The bigger chemical on his head could be classified as a tricyclic. The problem is that these structures are very similar and just a minor change can mean something totally different and there are lots and lots of different types. These are drugs that can be antidepressants, anti-psychotic or even more mundane anti-histamine, etc.. It might be possible to decipher it perfectly, but we also know that there is some liberty when it comes to the artwork of the show.
I think it is more important to realize that it is a mix of real chemistry, alchemy, voodoo, hieroglyphs, eastern Asian etc.
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