| Abstract
| - The basicity of 2-((bis(aminoethyl)amino)methyl)phenol (L) and the stability constants for the M(II)/L systems (M = Ni, Cu, and Zn) were determined in aqueous solution. L forms dinuclear complexes with all metal ions investigated showing [M2(H-1L)2]2+ stoichiometry with ligand/metal ratio of 2:2. Two mononuclear [MH-1L]+ species self-assemble giving the dinuclear complexes, which can be easily obtained as crystalline solids. The solid complexes were characterized by determining their crystal structures and by EPR and magnetic techniques.
- The basicity behavior and ligational properties of the ligand 2-((bis(aminoethyl)amino)methyl)phenol (L) towardNi(II), Cu(II), and Zn(II) ions were studied by means of potentiometric measurements in aqueous solution(298.1 ± 0.1 K, I = 0.15 mol dm-3). The anionic L-H- species can be obtained in strong alkaline solution; thisspecies behaves as tetraprotic base (log K1 = 11.06, log K2 = 9.85, log K3 = 8.46, log K4 = 2.38). L forms mono-and dinuclear complexes in aqueous solution with all the transition metal ions examined; the dinuclear speciesshow a [M2(L-H)2]2+ stoichiometry in which the ligand/metal ratio is 2:2. The studies revealed that two mononuclear[ML-H]+ species self-assemble, giving the dinuclear complexes, which can be easily isolated from the aqueoussolution due to their low solubility. This behavior is ascribed to the fact that L does not fulfill the coordinationrequirement of the ion in the mononuclear species and to the capacity of the phenolic oxygen, as phenolate, tobridge two metal ions. All three dinuclear species were characterized by determining their crystal structures, whichshowed similar coordination patterns, where all the single metal ions are substantially coordinated by three aminefunctions and two oxygen atoms of the phenolate moieties. The two metals in the dinuclear complexes are at shortdistance interacting together as shown by magnetic measurements performed with Ni(II) and Cu(II) complexes,which revealed an antiferromagnetic coupling between the two metal ions. The [Cu2(L-H)2]2+ cation shows a phasetransition occurring by the temperature between 100 and 90 K; the characterization of the compounds existing atdifferent temperatures was investigated using X-ray single-crystal diffraction, EPR, and magnetic measurements.
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