[show abstract][hide abstract] ABSTRACT: The reaction of chromium(III) nitrate hexa-hydrate, pyridine-2,6-diamine and 4-hydroxy-pyridine-2,6-dicarboxylic acid in a 1:2:2 molar ratio in aqueous solution resulted in the formation of the title compound, (C(5)H(8)N(3))[Cr(C(7)H(3)NO(5))(2)]·2H(2)O or (pydaH)[Cr(hypydc)(2)]·2H(2)O (where pyda is pyridine-2,6-diamine and hypydcH(2) is 4-hydroxy-pyridine-2,6-dicarboxylic acid). Each Cr(III )atom is hexa-coordinated by four O and two N atoms from two (hypydc)(2-) fragments, which act as tridentate ligands, in a distorted octa-hedral geometry. The O-Cr-O-C torsion angles between the two planes of the (hypydc)(2-) fragments [-99.81 (17) and 97.77 (17)°] indicate that these two units are almost perpendicular to one another. In the crystal structure, extensive O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds with D⋯A distances ranging from 2.560 (2) to 3.279 (3) Å, ion pairing, C-O⋯π [O⋯π = 3.166 (2) Å] and π-π stacking inter-actions between (hypydc)(2-) and (pydaH)(+) rings [with a centroid-centroid distance of 3.3353 (14) Å] contribute to the formation of a three-dimensional supra-molecular structure.
[show abstract][hide abstract] ABSTRACT: In the title compound, (C(4)H(14)N(2))[Cu(C(7)H(3)NO(4))(2)]·3H(2)O or (bdaH(2))[Cu(pydc)(2)]·3H(2)O (where bda is butane-1,4-diamine and pydcH(2) is pyridine-2,6-dicarboxylic acid), the Cu(II) atom is coordinated by four O atoms [Cu-O = 2.0557 (16)-2.3194 (16) Å] and two N atoms [Cu-N = 1.9185 (18) and 1.9638 (18) Å] from two chelating rings of the pydc(2-) anions, which act as tridentate ligands. The geometry of the resulting CuN(2)O(4) coordination can be described as distorted octa-hedral. The the two pydc(2-) fragments are almost perpendicular to one another [77.51 (11)°]. To balance the charges, two centrosymmetric protonated butane-1,4-diammonium, (bdaH(2))(2+) cations are present. In the crystal structure, extensive O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds [D⋯A = 2.720 (2)-3.446 (3) Å], ion pairing, C-O⋯π [O⋯π = 3.099 (2) Å] and π-π stacking inter-actions between the pydc(2-) rings [centroid-centroid distance = 3.5334 (15) Å] contribute to the formation of a three-dimensional supra-molecular structure.
[show abstract][hide abstract] ABSTRACT: In the title compound, (C(4)H(14)N(2))[Cd(C(7)H(3)NO(4))(2)]·2H(2)O, the Cd(II) ion is coordinated by four O atoms [Cd-O = 2.2399 (17)-2.2493 (17) Å] and two N atoms [Cd-N = 2.3113 (15) and 2.3917 (15) Å] from two tridentate pyridine-2,6-dicarboxyl-ato ligands in a distorted octa-hedral geometry. The uncoordinated water mol-ecules are involved in O-H⋯O and N-H⋯O hydrogen bonds, which contribute to the formation of a three-dimensional supra-molecular structure, along with π-π stacking inter-actions [centroid-centroid distances of 3.5313 (13) and 3.6028 (11) Å between the pyridine rings of neighbouring dianions].
[show abstract][hide abstract] ABSTRACT: A novel supramolecular structure of an s-Block metal ion, Ca(II) atom, formulated as (pnH2)2au][Ca2(H2O)2(Hhypydc)4]·4H2O (1), was synthesized and characterized by elemental analysis, IR, 1H and 13C NMR spectroscopies and single crystal X-ray diffraction. Compound 1 is a member of a large family of supramolecular metallic compounds recently derived from a proton transfer ion pair, (pnH2)(Hhypydc), where pn is propane-1,3-diamine and (Hhypydc)2-is 4-hydroxypyridine-2,6-dicarboxylate ion. Based upon the molecular structure analysis of the binuclear anionic complex, the coordination environment around each Ca(II) atom is pentagonal bipyramidal with seven-coordination number. The strong hydrogen bonding between hydroxyl groups of two neighboring anionic complexes produce the nice tape as X-like supramolecular structure. Optimization was carried out using two standard basis sets of 6-31G (d,p) for the single anionic complex (S) and LanL2MB basis set for the double anionic complexes (D) which describe the electrons of all atoms. As an interesting finding from our theoretical calculations, when we reoptimized the double complexes in the presence of strong hydrogen bond interaction between two hydroxyl groups, O3-H3A…O8ii (ii = x-1, y, z-1), it was revealed that the parallel position of ligands to each other was exactly like that of the solid state. The complexation reaction of H3hypydc with Ca2+ in aqueous solution was investigated by potentiometric pH titrations, the equilibrium constants and species distribution in various pHs. The for major complexes formed are described.
Journal of the Iranian Chemical Society 8(4). · 1.47 Impact Factor
[show abstract][hide abstract] ABSTRACT: Three new metal–organic compounds formulated as (H2bda)[Mn(pydc)2]·3H2O (1), (H2bda)[Zn(pydc)2]·3H2O (2), and (H2bda)3[Ce(pydc)3]2·4H2O (3) have been synthesized and structurally characterized by elemental analyses, IR, 1H and 13C NMR spectroscopies, and single crystal X-ray diffraction method. The asymmetric units of 1 and 2 contain three water molecules where in both compounds the corresponding metallic center is six-coordinated by two N and four O atoms as a distorted octahedral. The asymmetric unit of 3 contains four water molecules and the Ce(III) atom is nine-coordinated by three N and six O atoms in a distorted tricapped trigonal prism that the N atoms capping the faces. In the crystalline network of these three coordination compounds, hydrogen bonds, π–π stacking, and ion pairing play basic roles in the formation of supramolecular structures, in which they seem to be effective factor in the stabilization of the structure. The protonation constants of bda and pydcH2 and the (H2bda)(pydc) proton transfer equilibrium constants, the stoichiometry and stability of complexes of above mentioned ion pair with Mn2+, Ni2+, Cu2+, Zn2+, Cd2+, and Ce3+ metal ions in aqueous solution were investigated by potentiometric pH titration method. The stoichiometry of the most complexed species in solution was compared with corresponding crystalline complexes in the solid state.
The syntheses, X-ray crystal structures, and solution studies of three new coordination compounds based upon Mn(II), Zn(II), and Ce(III) atoms together with solution studies of previously synthesized coordination compounds by our research groups containing Ni(II), Cu(II), and Cd(II) atoms have been reported here, for the first time.