pH-specific hydrothermal assembly of binary and ternary Pb(II)-(O,N-carboxylic acid) metal organic framework compounds: correlation of aqueous solution speciation with variable dimensionality solid-state lattice architecture and spectroscopic signatures.

Hydrothermal pH-specific reactivity in the binary/ternary systems of Pb(II) with the carboxylic acids N-hydroxyethyl-iminodiacetic acid (Heida), 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid (Dpot), and 1,10-phenanthroline (Phen) afforded the new well-defined crystalline compounds [Pb(Heida)](n)·nH(2)O(1), [Pb(Phen)(Heida)]·4H(2)O(2), and [Pb(3)(NO(3))(Dpot)](n)(3). All compounds were characterized by elemental analysis, FT-IR, solution or/and solid-state NMR, and single-crystal X-ray diffraction. The structures in 1-2 reveal the presence of a Pb(II) center coordinated to one Heida ligand, with 1 exhibiting a two-dimensional (2D) lattice extending to a three-dimensional (3D) one through H-bonding interactions. The concurrent aqueous speciation study of the binary Pb(II)-Heida system projects species complementing the synthetic efforts, thereby lending credence to a global structural speciation strategy in investigating binary/ternary Pb(II)-Heida/Phen systems. The involvement of Phen in 2 projects the significance of nature and reactivity potential of N-aromatic chelators, disrupting the binary lattice in 1 and influencing the nature of the ultimately arising ternary 3D lattice. 3 is a ternary coordination polymer, where Pb(II)-Dpot coordination leads to a 2D metal-organic-framework material with unique architecture. The collective physicochemical properties of 1-3 formulate the salient features of variable dimensionality metal-organic-framework lattices in binary/ternary Pb(II)-(hydroxy-carboxylate) structures, based on which new Pb(II) materials with distinct architecture and spectroscopic signature can be rationally designed and pursued synthetically.

Synthetic, structural and solution speciation studies on binary Al(III)-(carboxy)phosphonate systems. Relevance to the neurotoxic potential of Al(III).

Efforts to delineate the interactions of neurotoxic Al(III) with low molecular mass substrates relevant to neurodegenerative processes, led to the investigation of the pH-specific synthetic chemistry of the binary Al(III)-[N-(phosphonomethyl) iminodiacetic acid] (Al-NTAP), Al(III)-[nitrilo-tris(methylene-phosphonic acid)] (Al-NTA3P), and Al(III)-[1-hydroxy ethylidene-1,1-diphosphonic acid] (Al-HEDP) systems, in correlation with solution speciation studies. Reaction of Al(NO(3))(3).9H(2)O with NTAP at pH 7.0 and 4.0 afforded the new species (CH(6)N(3))(4)[Al(2)(C(5)H(6)NPO(7))(2)(OH)(2)].8H(2)O (1) and (NH(4))(2)[Al(2)(C(5)H(6)NPO(7))(2)(H(2)O)(2)].4H(2)O (2), while reaction of Al(NO(3))(3).9H(2)O with NTA3P led to K(8)[Al(2)(C(3)H(6)NP(3)O(9))(2)(OH)(2)].20H(2)O (3). Complexes 1-3 were characterized by elemental analysis, FT-IR, (13)C, (31)P, (1)H NMR (for 1-2 solid state and solution NMR where feasible), and X-ray crystallography. The structures of 1-3 reveal the presence of uniquely defined dinuclear complexes of octahedral Al(III) bound to fully deprotonated phosphonate ligands, water and hydroxo moieties. The aqueous solution speciation studies on the aforementioned binary systems project a clear picture of the binary Al(III)-(carboxy)phosphonate interactions and species under variable pH-conditions and specific Al(III):ligand stoichiometry. The concurrent solid state and solution work (a) exemplifies essential structural and chemical attributes of soluble aqueous species, reflecting well-defined interactions of Al(III) with phosphosubstrates and (b) strengthens the potential linkage of neurotoxic Al(III) chemical reactivity toward O,N-containing (carboxy)phosphate-rich cellular targets.

Solution equilibrium characterization of insulin-mimetic Zn(II) complexes.

Solution speciation (stoichiometry and stability constants) of the insulin mimetic Zn(II) complexes of several bidentate ligands with (O,O), (N,O) or (S,O) coordination modes have been determined by pH-metry at 25 degrees Celsius and I=0.2M (KCl). All ligands were found to coordinate in a bidentate way forming mono, bis and tris complexes, besides a mixed hydroxo bis complex ZnL(2)(OH) detected in the slightly basic pH range together with the tris complex. Relationships between the stability data, lipophilicity of the complexes and earlier biological data are evaluated. The validity of the linear free energy relationships (LFER) between the proton and Zn(II) complexes and also between the VO(IV) and Zn(II) complexes is tested.

Correlations of synthetic, spectroscopic, structural, and speciation studies in the biologically relevant cobalt(II)-citrate system: the tale of the first aqueous dinuclear cobalt(II)-citrate complex.

Synthetic efforts targeting soluble species of Co(II) with the low molecular mass physiological ligand citric acid led to the isolation of the first dinuclear complex [Co(2)(C(6)H(5)O(7))(2)(H(2)O)(4)](2-), at pH approximately 5, in the form of its K+ (1) and Na+ (2) salts. Both 1 and 2 were characterized analytically, spectroscopically (FT-IR, UV/visible, EPR), and magnetically. Complex 1 crystallizes in the monoclinic space group P2(1)/n, with a = 10.348(5) A, b = 11.578(6) A, c = 12.138(6) A, beta = 112.62(2) degrees, V = 1342(1) A(3), and Z = 2. Complex 2 crystallizes in the monoclinic space group P2(1)/c, with a = 9.234(4) A, b = 11.913(4) A, c = 11.728(6) A, beta = 99.93(2) degrees, V = 1271(1) A(3), and Z = 2. X-ray crystallography on 1 and 2 reveals the presence of two Co(II) ions, in a dinuclear assembly, octahedrally coordinated by two citrate ligands in a tridentate fashion. The octahedral environment around each Co(II) is complemented by another singly bonded citrate belonging to the adjacent Co(II) unit and two water molecules. Magnetic susceptibility and EPR studies on 1, in the solid state, corroborate the X-ray results, indicating a weak interaction between the two Co(II) ions. Moreover, EPR and UV/visible studies in solution suggest that 1 does not retain its dimeric structure, yielding a mononuclear octahedral Co(II)-citrate species. Detailed speciation studies suggest the presence of a number of species including the mononuclear complex [Co(C(6)H(5)O(7))](-), optimally present around pH approximately 5. In consonance with EPR and UV/visible spectroscopy, [Co(C(6)H(5)O(7))](-) is likely the scaffolding unit on the basis of which the dimer [Co(2)(C(6)H(5)O(7))(2)(H(2)O)(4)](2-) is isolated from aqueous solutions. Collectively, this comprehensive study offers significant structural insight into the Co(II)-citrate speciation and the elucidation of the role of Co(II) in biological fluids.

Copper(II) and oxovanadium(IV) complexes of D-3-phosphoglyceric acid.

The complexes formed between D-3-phosphoglyceric acid and H(+), Cu(II) and VO(IV) were studied by pH-potentiometric and spectral (UV-Vis, EPR and CD) methods in order to describe the speciation of the metal ions and to determine the most probable binding modes in the complexes formed in these systems. The results show that, in the pH range between 2 and 4, mononuclear 1:1 complexes are formed through bidentate (MAH) or tridentate (MA) coordination of the ligand. At higher pH, when the proton competition for the central alcoholic-OH function decreases, alcoholate-bridged dinuclear species of composition M(2)A(2)H(-n) (n=1-3) become predominant. VO(IV) seems to have a higher tendency than Cu(II) to form such dinuclear complexes.

[Speciation of bioactive Al(III) and VO(IV) complexes in biological systems]. / Elettani hatású Al(III)- és VO(IV)komplexek speciációja biológiai rendszerekben.

The speciation of the toxic Al(III) and the beneficial VO(IV) in various biofluids and tissues is discussed in order to describe the solution state of these metal ions in the organism. The possibility and the importance of ternary complex formation with relevant biomolecules is emphasised. The importance of the biospeciation of Al(III) ion in its transport and involvement in neurological disorders, and of insulin mimetic VO(IV) complexes is discussed.