A DFT/TDDFT study on spectral effects of metal ion interactions with benzofurazan-based fluorescent probes

CAM-B3LYP DFT/TDDFT calculations have been performed on two fluorescent benzofurazan derivatives and their complexes with metal ions (Zn2+, Na+, K+, Mg2+ and Ca2+). Optimized structures of complexes and binding energies have been determined. Calculated vertical transition energies have been compared to available experimental data. Only one ligand binds effectively Zn2+ ion allowing metal orbitals to participate in frontier molecular orbitals which results in significant shifts in absorption and emission spectra. Modified structure of the other ligand makes ion binding less effective. It has been shown that proper reproduction of transition energies requires accounting for state-specific solvation.

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► CAM-B3LYP TDDFT calculations were performed on receptor-metal ion complexes.
► Zn2+ interacts strongly with the ligand, shifting absorption and emission maxima.
► State-specific solvation is necessary to reproduce spectral shifts.