ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 54, Number 5
JKCSEZ 54(5)
October 20, 2010 

A new N₄O₃ heptadentate ligand, N,N'-Bis(2-hydroxybenzyl)-1,3-bis[(2-aminoethyl)amino]-2-propanol(H-BAP· 4HCl)was synthesized. The hydrochloric acid salts of Br-BAP·4HCl, Cl-BAP·4HCl, CH₃O-BAP·4HCl and CH₃-BAP·4HCl containing Br-, Cl-, H-, CH₃O- and CH₃- groups at the para-site of the phenol group of the H-BAP were synthesized. The structures of the ligands were confirmed by C. H. N. atomic analysis and ¹H NMR, ¹³C NMR, UV-visible and mass spectra. The elemental stepwise protonation constants(logK_n^H) of the synthesized N₄O₃ ligands showed six steps of the proton dissociation. The orders of the overall dissociation constants(logβ_p) of the ligands were Br-BAP < Cl-BAP < H-BAP < CH₃O-BAP < CH₃-BAP. The orders agreed well with that of Hammett substituent constants(σ_p). The calculated stability constants(logK_ML) between the ligands and transition metal ions agreed well with the order of the overall proton dissociation constants of the ligands but they showed a reverse order in Hammestt substituent constants(σ_p). The order of the stability constants between the transition metal ions with the ligands were Co(II) < Ni(II) < Cu(II) > Zn(II) > Cd(II) > Pb(II).