Think INSIDE the box! Running NMR in the Glovebox

There are all sorts of different research areas in chemistry. Consider my path, for example. When I was just a young undergrad trying to find my calling, I loved tackling mechanisms for organic reactions, but I also loved “breaking all the rules” in inorganic chemistry. In trying to decide which route I wanted to take, Prof. Stephen Westcott introduced me to the best of both worlds: organo-metallic chemistry. You get all sorts of crazy colours and many of the molecules disobey the conventional rules! You need to be careful though, because many of them will react instantly with water and oxygen. And I mean instantly! For example, although an incredibly simple organometallic molecule, tert-butyllithium (t-BuLi) is incredibly dangerous^[1] since it catches fire at the slightest hint of air (Fig. 1^[2]).

Clips from Periodic Videos - by video journalist Brady Haran - https://www.youtube.com/watch?v=EmkBH-ncG1Y

FIGURE 1 - FIRE CAUSED BY RELEASE OF tBuLi SOLUTION (1.7 M in pentane) in air

But how are you supposed to do any chemistry if it will instantly react with the air around us?! Thankfully there are a variety of solutions out there, but our favourite is to use a “glovebox” (Fig. 2^[3]). There are several companies that build inert atmosphere boxes so you can freely manipulate your chemicals without having to worry about air leaching into your reaction. Using the antechamber on the side, you can cycle in glassware, chemicals, and even electronic equipment like balances and stir plates. Now you’ve got an oxygen-free environment ready for your chemicals!

Figure 2 – Inert atmosphere glovebox with small and large antechambers on the left

As is the life of most organometallic chemists, analysis by NMR involves several additional steps compared to chemistry done at the bench. For example, once you’ve performed a reaction in a glovebox, you need to take some special precautions to make sure that air doesn’t leach into your NMR tube once it comes out of the antechamber. Most people will either use septa combined with parafilm to prevent air from seeping in, or some may use Teflon-sealed “J-Young” tubes (Fig. 3^[4]) if their complex is really air-sensitive. Then it’s the drawn-out process of: Withdraw your sample through the antechamber, go to the NMR in the basement, obtain spectra, come back to the lab, and cycle it back into the glovebox via the antechamber if required. A royal pain? You bet.

Figure 3 – Teflon-sealed J-Young NMR tubes

One of the main complaints by organometallic chemists is that this process takes a lot more time than throwing on a plastic cap! Wouldn’t it be nice if there was an NMR small enough to fit in the confined space of a glovebox? If only that were possible…

If you ever wondered whether there is an NMR small enough to fit in a glovebox, here is your answer (Fig. 4)!

Figure 4 – Nanalysis NMReady-60e inside of an MBRAUN glovebox

However, not only is it small enough to fit inside, but it also is incredibly easy to get it in there! The NMReady-60 is an all-in-one instrument, making it very compact and portable. More importantly, the remarkably small dimensions means it can fit in places you might not normally be able to place an NMR, like the large antechamber (Fig. 5)!

Figure 5 – NMReady-60PRO being cycled into a glovebox through the large antechamber.

To test out the compatibility of the NMReady-60 with gloveboxes, we partnered up with MBRAUN, the market leader in glovebox workstations (Fig. 6). We also collaborated with fellow Albertan organometallic chemist, Prof. Hayes at the University of Lethbridge. The NMReady-60 could be cycled into the box easily via the large antechamber, and its minimal footprint ensures there was still plenty of room in the glovebox for chemistry research (Figs. 7-8). When not in use, the instrument was able to shim on itself, and made acquisition of NMR spectra much easier than having to frequently cycle in-and-out of the box.

Figure 6 – NMReady-60PRO being used inside an MBRAUN glovebox.

Figure 7 – Obtaining a 1H NMR spectrum inside an operational glovebox at the University of Lethbridge.

Figure 8 – Phasing the peaks of an ethyl group on the NMReady-60PRO inside a glovebox.

Now whenever you need to keep an eye on a reaction in the glovebox, you can do so with NMR inside the box!

References
^[1]https://cen.acs.org/articles/87/i31/Learning-UCLA.html
^[2]https://i.imgur.com/x6lNqz7.mp4 (Viewed Mar 29 2018); https://www.youtube.com/watch?v=EmkBH-ncG1Y (Viewed Nov 17 2020)
^[3]http://drexel.edu/materials/news-events/archive/2016/August/Research-Facilities-Expansion/
^[4]https://www.gpescientific.co.uk/products/j-young/nmr-valves/NMR-Valve-with-Tube-Attached