Valence tautomers are bistable molecules of potential interest for magnetic storage and spintronic devices which can be switched between a low-spin and a high-spin state by tuning different external parameters, as the temperature or, more interestingly, through light irradiation. Here we plan to study by means of zero field and longitudinal field muSR the spin fluctuations in Cobalt:dioxolone valence tautomer when it is driven to the high spin S=1 CoIISQ state either thermally, by heating up the system above 120 K, or, at low temperature, by infrared light irradiation.