I came across this article on electrochomic displays. It mentions Ethyl Viologen as an electochromic chemical. I would like to attempt an experiment to showcase it's electrochomic properties but don't really know where to start.

First off, where to get some. Googling I came across these, three, pages. Will one of these work? If not where do I get some? Or do I need to synthesize it (if so how)?

Second, what to do with it once I have it? I take it there's more to it than just sticking some electrodes in a beaker of it.

The article states, "If the EV-molecule absorbs a second electron, EV turns pale blue. This reduction however is irreversible and definitely not wanted." What care (if any) do I need to take to avoid this?

Sorry if I ask something obvious, I'm very inexperienced with chemistry.
Thank you.

  • $\begingroup$ I know it's been a while since you asked this question, but just remember to be careful with the viologens, as they are fairly toxic. Also, if you still want an answer I can try to help. What equipment do you have access too? Do you have fume hoods, a potentiostat, etc..? $\endgroup$
    – Sean Doris
    Commented Feb 26, 2016 at 6:54

1 Answer 1


[…] I'm very inexperienced with chemistry.

Have a look the material safety datasheet (MSDS) of ethyl viologen dibromide and pay attention to the H-statements:

H302 Harmful if swallowed.
H312 Harmful in contact with skin.
H315 Causes skin irritation.
H319 Causes serious eye irritation.
H332 Harmful if inhaled.
H335 May cause respiratory irritation.

Can you handle this?

You asked:

what to do with it once I have it? I take it there's more to it than just sticking some electrodes in a beaker of it.

It is not that simple.

It is true that 4,4'-dialkyl pyridinium dications undergo a reversible one-electron reduction. This can be achieved by applying a voltage or by electronic excitation in the presence of an electron donor.

However, the resulting radical cations are very sensitive to oxygen and they have been used as probes to monitor oxygen permeation in polymers. With other words, you would have to exclude oxygen from your setup for a lasting colour effect.

In summary, I'd rather advise against the use of ethyl viologen for showcasing, unless the experiments are performed by professionals in a safe environment.


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