crystals and purity, waiting for number 3

My previously mentioned crystals came through for me and gave a nice structure with a decent R factor. 5.9, which is fair, for small molecule work the goal is really less than 5, but 5.9 is fine with me. I might try to solve the structure myself just to see if I can't get it down a little farther. I'm guessing that the staff crystallographer just punched the "solve" button and went with the computer answer, so I could probably shave a few more thenths off the R factor with some careful work. Don't hold your breath though.

The next success dates back to something I've been trying to do since the first week I arrived here. In the very first post I made I referred to a compound I was attempting to sublime in an effort to purify it. Purification of this product has been an absolute pain in the tuckus. Crystallization (via layering, slow cooling, slow evaporation, crashing) sublimation, chromatography, and chemically protecting/deprotecting have not worked at all. What did work was just decreasing the amount of material that I was trying to make at once. There's no reasonable explanation for why this would work, but its tough for me to worry too much about something that worked out well for me. The NMR shows better than 99% purity. Awesome.

So if good things come in threes that means I should have something else good coming my way. Today I'll be working on the Ir recycling by flipping the switch on the muffle furnace and letting that sucker plug away all day. I've been having trouble determining what the right temperature is that the iridium oxide needs to be at in order to decompose to the metallic iridium. I haven't really found any reliable numbers for this, but Wikipedia suggests that 1100 C is just about where I need to be. Please note that Wikipedia is not a credible source. Not that's its wrong, but its like writing a book report and citing Cliff's Notes. The muffle furnace I'll be using maxes out at 1100 C, but we'll see just how far I can push it. 1200 C would be nice, just to make sure that the job gets done.

salespeople

A short commentary on salespeople.

From time to time in the course of working in a research lab it may become necessary to order some expensive pieces of equipment. I don't relish the experience of talking to sales people but for the most part this is mitigated by the fact that they want to sell stuff to you. Something about commission, I'm sure. What baffles me is that when I need specific information from them, and they get all cagey, like all of a sudden they don't want this sale to continue if it means looking something up or doing a little math. Let me clue in all of the salespeople who I know must read this blog. (*cough*) Price is an object to a graduate student only to a certain extent, after that, the most important things in closing a deal is expediency and minimization of hassle. I don't work in the Purchasing and Acquisions office, I'm a grad student. My patience for paperwork is very thin and if there are two vendors offering nearly the same services, I will take the one that is fast and helps me through my paperwork over the one which is 10% cheaper. Valuable information for anyone trying to sell something to a chemist in my position.

guarded optimism

The crystals I sent the X-ray lab seem to have held up in the mounting oil and diffracted well enough. The strong scattering (shown in the picture) and unit cell dimensions indicate some sort of monomer with one heavy atom (the metal atom) per unit cell. I don't have the solved structure in hand yet, but I'm ready to declare victory as far as getting a quality crystal. I've seen better, these were pale orange needles. Not too shabby though.

X-ray quality crystals were grown from a standing cooled solution in heptane over several weeks at a temperature of -35 C.

a break from recycling, and some crystals

Finally, some good news. But first an update on the frustrations of the Ir recycle project. The setup for chlorination was tested, but due to operator error, some adjustments may have to be made. I'm suspicious that the dedicated gas regulator for the Cl2 gas tank is corroded to the point of uselessness, however this is no excuse for ineptitude, at least not yet. In better news, I have located a muffle furnace, so perhaps this is an end to the current destruction of crucibles from around the department. More on that later.

CRYSTALS! A vial left in the freezer has yielded some needly orange crystals. Perhaps not the best for crystallographic analysis, but the crystallographer here thought they would be just fine. Currently I'm awaiting time on the diffractometer, so we'll wait before I declare total success. I'm still counting it as a triumph to get crystals at all, though.

Ir recycling step 5.1

The thermal shock on the crucibles has proved to be too much. Recall that the Meker burner did not generate enough heat to reduce the ash mixture to elemental material and salts, but it did come close. The solution then, or so I thought, was to use more Meker burners set up in a tripodal fasion. This (I patted myself on the back a few times for this) would allow greater control over slow heating as well as provide more actual area on on the crucible which was being heated so as to not develop "hot spots" on the crucible itself (slow heating is ineffective if the thermal shock is due to one area of the crucible expanding while another cool area does not.)

I set up (painstakingly) a couple of stands with Meker burners perfectly in place for the tripod along with the crucible at the optimal height and then started up all the Meker burners at the lowest possible gas flow. I increased the gas flow slowly on each of the burners over the course of about twenty mintues, carefully monitoring all of the surroundings to make sure they were not overheating.

Long story short the heat load was too much for the dry powder fire extinguisher which comes standard on all of the hoods in the lab. The heat triggered nozzle fired fine yellowish powder all over myself, the setup I was so proud of and half of the lab. A picture (of course) of the misery will follow shortly after I get it off of Krista's camera.