Microwave-assited synthesis and characterization of tetra-aza-crown ether and cryptand derivatives

Crown ethers are widely utilized for metal complexation due to their affinity for cations, stemming from their hydrophobic outer and hydrophilic inner cavity structures. These compounds, which exhibit selective binding to different ions depending on the type and number of donor atoms and functional groups, are also potentially applicable for the removal of metal ions from liquid media due to their heteroatom content. In this thesis, crown ether derivatives of benzoguanamine (2,4-diamino-6-phenyl-1,3,5-triazine) and polyethylene glycol dihalides were synthesized via the SN2 mechanism using the microwave-assisted method in adherence to green chemistry principles. The synthesized compounds were thoroughly characterized using FTIR, ¹H-NMR, ¹³C-NMR, and MS techniques. Eight different synthesized ligands were evaluated for their complexation affinity with Fe²⁺, Fe³⁺, Li⁺, Na⁺, K⁺, Cr³⁺, Mg²⁺, Ca²⁺, Ag⁺, Al³⁺, Mn²⁺, and Sn²⁺ cations. Notably, the complexes formed with Fe²⁺ exhibited a significant increase in fluorescence intensity, while Fe³⁺ caused fluorescence quenching. These variations were explained at the molecular level and compared with findings from the literature. This thesis provides a significant contribution to the synthesis of aza-crown ethers and cryptand derivatives, deepening the understanding of metal-ligand interactions and paving the way for advancements in the development of fluorescence sensors.