PDA for PDIs!


This paper caught my eye because I recalled my one regular commenter (come on dear readers…where are you? :’-( ) working with perylenes in the past. The reactant in the middle is imide-substituted perylene diimide, PDI. DMP PDI, compound 1a, has some interesting solid-state photochemical quirks, so who knows, substituting the perylene core could lead to the next big thing in photonic organics. So the author says.

The first reaction described looks less than impressive: for 1a, 26% came out a mixture of dibrominated isomers (1,6-3a and 1,7-3a), 57% came out monobrominated, and 15% remained unreacted. Restricted rotation of the bulky R groups about the C-N bond meant two isomers for each potentially brominated carbon. The author goes on to describe a reaction using a refluxing solution of bromine that gives exclusively dibrominated product overnight, with a 1,7/1,6 ratio of 3:1. The regioisomers can be separated by recrystallization from a 1:1 solution of dichloromethane and hexane.

Sonogashira coupling of 2a with TMS acetylene works, as does nucleophilic substitution by piperidine.


Bromination causes an interesting “core twist” vibration involving, well, the twisting of the perylene core. Energy barriers associated with the motion were relatively low and thus interconversion between the two “twist states” of the molecule is relatively easy.

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4 Comments

  1. Not only in the past, but also in the near future…red crystals are lucky for me, I suppose. I kinda thought about blogging about this paper, but there’s a cooler one on perylenes out in…Nature Materials, is it? I’ll email it to you if I write about it because UK didn’t get that journal last I checked. Too bad.
    Someone at Northwestern (Wasielewski or Marks, can’t remember which) already did the core functionalization thingie. I wonder if the TMSA is really that effective at solubilizing the perylene core–I’d think it would all have to be due to twisting the beautifully flat rings and breaking up the pi-stacking. Too bad…the two are not mutually exclusive…I’ll tell you more about that project sometime, maybe.

    Reply

  2. How to get readers/comments:
    -Update at least twice a week
    -Include lots of pictures in posts
    -Comment frequently elsewhere
    -Ask questions you KNOW people will probably answer (this one’s iffy)

    Reply

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