Abstract A new cyclam-based ligand,[4, 8, 11-tris (phosphonomethyl)-1, 4, 8, 11- tetraazacyclotetradec-1-yl] acetic acid (H 7 te3p1a) was synthesised and characterised. The potentiometricand 31 P NMR spectroscopic titrations of the complexes inan aqueous solution at an ionic strength of 0.10 or0. 50 mol dm–3 in [N (CH 3) 4] NO 3, respectively, indicated that the ligand is highly basic. The stepwise protonations were dominated by ...