Synthesis of Fluorescent Diphenylanthracene-Based Calix[4]arene Derivatives and their Complexation with Alkali Metal Cations

Two novel fluorescent calix[4]arenes comprising diphenylanthracene moiety at the lower rim were synthetizedand their complexation with alkali metal cations in acetonitrile/dichloromethane and methanol/dichloromethane mixtures (phi = 0.5) was studied experimentally and by classical molecular dynamics and quantum chemical calculations. The monosubstituted calixarene derivative (L1) proved to be a poor cation receptor, whereas the ester-based macrocycle (L2) exhibited rather high affinity towards lithium, sodium and potassium cations, particularly in MeCN/CH2Cl2. All complexation reactions were enthalpically controlled, whereby the overall stability was the largest in the case of sodium complex. The computational investigations provided an additional insight into the complexation properties and structures of complex species. The molecular dynamics simulations indicated the occurrence of inclusion of solvent molecules in the calixarene hydrophobic cavity of the free and complexed ligand, which was found to significantly affect the complexation equilibria.