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

Two new polyazamacrocycles 1,4,7-triazacyclononane-1,4,7-triyltrimethylenetris(phosphinic acid) (H(3)L(1)) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayltetramethylenetetrakis(phosphinic acid) (H(4)L(2)) were synthesised and their acid-base and complexing 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 range. 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) forms more stable complexes with larger cations such as Cd2+ or Pb2+ than with the cations of the first transition row. This selectivity is much better than for analogous macrocycles bearing carboxymethyl or methylenephosphonic pendant groups.