The resolution of this conundrum was only reached after analysing the pulse ESR results (see below). The conclusion is that the FAAF spectra in figure do indeed arise from a mixture of a doublet component, akin to AAF, and a triplet component (see also table ). The doublet component tends to dominate the spectra with a weighting of 50-90%. Importantly, its exact weighting is not reproducible between different samples; it is non-trivially dependant on preparation conditions. In the SI, we explore further the effects of different parameters (oxygen, solvent, light, temperature, storage times) on the appearance of the spectra and on the relative weighting of the doublet and triplet components. Although the results are not conclusive, the doublet component observed in liquid solutions of FAAF is likely caused by a combination of the following: (1) interactions with molecular oxygen, (2) interactions with light, (3) interactions with the solvent, and (4) intermolecular interactions (e.g. 𝜋-stacking). All these factors are also consitent with a degradation of the triplet state to another fluorenyl-based doublet species. Although the doublet/triplet ratio is not reproducible, the hyperfine couplings of the two components are persistently the same between different samples, preparation methods, and storage times. Importantly, all the hyperfine couplings of the triplet component are approximately half of those in the doublet component. As discussed in the SI, this halving of the hyperfine interaction in the triplet is reproduced by the DFT results and it can also be explained intuitively by invoking the Pauli exclusion principle.