Absorption and emission UV-Vis spectra of the TRITC fluorophore molecule in solution: a quantum mechanical study

The absorption and emission properties as well as the electronic structure in the ground (S(0)) and excited (S(1)) states of tetramethylrhodamine isothiocyanate (TRITC) fluorophore molecule have been investigated by time-dependent density functional theory (TD-DFT). The effect of water and ethanol solvents on the structure and optical properties of the dye was taken into account by using both explicit and implicit solvent models, as well as combinations of them.Different hybrid and long range corrected functionals have been tested in reproducing absorption and emission transition energies. It has been found that the B3LYP functional coupled with mixed explicit/implicit solvent models reproduces correctly experimental data concerning both the solvent and Stokes shifts. This work presents a first step to a more challenging project devoted to the development of integrated multiscale approaches and protocols for studying optical properties of fluoroprobes embedded in biological systems and/or encapsulated in nanoparticles of technological interest.