A DFT study on the structural and optical properties and cation selectivities of some metal-coumarin-crown ether complexes

Macrocyclic ethers are well-known molecules because of their high cation-binding capacities. They form stable complexes with alkaline and soil alkaline metals through strong oxygen bridges in solution. For enhanced optical properties, a new series of crown ethers was synthesized with a coumarin ring fused to it. The effects of the position of the coumarin ring, the type of the substituent on the coumarin ring, and the size of the crown on the optical properties of the material were studied according to the density functional theory (DFT) method at the B3LYP/6-31g(d) level of theory in the gas phase as well as in the solvent medium. The ion selectivities of different coumarin-crown ether molecules were also studied by calculating the metal-binding energies at the same level of theory. The excited-state electronic energies were calculated by using the time-dependent density functional theory (TDDFT) method, and the theoretical UV absorption spectra of the studied molecules were plotted and compared to the experimental spectra if available.