The syntheses of N,N '-bis-[(2-pyridylmethyl)]-1,3-diamido-Ni(II) Ͻ Cu(II), and this is confirmed by the potentiometric data (papH 2 , aqueous solutions; logβ ML [Co(II)] = 1.75; propane (papH 2 ) and N,N '-bis-[(2-pyridylmethyl)]-1,3diamido-2-hexadecylpropane (C 16 papH 2 ) are reported logβ MLH-2 [Ni(II)] =-11.49; logβ ML [Cu(II)]=3.41; logβ MLH-2 -[Cu(II)] = -4.491; logβ ML [Zn(II)] = 1.87). The structural data together with the results of potentiometric titrations of papH 2 with Co(II), Ni(II), Cu(II) and Zn(II), spectroscopic and (X-ray and MM) indicate that, due to the ortho protons of the pyridyl groups and in dependence of the electronic electrochemical data of [Ni(pap)] and [Cu(pap)], structural studies involving the X-ray analyses of the metal-free papH 2 configuration of the metal center, there is a considerable tetrahedral twist of the central MN 4 chromophores {square ligand and the corresponding Ni(II) and Cu(II) complexes [Ni(pap)] ϫ 2 H 2 O and [Cu(pap)]
ϫ 3 H 2 O, and force-field planar: θ = 0°; tetrahedral: θ = 90°; [Co(pap)]: θ = 15°(MM); [Ni(pap)]: θ = 16°(X-ray), 16°(MM); [Cu(pap)]: θ = 18°(X-calculations (MM) of [Co(pap)], [Ni(pap)], [Cu(pap)] and [Zn(pap)] and the corresponding complexes of the ligand ray), 18°(MM); [Zn(pap)]: θ = 23°(MM)}, and this may be enhanced by ortho-methyl substitution of the pyridyl donors with ortho-methyl-substituted pyridyl groups (Me 2 papH 2 ); the results of metal ion transport [Co(II), Ni(II), Cu(II) and {[Co(Me 2 pap)]: θ = 20°(MM); [Ni(Me 2 pap)]: θ = 20°(MM); [Cu(Me 2 pap)]: θ = 24°(MM); [Zn(Me 2 pap)]: θ = 31°(MM)}, Fe(II)] from aqueous solutions through C 16 papH 2 containing dichloromethane phases are also given. The extractability and thus possibly a decrease in the complex stability of Cu(II) and Ni(II) in favor of Zn(II). with C 16 papH 2 increases along the series Fe(II) Ͻ Co(II) Ͻ