1/27/2007

i really can't convey how exciting this is

This isn't Chemical Quantum Images, so you won't usually see much theoretical chemistry here. But here's an exception, and a link to the paper. (Unlike the last one I posted, this is very very new. Excimer and I were fighting over who got to post it.)
If you're not familiar with pentacene, it's a pretty blue compound that's seen a lot of use as a p-type material in thin film transistors.[1] Winkler & Houk are evidently interested in the possibility of making n-type semiconductors by throwing in some nitrogen:


I'm not going to get into too much detail here, because there are tables and tables and tables of data and better explanations than I could ever give in the paper, but there's some speculation about the crystal packing and other properties of this thing shown above. This is very, very exciting.

What's even more exciting is that it's a theoretical paper. So...who wants to make the stuff and test it out?


[1] There's room for improvement. It's not well-advised to try to handle pentacene in solution. This is partially because it's damn near insoluble--good luck getting it INTO solution in the first place! Also, even if you get a little of it to dissolve, it won't be in solution for long. Even in very-carefully-deoxygenated solvent, kept in the dark, it still falls apart. Well, more accurately, it dimerizes to form a butterfly-looking thing.

8 comments:

milkshake said...

"Where is will there is way"

Here is a possible cheap chemistry that is short and terrible:

2,6-lutidine is brominated in 20% oleum with bromine at 175C for 24 hours to produce 3,5-diBr-2,6-lutidine.

Buchwald bis-arylation with 5-amino-2-cyanopyridine (Aldrich) would produce 3,5-bis-(2'-CN-5'-pyridilamino)-2,6-lutidine that would be double-tosylated on NH groups (sodium hydride, TsCl). Heating this double tosylated intermediate with a strong base like NaH or NaOtBu under oxygen would perhaps produce the cyclized/oxidized product.

Andrew said...

That is exactly the meaning of 'throwing some N into something' in term of synthetic chemistry.

GCT said...

"[1] There's room for improvement. It's not well-advised to try to handle pentacene in solution. This is partially because it's damn near insoluble--good luck getting it INTO solution in the first place! Also, even if you get a little of it to dissolve, it won't be in solution for long. Even in very-carefully-deoxygenated solvent, kept in the dark, it still falls apart. Well, more accurately, it dimerizes to form a butterfly-looking thing."

I had the same problem with hydroxy-methyl-ferrocene, it almost seemed as if it didn't dissolve in water because the sample was in the form of a very fine powder. I air bubbled the solution around it and some of it went into the solution; haven't tried to ultrasonicate to improve upon the matter though.

GCT said...

....Correction, bubbled it with Argon gas....

Ψ*Ψ said...

Ya know, I didn't try sonication. I doubt it would be a good idea, though. Too short-lived in solution.

milkshake said...

Sometimes adding groups like trifluoromethyl into one's molecule does wonders for solubility. You know, it is the pi-stacking in the crystal that lowers the solubility, anything that disrupts is will increase solubility indirectly (besides, solvation of CF3 groups is not as bad either)

Ψ*Ψ said...

Wellllll...if you look at a crystal structure of pentacene, the "pi-stacking" is really only along one axis. There's more of an edge-to-face thing going on. That said, it's entirely possible to have better pi-stacking with wonderful solubility as well...
Before I digress any further, I wonder about the solubility of the compounds listed in the paper?

Excimer said...

Those compounds don't actually exist (yet), but I imagine they'd be as brickdust-y as anything.