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Ionophoric ideality for the extraction of small metal cations by means of aza-macrocycles and 9-crown-3, 10-crown-3, 11-crown-3, or 12-crown-3 crown ethers

Triaza macrocyles ionophorically bound to small cations
(Illustration by Lindy Arrowood, Scientific Illustrator ONU-6207 Kankakee, IL 60901)

Bill Brower and Douglas Armstrongb

a169 1/2 South Schuyler Avenue, Kankakee, Illinois 60901, USA
bOlivet Nazarene University, Department of Chemistry, PO Box 592, Kankakee, IL 60901-0592, USA


The cavities of smaller crown ethers and azacylces have the ionophoric ability to bind to small metal cations. The most effective ring structure is difficult to determine due to non- correlative publications. The crown ether may be more efficient when containing one or two nitrogen heteroatoms. However, azacylces such as Cyclen may have a higher susceptibility to cationic extraction than the ethers. The addition of ligating amino side-arms is another factor that may increase extractive competence. Once ideally customized through organometallic chemical engineering, the structure could be serviceable in the commercial collection of metals from mineral springs or ocean water, as well as a purifying agent for waste water.

A Tolkienian Dilemma
Which Ring?

Various publications have studied various rings and determined several to be highly effective ionophores. But those that test small crown ethers ignore the azacycles. Others that include sidearm possibilities don't investigate the smaller ring radii. Of course, this is all dependent on which metal is being extracted.

Side arm possibilities

Although the azacycles appear most viable, study of the smaller ethers and side arm manipulation are worthy of investigation.