Synthesis, protonation constants of a series of triazamacrocycle methylenephosphonic acids

Four six-basic phosphonic acids, 1,4,7-triazacyclononane-N,N′,N′-tris(methylenephosphonic acid) (NOTP), 1,4,7-triazacyclodecane-N,N′,N′-tris(methylenephosphonic acid) (DETP), 1,4,7-tri-azacycloundecane-N,N′,N′-tris(methylenephosphonic acid) (UDTP), and 1,4,7-triazacyclotridecane-N,N′,N′-tris(methylenephosphonic acid) (TDTP), were synthesized by the modified Mannich reaction under the gentle conditions. The protonation properties of the four polyamino polymethylenephosphonic acids are investigated by means of potentiometric titration in aqueous medium at 25 ± 0.1°C and an ionic strength I = 0.1 mol·L⁻¹ KNO₃. The successive protonation constants of ligands are obtained separately. The results show that the size of the ligands’ cavity play an important role in their protonations. © 1998 John Wiley & Sons, Inc. Lab Robotics and Automation 10: 229–233, 1998