A conceptual density functional theory approach to substituent effects in fluorescence processes: The case of naphthalimide derivatives

The theoretical framework of conceptual density functional theory is applied to the study of molecular excitations by considering that the differences between the ground and excited state electronic densities may be treated as if they were the consequence of intramolecular charge transfer processes. Through this approach, it is found that the hardness is directly related with the absorption and emission energies, and that the dual descriptor provides a description of the regions of the molecule where charge is added or removed, that in its condensed form leads to an estimation of the effective charge involved in the excitation. All this chemically significative information is then used to analyze the effects of the substituent in the fluorescence of naphthalimide derivatives. Conceptual density functional theory is used to study molecular excitations by considering that these can be seen as intramolecular charge transfer processes. Thus, it is found that the hardness is directly related with the absorption and emission energies, and that the dual descriptor shows the regions of the molecule where charge is added or removed. This chemically significative information is then used to analyze the effects of the substituent in the fluorescence of naphthalimide derivatives.