Development of fluorescent sensors for metal ions is of great interest due to its potential applications in environmental, biological and medical science. It is believed that the mechanisms associated with fluorescence “turn-on” and “turn-off” upon metal ion binding involve delicate interplay among PET (photoinduced electron transfer), CHEF (chelation enhanced fluorescence), and CHEQ (chelation enhanced quenching) effects. However, there is no general rule that can be used to predict whether a certain combination of sensor and metal ion would exhibit fluorescence enhancement or quenching. Thus, computational methods such as DFT and time-dependent DFT have been heavily used to understand the underlying sensing mechanisms for a given fluorescence sensor. However, the performances of available exchange-correlation (XC) functionals have not been evaluated systematically for such application and there is no clear guidance on the choice of XC functional. In the present work, we report the results of our initial benchmark testing on the performance of popular XC functionals in the applications of fluorescence sensors. We tested three different classes of XC functionals: B3LYP, CAM-B3LYP and wB97X-D, and included two distinct groups of sensors: tethered, in which the fluorophore is separated from the metal binding site by a linker, and non-tethered, in which the fluorophore is an integrated part of the ligand. We optimized the ground and excited state geometries of bare sensors and their complexes with three metal ions (Zn2+, Cd2+, Hg2+) with a common solvation model. With the optimized structures, we computed three important properties regarding fluorescence sensors: absorption, emission frequencies as well as the binding free energies (DGbind) for metal ions. We will discuss the impact of different choices of XC functionals on these properties and their performances with respect to the available experimental data.

DFT and TD-DFT studies of fluorescence sensors for metal ions: Benchmark testing on the performance of three exchange-correlation functionals (B3LYP, CAM-B3LYP and ωB97X-D)

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.