1,10-phenanthroline derivatives as ionophores for alkali metal ions

A number of 1,10-phenanthroline derivatives such as 2,9-dialkyl phenanthroline derivatives, biscrown derivatives which include crown ether moieties via amide groups at the 2 and 9 positions, and oligomethylene bridged phenanthrolines which work as ionophores have been synthesized. Their properties not only as sensing agents for ion-selective electrodes (ISEs) and fluorometry, but also as agents for selective ion transport have been investigated. It has been found that 2,9-dibutyl-1,10-phenanthroline is an excellent Li+-sensing agent for both ISEs and fluorometry. 1,6-Bis(9-butyl-1,10-phenanthrolin-2-yl) which is one of the bridged bisphenanthrolines, exhibits high selectivity toward Li+ among alkali and alkaline earth metal ions in a liquid membrane system. The phenanthroline derivative with bis(benzo-15-crown-5) moieties functions as a highly selective K+ carrier. The relationship between their structure and functions is also discussed.