抄録
Metal complexation behaviors of two linear triphosphate ligand anion analogs, triphosphate, P3, and diimidotriphosphate, P3(NH)2, have been studied systematically by a potentiometric titration method. The stability constants of the ML complexes of several divalent metal ions with P3(NH)2 are always larger than the corresponding complexes with P3 anions. The order of the stability constants of the ML complexes follows the Irving-Williams order, which indicates that non-bridging oxygen atoms of P3(NH)2 molecule are involved in complexation. Enthalpic and entropic changes upon ML complexation of Mg2+, Ca2+, and Cu2+ have been determined, and it was concluded that the stereo-chemical adjustment of the two ligand molecules to a metal ion may be changed drastically with the slight structural change in the ligand molecules.
