Having established the broad f eatures of the spectroscopic characteristics in the solution and microcrystalline solid states of ROR′-DADQs, we investigated the corresponding responses in the amorphous state of these compounds prepared through simple drop cast and melt-quench processes described in the Experimental section. The absorption spectra (Figure ) Please do not adjust margins Please do not adjust margins variations in the molecular environments. The f luorescence emission spectra (Figure ) resemble closely those of the solutions in terms of the peak positions, but have intensities intermediate between that of the solution and the microcrystalline solids; the latter is revealed by the FEE of the A f orms collected in Table . These observations are consistent with the lower density of molecular packing expected in the A state compared to the C f orm. As the f luorescence spectral peak provides a precise signature of the A or C nature of the DADQs (blue shif t and enhancement on crystallization), we have monitored the status of the A f orm by recording the temporal evolution of the spectra (Figures ). Interestingly, the A f orm of the RO2-DADQs remains stable over several days with no indication of crystallization; the only deviation is seen in the case of n-4O2 which shows signs of change af ter ~ 4 days (Figure ). On the other hand, the RO3-DADQs transf orm f rom the A to the C state within a matter of hours or at most a day, showing the preponderance towards the latter f orm (Figure ); the changes are so quick that the spectra of the A f orm could not be recorded in the case of n-3O3 and n-4O3. DSC provides a direct visualization of the melting/crystallization events, and variation of the scan speed can be used to induce the f ormation of the A or C f orms. In order to observe the behavioral trends, we carried out three types of thermal cycling experiments on each compound: (i) slow heatingslow cooling, (ii) slow heatingmoderately f ast coolingslow heating, and (iii) slow heatingf ast coolingslow heating; the slow, moderately f ast, and f ast rates correspond to 2, 10 and 20 °C min -1 respectively. These experiments were designed to see if crystallization f ails to occur on cooling the melt (indicating the stabilization of the A f orm), whether the enthalpy changes are dependent on the cooling/heating rate or if there are hysteresis eff ects (revealing an ambivalence towards A or C f orms), and whether a recrystallization occurs when the cooled sample is heated again (suggesting the f easibility of reversible phase change). The thermograms of RO2-DADQs (Figure ) show that no crystallization occurs on cooling or even on s ubsequent heating, under any of the rate conditions, except in the case of slow heatingf ast coolingslow heating of n-4O2. The dominance of the A f orm is evident once again, with a slight tendency towards crystallization with the longest R chain compound; the latter observation is consistent with the temporal variation of the spectroscopic signature noted above. Table provides the quantitative data on the transition temperatures and enthalpies.