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 (S0) andexcited (S1) states of tetramethylrhodamine isothiocyanate (TRITC) fluorophore molecule havebeen investigated by time-dependent density functional theory (TD-DFT). The effect of waterand ethanol solvents on the structure and optical properties of the dye was taken into accountby 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 absorptionand emission transition energies. It has been found that the B3LYP functional coupled with mixedexplicit/implicit solvent models reproduces correctly experimental data concerning both the solventand Stokes shifts. This work presents a first step to a more challenging project devoted to thedevelopment of integrated multiscale approaches and protocols for studying optical propertiesof fluoroprobes embedded in biological systems and/or encapsulated in nanoparticles oftechnological interest.