A New Tris(phosphonomethyl) Monoacetic Acid Cyclam Derivative: Synthesis, Acid-Base and Metal Complexation Studies
Abstract
Cyclam-based ligand, H(7)te3p1a, was synthesised and characterised. The ligand is highly basic and the stepwise protonations is dominated by extensive proton relocations.
The Cu(2+) complexes exhibited very high stability, those of Zn(2+), Cd(2+), Pb(2+), La(3+), Sm(3+), Gd(3+), Ho(3+) and Lu(3+) presented high stability while that of Ca(2+) had lower stability, as expected. Three phosphonate moieties are bound in the Cd(2+) complex and several isomer species were present in solution of the Zn(2+) complex.
A major isomer was stabilised in solution upon heating where only one of the methylphosphonate arms was coordinated to the metal centre and this isomer probably adopts a distorted square pyramidal (type I conformation of the cyclam ring).