August 13, 2007

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.

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