Complexation of macrocyclic compounds with mono-, di- and trivalent transition and heavy metal ions in 90% (v/v) DMSO plus water medium

Stability constants in 90% (v/v) DMSO +water mixture were evaluated for the complexes of Ag(I), Co(II), Cu(II), Mn(II), Ni(II), Zn(II), Pb(II), Cr(III) and Fe(III) with the macrocyclic compounds, namely, 15-crown-5, benzo-15-crown-5, 18-crown-6, dibenzo-18-crown-6, dicyclohexano-18-crown-6, dibenzo-24-crown-8 and dicyclohexano-24-crown-8 by conductometric titrations. A potentiometric study of complexes of Ag(I) and Cu(II) was also undertaken to compare the results with those obtained by conductivity measurements, which were found to be in good agreement with each other. In addition, complexation studies of Ag(I) and Cu(II) with 1,4,8,11-tetraazacyclotetradecane, 1,4,10-trioxa-7,13-diaza-cyclopentadecane, 5,6,14,15-dibenzo-1,4-dioxa-8,12-diazacyclopentadeca-5,14-diene and 7,16-dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane were carried out by potentiometry to study the effect of the heteroatom. nitrogen. The complexation studies indicate 1:1 complex formation between the metal ion and crown ether, and the log K-ML(n+) values are in the range 1-20. The limiting molar conductivities of the metal ions and their crown ether complexes were also determined. (C) 2002 Published by Elsevier Science Ltd.