A stable and sensitive luminescent photoprobe based on tris(3‐acetylindole) terbium(III) complex: Molecular modeling, luminescence quenching, and Ab initio molecular dynamics

Abstract

We have been successfully used a new photoprobe based on Tb(III)(3‐acetyleindole)3 complex (TbAcI) as a novel, sensitive, accurate, and precise sensor for detecting shallow concentration (pico) of epinephrine (EPI) in different serum samples. Here, we report on and discuss the molecular structure of the interacting species using density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT). The simulation results reveal the strong binding energy of TbAcI (−148.95 kcal/mol) and explain the outcomes of Stern‐Volmer bimolecular quenching analysis due to EPI's presence in the proximity (at 3.22 Å apart from Tb ion) of the emissive TbAcI. The bimolecular quenching rate constant (k2) obtained from the Stern‐Volmer rate constant (Ksv) and the complex luminescence lifetime points to a diffusion‐controlled dynamic quenching. We used the Ab initio molecular dynamic (AIMD) simulations to explain EPI's effect on the TbAcI molecular kinetic energy changes in its S1 state. Quenching begins at 14 fs when the EPI‐TbAcI distance is about 3.22 Å. The excited state AIMD simulations proposes a new opportunity for future research on luminescence quenching.