The excited state dynamics of a molecule can change significantly upon the addition of a functional group. This is because the functional group can alter the electronic structure, energy levels, and vibrational modes of the molecule. Some of the possible changes include:1. Shifts in absorption and emission spectra: The addition of a functional group can change the energy levels of the molecule, leading to shifts in the absorption and emission spectra. This can affect the color of the molecule and its photophysical properties.2. Changes in excited state lifetimes: The presence of a functional group can influence the rate of non-radiative decay processes, such as internal conversion and intersystem crossing, which can alter the excited state lifetimes of the molecule.3. Changes in excited state reactivity: The addition of a functional group can change the reactivity of the molecule in its excited state, leading to different photochemical reactions or energy transfer processes.4. Changes in solvation dynamics: The functional group can affect the solvation dynamics of the molecule in its excited state, which can influence the overall excited state dynamics.Ab initio calculations in computational chemistry can be used to predict these changes in excited state dynamics upon the addition of a functional group. These calculations are based on first principles, meaning that they do not rely on any empirical data or approximations. By solving the Schrödinger equation for the molecule, ab initio methods can provide information about the electronic structure, energy levels, and vibrational modes of the molecule, both in its ground state and excited states.By comparing the results of ab initio calculations for the molecule with and without the functional group, it is possible to predict the changes in excited state dynamics upon the addition of the functional group. However, it is important to note that ab initio calculations can be computationally expensive, especially for large molecules or complex functional groups. In such cases, more approximate methods, such as density functional theory DFT or semi-empirical methods, may be used to obtain similar insights with reduced computational cost.