Linear Relationship Between Emission Quantum Yield and Stokes Shift in 3-Styryl Aza-Coumarin Based Dyes in the Presence of Cyclodextrins

The effect of the cyclodextrins inclusion on the Stokes shifts and emission quantum yield of three 3-styryl aza-coumarin dyes (SACs) was experimentally and theoretically studied. Preliminary results show a rela-tionship between the emission quantum yield and the calculated binding constants. Supramolecular inclusion was supported by changes in the fluorescence spectra, high-resolution mass spectrometry and molecular dynamics studies. 2,6-di-O-methyl-b-cyclodextrin (DM -b-CD) presented higher binding constants than b-cyclodextrin (b-CD), along with up to a 6-fold increase in emission quantum yield for the SACs. Additionally, a linear negative correlation was obtained between the Stokes shift and the emis-sion quantum yield. This linear and empirical relationship was explained by the action of a unique intramolecular rotation and charge transfer phenomenon in the dyes, which was modulated by cyclodex-trins, and supported by calculations based on density functional theory.(c) 2023 Elsevier B.V. All rights reserved.