Hossein Aghabozorg

Chromium(III) and Calcium(II) complexes obtained from dipicolinic acid: Synthesis, characterization, X-Ray crystal structure and solution studies

The Cr(III) and Ca(II) complexes (dmpH)[Cr(pydc)2]•H2O (1) and [Ca2(pydc)2(H2O)6].2pydcH2 (2) were synthesized by reaction of 2,9-dimethyl-1,10-phenanthroline (dmp) and pyridine-2,6-dicarboxylic acid (pydcH2) with Cr(NO3)3 and Ca(NO3)2, respectively, and characterized using IR spectroscopy, single crystal X-ray diffraction method and solution studies. The space group and crystal system of these two compounds are P21/c and monoclinic. The crystal dimensions are a = 9.785(3) Å, b = 25.671(4) Å, c = 9.3402(16) Å, β = 90.790(17)° for (1) and a = 9.1319(4) Å, b = 14.8430(8) Å, c = 12.2449(7) Å, β = 98.227(5)° for (2). In complex (1), a water molecule presents in the crystal packing, linking the anionic and cationic fragments together by hydrogen bonding and thus increases the stabilization of crystal lattices. In complex (2), the coordinated water molecules relate each dimer to adjacent dimers forming infinite molecular ribbons by strong hydrogen bondings. Hydrogen bonding and ion pairing play an important role in stabilizing these crystals. The complexation reactions of pydc, dmp and pydc+dmp with Cr3+ and Ca2+ ions in aqueous solution were investigated by potentiometric pH titrations and the equilibrium constants for all major complexes formed were evaluated.

The Synthesis of a New Thiophene-Derivative Schiff's Base and Its Use in Preparation of Copper-Ion Selective Electrodes

A highly selective and sensitive PVC-membrane electrode for Cu(II) ion was developed by using a new thiophene-derivative Schiff’s base. The electrode exhibits a Nernstian slope of 29.3 � 0.7 mV per decade at 25 � C over a very wide concentration range (1.0610 � 1 – 6.0610 � 8 M) with a detection limit of 2.0610 � 8 M (1.28 ng/mL). The ion selectivity of this electrode for Cu 2þ was greater than 3.0610 3 times over various metal ions. It was successfully applied to the determination of trace amounts of copper in Iranian black tea, and as indicator electrode, in potentiometric titration of copper ion.

Separation and preconcentration of trace amounts of lead on octadecyl silica membrane disks modified with a new S-containing Schiff's base and its determination by flame atomic absorption spectrometry

Abstract A synthetic procedure was developed for the preparation of a new S-containing Schiffs base [ethane amine, N , N′ -bis(2-thienyl methylene)]. The resulting compound (L) was used as a modifier in octadecyl silica membrane disks for solid phase extraction and flame absorption spectrometric determination of lead in water samples. Extraction efficiency and influence of flow rates, pH, type and minimum amount of stripping acid were investigated. The maximum capacity of the membrane disks modified by 5 mg of the (L) used was found to be 700 μg Pb 2+ . The limit of detection of the proposed method is 16.7 ng ml −1 . The method was applied to the recovery of Pb 2+ ions from different synthetic samples and spring water samples.

A Brief Review on Formation of (H2O)n Clusters in Supramolecular Proton Transfer Compounds and Their Complexes

Abstract“Water clusters”, group of water molecules held together by hydrogen bonds, have been the subject of a number of intense experimental and theoretical investigations because of their importance in understanding cloud and ice formation, solution chemistry, and a large number of biochemical processes. “Water clusters” can play an important role in the stabilization of supramolecular systems both in solution and in the solid state and there is clearly a need for chemists a better understanding of how such aggregates influence the overall structure of their surroundings. The present brief review deals with (H2O)n clusters, identified/observed crystallographically upon 170 crystal structures of synthesized coordination compounds based upon proton transfer compounds by Hossein Aghabozorg’s research groups since 2000. The structural details of water clusters, (H2O)n, n = 2, 3, 4, 5, 6, 7, 8, 9, 15, 16 and ∞ are described systematically.

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.

Synthesis and crystal structure determination of 2,2'-sulfinyl-bis(4-methyl phenol) and 2,2'-thio-bis(4-methyl phenol)

2,2′-Sulfinyl-bis(4-methyl phenol) 3 and its thio derivative have been synthesized in this work. The reduction process of sulfoxide 3 to its thio derivative 5 was accomplished in the presence of Zn/AcOH/SiO2, under microwave irradiation. The structures have been confirmed by spectroscopic (IR, 1HNMR, 13CNMR) and single crystal x-ray diffraction methods. 2,2′-Sulfinyl-bis(4-methyl phenol) 3 crystallizes in the space group Cc of the monoclinic system with four molecules in the unit cell of dimensions a = 11.425(2) Å, b = 13.530(2) Å, c = 9.5215(17) Å, β = 117.289(4) Å, and 2,2′-thio-bis(4-methyl phenol) 5 crystallizes in the space group P 212121 of the orthorhombic system with four molecules in the unit cell of dimensions a = 9.021(1) Å, b = 10.523(2) Å, c = 13.607(2) Å, α = 90. The structures have been refined to final values for the crystallographic R factor of 0.0189(3) and 0.0248(5) based on 2999 and 3720 observed independent reflections respectively.

Ultratrace determination of lead, cadmium and copper in environmental and biological samples by atomic absorption spectrometry after their separation and preconcentration using octadecyl silica membrane disks modified with a new n–s schiff base

Pb(II), Cd(II) and Cu(II) ions were separated and preconcentrated by solid-phase extraction on octadecyl-bonded silica membrane disks modified with a new S–N-containing Schiff base (bis-2-thiophenal propandiamine) (BTPD) followed by elution and atomic absorption spectrometric detection. The method was applied as a separation and detection method for lead(II), cadmium(II) and copper(II) in environmental and biological samples. Extraction efficiency and the influence of sample matrix, flow rate, pH, and type and minimum amount of stripping acid were investigated. The maximum capacity of the membrane disks modified by 4 mg of BTPD was found to be 668 ± 10, 480 ± 8 and 454 ± 7 µg of lead, cadmium and copper, respectively. The limit of detection of the proposed method is 0.25, 0.01 and 0.02 ng/mL for lead, cadmium and copper, respectively.

SYNTHESIS AND CRYSTAL STRUCTURE OF MN(II) AND HG(II) COMPOUNDS AND SOLUTION STUDIES OF MN(II), ZN(II), CD(II) AND HG(II) COMPOUNDS BASED ON PIPERAZINEDIIUM PYRIDINE-2,3-DICARBOXYLATE

Novel metal organic frameworks including {(pipzH2)[Mn(py-2,3-dc)2]·7.75H2O}n, 1, {(pipzH2)[Zn(py-2,3-dc)2]·4H2O}n, 2, [Cd(py-2,3-dc)(H2O)3]n, 3 and {(pipzH2)[Hg4Cl10]}n, 4, in which pipz is piperazine and py-2,3-dcH2 is pyridine-2,3-dicarboxylic acid were synthesized applying a proton transfer ion pair i.e. (pipzH2)(py-2,3-dcH)2 and corresponding metallic salts and studied by IR, 1H NMR, 13C NMR spectroscopy and single crystal X-ray diffractometry. The space group of compounds 1 and 4 are P21/c and C2/c of monoclinic system, respectively. The crystal dimensions are a = 20.108(2) Å, b = 19.910(2) Å, c = 12.997(1) Å, β = 94.354(2)° for 1 and a = 15.940(1) Å, b = 11.2690(9) Å, c = 11.1307(9) Å, β = 90.685(2)° for 4. The crystal structures of 2 and 3 have been reported previously. However, their solution studies are discussed here. The compounds had all polymeric structures. Although ZnII, CdII and HgII were elements of the same group, their behavior against the ion pair was essentially different. Various supramolecular interactions mainly hydrogen bonds of the type O-H⋯O, N-H⋯O, C-H⋯O, N-H…Cl and C-H⋯Cl were observed in the structures. There was an unusual and huge water cluster in the structure of compound 1. The solution states of compounds 1–4 were studied and reported. The protonation constants of pipz and py-2,3-dc, the py-2,3-dc/pipz proton transfer equilibrium constants and stoichiometry and stability of the system with Mn2+, Zn2+, Cd2+ and Hg2+ ions in aqueous solution were investigated by potentiometric pH titrations.

Propane-1,2-diammonium bis­(6-carboxy­pyridine-2-carboxyl­ate) dihydrate

The reaction of propane-1,2-diamine (pn) and pyridine-2,6-dicarboxylic acid (pydcH2) in a 1:2 molar ratio in aqueous solution resulted in the formation of the title compound, C3H12N2 2+·2C7H4NO4·2H2O or (pnH2)(pydcH)2·2H2O. The structure contains two monoanionic deprotonated forms of pyridine-2,6-dicarboxylic acid molecules (pydcH)−, a diprotonated propane-1,2-diamine (pnH2)2+, and two water molecules. A significant π–π stacking interaction is observed between the pyridyl rings of the (pydcH)− fragments, with a face-to-face distance of 3.6194 (9) Å. In the crystal structure, a wide range of non-covalent interactions consisting of ion pairing, hydrogen bonding [of the types of O—H⋯O, N—H⋯O, N—H⋯N and C—H⋯O, with D⋯A distances in the range 2.454 (2)–3.222 (2)Å] and π–π stacking interactions [centroid–centroid distance = 3.6194 (9) Å] connect the components into a supramolecular structure.

Bis(guanidinium) bis­(4-hydroxy­pyridine-2,6-dicarboxyl­ato-κ3O2,N,O6)nickel­ate(II) dihydrate

The reaction of nickel(II) nitrate hexahydrate, guanidine (G) and 4-hydroxypyridine-2,6-dicarboxylic acid (hypydcH2) in a 1:2:2 molar ratio in aqueous solution resulted in the formation of the title compound, (CH6N3)2[Ni(C7H3NO5)2]·2H2O or (GH)2[Ni(hypydc)2]·2H2O. The six donor atoms of the two 4-hydroxypyridine-2,6-dicarboxylate or (hypydc)2− ligands form a distorted octahedral arrangement around the NiII centre. Considerable C—O⋯π stacking interactions between the CO groups of carboxylate fragments and the pyridine rings of (hypydc)2− with a distance of 3.3212 (8) Å are observed. In the crystal structure, a wide range of noncovalent interactions consisting of hydrogen bonding (of the types O—H⋯O and N—H⋯O), ion pairing, and π–π [centroid–centroid distance 3.8037 (5) Å], N—H⋯π and C—O⋯π stacking interactions connect the various components into a supramolecular structure.