SYNTHESIS AND COMPLEXING PROPERTIES OF POLYAZAMACROCYCLES WITH PENDANT N-METHYLENEPHOSPHINIC ACID

Two new polyazamacrocycles cyclononane-1,4,7-triyltrimethylenetris(pho sphinic acid) (H(3)L(1)) and -1,4,7,10-tetrayltetramethylenetetrakis(p hosphinic acid) (H(4)L(2)) were synthesised and their acid-base and co mplexing properties with Mg2+, Ca2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Pb2+ determined pH-metrically at 25 degrees C and at an ionic strength of 0.1 mol dm(-3) (KNO3). Both form 1:1 complexes over a wide pH rang e. The stability constants of H(3)L(1) with transition metals tay in a narrow region and point to non-selectivity of the ligand; H(4)L(2) fo rms more stable complexes with larger cations such as Cd2+ or Pb2+ tha n with the cations of the first transition row. This selectivity is mu ch better than for analogous macrocycles bearing carboxymethyl or meth ylenephosphonic pendant groups.