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 V2shows maximum shift in reduction potential(ΔE)with Ca(Pic)2. The observed sequence for the shifting in reduction potential(ΔE)between V2and their complexes is V2calcium picrate (42 mV) > V2potassium picrate (33 mV) > V2lithium picrate (25 mV) > V2sodium picrate (18 mV) > V2magnesium picrate (15 mV). These findings are also supported by results of extraction, back extraction and transport studies. Ionophore V2complexed 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.