Stabilities and Coordination Modes of α-Alaninephosphonic Acid in Copper(II) Heteroligand Complexes with Ethylenediamine, Diethylenetriamine or N,N,N′,N′,N″-Pentamethyldiethylene Triamine in Aqueous Solution

Abstract

− species is formed in basic solution. Our spectroscopic results indicate tetragonal geometry for the [Cu(en)(α-Ala(P))] species, geometry slightly deviated from square pyramidal for the [Cu(dien)(α-Ala(P))] complex and strongly deviated from square pyramidal towards trigonal bipyramidal for the [Cu(Me 5 dien)(α-Ala(P))] species. The coordination modes in these heteroligand complexes are discussed.

A Comparative Study of Stabilities and Coordination Modes of β-Alaninephosphonic Acid in Copper(II) Heteroligand Complexes with Ethylenediamine, Diethylenetriamine or N,N,N′,N′,N″-Pentamethyldiethylene Triamine in Aqueous Solution

“…Analogous results were obtained for ternary systems of the same polyamines and phosphonic acid [3, 4] and for different amino acids in copper(II) solutions [5, 6]. …”

“…According to these data, heteroligand complexes with [Cu(L 1 )(β-Ala(P))] stoichiometry are formed in all of the studied ternary systems. However, the concentrations of these species in the present systems are distinctly lower than the concentrations of the heteroligand complexes formed in the ternary systems studied by us earlier with the same polyamines and glycinephosphonic acid [3] or with α-alaninephosphonic acid [4]. In the Cu 2+ –en–β-Ala(P) ternary system the hydroxo heteroligand [Cu(en)(β-Ala(P))H −1 ] − species also occur in basic solution.…”

“…Values of this parameter close to −1 were obtained for the heteroligand species of tetragonal geometry studied by us earlier, formed by ethylenediamine and other phosphonic acids [3, 4], aminoacids [5, 6], and aminohydroxamic acids in copper(II) solutions [11]. However, in the case of the heteroligand complexes [Cu(L 1 )(β-Ala(P))] with dien or Me 5 dien (Table 1, row 7), the values of Δlog 10 K are clearly lower, most probably because of the lower (than six) coordination number of Cu 2+ .…”

“…Our research work on heteroligand complexes with some polyamines and aminophosphonic acids such as glycinephosphonic acid (Gly(P)) and α-alaninephosphonic acid (α-Ala(P)), which are analogues of amino acids, have shown that the substitution of the carboxylate group by the phosphonic function distinctly changes the coordination ability of the ligand in ternary systems [3, 4]. The studies have also demonstrated that, in the heteroligand complexes, the geometry around copper(II) is closely related to the type of polyamine, i.e., to the number of nitrogen atoms of the polyamines which are potential coordination sites.…”

“…The arrangement of the donor atoms in β-derivatives of aminophosphonic acid allows for the formation of a six-membered chelate ring. Thus, it seems to be interesting to investigate whether such structural arrangement of the ligand affects the coordination geometry of the heteroligand complexes to the same extent as was observed in the ternary systems with an α-derivative of aminophosphonic acid [3, 4], amino acids [5, 6] or aminohydroxamic acids [7–11]. …”