Photophysics and excited-state proton transfer of 2′-hydroxy-2-trans-styrylquinoline

The ESPT were observed for ground-state hydrogen-bonding complex between 2-StQ-2OH and 2,2,2-trifluoroethanol (TFE) or with triethylamine. In aqueous solution, ESPT can only be observed in α-cyclodextrin (α-CD) inclusion complex. The dielectric constant values of the α-CD cavities probed by 2-StQ-2OH and 2-StQ-2OMe are 8.5 and 6.3, respectively, because of the difference in size of the probe molecule inside the cavity.