Background chemical structure is DPPH (2,2-diphenyl-1-picrylhydrazyl), which is a common laboratory chemical used as a source of free radicals (that dot 'on' the nitrogen). Most STEM students have probably used this chemical at least once in an experiment determining the antioxidant activity or 'Vitamin C concentration' of fruit or vegetable juice. Prolly in high school or middle school too.

You know, that deep purple 'liquid' you add Vitamin C (or fruit juices) to decolorize it.

Never used it myself, or at least, there's a dark black hole inside my memories where I store all of my chemistry experience... *SHUDDER*
Which is why I was extremely grateful that my Engineering degree (Computer) did not require it. :D