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Designing a highly active, cost-effective, poison-resistant, and durable noble-metal-free electrocatalyst is essential for improvement of direct methanol fuel cells performance. In this work, Ni-doped MoSe2nanosheets were successfully synthesized and integrated with carboxylated multiwalled carbon nanotube (f-MWCNT). The formation of Ni-doped MoSe2/f-MWCNT was confirmed with field emission scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy techniques. The prepared nanocomposite was used as an electrochemical catalyst for methanol electro-oxidation. The Ni-doped MoSe2/f-MWCNT electrocatalyst displayed a low onset potential of 0.33 V and methanol oxidation reaction (MOR) activity of 630 mA/cm2at 0.8 V vs. Ag/AgCl after addition of 1 M methanol in alkaline solution. The proposed electrocatalyst also presented outstanding stability with 90% of its MOR activity retention even after 8000 s. With its facile synthesis, excellent catalytic performance and high stability, Ni-doped MoSe2/f-MWCNT is promising as an inexpensive, CO-resistant and efficient anode catalyst for MOR.

The 19 new inorganic–organic hybrid compounds based on Keggin, Preyssler and Wells–Dawson types of tungstoheteropolyanions and fairly complete series of essential amino acids were prepared and the structure of these materials investigated on the basis of CHN analysis and multi-spectroscopic investigations (IR, 1HNMR and 13CNMR). Changes in position and shape of asymmetric stretching vibration bands in finger print regions of polyoxometalates (POMs) were identified in all FT-IR spectra. These changes are related to noncovalent interactions between POM surface oxygen atoms and the bio-organic molecules. In reported compounds, 12 natural amino acids out of 20 (i.e., alanine, glycine, glutamine, asparagine, methionine, cysteine, leucine, arginine, threonine, aspartic acid, disodium glutamate) have participated.

Pyridine-2,4-dicarboxylic acid (py-2,4-dcH2) and creatinine (creat) with MCl2·6H2O (M = CoIIand NiII) formed two isomorph supramolecular coordination compounds. Their three-dimensional supramolecular architecture is formed not only by simple proton transfer from pyridine-2,4-dicarboxylic acid to creatinine, but also by other very important non-covalent interactions, especially the ion pairing, hydrogen bonds, C–H···π, N–H···π and C–O···π interactions. In these complexes, pyridine-2,4-dicarboxylate acts as a bidentate ligand and the lattice is composed of anionic hexacoordinated complex, [M(py-2,4-dc)2(H2O)2]2−(M = CoIIand NiII), creatinium counter ion, (creatH)+, and two uncoordinated water molecules. The complexation equilibrium and stabilities of proton transfer, binary and ternary complexes of pyridine-2,4-dicarboxylic acid as a primary ligand and creatinine as a secondary ligand with Co2+and Ni2+transition metal ions in comparison with X-ray crystal structures in solid state have studied.

Three new organic–inorganic hybrid materials based on two important heteropolyoxometalates namely Preyssler (=K12.5H1.5[Na(H2O)P5W30O110]·35H2O) and Wells–Dawson (=K6[P2W18O62]·10H2O) anions, namely, (Hpro)9(Hleu)3K2[Na(H2O)P5W30O110]·25H2O (1), (Hpro)4(Hasp)[HP2W18O62]·20H2O (2), and (Hpro)11K3[Na(H2O)P5W30O110]·18H2O (3) where pro, leu, and asp are proline, leucine, and asparagine, respectively, were prepared and identified by elemental analysis, infrared and proton nuclear magnetic resonance spectroscopies, and thermogravimetric analysis. The hybrid materials are made up of positively charged amino acids, [Na(H2O)P5W30O110]14−and [P2W18O62]6−anions, and H2O molecules of crystallization. These constituents’ fragments held together into a three-dimensional supermolecular network through non-covalent interactions. The protonation constants of the amino acids used, and Preyssler and Wells–Dawson species in all possible protonated forms, the equilibrium constants for binary systems of proline–asparagine and proline–leucine, and the stoichiometry and stability constants of the corresponding binary and ternary hybrids with Preyssler and Wells–Dawson heteropolyoxometalates in aqueous solution were investigated by potentiometric pH titration method. The stoichiometries of the most hybrid species in solution were compared with the corresponding hybrids in the solid phase, in detail.

In this study, the solution chemistry and solid-state structures of a novel proton transfer compound, (pipzH2)(pyc)2·H2O 1, and three metal–organic complexes of [Mn(pyc)2(H2O)2]2·2H2O 2, [Ni(pyc)2(H2O)2]·H2O 3and [Cu(pyc)2H2O]n4, (pyc = pyridine-2-carboxylate, pipz = piperazine) were investigated. On the basis of crystallographic data, each MIIion is coordinated to pyridine-2-carboxylate as bidentate ligand. Furthermore, these complexes form a three-dimensional structure by a variety of noncovalent interactions such as extensive O–H···O, O–H···N, N–H···O, N–H···N, C–H···O hydrogen bonds, C–H···π and C–O···π interactions. The equilibrium constants for the binary pyc-pipz proton transfer system, the stoichiometry and stability of complexation of this system with Mn2+, Ni2+and Cu2+ions in aqueous solution were investigated by potentiometric pH titration method. In each case, the stoichiometry of the dominant metal complex species in solution was compared with that obtained from the crystal structure.

Abstract: The new compounds, (phhyH)2(pydc), 1 and (phhyH)[Ni(pydc)(pydcH)].3H2O, 2, phhy: phenylhydrazine, pydcH2: pyridine-2,6-dicarboxylic acid, were synthesized and characterized by IR, 1H NMR, 13C NMR and UV spectroscopy. The structure of 2 was determined by X-ray crystallography. In the crystal structure, the metal ion was six coordinated by two tridentate (pydc)2− and (pydcH)− groups and each anionic complex unit, [Ni(pydc)(pydcH)]− was accompanied by one (phhyH)+ as counter ion and two water molecules. In compound 2, a large number of O-H⃛OO, N-H⃛O and C-H⃛O hydrogen bonds were observed. These interactions as well as other noncovalent interactions such as ion pairing, C-O⃛π and π-π stacking play an important role in the formation and stabilization of the crystal lattice. In the solution study, the equilibrium constants for the binary pydc-phhy proton transfer system, the stoichiometry and stability of complexation of this system with Ni2+ ion in aqueous solution were investigated using potentiometric pH titration method. The stoichiometry of the most abundant species in the solution was compared to the crystalline cited metal ion complexes.

Abstract: The morphology of plasticized sulfur with styrene (STY) and dicyclopentadiene (DCPD) was studied using scanning electron microscopy, to investigate the influence of type of additive and time on the rate of conversion of β- to α-structure. The results revealed that major part of plasticized sulfur with STY converted to α-phase after 30 days. While the DCPD-plasticized sulfur mostly possessed a β-structure and only a minor part was converted to α-structure with the elapse of time. The thermal behavior of sulfur, molten sulfur, and the plasticized sulfur samples were studied by thermogravimetry (TG) and differential scanning calorimetry (DSC), 522 days after their preparation. The results clearly revealed that, among different samples studied, the DCPD-plasticized sulfur possesses the highest thermal stability. The effect of addition of micro- and nanosilica, as modifiers, on the morphology and thermal behavior of the STY-plasticized sulfur was also studied. It was found that the presence of the above fillers to the matrix of STY-plasticized sulfur not only caused the creation of some cracks in the sample, but also could not block the conversation of β- to α-structure.

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.

Abstract: In this work, the antiradical activity of fresh and aged skins of two Iranian varieties of pomegranate husk and pistachio hull was measured in order to assess their concentration in antioxidant potential usable in various fields. The radical scavenging capacity (RSC) of pomegranate husks and pistachio hulls samples were studied using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH.) assay. To determine the RSC and stoichiometric factor of the samplers, the second-order rate constants (k 2) and total H-atom-donating capacities (n) for the oxidation of polyphenol extracts by DPPH. were evaluated. The resulting k 2 values were also compared with those of the natural and synthetic antioxidants. The order of relative second-order rate constants in methanol at 25 °C found to be pomegranate husk > gallic acid > tannic acid > pistachio hull. Furthermore, the RSCs based on the calculation of area under kinetic curve (AUC), total stoichiometric factor of natural phenolics and commercial antioxidants were also compared.

Abstract: A novel coordination polymer of zinc(II) atom, [(pipzH2)[Zn(pyzdc)2].6H2O]n (1) (H2pyzdc and pipz are pyrazine-2,3- dicarboxylic acid and piperazine, respectively), was successfully synthesized under hydrothermal conditions and structurally characterized by means of elemental analysis, FTIR, TGA and SEM. Polymer 1 was further structurally characterized by single crystal X-ray diffraction consisting of 1D-polymeric units. The crystal structure of the title polymer consisted of polymeric Zn complex anions and discrete piperazindiium cations. The Zn cation, located on the inversion center, was N,O-chelated by two (pyzdc)2− anions in the basal plane, and was further coordinated by two carboxyl O atoms from the adjacent pyzdc anions in the axial directions with a longer Zn-O bond distance of 2.1746(15) Å, forming a distorted ZnN2O4 coordination geometry. The pyzdc anions bridged the Zn cations to the one-dimensional polymeric chains running along the crystalographic b axis. The (pipzH2)2+ linked with the complex chains via kinds of hydrogen bonds. The polymer 1 crystallized in the monoclinic space group P21/n with Z = 2. The cell parameters of the title polymer were a = 6.5318(16) Å, b = 17.492(4) Å, c = 10.688(3) Å and β = 100.841(4)°. The polymer 1 bears ion-pairing interactions, O-H⃛O, N-H⃛O, and C-H⃛O hydrogen bonds as main factors in the formation of its 1D supramolecular architecture. Obtained results from TGA showed that the title polymer was thermally quite stable, and so its framework possessed remarkable thermal stability up to 700 °C. The SEM analysis verified that layers present in 1 were formed in Nano-sized particle. The protonation constants of acridine (Acr), H2pyzdc, and pipz as the building blocks of the proton transfer systems including pyzdc-Acr in mixed 20% dioxane-80% water (V/V) solvent and pyzdc-pipz in aqueous solvent, and the corresponding stability constants of these systems were determined by potentiometric study. The stoichiometry and stability of complexation of these systems with Zn2+ ion were investigated by potentiometric pH titration method. The stoichiometry of the most complex species in the solution was compared with the corresponding crystalline metal ion complexes.

Abstract: Calix[4]crown-6 (L) was synthesized and the stoichiometry and stability of its complexes with alkali, alkaline earth, Ag+, Tl+ and NH4+ ions were studied conductometrically in acetonitrile solution. The resulting 1:1 Ba2+-L complex was found to be the most stable one among all cation complexes studied. The optimized structures of the ligand and its Ba2+ complex are also reported. Based on the findings, L was used as a suitable ionophore to prepare a PVC-membrane selective electrode for Ba2+ ion. The electrode revealed a Nernstian behavior over wide barium ion concentration 1.0 × 10−6 to 1.0 × 10−3 M with only little trace of 7.1 × 10−7 M. The potentiometric responses were found to be independent of the pH of test solutions in the range of 4.0–10.0. The proposed electrode response time of about 10 s proved to be highly selective for Ba2+ ion over a wide variety of cations including alkali, alkaline earth, transition and heavy metal ions. The sensor could be used for at least three months without any noticeable deviation. The practical utility of the proposed electrode was also examined.

Abstract: The aqueous reactions of zinc(II) and cadmium(II) nitrate and pyridine-2,6-dicarboxylic acid, (pydcH2), with 9-aminoacridine, (AAcr), resulted in the formation of two new proton transfer compounds, (AAcrH)2[Zn(pydc)2].3H2O (1) and (AAcrH)2[Cd(pydc)2].4H2O (2). The compounds were characterized using IR spectroscopy and single crystal X-ray diffraction. Both compounds crystallized in the triclinic crystal system, space group $$P\bar 1$$, with two molecules per unit cell. The anions were six-coordinate complexes with distorted octahedral geometries around the Zn(II) and Cd(II) centers. The dihedral angles indicated that the two (pydc)2− ligands were almost perpendicular to each other. The complex anions of [M(pydc)2]2- were neutralized with (AAcrH)+ cations. These cations formed extended stacks throughout the structures. The water molecules clustered around cyclic tetramers, bridging the anions and forming a link to the aminoacridiunium stacks. A potentiometric pH titration method was used to investigate the protonation constants of AAcr and pydc, the pydc-AAcr proton transfer equilibrium constants, and the stoichiometries and stabilities of complex formation with Zn2+ and Cd2+ ions in 50% dioxane-50% water.

Abstract: Three complexes (bpyH)[Fe(pydc)2].4H2O (1), [Co2(pydc)2(μ-bpy)(H2O)4].4H2O (2) and [Ni(pydc)(bpy)(μ-bpy)]4.8H2O (3) were prepared from the reaction between pyridine-2,6-dicarboxylic acid, pydcH2, and 4,4′-bipyridine, bpy, with FeCl2.4H2O, CoCl2.6H2O and NiSO4.6H2O, respectively. The complex (1) crystallizes in the space group $$P\bar 1$$ of the triclinic system and contains two molecules per unit cell. The structure has been refined to a final value for R factor of 0.0355 based on 4922 reflections. The crystal structure shows that Fe(III) is coordinated to two pyridine-2,6-dicarboxylate ligands. The complexes (2) and (3) crystallize in the space group P21/c of the monoclinic system and contain two molecules per unit cell. The structure (2) has been refined to a final value for R factor of 0.0295 based on 2249 reflections. The molecular structure (2), which is a binuclear complex, contains two pyridine-2,6-dicarboxylate ligands, and a 4,4′-bipyridine bridge ligand. The structure (3) has been refined to a final value for R factor of 0.0579 based on 7721 reflections. In this structure, which is a tetramer complex, pyridine-2,6-dicarboxylate and 4,4′-bipyridine fragments act as a tri- and bidentate ligands, respectively. The protonation constants of 4,4′-bipyridine and pyridine-2,6-dicarboxylate, the equilibrium constants for the pydc-bpy system and the stoichiometry, and stability of complexation of this system with Fe3+, Co2+ and Ni2+ ions in a aqueous solution were investigated by potentiometric pH titration method. The stoichiometry of the most complexes species in solution was found to be very similar to the crystalline cited metal ion complexes.

Abstract: Nanocrystals provide a confinement effect for nanoscale engineering. In this work the cadmium selenide quantum dot and its nanoparticle films have been deposited by chemical bath deposition method (CBD). Effects of deposition time, pH and annealing operation on the optical and structural of CdSe nanoparticle film were studied. The energy band gap, structure and morphology of the samples are investigated by X-ray diffraction (XRD), UV-Vis spectrometer and scanning electron microscope (SEM). It was found that the optical band gap, nanoparticle size and thin film configuration are changed by varying pH, deposition time and annealing operation.

Abstract: Two compounds containing a proton transfer ion pair (pipzH2)(btcH2), 1, and its Co(II) complex, were synthesized and characterized using IR spectroscopy and single crystal X-ray diffraction method. The chemical formula is {(pipzH2)[Co(btc)(H2O)4].4H2O}n for Co(II) complex, 2, (pipz:piperazine, btcH4:benzene-1,2,4,5-tetracarboxylic acid). The space group and crystal system of both compounds are $$P\bar 1$$ and triclinic. The proton transfer ion pair 1 was prepared by the reaction between piperazine and benzene-1,2,4,5-tetracarboxylic acid, and its Co(II) complex, 2, was synthesized by the reaction of 1 with cobalt(II) sulphate. The complex 2 is a polymeric substance with Co(II) atoms linked by two O atoms from one benzene-1,2,4,5- tetracarboxylate. In both crystal structures, a wide range of noncovalent interactions consisting of hydrogen bonding (types of OH ⃛O, N-H⃛O and C-H⃛O) and ion pairing interactions connecting the various components into a supramolecular structure. There are also C-H⃛O and C-H⃛π intermolecular interactions in compound 2 which take part in the stabilization of molecular packing. The protonation constants of pipz and btcH4, the equilibrium constants for the btcH4-pipz proton transfer system and the stoichiometry and stability of this system with Co2+ ion in aqueous solution were investigated by potentiometric pH titrations. The stoicheiometry of one of the most abundant complexed species in solution was found to be the same as that of the crystalline cobalt(II) complex.

Abstract: Two novel compounds with formulae [Sn2(pydcH)2(H2O)2O]n, 1, and (4,4′-bpyH2)0.5[Pb(pydc)2(4,4′-bpyH)].4,4′-bpy.4H2O, 2, were obtained from a one-pot reaction between pyridine-2,6-dicarboxylic acid (pydcH2) and 4,4′-bipyridine (4,4′-bpy) with corresponding Sn(II) and Pb(II) salts. In compound 1 with a polymeric structure, each Sn(II) atom is six-coordinated by one water molecule, two (pydcH)− groups and one oxide group resulted in a coordination polymer. Compound 2 has a seven-coordinated environment around Pb(II) atom by two (pydc)2− groups and one (4,4′-bpyH). The anionic complex is balanced by half a (4,4′- bpyH2)2+ as counter ion. There are four uncoordinated water molecules and one 4,4′-bpy in the crystal lattice. Therefore, in compound 2, we have neutral, mono- and biprotonated forms of 4,4′-bipyridine, simultaneously. Several interactions including O-H⋅⋅⋅ O, O-H⋅⋅⋅EN and C-H⋅⋅⋅O hydrogen bonds, ion pairing, C-O⋅⋅⋅π (O⋅⋅⋅Cg 3.324(3) Å and 3.381(3) Å in 1 and O⋅⋅⋅Cg 3.346(4) Å in 2), C-H⋅⋅⋅π (C⋅⋅⋅Cg 3.618(4) Å in 2), and π⋅⋅⋅π stackings (with Cg ⋅⋅⋅ Cg distances of 3.613(2) and 3.641 (2) Å in 2) are present to expand and stabilize the structure. The complexation reactions of bpy and pydc-bpy with Sn2+ and Pb2+ ions in aqueous solution were investigated by potentiometric pH titrations, and the resulting equilibrium constants and species distributions at various pHs for major formed complexes are described.

Abstract: The chemiluminescence (CL) arising from reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with hydrogen peroxide in the presence of a diethyl-2-(cyclohexylamino)-5-[(E)-2-phenyl-1-ethenyl]-3,4-furandicarboxylate as a novel fluorescer (Flu) has been studied. The relationship between the chemiluminescence intensity and concentrations of TCPO, sodium salicylate, hydrogen peroxide and fluorescer is reported. The chemiluminescence parameters including intensity at maximum CL, time at maximum intensity, total light yield, theoretical maximum level of intensity and pseudo-first-order rate constants for the rise and fall of the CL burst (kr and kf) were evaluated from computer fitting of the resulting intensity-time plots. The activation parameters Ea, ΔHΔ, ΔSΔ and ΔGΔ for the rise and fall steps were evaluated from the temperature dependence of kr and kf values.

Abstract: A simple and sensitive method was developed for the analysis of preservatives sodium benzoate, methylparaben and propylparaben in nystatin suspensions by reversed-phase high performance liquid chromatography (HPLC), equipped with a C18 column and PDA detector. The mobile phase was a mixture of acetonitrile and acetate buffer of pH 4.4 (35:65 v/v). Under the optimized experimental conditions, separation of the preservatives was achieved in less than 20 min. The limits of quantifications (LOQs) and the linear dynamic ranges (LDRs) of sodium benzoate, methylparaben and propylparaben were 0.3 and 50–1000 μg Ml−1, 0.5 and 50–600 μg ml−1 and 0.3 and 50–900 μg ml−1, respectively; the respective precisions (%RSD) at 500 μg ml−1 level were 0.72%, 0.73% and 0.51% (n = 6). The average recoveries of sodium benzoate, methylparaben and propylparaben for spiked nystatin samples were obtained as 98%, 97% and 98%, respectively.

Abstract: 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.

Abstract: 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 P2 1/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.

Abstract: The homonuclear water-soluble and air stable compounds (dmpH) (H5O2) au][M(pydc)2].0.5H2O (M = Ni(II) (1), Cu(II) (2), Zn(II) (3); pydcH2 = pyridine-2,6-dicarboxylic acid, dipicolinic acid, dmp = 2,9-dimethyl-1,10-phenanthroline) have been prepared by self-assembly synthesis in aqueous solution at room temperature, and characterized by IR, 1H NMR, 13C NMR, elemental analysis and X-ray diffraction single crystal analyses for 1, 2 and 3. The complexes 1–3 represent the isostructural features. Extensive hydrogen bonding interactions involving all aqua ligands, dipicolinate oxygens and lattice water molecules further stabilize the complex units by linking them to form three dimensional polymeric networks. The stoichiometry and stability of the all three complexes in aqueous solution were investigated by potentiometric pH titration.

Abstract: Charge-transfer complexation of iodine with a new benzo-substituted macrocyclic diamide 5,6,7,8,9,10-hexahydro-2H-1,13,4,7,10-benzodioxatriazacyclopentadecine-3,11(4H,12H)-dione (L) with iodine was studied spectrophotometrically in chloroform, dichloromethane and their 1:1 (v/v) mixture. The observed time dependence of the charge-transfer band and subsequent formation of I3- ion are related to the slow formation of the initially formed 1:1 L.I2 outer complex to an inner electron donor-acceptor (EDA) complex, followed by fast reaction of the inner complex with iodine to form a triiodide ion, as follows: L + I2 → L.I2 (outer complex), fast L.I2 (outer complex) → (L.I+)I- (inner complex), slow (L.I+)I- (inner complex) + I2 → (L.I+)I3-, fast The pseudo-first-order rate constants for the transformation process were evaluated in different solvent systems. The stability constants of the resulting EDAr complexes were also evaluated and the solvent effect on their stability is discussed. The resulting complexes were isolated and characterized by FTIR and 1H NMR spectroscopy.

Abstract: The coordination properties towards different metal ions of a new class of mixed N/S-, and N/S/O-donor macrocycles containing the 1,10-phenanthroline sub-unit in the cyclic framework are reviewed. The conformational constraints imposed by the heteroaromatic fragment onto the aliphatic portion of the ring determine the coordination mode of these ligands which can stabilise low-valent Ni+, Pd+, Pt+, and Rh+ metal complexes. Structural and thermodynamic aspects of the coordination chemistry of these ligands are considered together with possible applications as building blocks in the synthesis of multi-centred systems, and as template in the construction of extended polyiodide networks. However, solution studies demonstrate the inability of these ligands to work as selective and specific fluorescent chemosensors for heavy transition and post-transition metal ions and the formation constants evaluated for the formation of 1:1 complexes with Pb2+, Cd2+, Hg2+, Cu2+, and Ag+ in acetonitrile are of the same order of magnitude. Nevertheless, some of these macrocyles are extremely effective to recognise Cu2+ or Ag+ over the other metal ions in transport processes, and have been successfully used as neutral ionophore in the construction of PVC-based ionselective electrodes and supported liquid membranes for analytical detection and separation, respectively, of these metal ions.

A novel 1:2 proton transfer self‐associated compound LH2, (GH+)2(pydc2—), was synthesized from the reaction of dipicolinic acid, pydcH2, (2, 6‐pyridinedicarboxylic acid), and guanidine hydrochloride, (GH+)(Cl—). The characterization was performed using IR, 1H and 13C NMR spectroscopy and single‐crystal X‐ray diffraction. LH2· H2O crystallizes in the space group C2/cof the monoclinic system and contains eight molecules per unit cell. The unit cell dimensions are: a= 26.480(5)Å, b= 8.055(2)Å, c= 14.068(3)Å. The first coordination complex (GH)2[Cd(pydc)2] · 2H2O, was prepared using LH2and cadmium(II) iodide, and characterized by 1H and 13C NMR spectroscopy and X‐ray crystallography. The crystal system is triclinic with space group P1¯ with one molecule per unit cell. The unit cell dimensions are: a= 8.5125(7)Å, b= 11.0731(8)Å, c= 13.2404(10)Å. The cadmium(II) atom is six‐coordinated with a distorted octahedral geometry. The two pydc2—units are almost perpendicular to each other. The protonation constants of the building blocks of the pydc‐guanidine adduct, the equilibrium constants for the reaction of pydc2—with guanidine and the stoichiometry and stability of the Cd2+complex with LH2in aqueous solution were accomplished by potentiometric pH titration. The solution studies strongly support a self‐association between pydc2—and GH+with a stoichiometry for the CdIIcomplex similar to that observed for the isolated crystalline complex. In fact, the [Cd(pydc)2]2—complex was found as the most abundant species in solution (> 90 %) at a pH >5.

A highly selective membrane electrode for the determination of ultratrace amounts of lead was prepared. The PVC membrane electrode based on 2-(2-ethanoloxymethyl)-1-hydroxy-9,10-anthraquinone (AQ), directly coated on graphite, exhibits a good Nernstian response for Pb(II) ions over a very wide concentration range (1.0×10⁻⁷–1.0×10⁻² M) with a limit of detection of 8.0×10⁻⁸ M. It has a fast response time of ca. 10 s and can be used over a period 2 months with good reproducibility (SD=±0.2 mV). The electrode revealed a very good selectivity respect to common alkali, alkaline earth, transition and heavy metal ions and could be used in the pH range of 3.5–6.8. It was used as an indicator electrode in potentiometric titration of lead ions with chromate and oxalate, and in indirect determination of lead in spring water samples.

A highly selective membrane electrode for the determination of ultratrace amounts of lead was prepared. The PVC membrane electrode based on 2‐(2‐ethanoloxymethyl)‐1‐hydroxy‐9,10‐anthraquinone (AQ), directly coated on graphite, exhibits a good Nernstian response for Pb(II) ions over a very wide concentration range (1.0×10−7–1.0×10−2M) with a limit of detection of 8.0×10−8M. It has a fast response time of ca. 10 s and can be used over a period 2 months with good reproducibility (SD=±0.2 mV). The electrode revealed a very good selectivity respect to common alkali, alkaline earth, transition and heavy metal ions and could be used in the pH range of 3.5–6.8. It was used as an indicator electrode in potentiometric titration of lead ions with chromate and oxalate, and in indirect determination of lead in spring water samples.

Solubilities of four thioxanthone derivatives in supercritical CO2 have been measured at the temperatures (308, 318, 328, 338, and 348) K in a pressure range from (122 to 355) bar. The measurements have been performed by using a simple static-sampling type apparatus. The effects of temperature, pressure, and density of carbon dioxide on solubility of thioxanthone derivatives have been investigated. The measured solubilities were correlated using a semiempirical model. The calculated results show satisfactory agreement with the experimental data.

The equilibrium solubilities of four recently synthesized aminoanthraquinones in supercritical CO2 have been measured over a temperature range of 308 to 358 K and a pressure range of 122 to 358 bar, using a simple static method. The solubility data were correlated by a semiempirical model. The calculated results show satisfactory agreement with the experimental data.

The equilibrium solubilities of five recently synthesized anthrones have been measured in supercritical carbon dioxide using a simple and reliable static method. The measurements were performed in the pressure range (101−355) bar at the temperatures (308, 318, 328, 338, and 348) K. The measured solubilities were correlated using a semiempirical model. The calculated results show satisfactory agreement with the experimental data.

ABSTRACTNew potentiometric membranesensorsresponsive to Pb(II) have been developed. The membrane sensors are based on three different 9, 10-anthraquinone derivatives. The electrode based on 1, 4-bis (prop-21-enyloxy)-9, 10-anthraquinone exhibits a good Nernstian response for Pb(II) ions over a wide concentration range (2.5×10−6- 1.0×10−2M) with a slope of 29.8 mV decade−1. Detection limit is 1.5×10−6M. The response time of the sensor is 15s and the useful working pH range is 4.7-6.8. The membrane can be used for more than 4 months without any considerable divergence in potentials. The electrodes revealed comparatively good selectivities with respect to alkali, alkaline earth and some transition and heavy metal ions. It was used as an indicator electrode in potentiometric titration of lead ions (with sulfate and oxalate ions), and for the determination of lead in waste waters.

The equilibrium solubilities of four hydroxyxanthone derivatives have been measured in supercritical carbon dioxide using a simple and reliable static method. The measurements were performed in the pressure range 74.0−354.6 bar at the temperatures 32, 45, 55, 65, and 75 °C. The order of solubility observed for the compounds used was discussed in terms of their possible intra- and intermolecular H-bonds and polarities. The measured solubilities were correlated using a semiempirical model. The calculated results show satisfactory agreement with the experimental data.