Tris(carboxymethyl)oxatriazamacrocycles and their metal complexes

摘要: The protonation constants of H3L1 [4,8,12-tris(carboxymethyl)-1-oxa-4,8,12-triazacyclotetradecane] and H3L2 [4,7,11-tris(carboxymethyl)-1-oxa-4,7,11-triazacyclotridecane] the stability complexes formed by both with alkaline-earth metal ions, divalent first-row transition-metal Cd2+, Pb2+ Fe3+ were determined potentiometric methods, at 25 °C ionic strength 0.10 mol dm–3 in tetramethylammonium nitrate. co-ordination properties ligands for ions are quite different. 13-membered macrocycle, (L2)3–, exhibits fairly high but unsatisfactory selectivity ions. 14-membered ligand, (L1)3–, is very selective same series difference between its Cu2+ Mn2+ being 10.96 log units that Zn2+ 7.29 units, constant complex sufficiently possible quantitative determination pH values higher than 7. However, complexation behaviour (L1)3– similar to corresponding bis(carboxymethyl) derivative, therefore difficult preparation does not compensate benefits. Increase size macrocycle cavity leads a sharp decrease involved mainly electrostatic interactions (the Pb2+). Cobalt(II) also undergo significant increase [ZnL1]– much lower [ZnL2]–. Ni2+ macrocycles have about constants. To explain these results it proposed all donor atoms which form interactions, although distances principally orientation lone pairs electrons gradually more disfavoured increasing size. Complexes effects, each able choose from most appropriate their strict preferences. So Co2+, adopt five- or six-co-ordination potentially seven-co-ordinate ligands, as shown electronic EPR spectroscopic measurements solution magnetic moments complexes.