Optical Signatures of OBO Fluorophores: A Theoretical Analysis.

Dioxaborines dyes, based on the OBO atomic sequence, constitute one promising series of molecules for both organic electronics and bioimaging applications. Using Time-Dependent Density Functional Theory, we have simulated the optical signatures of these fluoroborates. In particular, we have computed the 0-0 energies and shapes of both the absorption and the emission bands. To assess the importance of solvent effects three polarization schemes have been applied within the Polarizable Continuum Model: the linear-response (LR), the corrected linear-response (cLR), and the state-specific (SS). We show that the SS approach is unable to yield consistent chemical trends for these challenging compounds that combine charge-transfer and cyanine characters. On the contrary, LR and cLR are more effective in reproducing chemical trends in OBO dyes. We have applied our computational protocol not only to analyze the signatures of existing dyes but also to design structures with red-shifted absorption and emission bands.