Influence of d-Electron Divalent Metal Ions in Complex Formation with L-Tartaric and L-Malic Acids.

Binary complexes of α-hydroxy acids (L-Tartaric acid and L-Malic acid) with d-electron metal ions (copper, cobalt, nickel) were investigated. Potentiometric measurements have been performed in aqueous solution with computer analysis of the data for determination of the stability constants of complexes formed in the studied systems. The coordination mode of the complexes was defined using spectroscopic methods: electron paramagnetic resonance (EPR), ultraviolet-visible (UV-Vis), circular dichroism (CD), and infrared (IR). Results of the equilibrium studies have provided evidence for the formation of dimers with copper(II) ions and monomers with cobalt(II) and nickel(II) ions.

Thermodynamic and Spectroscopic Studies of the Complexes Formed in Tartaric Acid and Lanthanide(III) Ions Binary Systems.

Binary complexes of tartaric acid with lanthanide(III) ions were investigated. The studies have been performed in aqueous solution using the potentiometric method with computer analysis of the data for detection of the complexes set, determination of the stability constants of these compounds. The mode of the coordination of complexes found was determined using spectroscopy, which shows: Infrared, circular dichroism, ultraviolet, visible as well as luminescence spectroscopy. The overall stability constants of the complexes as well as the equilibrium constants of the reaction were determined. Analysis of the equilibrium constants of the reactions and spectroscopic data allowed the effectiveness of the carboxyl groups in the process of complex formation.

New coordination compounds of citric acid and polyamines with lanthanide ions - potential application in monitoring the treatment of cancer diseases.

Non-covalent interaction in the binary systems of polyamines (putrescine, spermidine, spermine) with citric acid and complex formation in the binary as well as ternary systems of lanthanide(III) ions, citric acid and polyamine have been investigated. The studies were performed in aqueous solution. The overall stability constants of the complexes were determined using the potentiometric method with computer analysis of the data. Only mononuclear type of complexes were found in the ternary systems and polyamines were located in the outer as well as inner coordination sphere. Non-covalent interaction between biogenic amines and citric acid in the binary and ternary systems were confirmed on the basis of the equilibrium constants analysis and spectroscopic studies.

Carboxyl groups of citric acid in the process of complex formation with bivalent and trivalent metal ions in biological systems.

Binary complexes of citric acid (H3L - protonated form, H2L and HL - partly protonated forms, L - fully deprotonated) with d- and f-electron metal ions were investigated. The studies have been performed in aqueous solution using the potentiometric method with computer analysis of the data, electron paramagnetic resonance, infrared, visible as well as luminescence spectroscopies. The overall stability constants of the complexes were determined. Analysis of the equilibrium constants of the reactions and spectroscopic data has allowed determination of the type of coordination and effectiveness of the carboxyl groups in the process of complex formation. On the basis of potentiometric titration for d-electron were found dimeric and monomeric type of complexes and for f-electron four type of complexes: MHL, ML, ML(OH) and ML(OH)2.

Coordination properties of N,N'-bis(5-methylsalicylidene)-2-hydroxy-1,3-propanediamine with d- and f-electron ions: crystal structure, stability in solution, spectroscopic and spectroelectrochemical studies.

Template reaction between 5-methylsalicylaldehyde and 2-hydroxy-1,3-propanediamine in the presence of copper ion led to dinuclear and mononuclear copper(ii) complexes [Cu2L(CH3COO)(CH3OH)](CH3OH) (1) and [CuHL](CH3OH) (2), where H3L is N,N'-bis(5-methylsalicylidene)-2-hydroxy-1,3-propanediamine. The result of the reactions between 5-methylsalicylaldehyde and 2-hydroxy-1,3-propanediamine in the presence of lanthanide ions and/or copper(ii) ion was N,N'-bis(5-methylsalicylidene)-2-hydroxy-1,3-propanediamine (H3L B) or [CuHL](CH3OH) (2), respectively. Structures of the compounds were determined by single-crystal X-ray diffraction and physicochemical methods. The microstructures and phase compositions of crystals were studied by scanning electron microscopy (SEM). In dinuclear complex [Cu2L(CH3COO)(CH3OH)](CH3OH) (1), two copper(ii) ions are bond to one H3L ligand and one acetate ion. Coordination modes of the two copper centers are different: the geometry of copper 1 is almost ideal square-planar, while that for copper 2 can be described as tetragonal pyramidal. In complex [CuHL](CH3OH) (2), the copper(ii) ion is four coordinated and the coordination, rather than square-planar, can be described as flattened tetrahedral. Formation of complexes between copper(ii) or lanthanide ions with N,N'-bis(5-methylsalicylidene)-2-hydroxy-1,3-propanediamine (H3L) was also studied in solution by pH potentiometry. It should be mentioned that the complexes of lanthanide ions exist only in solution. Additionally, the salen-type ligand H3L and its dinuclear and mononuclear copper(ii) complexes were studied by cyclic voltammetry, and their spectroelectrochemical properties were examined.

The trimorphic structure of N,N'-bis(5-methylsalicylidene)-4-methyl-1,3-phenylenediamine.

The new Schiff base ligand, N,N'-bis(5-methylsalicylidene)-4-methyl-1,3-phenylenediamine (H2L), has been prepared by condensation of 5-methylsalicylaldehyde with 4-methyl-1,3-phenylenediamine. It was found that this ligand crystallizes in the monoclinic space group P21/c, with Z' = 1. Further studies showed that - as a result of the one-pot metal-promoted reactions - three different polymorphic forms of H2L were obtained, with different numbers (1, 3 or 4) of symmetry-independent molecules depending on the lanthanide metal ion present in the reaction media: La (Z' = 3), Nd (Z' = 4), Sm, Tb, Ho and Yb (all Z' = 1); the last form is identical with that obtained by crystallization of the ligand itself. The geometrical features of all eight independent molecules of H2L are very similar. The relatively strong intramolecular O-H...N hydrogen bonds stabilize almost co-planar conformations of terminal rings and C-C=N-C linkers, at the same time strong hydrogen-bond donors and acceptors involved in these interactions cannot take part in the determination of supramolecular architecture. Therefore, weak intermolecular interactions are important and this can be regarded as one of the reasons for packing conflicts that lead to the presence of polymorphic forms and multiple molecules. The pseudosymmetries are observed in both forms with Z' > 1 and the degree of pseudosymmetry is described by the values of appropriate combinations of the coordinates. In order to elucidate the differences in crystal structures the Hirshfeld surface method was applied. It shows that there are only small differences in the surface shape and in the fingerprint plots; however, the volumes of voids in three structures are significantly different.