A Theoretical Investigation of the Selectivity of Aza-Crown-Ether Structures Chelating Alkali Metal Cations for Potential Biosensing Applications

Aza-crown ether structures have been proven effective in constructing fluorescent biosensors for selectively detecting and imaging alkali metal ions in biological environments. However, choosing the right aza-crown ether for a specific alkali metal ion remains challenging for synthetic chemists because theoretical guidance on the chelating activities between aza-crown ethers and alkali metal ions has not been available up to now. Predicting the physical properties of the chelator-metal complexations poses a greater challenge due to the numerous quantum mechanical functionals and basis sets to be used in any theoretical investigation. In this study, we report a theoretical investigation of different aza-crown ether structures and their bindings with different alkali metal ions, which will establish theoretical models to be used for synthesis design by portraying a novel relationship between the binding energies and charge transfer. Furthermore, the calculations can serve as a performance overview of the different types of functionals in Jacob's ladder of chemical accuracy classification.