CHROMOGENIC AND FLUOROGENIC GROWN ETHER COMPOUNDS FOR THE SELECTIVE EXTRACTION AND DETERMINATION OF HG(II)

Two novel crown ether compounds, N,N'-bis(2-hydroxy-5-nitrobenzyl)-4,13-diazadibenzo-18-crown-6 (CCE) and N,N'-bis(7-hydroxy-4-methylcoumarin-8-methylene)-4,13-diazadibenzo-18-crown-6 (FCE), have been synthesized as potential reagents for the selective extraction and determination of heavy metal ions, Characterizations of the acid-base reactivity and the heavy metal ion extraction capabilities are reported, Both CCE and FCE undergo four-step ionization processes with associated tautomeric transformations and form stable complexes with divalent metal cations that can be extracted into 1,2-dichloroethane, Extraction constants for Ba(II), Ca(II), Cd(II), Cu(II), Hg(II), Pb(II), and Sr(II) have been determined for both reagents, For CCE, the extraction order is Hg(II) much greater than Pb(II) > Cu(II) > Cd(II) > Ca(II) > Sr(II) > Ba(II), whereas the order for FCE is Hg(II) much greater than Cu(II) > Pb(II) > Cd(II) > Ca(II) > Sr(II) > Ba(II), The selectivity of CCE for Hg(II) over the next-best-extracted cation, Pb(II), is similar to 2 x 10(7) and that of FCE for Hg(II) over next-best-extracted cation, Cu(II), is similar to 5 x 10(6), Potential applications to chemical analysis, based on the unprecedented selectivity of both reagents for Hg(II), are briefly examined.