First of all, we notice that the global minimum structure nicely matches with available data from both static and time-resolved fluorescence measurements, namely, the S0 -S1 energy gap at the emission maximum, the fluorescence lifetime, and the oscillator strength that can be derived from them, according to Eq. 2 (see Table ). Therefore, we compared the fluorescence lifetime for the optimized excimer geometries 1-8 with the characteristic time of the intermolecular reorganization leading to the 3.1 conformer (cluster 9 will be discussed below). The results are summarized in Table , where both the forward and backward reactions are considered. The associated times were estimated from the Eyring equation in transition state theory as