The ^1H NMR spectra of BPHA and Zn(II)-BPHA have been determined in the pD range 0.8-12.4. In contrast to DTPA and TTHA, the chemical shifts of the methylene protons a in the terminal carboxymethyl groups and b in the middle carboxymethyl groups of BPHA change alternatively with the increasing pD value. For Zn(II)-BPHA, there are three kinds of ^H NMR spectra. In the range pD<6, there exists a sharp peak characteristic of a free NH^+(CH~2COO^-)~2 moiety. From 6 to 9, no sharp single peak exists indicating all nitrogen atoms are coordinated; After pD>9, a sharp single peak appears at 3.14 indicating that an iminodiacetate group is again free except the nitrogen is not protonized.

Key words: ZINC COMPLEX, PROTON MAGNETIC RESONANCE SPECTROMETRY, PROPANEDIAMINE P, ACETIC ACID P