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

Anna Kamecka

doi:10.1007/s10953-012-9914-4

Abstract

Solution equilibrium studies on Cu2+–L1–L2 ternary systems have been performed by pH-potentiometry, UV–Vis spectrophotometry and EPR methods {where L1 corresponds to a polyamine such as ethylenediamine (en), diethylenetriamine (dien), N,N,N′,N′,N″-pentamethyldiethylenetriamine (Me5dien)} and L2 denotes 2-aminoethylphosphonic acid (β-alaninephosphonic acid)}. The results suggest the formation of heteroligand complexes with [Cu(L1)(β-Ala(P))] stoichiometry in all of the studied systems. Additionally, in the system with en, [Cu(en)(β-Ala(P))H−1]− is formed in basic solutions. Our spectroscopic results indicate tetragonal geometry for the [Cu(en)(β-Ala(P))] species, a geometry slightly deviated from square pyramidal for the [Cu(dien)(β-Ala(P))] complex, and somewhat stronger geometry distortion was present for the [Cu(Me5dien)(β-Ala(P))] complex. The coordination modes in these heteroligand complexes are discussed.

Highlights

Aminoalkylphosphonic acids occupy an important place among the various compounds containing a P–C bond and the amino group because they are analogues of natural amino acids, the ‘building blocks’ of peptides and proteins
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 a-derivative of aminophosphonic acid [3, 4], amino acids [5, 6] or aminohydroxamic acids [7,8,9,10,11]
The dissociation constants for the ligands and the stability constants of the complexes formed in the binary systems were redetermined under the same experimental conditions as those applied for the ternary systems

Summary

Introduction

Aminoalkylphosphonic acids occupy an important place among the various compounds containing a P–C bond and the amino group because they are analogues of natural amino acids, the ‘building blocks’ of peptides and proteins. Their utilities as enzyme inhibitors, anticancer agents, antibiotics, neuromodulators, plant growth regulators and herbicides, antibacterial compounds, and many other technical and industrial applications such as chelating agents and scale inhibitors have attracted the interests of chemists for a long time [1, 2]. The differences between the complex-forming properties of aminophosphonates and aminocarboxylates in ternary systems have been explained by differences in basicity, charge and size of the ÀPO23À and –COO- groups

Chemicals

Potentiometric and Spectroscopic Studies

Results and Discussion

Conclusions