Diversity in coordination behavior of dipicolinic acid with lead(II), calcium(II), and nickel(II) in the presence of pyrazine and 2-amino-4-methylpyridine spacers in construction of three supramolecular architectures

Complexation of 1,3-dihetaryl-5-phenyl-2-pyrazoline Derivatives with Polyvalent Metal Ions: Quantum Chemical Modeling and Experimental Investigation

1,3,5-Triaryl-2-pyrazoline derivatives with a pyridine ring in position 1 and 2-benzimidazolyl or 2-benzothiazolyl bicycles in position 3 were synthesized. Spectral properties in solvents of similar polarity, i.e. aprotic acetonitrile and in protic methanol, were studied, complexation with cadmium and mercury ions in acetonitrile was elucidated as well. Quantum-chemical modeling with application of the elements of Bader's atoms-in-molecules (AIM) theory of the title molecules conformational structure and 1:1 stoichiometry complexes formed with polyvalent metals of various nature (Mg, Zn, Cd, Pb, Hg, Ba) was conducted. The principal possibility of “nitrogen-sulfur” switching of the metal ions binding sites for the benzothiazole derivative was revealed, and makes possible to classify this compound as “smart ligand”.

Crystal and molecular structure of [Ni{2-H2NC(=O)C5H4N}2(H2O)2][Ni{2,6-(O2C)2C5H3N}2]·4.67H2O; DFT studies on hydrogen bonding energies in the crystal

[Ni{2-H₂NC(=O)C₅H₄N}₂(H₂O)₂][Ni{2,6-(O₂C)₂C₅H₃N}₂]·4.67H₂O, a new complex salt containing a bis(2,6-dicarboxypyridine)nickel(II) anion and a bis(2-amidopyridine)diaquanickel(II) cation, was synthesized and characterized. The crystal is stabilized by an extensive network of hydrogen bonds. Alternate layers of anions and cations/water molecules parallel to (010) can be distinguished. Computational studies of the network packing of the title compound by high-level DFT-D/B3LYP calculations indicate stabilization of the networks with conventional and non-conventional intermolecular O-H...O, N-H...O and C-H...O hydrogen bonds along with π-stacking contacts. Due to the presence of water molecules and the importance of forming hydrogen bonds with the involvement of water clusters to the stability of the crystal packing, the importance and role of these water clusters, and the quantitative stability resulting from the formation of hydrogen bonds and possibly other noncovalent bonds such as π-stacking are examined. The binding energies obtained by DFT-D calculations for these contacts indicate that hydrogen bonds, especially O-H...O and N-H...O, control the construction of the crystalline packing. Additionally, the results of Bader's theory of AIM for these interactions agree reasonably well with the calculated energies.

Synthesis and characterization of some metal complexes of a proton transfer salt, and their inhibition studies on carbonic anhydrase isozymes and the evaluation of the results by statistical analysis

A novel proton transfer compound (HMeOABT)(+) (HDPC)(-) (1) and its Fe(III), Co(II), Ni(II) and Cu(II) complexes (2-5) have been prepared and characterized by spectroscopic techniques. Complex 4 has distorted octahedral conformation revealed by single crystal X-ray diffraction method. Structures of the other complexes might be proposed as octahedral according to experimental data. All compounds were also evaluated for their in vitro inhibition effects on hCA I and II for their hydratase and esterase activities. Although there is no inhibition for hydratase activities, all compounds have inhibited the esterase activities of hCA I and II. Data have been analyzed by using a one-way analysis of variance. The comparison of the inhibition studies of 1-5 to parent compounds indicates that 1-5 have superior inhibitory effects. The inhibition effects of 2-5 are also compared to inhibitory properties of the metal complexes of MeOABT and H2DPC, revealing an improved transfection profile.

Di-μ-chlorido-bis-[(2-amino-4-methyl-pyridine-κN)-chloridomercury(II)]

In the centrosymmetric dinuclear title compound, [Hg(2)Cl(4)(C(6)H(8)N(2))(2)], the Hg(II) ion is four-coordinated by one pyridine N atom from a 2-amino-4-methyl-pyridine ligand, one terminal Cl atom and two bridging Cl atoms. A distorted tetra-hedral geometry is formed around each Hg(II) ion. The crystal packing is stabilized by intra- and inter-molecular N-H⋯Cl hydrogen bonding. There are also π-π stacking inter-actions in the structure, with centroid-to-centroid distances of 3.594 (6) Å.

Bis(8-hy-droxy-2-methyl-quinolinium) bis-(pyridine-2,6-dicarboxyl-ato)-nickelate(II) methanol monosolvate monohydrate

In the title compound, (C(10)H(10)NO)(2)[Ni(C(7)H(3)NO(4))(2)]·CH(3)OH·H(2)O, the coordination geometry of the Ni(II) atom can be described as distorted octa-hedral. In the crystal, noncovalent inter-actions play an important role in the stabilization of the structure, involving O-H⋯O, N-H⋯O and weak C-H⋯O hydrogen bonds and π-π stacking inter-actions between the pyridine rings of the pyridine-2,6-dicarboxyl-ate ligands [centroid-centroid distance = 3.7138 (15) Å] and between the 8-hy-droxy-2-methyl-quinolinium cations [centroid-centroid distances = 3.6737 (15), 3.4434 (14), 3.6743 (15), 3.7541 (16), 3.5020 (15) and 3.7947 (15) Å].

Hydrothermal synthesis, experimental and theoretical characterization of a novel cocrystal compound in the 2:1 stoichiometric ratio containing 6-methyluracil and dipicolinic acid

This paper reports the hydrothermal synthesis, experimental and theoretical studies of a novel cocrystal compound in the 2:1 stoichiometric ratio of 6-methyluracil (6mu) and dipicolinic acid (pydcH(2)) formulated as [6mu](2)[pydcH(2)] (1), for the first time. DFT calculations were performed to access the most possible geometry of the title cocrystal compound. All calculations were carried out with the B3LYP hybrid density functional level and 6-311+G(d,p) basis sets. The vibrational frequencies together with the (1)H and (13)C NMR chemical shifts have been calculated on the fully optimized geometry of 1. The theoretical results are in good agreement with the experimental and solution data. The theoretical, solution, and experimental (elemental analysis, mass spectrometry, FTIR, (1)H and (13)C NMR spectroscopies) results confirmed our proposed structure for 1 in the 2:1 stoichiometric ratio of 6mu and pydcH(2), respectively. The protonation and equilibrium constants of 6mu and pydcH(2) and constituent systems were determined by potentiometric studies and the corresponding distribution diagrams depicted.

Bis(8-hy-droxy-2-methyl-quinolinium) bis-(pyridine-2,6-dicarboxyl-ato)cuprate(II) methanol monosolvate monohydrate

The title compound, (C₁₀H₁₀NO)₂[Cu(C₇H₃NO₄)₂]·CH₃OH·H₂O was prepared by the reaction of copper(II) nitrate hexa­hydrate, 8-hy­droxy-2-methyl­quinoline, and pyridine-2,6-dicarb­oxy­lic acid in a 1:2:2 molar ratio in an aqueous solution. The geometry of the resulting CuN₂O₄ coordination can be described as distorted octa­hedral. In the crystal, there are several inter­molecular O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds. An intra­molecular N—H⋯O hydrogen bond occurs in one of the cations. Considerable π–π stacking inter­actions are also observed between the aromatic rings of the cations, with centroid–centroid distances of 3.4567 (13), 3.5342 (14), 3.6941 (14) and 3.4568 (13) Å. These non-covalent inter­actions connect the components, forming a three-dimensional supra­molecular structure.