I can only boast of my passion for science and not of any credentials. I ask because I am curious, and it is not the type of question one can easily Google! What if the key to discovering and unlocking the secrets of dark matter and energy lie in the Island of Stability? Am I missing a vital reason that outright contradicts an attempted connection between the two?
The main thing we know about dark matter is that it does not interact electromagnetically. That is what makes it "dark": it neither emits nor occludes light in any band.
Heavy nuclei (with or without electrons) would interact electromagnetically just like all other nuclei and atoms. We'd see their spectra imposed on all extra-galactic light: we couldn't miss it.
So, no. Not a chance.