Synthesis and complexing properties of polyazamacrocycles with pendant N-methylenephosphinic acid
- 1 January 1995
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 7,p. 1133-1137
- https://doi.org/10.1039/dt9950001133
Abstract
Two new polyazamacrocycles 1,4,7-triazacyclononane-1,4,7-triyltrimethylenetris(phosphinic acid)(H3L1) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayltetramethylenetetrakis(phosphinic acid)(H4L2) were synthesised and their acid–base and complexing properties with Mg2+, Ca2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Pb2+ determined pH-metrically at 25 °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 H3L1 with transition metals lay in a narrow region and point to non-selectivity of the ligand; H4L2 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.Keywords
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