Electropolymerization of magnesium 5,15-di(<Emphasis Type="Italic">n</Emphasis>-methoxyphenyl)porphine

The process of electroxidative polymerization of magnesium 5,15-di(n-methoxyphenyl)porphine MgP(MeOPh)₂ is studied. The presence of substituents in positions 5 and 15 of the porphine macroring makes reactive two of its four meso positions, which allows new bonds to be formed only in the opposite positions 10 and 20. As a result, the process of electropolymerization of this substituted monomer at its oxidation can produce only linear chains, in contrast to unsubstituted magnesium porphine MgP for which the polymer structure can both be linear and contain zigzag and/or cruciform fragments.     

Spectroelectrochemical determination of the redox equivalent of magnesium porphine in the course of its electrooxidation

The spectroelectrochemical method has been applied for studying the electropolymerization of magnesium porphine with the aim to determine the number of electrons consumed per monomer molecule, which allows one to find out the number of bonds between the units in the resulting polymer. Based on the results, a conclusion has been made about the structure of macrochains of the basic representative of a new family of electroactive materials, magnesium porphine     

Crystalline Materials with Large Channels or Cavities – Synthesis and Crystal Structure of an Iron(III) tetra(4‐carboxyphenyl)‐porphine

Tetra(4‐carboxyphenyl)‐porphine iron(III) chloride · 2 CH₃COOH · 4 H₂O ( 1 ) was prepared via a hydrothermal synthesis approach starting from FeCl₂ and 5,10,15,20‐tetrakis‐(4‐carboxyphenyl)‐21 H,23 H‐porphine in glacial acetic acid in the presence of KOH as a base and ytterbium(III) acetate as a template. Compound 1 was characterized by single crystal X‐ray diffraction and elemental analysis. Space group: P 1, Z = 2, unit cell dimensions at 200 K: a = 9.282(2), b = 20.239(5), c = 22.239(5) Å, α = 92.49(3), β = 99.87(3), γ = 90.78(3)°, R₁ (observed) = 0.132, wR₂ (all data) = 0.395. The architecture of the structure is determined by interporphyrin hydrogen bonding. Four iron porphyrin units form a very wide open channel with dimensions of circa 15.7 Å × 15.7 Å. No interpenetrating is observed.     

Direct synthesis of magnesium porphine via 1-formyldipyrromethane

The reaction of 1-formyldipyrromethane (100 mM) in toluene at 115 degrees C containing DBU (10 mol equiv) and MgBr2 (3 mol equiv) in the presence of air affords the magnesium chelate Mg(II) porphine in 30-40% yield. The advantages of the new method include simplicity, high concentration, chromatography-free purification, gram-scale synthesis, and avoidance of the poorly soluble free base porphine. Mg(II) porphine exhibits good solubility in common organic solvents and is a valuable core scaffold for derivatization.     

The self-assembly of porphine molecules on NaCl pre-covered Cu(110) surface

The self-assembly of porphine molecules on NaCl pre-covered Cu(110) surface has been investigated at a single molecular level by scanning tunneling microscopy. The pre-grown NaCl stripe pattern has been partly interrupted due to the adsorption of porphine molecules at RT. Annealing the sample at 333 K and 423 K gradually promotes the formation of self-assembly network composed of porphine molecules and Cu atoms. Annealing at 473 K helps to convert this self-assembly structure into organometallic nanoribbon through C–Cu–C connecting.     

Some color reactions for magnesium

Summary The application of several dyestuffs for the detection of magnesium in strongly alkaline medium has been examined. In all cases cobalt and nickel give the same test as magnesium and manganese in some. Methods for the sensitive detection of magnesium in presence of other cations have been discussed. Titan yellow is a very delicate reagent for magnesium and more specific than 1·2·5·8 oxyanthraquinone. The latter reacts also with beryllium, lanthanum and cadmium, whereas these elements do not form a colored compound with titan yellow. A mixture of titan yellow and magnesium chloride can be used as a reagent for hydroxyl ions; the sensitivity being dependent upon the magnesium concentration. The reaction can also be applied as a spot test on filter paper. Anilin yellow S (Kahlbaum) reacts very sensitively with lanthanum and copper in weakly acid medium (acetate buffer p H around 5,0).     

Rayleigh light scattering from hydrogen‐bonded dimers of small astrophysical molecules

High level ab initio calculations of the Rayleigh scattering activities of the hydrogen‐bonded dimers of formic acid (HCOOH), nitrosyl hydride (HNO), and hydrogen cyanide (HCN) molecules have been performed. All these molecules have already been detected in interstellar space and are of great importance from the astrochemical point of view. The geometries of the homo‐ and hetero‐dimers have been optimized using Hartree–Fock and second‐order Møller‐Plesset perturbation theory. Dipole moment, mean dipole polarizability, and polarizability anisotropy have been calculated utilizing Pople‐type 6‐311++G(d,p) and Dunning's aug‐cc‐pVDZ basis sets for all the complexes. The polarizabilities are then used to calculate and analyze the Rayleigh scattering parameters. The results for the dimers, HCN···HCN, HCOOH···HCOOH, HNO···HNO, HCN···HCOOH, HCN···HNO, and HNO···HCOOH are compared with those of the isolated molecules, HCN, HCOOH, and HNO to see the effect of hydrogen bond formation on the molecular interaction with radiation. © 2011 Wiley Periodicals, Inc.     

Sublimation enthalpy of dye molecules measured using fluorescence

We present an in-flight fluorescence detection scheme for molecular beams which is applied to determine the enthalpy of sublimation of dye molecules. We investigate tetraphenylporphyrin (TPP), porphine, and nile red, which are believed to be suitable candidates for molecular de Broglie wave interferometry. The measured values are H(sub)(TPP)=142+/-3 kJ/mol, H(sub)(porphine)=87+/-3 kJ/mol, and H(sub)(nile red)=66+/-2 kJ/mol. For TPP, sublimation enthalpies differ in the literature by more than a factor of 2. Our measurements confirm a value at the lower end of this scale. We discuss changes in the character of the molecular flow with the source temperature as a prime reason for discrepancies in the published data.     

Investigation of structures of PEO‐MgCl2 based solid polymer electrolytes

The crystallinity of polyelectrolytes has long been known to affect their ionic conductivity, but the effects of water of hydration on polyelectrolyte structure are not commonly studied. Here, polymer complexes consisting of poly(ethylene oxide) (PEO) with magnesium chloride (anhydrous MgCl₂, MgCl₂·4H₂O, and MgCl₂·6H₂O, respectively) have been prepared by a mixed‐solvent method. Fourier transform‐infrared measurements indicate each magnesium chloride salt can coordinate with PEO to form a complex. The structures of (PEO)_xMgCl₂·4H₂O and (PEO)_xMgCl₂·6H₂O complexes are similar, whilst the structure of (PEO)_xMgCl₂ complex is different to both. Wide angle X‐ray diffraction studies indicate in each polymer complex system the crystallization of PEO is depressed by the interaction of magnesium cation with the ether oxygen of PEO. PEO in (PEO)_xMgCl₂ and (PEO)_xMgCl₂·4H₂O are shown to be amorphous, but in (PEO)_xMgCl₂·6H₂O it is crystalline. Polar optical microscopy images indicate in each PEO/magnesium chloride system the crystalline morphology clearly changes with the increase of magnesium salt content. The reason for the formation of the spherulites with special morphology are the strong interaction between magnesium cation and ether oxygen of PEO, and the different evaporation rates of ethanol and chloroform in mixed solvent. A better understanding of the effects of hydration on polyelectrolyte crystallinity can help in improving their use in a variety of applications. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys. 2013, 51, 1162–1174     

Preparation of cobalt polyporphine and its catalytic properties in oxygen electroreduction

A new member of the polyporphine series—cobalt polyporphine of type I (pCoP-I)—was prepared from the starting magnesium polyporphine of type I (pMgP-I) by ion exchange, i.e. by sequential processing of the pMgP-I polymer film on the electrode surface with solutions of trifluoroacetic acid (forming metalfree polyporphine of type I, pH₂P-I) and cobalt(II) acetate in organic solvents. The completeness of each stage of ion exchange can be judged from the change in the electrochemical and spectral characteristics of the obtained polymer films of unsubstituted porphine (?H2P-I) and cobalt porphine (pCoP-I) of type I. Oxidative transformation of this polyporphine pCoP-I was performed, which led to the formation of additional bonds between the neighboring porphine units in the polymer film (transition of polymer of type I into polymer of type II, pCoP-II). The behavior of the polymer films of cobalt polyporphine of types I and II in oxygen electroreduction was studied. The films showed catalytic activity in this process.     

Synthesis of magnesium oxychloride nanorods with controllable morphology and their transformation to magnesium hydroxide nanorods via treatment with sodium hydroxide

In this paper, the formation of magnesium oxychloride (Mg_x(OH)_yCl_z·nH₂O) nanorods from the system MgO-MgCl₂-H₂O is investigated thoroughly. By systematically changing the adding amounts of the three starting materials, short nanorods (<1 μ) or long nanorods (up to 20 μ) were obtained readily with the aspect ratio in the range of 10–70. The mechanism of the crystal growth and the change of the crystal phase from 5Mg(OH)₂·MgCl₂·8H₂O (phase 5) to 3Mg(OH)₂·MgCl₂·8H₂O (phase 3) is also discussed. The products were characterized by transmission electron microscopy X-ray diffraction, energy-dispersive X-ray spectroscopy, and thermogravimetric analysis. The resulting magnesium oxychloride nanorods were further transformed to magnesium hydroxide (Mg(OH)₂) nanorods with the shape remained by treating with NaOH at room temperature. The results shown in this paper indicate a facile pathway to produce magnesium oxychloride or magnesium hydroxide nanorods with controllable morphology on large scale.     

Chemistry of borate in salt lake brine (XXXIV)

The crystallization processes of hydrated Mg-borates, boric, magnesium hydroxide and Mg-oxychloride from MgO-B₂O₃-18%MgCl₂-H₂O supersaturated solution at 20°C have been studied by kinetic method. The crystallization solid phases were characterized by X-ray powder diffraction, IR spectra, thermal analysis and chemical analysis. The liquid-solid phase diagram of thermodynamic nonequilibrium state has been given. In this phase diagram, there exist eight crystallization fields, boric acid(H₃BO₃), trigomagneborite(MgO · 3B₂O₃ · 7.5H₂O, MgO · 3B₂O₃ · 7H₂O), hungchaoite(MgO · 2B₂O₃ · 9H₂O), inderite(2MgO · 3B₂O₃ · 15H₂O), chloropinnoite(2MgO · 2B₂O₃ · MgCl₂ · 14H₂O), magnesium hydroxide(Mg(OH)₂) and magnesium oxychloride (5Mg(OH)₂ · MgCl₂ · 8H₂O).     

On spectroscopic properties and isotope effects of vibrationally stabilized molecules

Results of quantum and semiclassical calculations obtained for two different potential-energy surfaces are used to discuss spectroscopic properties and isotope effects of the linear IHI and IDI molecules. The potentials are a purely repulsive LEPS surface and a DIM-3C potential with two van der Waals type minima for equivalent IH ··· I and I ··· HI configurations. Both systems are dominated by the effect of vibrational bonding giving rise to some very unusual spectroscopic phenomena, which are discussed in detail. The different vibrational frequencies and rotational constants are roughly estimated as ν₁ = 120 (100) cm^?1, ν₂ = 280 (210) cm^?1, ν₃ = 360 (160) cm^?1 and B = 0.0194 (0.0196) cm^?1 for IHI (IDI). A detailed discussion of the dependence of ν₁, ν₂ and B on ν₃, their sensitivity to variations of the potential-energy surface, and a comparison with the vibrational frequencies of I₂ and HI (ID) is given. It is predicted that there exists only one excited level of the antisymmetric stretching mode. The numbers of symmetrical stretching and bending levels are fairly constant or may even decrease upon deuteration. Simultaneously deuteration destabilizes the molecule. These unusual phenomena are rationalized by our calculations. A set of criteria for observing infrared and Raman bound-to-bound and bound-to-resonance state transitions are presented for the IHI and IDI molecule.     

Interaction of methane molecules

Potential-energy curves for CH₄·CH₄ have been calculated using the SCF LCAO MO method. Six different mutual orientations of the molecules have been considered and several basis sets have been employed. An analytical potential has been fitted to the computed energy values and used in a Monte Carlo calculation to yield a spherically averaged CH₄·CH₄ potential. The potential, if corrected for dispersion interaction, agrees fairly well with that derived from thermophysical data. At short distances it disagrees with the potentials derived from scattering experiments which, however, are also incompatible with the experimental potential for large distances.     

A new hydrate of magnesium carbonate,MgCO3·6H2O

During investigations of the formation of hydrated magnesium carbonates, a sample of the previously unknown magnesium carbonate hexahydrate (MgCO₃·6H₂O) was synthesized in an aqueous solution at 273.15 K. The crystal structure consists of edge‐linked isolated pairs of Mg(CO₃)(H₂O)₄ octahedra and noncoordinating water molecules, and exhibits similarities to NiCO₃·5.5H₂O (hellyerite). The recorded X‐ray diffraction pattern and the Raman spectra confirmed the formation of a new phase and its transformation to magnesium carbonate trihydrate (MgCO₃·3H₂O) at room temperature.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. XXIV. Darstellung und Eigenschaften von Tetrabenzylmolybdän und -uran

Contributions to the Chemistry of Transition Metal Alkyl Compounds. XXIV. Preparation and Properties of Tetrabenzyl Molybdenum and Tetrabenzyl Uranium Tetrabenzyl molybdenum, (C₆H₅CH₂)₄Mo, can be obtained by the reaction of MoCl₄ · 2 THF with dibenzyl magnesium. The compound forms darkbrown crystals, which are stable at room temperature. The analogous reaction of UCl₄ · 3 THF with dibenzyl magnesium yields a reddish brown complex of tetrabenzyl uranium of the formula (C₆H₅CH₂)₄U · MgCl₂. The synthesized compounds are characterized more in detail.     

Crystallographic,spectroscopic and electrochemical characterization of pyridine adducts of magnesium(II) and zinc(II) porphine complexes

A new purification method of magnesium(II) and zinc(II) porphine complexes (MgP and ZnP, respectively) by crystallization of their respective pyridine adducts is described. Pure MgP and ZnP can be regenerated by removal of the coordinated pyridine ligands by heating at 200 °C under vacuum. X-ray crystallographic structures of the pyridine adducts are presented for the first time. NMR analyses of the adducts reveal the coordination of two pyridine molecules. Electrochemical as well as UV-vis absorption spectroscopy analyses in DMF of MgP·(Py)₂, ZnP·(Py)₂, MgP and ZnP indicate that pyridine adducts are totally dissociated. Besides, oxidation peaks of these complexes are totally irreversible, revealing a high reactivity of the oxidized species. Electrolyses at the first oxidation potential lead to the formation of the meso-meso (ZnP)₂ and (MgP)₂ dimers, oligomers and polymers on the electrode surface, as attested by MALDI-TOF mass spectrometry and UV-vis absorption spectroscopy analyses of the crude solution.     

A computational study on the nature of the halogen bond between sulfides and dihalogen molecules

The characteristics and nature of the halogen bonding in a series of B···XY (B = H₂S, H₂CS, (CH₂)₂S; XY = ClF, Cl₂, BrF, BrCl, Br₂) complexes were analyzed by means of the quantum theory of “atoms in molecules” (QTAIM) and “natural bond orbital” (NBO) methodology at the second-order Møller-Plesset (MP2) level. Electrostatic potential, bond length, interaction energy, topological properties of the electron density, the dipole moment, and the charge transfer were investigated systematically. For the same electron donor, the interaction energies follows the B···BrF > B···ClF > B···BrCl > B···Br₂ > B···Cl₂ > B···ClBr order. For the same electron acceptor, the interaction energies increase in the sequence of H₂S, H₂CS, and (CH₂)₂S. Topological analyses show these halogen bonding interactions belong to weak interactions with an electrostatic nature. It was found that the strength of the halogen-bonding interaction correlates well with the electrostatic potential associated with halogen atom and the amount of charge transfer from sulfides to dihalogen molecules, indicating that electrostatic interaction plays an important role in these halogen bonds. Charge transfer is also an important factor in the halogen bonds involved with dihalogen molecules.     

Solubility in the magnesium chlorate-carbamide-water system at 50°C

The solubility of phases in the magnesium chlorate-carbamide-water system was studied by the isothermal solubility method at 50°C. The crystallization branches of carbamide, magnesium chlorate hexahydrate, Mg(ClO₃)₂ · 6CO(NH₂)₂, Mg(ClO₃)₂ · 4CO(NH₂)₂ · 2H₂O, and Mg(ClO₃)₂ · 2CO(NH₂)₂ · 4H₂O were revealed in the phase diagram.     

Hydrodynamic invariant of polymer molecules

The theories of hydrodynamic properties of macromolecules in solution leading to an invariant relationship between the values of the intrinsic viscosity, [η], the molecular weight, M, and the translational friction coefficient of the molecule, f, have been considered. The review of experimental data comprising as much as about 2000 fractions of various polymers suggests that for all flexible-chain and moderately rigid-chain molecules the hydrodynamic parameter A₀ = kη₀(M[η]/100)^1/3f^?1 is actually an invariant independent of the chain length and the thermodynamic strength of the solvent and for moderately polydisperse samples also independent of the degree of their polydispersity. For polymers with very rigid chains the parameter A₀ has a high value over the experimentally investigated range of M. These conclusions make it possible to recommend the use of the following average experimental values of the invariant A₀ for the determination of M of polymers from the values of [η] and f: for flexible-chain and synthetic polymers with moderately high chain rigidity (3.2 ± 0.2) · 10^?10, for polymers with high chain rigidity (3.7 ± 0.4) · 10^?10, and for cellulose derivatives and other polysaccharides with molecular dispersity of nonelectrolyte solutions (3.30 ± 0.30) · 10^?10 erg deg^?1 mol^?1/3. The fact that the experimental value of A₀ = 3.2 · 10^?10 does not coincide with the value of A_∞ = 3.8 · 10^?10 erg deg^?1 mol^?1/3 predicted by the theories of translational friction and viscosity of macromolecules implies that the theoretical values of P_∞ = 5.11 and Φ_∞ = 2.8 · 10²³ mol^?1 are mutually incompatible and these theories require further development.