Benzene Inclusion Compound (AKA Purple Crystals)

We actually started this experiment on 9-1-11, but it's taken us a while to figure this whole blog thing out, so we'll try and get this up to speed with where we are now in the experiment! We made a dark purple/blue solution on the first day of the experiment, which is a metal complex named trans-bis(ethylenediamine)di-N-thiocyanatonickel (II). This was separated into two vials: we didn't add anything to one, and to the other we added benzene which sat on top of the purple solution like oil on water. Very small, light purple crystals began to form about 30 minutes after we added the benzene, and they formed right at the meeting place of the benzene and the purple solution.

After our long Labor Day weekend, we analyzed the benzene inclusion crystals. The pure solution (the one without the added benzene) had only the very beginnings of crystals on the sides, so that might not be ready for analysis for another week.

It was very hard to get the crystals out of the bottle because the texture most resembled a grape slushie, so this was a time-consuming part of the process. We were surprised at the amount of crystals that formed- almost the whole vial was filled with them!



We used vaccuum filtration to separate the crystals from the solution they were in, and then dried them in the oven for an hour until they looked like this:

We used the Mel-temp device to find the melting point range of these crystals (a very cool piece of equipment where you can see a tiny portion of your sample melt through a microscope lens). We will just have to wait and see how the pure crystals compare to these ones!