Fluorescence turn-on and turn-off mechanisms of a dual-selective chemosensor of Bi3+ and pH changes: Insights from a theoretical perspective

Insights into the selective sensing mechanism of a luminescent Cd(II)-based MOF chemosensor toward NACs: roles of the host–guest interactions and PET processes

“…However, the PET process cannot be clearly explained only with this criterion of energy of the MO. Recently, we reported a theoretical procedure that allowed to confirm the existence of a state with the suitable electronic configuration and energy for the PET mechanism to occur on a molecular chemical sensor [77]. Therefore, in order to investigate whether the excited state of the interacting system Cd-MOF/pNA has the electronic configuration that favors photoinduced charge transfer, CAS(10/ 10)SCF/NEVPT2 calculations were performed.…”

Understanding the Deactivating/Activating Mechanisms in Three Optical Chemosensors Based on Crown Ether with Na+/K+ Selectivity Using Quantum Chemical Tools

“…This analysis displayed that PET was possible in the free sensors as well as in the K + complexes which did not explain the CHEF effect by the metal‐sensor interaction. Using this framework, our group demonstrated that the transduction mechanisms in the single and dual‐selective sensors can be correctly described considering not only the relative energies and electronic structure of the S 0 , but also of the first excited singlet and triplet states (S 1 or T 1 ) together with the kinetic parameters of the electron transfer and emission deactivation process, as well as other theoretical tools like the interaction energy of fragments through the Morokuma‐Ziegler decomposition scheme [8,12,15,34] . This theoretical protocol displayed excellent results to explain and to predict the optical properties, the transduction mechanisms, and the selectivity of several luminescence chemosensors.…”

“…In this framework, optical chemosensors are simple devices used for continuous monitoring [4–6] of metal ions in situ and in vivo [7–10] since the optical properties, like the luminescence, can be changed upon the interaction with the analyte leading to a Chelation Enhanced Fluorescence (CHEF) [11,12] or a fluorescence quenching effect (CHEQ) [13–15] . These effects are determined by a series of transduction mechanisms [16,17] based on Energy Transfer (ET) [18–21] and Charge Transfer (CT) [20,22–24] .…”

“…In this sense, the understanding of the transduction mechanisms in analytes sensing is an important factor towards achieving this goal. As these mechanisms depend on the careful tuning of the electronic and molecular structure of the sensors, theoretical calculations have been a powerful tool in understanding and predicting the electronic properties and the transduction mechanisms in the recognition of several analytes like metal ions, [25,33,37,38] anions, [39–41] pH, [15,42] contaminant and/or explosive organic compounds [25,43]…”

“…Additionally, computational studies have been based mainly on the analysis of the frontier molecular orbital (FMO) energy and the molecular structures employing the Density Functional Theory (DFT) and Time‐Dependent Density Functional Theory (TD‐DFT) methods [26,44–46] . The FMO analysis has allowed to study the optical properties and to propose the possible mechanism of sensing and selectivity of optical sensors; however, several reports have shown that if these studies focus only on the ground state (S 0 ) electronic structure and without taking into account the analyte‐sensor interaction, erroneous conclusions can be reached [12,15,26,34] . For example, Briggs and Besley in 2015 reported the theoretical study of the electronic structure and PET processes in a K + fluorescent chemosensor based on crown ethers [26] .…”