Anna Kamecka

Interactions of zinc(II), magnesium(II) and calcium(II) with aminomethane-1,1-diphosphonic acids in aqueous solutions

Abstract Complex formation equilibria of the aminomethane-1,1-diphosphonic acids with Zn II , Mg II and Ca II have been studied by potentiometric pH titrations and by means of NMR spectroscopy. The ligands exhibit a strong tendency to form protonated species over a wide range of pH. The most efficient binding mode in all the studied systems is the formation of the six-membered chelate ring involving oxygens of both phosphonate groups. An evident preference for the formation of multinuclear complexes is noted in the case of zinc(II). Magnesium demonstrates preference for mononuclear complexes, whereas calcium(II) tends to form insoluble species with most of the studied ligands. The structures of the main complex species are discussed with respect to the priorities in the hydrogen-bond network organization in solid state.

Potentiometric and spectroscopic studies of the copper(II) complexes with some aminodiphosphonic acids in aqueous solution

The stoichiometries and stability constants of the copper(II) complexes with seven aminodiphosphonates [R–N(CH2PO3H2)2, L] containing iminomethylenephosphonate moieties have been determined pH-metrically at 25°C and at an ionic strength of 0.20 mol dm−3 (KCl). The results suggest for L=1–6 only equimolar species: [Cu(H2L), [Cu(HL), [CuL] and two hydroxo [CuH−1L] and [CuH−2L], in the pH range of 2–11.5, the only difference is the presence of an additional [Cu(H3L)] species (∼15%) at low pH for N-3-picolyliminodi(methylenephosphonic) acid. For L=7 the model contains protonated and non-protonated 1:2 species. From the comparative analysis of the stability and the spectroscopic (UV–VIS and EPR) data it has been established that the ligands in [CuHL] and [CuL] are tridentate; the formation of two five-membered chelate rings leads to very stable complexes. The LMCT bands from O− (PO32−) and Nimino to Cu2 are at 225–231 and 302–277 nm.

Potentiometric and spectroscopic studies of the cobalt(II), nickel(II) and manganese(II) complexes with some aminodiphosphonic acids in aqueous solution

Abstract The stoichiometries and stability constants of the manganese(II), cobalt(II) and nickel(II) complexes with seven aminodiphosphonates [RN(CH 2 PO 3 H 2 ) 2 , L] containing iminomethylenephosphonate moieties have been determined pH-metrically at 25°C and at an ionic strength of 0.20 mol dm −3 (KCl). The results suggest for L= 1 – 6 only equimolar species: [M(H 2 L)], [M(HL)] − , [ML] 2− and hydroxo [MH −1 L] 3− , in the pH range of 3–11.5, the only difference is the presence of an additional [M(H 3 L)] + species at low pH for N -3-picolyliminodi(methylenephosphonic) acid. For L= 7 the models contain protonated and non-protonated 1:2 species. From the comparative analysis of the stability and the spectroscopic (UV–VIS) data it has been established that the ligands coordinate to the metal ions only by the phosphonate group(s) in a monodentate or bidentate manner. The LMCT bands from O − (PO 3 2− ) to Ni 2+ are at 222–211 nm.

Interactions of zinc( II ), magnesium( II ) and calcium( II ) with iminodimethylenediphosphonic acids in aqueous solutions†

N-Substituted iminodimethylenediphosphonic acids exhibited high complexation efficiency towards zinc(II), magnesium(II) and calcium(II) ions. This results from both dinegatively charged phosphonate groups as well as the imino-nitrogen present in their structure. A significant preference for an equimolar stoichiometry and a formation of tridentate bonded species has been demonstrated in these systems. The only exception is the N-tetrahydrofurylmethyliminodimethylenediphosphonic acid with a tetrahydrofuryl moiety placed in the sterically favoured position that allows its oxygen atom to be an effective metal binding site. Iminodimethylenediphosphonic and N-methyliminodimethylenediphosphonic acids behave quite differently upon zinc(II) complexation forming presumably layered two-dimensional polymeric species. These species disappear upon dilution. The crystal structure of N-methyliminodimethylenediphosphonic acid has also been determined. A unique 3-D arrangement of this compound with a tetramer as a basic building unit has been indicated.

Review: Solution equilibria of ternary complexes formed from copper(II), aliphatic amines, and bioligands

This review provides a summary of the coordination chemistry of ligands in the ternary system: copper(II)–aliphatic amine–bioligand, where amine = ethylenediamine – En, diethylenetriamine – Dien, or N, N, N′, N″, N″-pentamethyldiethylenetriamine – Me5dien, and bioligand = selected amino acid, aminohydroxamic acid, or aminophosphonic acid, in aqueous solution. We would like to show the specific interactions of copper(II) in ternary systems in the context of complex equilibria chemistry. Graphical abstract

Angular Overlap Studies of Mono-(Aminodiphosphonato)Copper(II) Complexes in Aqueous Solutions

Electronic absorption spectra of copper(II) complexes with iminodimethylenephosphonates R-N(CH2PO3H2)2 type (L, R-dmp), in aqueous solution have been characterized and quantitatively interpreted. The geometry of species in aqueous solution at pH 7–8 has been assumed on the basis of our previous combination of UV spectrophotometric measurements and ESR spectra, as well as data obtained from potentiometric titration. The ligand-field spectra (d–d transitions) of the [CuL(H2O)x]2− chromophores (where x = 2, 3) have been treated by the angular overlap model (AOM) and C2v symmetry. Low-symmetry splittings of the broad asymmetric bands in the spectra of solutions at room temperature were resolved by Gaussian analysis. The effect of the σ and π bonding of the tridentate (and tetradentate) ligands (with oxygen-donor and nitrogen-donor ligators) on the central metal ion has been described in the ligand-field framework.