Characterization of Anthraquinone-DerivedRedox Switchable Ionophores and Their Complexes with Li+, Na+, K+, Ca+, and Mg+Metal Ions

Anthraquinone derived redox switchable ionophores 1,5 bis (2-(2-(2-ethoxy) ethoxy) ethoxy)anthracene-9,10-dione (V1) and 1,8-bis(2-(2-(2-ethoxy)ethoxy)ethoxy) anthracene—9,10-dione (V2) have been used for isolation, extraction and liquid membrane transport studies of Li+, Na+, K+, Ca2+ and Mg2+ metal ions. These isolated complexes were characterized by melting point determination, CV and IR, 1H NMR spectral analysis. Ionophore V2 shows maximum shift in reduction potential (ΔE) with Ca(Pic)2. The observed sequence for the shifting in reduction potential (ΔE) between V2 and their complexes is V2 calcium picrate (42 mV) > V2 potassium picrate (33 mV) > V2 lithium picrate (25 mV) > V2 sodium picrate (18 mV) > V2 magnesium picrate (15 mV). These findings are also supported by results of extraction, back extraction and transport studies. Ionophore V2 complexed with KPic and showed much higher extractability and selectivity towards K+ than V1. These synthetic ionophores show positive and negative cooperativity towards alkali and alkaline earth metal ions in reduced and oxidized state. Hence, this property can be used in selective separation and enrichment of metal ions using electrochemically driven ion transport