystalWorks (production version)

F4GRX SÃ©bastien Jun 19

@sellathechemist @anne_twain holy crap at the process.

Ed Davies Jun 20

@sellathechemist

The point is that you make a molecules which is a kind of accident waiting to happen - fuel and oxidizer in one molecules - and when they go, they make this super-stable N2 molecule.

Thank for this: both an “ahah!” and “doh!” moment for me. I knew that N₂ was very stable (hence nitrogen fixing being a bit of biological magic) and that many explosives were unstable molecules containing multiple nitrogen atoms.

These two facts seemed to be sort of contradictory but this explains how they fit together and where the energy comes from. Am I right to think of it as the N-N bonds “collapsing” to form N₂ which releases energy and also allows the other atoms in the molecule to get together for oxidation which also releases energy?

SellaTheChemist Jun 20

@edavies @anne_twain Yes. The precise mechanism by which things happen would require more detailed computation but effectively that's the case.
What is critical here is the speed at which this happens and the fact that you take condensed matter and convert it to gas.
Typically in an explosive you have two things operating together - first the formation of gas that will expand because of weak intermolecular forces, and second the energy release that raises the temperature. 1/n

SellaTheChemist Jun 20

@edavies @anne_twain If you want to get nerdy about this, the first part is the "entropic" part - having lots of molecules of gas spreads the original energy out into lots of little mobile particles.
The second is the "enthalpic" part where the difference in energy is expressed as "heat" i.e. temperature rise, which then amplifies the expansion of the gas being formed.
Most explosives are a combination of these two parts - there is bang (expansion) and there is fire ("heat"). 2/n

Dr Susi Arnott Jun 19

@sellathechemist @anne_twain
Great thread from former #SciCom award winner:)
If the 6 Ns are truly in a row not a ring, the ones on the ends must feel pretty special (?) And great reminder of how stupendous biological systems can be #nitrogenfixation