A test of the predictive capability of our current structure -phase correlations in ROR′-DADQs would be the exploration of the potential PCM characteristic of n-4O2. The DSC data (Figure , Table ) show that the C f orm can be melted at 150 °C and quenched quickly to obtain the A f orm, stable under ambient condition. Slow heating of the A f orm at ~ 105 °C causes recrystallization to the C f orm. We have carried out this sequence of operations multiple times to explore the PCM behavior. The optical image of the C and A f orms with their f luorescence emission colors are shown in Figure ; the f luores-cence emission spectra recorded in each state and the plot of the spectral intensity illustrating the f unctional response switching are shown in Figures and respectively, demonstrating that this material is a new entrant to the group of f unctional molecular PCMs.