9/07/2007

yet another perylene

I know perylene diimides are nothing new for CBC.[1] I can't give you something new every week, you know, because I can only work on so many projects at once. But they're still pretty, no matter how often I see them.[2] (Or how much I hate trying to crystallize them, either, for that matter.) Which is why the entire point of this post is to put up yet another picture...[3]

So here's another perylene! Lots of it, at that.


[1] Yeah, yeah. Here they are in case you're new and missed them. I think that's all of them, anyway.
[2] I like the look of the kinda-concentrated solutions the most. They're a bright, blood-red color. Takes some finagling to get that much of them into solution, though.
[3] Can you tell what my strategy for overcoming blogger's ennui is? (See [1] if any doubt remains.)

18 comments:

Excimer said...

I think it's pretty obvious how I take care of blogger's ennui. But it's nice to see some purty colors up here again.

sam said...

did you spill any?

Ψ*Ψ said...

No, but that's close to the right color...

Uncle Al said...

The recrystallization solvent of last resort is hot DEET. It boils near 300 C and dissolves just about everything short of glassware.

Hot NMP for starters. Absent cooperation, soxhlet with ceramic thimble as recrystallizer for bp = 200 C. Solute eventually makes it down into the boiler, accumulates, and grows. Lots of glass wool insulation topped with a loose aluminum foil wrap for that one.

Think about your condenser and its possible failure. Don't use a crappy thin-wall RB for the boiler - and check for star cracks. What is a stir bar's Curie temp?

Alexander said...

Ah, 24/40 joint... looks so unusual every time I see one!

Rich Apodaca said...

Beautiful color. What's the structure of the one you made?

Chemgeek said...

What's so unusual about seeing a 24/40 joint. Especially on a 1L flask.

I assume you never do stuff on a large scale.

Of course, there is nothing more lame-looking than a 50mL RB flask with 24/40 joint. That's funny looking.

Ψ*Ψ said...

50mL roundbottoms with large joints seem especially prone to getting stuff in bump traps, but at least it's easy to stuff a brush in there to clean them.
I'm not really willing to say anything about the perylenes I make except that there are side chains stuck on the nitrogens. You'll see a very excitable post when/if something from this project gets published, and the structures will be there.
As for recrystallization...many solvents will work for that and it's not difficult. The annoyance is that there's always a blanket-like film of teeny little crystals--clean enough, yes, but not x-rayable by any means. IME, perylene diimide single crystals require patience, chloroform, and lots of luck. Soxhlet may not be a bad idea, though. Maybe I'll give it a shot in the future.

Ψ*Ψ said...

Oh, oops! (I shouldn't say anything about single crystals without also mentioning that the crystallographer here is incredibly good at what he does and one of the nicest people in the department.)

GMC2007 said...

This is a wonderful color to achieve by organic means and you are obviously a particularly cultured chemist. Are there any colors that are particularly difficult to engineer? Do your di-imides have any tendency to go into sulfuric acid?

Ψ*Ψ said...

Actually, everything I'm working on at the moment happens to be red :) We're not exactly in the business of making dyes so much as making semiconductors that happen to be very colorful (definitely a plus to working in this lab). On any given day I could probably dig through a few drawers and pull out a rainbow of compounds.
Sulfuric acid dissolves not only the diimides but also perylene dianhydride (which is kinda impressive, since I haven't found anything else that will do so).

Alexander said...

You'd never find 24 joint where I work, only 29 for 0.25-3L flasks. I don't know why.

BTW, 3L flask with 24 joint looks quite lame, too.

Uncle Al said...

Low solublity is not controlling for growing x-ray quality crystals,

J. Appl. Cryst. 4 333 (1971)

Thiele-Dennis tube as a melting point apparatus, then Umpolung! You only need it 0.1 mm in diameter.

Perhaps vertical thermal zone sublimation for perylenediimides, in hard vacuum.

GMC2007 said...

Sulfuric acid is indeed funky stuff and I have found that it also dissolves clothing although often this only becomes apparent after laundering. One can make a loose analogy between sulphuric acid and water in that they have both have matched hydrogen bonding functionality. I don’t know the extent of ionization of pure sulphuric acid but this will affect its properties.

Triflic acid might be interesting to take a look at because it is like a monobasic sulphuric acid. Trifluoromethanephosphonic acid is dibasic like sulphuric acid but I’d expect it to be less acidic than triflic acid. I’m guessing that your di-imides get protonated when they go into sulphuric acid so there are two factors that influence the thermodynamics of dissolution. These are how easily the acid donates protons and how well the ions are solvated. I think triflic acid would be a better proton donor than sulphuric acid but a worse solvator. In this case you may find that adding some triflic acid to the sulphuric acid makes it a more effective solvent even if triflic acid itself is a less effective solvent

Ψ*Ψ said...

I think I might have been misunderstood--the derivatives I'm making are actually pretty soluble in DCM, chloroform, toluene, etc.
I've never tried sublimation with these, because I've gotten x-rayable single crystals of these from solution.

GMC2007 said...

Sounds like it. I don't know what you're making and thought that it might have been something large and particularly insoluble. I wasn't thinking of sulfuriuc acid for crystallization. More just interest in solvation processes for 'different' (from a pharma perspective) molecules. Best of luck with your experiments!

milkshake said...

I think the flask is full of a freshly-spilled blood.
(Ninjas fill their 1L flasks with blood from impertinent by-standers and they don't even think twice about it.)

Ψ*Ψ said...

Milkshake wins.