Indeed, tholin turns out to be incredibly chemically complex. Ultra-high-resolution mass spectrometry measurements I analyzed while in graduate school demonstrated that tholin contains at a minimum 10,000 different molecular formulas, which, once you account for different structures (isomers), could mean hundreds of thousands of different compounds! We have detected molecules in tholin with masses equivalent to about 80 carbon atoms, although we know that much heavier ions are present in Titan’s atmosphere!

A final note on nomenclature: one of the biggest difficulties with the word "tholin" is that it is incredibly nonspecific. The best analogy I have been able to come up with is “salad”. Salad, like tholin, is a mixture of a number of different compounds and spans a fairly broad range of materials. Most of us would agree on a case-by-case basis whether or not something is a salad, but the definition is not at all specific and the material itself depends on the starting materials, preparation, temperature, etc. We sometimes refer to “Titan tholin” or “Triton tholin” but even then you would need to ask about temperature, energy source, precursor gas or ice mixture, etc. to get an actual understanding of what the material is. Personally, I try to use the word “tholins” only when describing the laboratory-produced samples, in part because we do not really know yet how similar the material we produce in the lab is to the material found on places like Titan or Triton (or Pluto!). In fact, I usually call the samples produced in my laboratory “Titan aerosol analogues” rather than “tholins.”