The molar extinction coefficients at the band of maximum intensity (360-370 nm and 410-430 nm for compounds 4a-d and 6a-d, respectively) also experiences a dependence on the solvent polarity as well as on the donor or acceptor peripheral groups (Table and). Indeed, the maximum absorbance is obtained for chloroform (35.3 and 55.1•10 3 M -1 •cm -1 , for 4c and 6a, respectively) while the minimum corresponds to ethanol (27.5 and 52.2•10 3 M -1 •cm , for 4c and 6a, respectively). Molecular modeling of the absorption spectra, reported in SI (Figure ), reproduces well the global features of the experimental bands when considering dynamic and vibrational effects through a Wigner sampling of the Franck-Condon region. The fluorescence spectra were obtained under excitation at the maximum absorbance and are given in Figure -S1 and Tables 1-S1. The maximum of the fluorescence band is red-shifted when increasing the solvent polarity and Lippert-Mataga diagrams confirm a higher dipole moment for the excited than for the ground state (Figure ). In all solvents, the fluorescence quantum yields of the compounds bearing hydroxy or alkoxy moieties (4a-c and 6a-c) are low and do not exceed 3%. In contrast, compounds 4d and 6d (amine donor) have quantum yields of about 11% (Table and). The low fluorescence quantum yields could be explained by other competitive non-radiative deexcitation pathways, such as photoisomerization or vibrational relaxation. As shown in Figure the natural transition orbitals (NTOs) obtained for the lowest laying excited states show a different behavior depending on the presence of the oxo or malonitrile substituent. Indeed, compound 4d shows a low energy absorption which is dominated by two main diabatic states, namely nπ* and ππ* transition. This pattern is absolutely coherent with the behavior of other similar CC derivatives namely 4a and 4b and may also explain the slight solvent dependency observed for absorption and emission. Furthermore, as it will be detailed later, the electronic density reorganization involving the population of antibonding orbitals localized on the styryl double bond, pointing to a possible photoisomerization. The presence of malonitrile moiety in 6d significantly modifies the excited state landscape. The lowest excited state can now be described as a ππ* involving the malonitrile and the styryl double bond, while the second excited state accumulates electronic density on the phenyl ring directly bound to the pyran (D) while S3 appears slightly more localized on the malonitrile substituent. Even from this first qualitative analysis a different photochemical behavior can, therefore, be surmised, since the photoisomerization pathway appears less favorable than in the original CC analogous.