Chill Out

Thanks to the generosity of several faculty members and financial help from the Paul M.Cook Innovation Fund, the X-ray diffraction facility recently purchased a new low temperature device. The Cryostream 700 fromOxford Cryosystems arrived in six boxes and the assembly was straight forward. I was a little reluctant to drilling holes in the base of our diffractometer enclosure, but with the help of Ed Udas, everything worked very well. The Varibeam support stand is robust and allowed me to mount the Cryostream precisely where I wanted it, without interfering with the moving parts of the diffractometer. The gears on the Varibeam make adjusting the exact position of the coldhead easy and precise.

When I first switched on the Cryostream controller I expected that something would go wrong. It always does. But here: nothing – no faulty connection of the tubing, no defective chip in the controller, no problems with the pump or the dry air unit. Everything worked quite smoothly and the device cooled down to 100K within 20 minutes. After about 10 days I shut down the system to include the Line Drier and to install the auto refill system, which, of course, was not delivered together with the Cryostream (that would have been too easy). That took a couple of hours and afterwards the Cryostream cooled down again to 100K without any problems. It has been operating at that temperature since and many datasets have been collected.

With our old setup we had a big problem with the formation of ice on the sample, especially when the humidity in the lab was high. This problem simply does not exist any more. Now we can collect data whenever we want to and not only when the humidity level allows it. Another point is the quality of the diffraction data collected with the new setup: it is excellent. Everybody knows that low-temperature data is better, but to actually experience it is a different story. At -80º C many tert-butyl, iso-propyl, CF3 and Cp* ligands were disordered, and now we have practically no disorders at all. The average merging R-values have improved too, and most refinements are much less of a hassle than before. Long story short: the X-ray diffraction facility of the MIT chemistry department produces more and better structures and makes better use of its excellent diffractometer thanks to the Cryostream 700.

See pictures of the Cryostream

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