COMPLEXATION PROPERTIES OF ,13-TETRAOXA-7,16-DIAZACYCLOOCTADECANE-7-MALONATE, RAOXA-7,16-DIAZACYCLOOCTADECANE-7,16-BIS(MALONATE) AND ,16-DIAZACYCLOOCTADECANE-7,16-BIS(A-METHYLACETATE)

The macrocycles raoxa-7,16-diezacyclooctadecane-7,16-bis(malonate) (od dm), -7-malonate (odmm) and -7,16-bis(alpha-methylacetate) (oddp) have been synthesized. Their protonation constants and the stability const ants of their complexes ML with Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Zn2+, Cd 2+ and Pb2+ have been determined by pH-potentiometry at a 1:1 metal-to -ligand ratio. The macrocycle oddm possesses high selectivity for the large metal ions. The complex [Sr(oddm)](2-) is two orders of magnitud e more stable than [Ca(oddm)](2-) and the stability constant of [Pb(od dm)](2-) is six orders of magnitude larger than that of the correspond ing zinc complex. The complexes of oddm with large metal ions (Sr2+ an d Ba2+) possess rigid structures. while the average lifetimes of the m etal-donor bonds are relatively large, and this is indicated; by the a ppearance of multiplet, signals in the H-1 NMR spectra.