Magnesium octa[(4′-benzo-15-crown-5)oxy]phthalocyaninate in water micellar solutions of sodium deoxycholate

Aggregation of magnesium octa-[(4′-benzo-15-crown-5)oxy]phthalocyaninate (Mgcr₈Pc) in solutions of biocompatible anionic surfactant, sodium deoxycholate (SDC), was studied. It was shown using the electron absorption spectra that formation of Mgcr₈Pc monomers in micellar solutions of SDC is affected by both increased surfactant concentration and by changes in the ionic strength of solution after sodium chloride is added. The effect of the chemical structure of biocompatible anionic surfactant on monomerization of crown-containing phthalocyanines was identified; this fact opens new possibilities for using this family of compounds for fluorescent diagnosis and photodynamic therapy.     

New Hybrid Materials Based on Nanostructured Aluminum Oxyhydroxide and Terbium(III) Bis(Tetra-15-Crown-5-Phthalocyaninate)

A new method was developed for preparation of hybrid functional nanostructures through interaction between terbium complex with tetra-15-crown-5-phthalocyanine Tb[(15C₅)₄Pc]₂ and the surface of highly porous nanostructured aluminum oxyhydroxids (NAOs). It was shown that immobilization of phthalocyaninate on an NAO surface may be reversible upon a sorption from the solution in chloroform, and irreversable, when the adsorption occurred on the NAO surface that was chemically modified using methyltrimethoxysilane and annealed at the temperature ranging from 500 to 1100°С (NAOM). Nanostructure and chemical properties of the obtained hybrid nanomaterials were studied with the use of different methods: scanning electron microscopy, XRD, IR and diffuse reflectance spectroscopy. The sensor properties of the obtained Tb[(15C₅)₄Pc]₂//NAO and Tb[(15C₅)₄Pc]₂//NAOM hybrid nanostructures were studied when they interacted with ammonia and iodine vapors. It was shown that the phthalocyaninate complex on the NAO surface was liable to reduction, while the phthalocyaninate complex on the modified NAOM surface was liable to oxidation.     

Supramolecular assembly of sandwich-type heteroleptic lanthanum (porphyrinato)(phthalocyaninates)

Concentration and cation-induced supramolecular assembly of heteroleptic double- and triple-decker [An₄P]La[(15C5)₄Pc] and [An₄P]La[(15C5)₄Pc]La[An₄P] lanthanum complexes (An₄P²⁻ = 5,10,15,20-tetra-(4-methoxyphenyl)-porphyrinate dianion and(15C5)₄Pc²⁻ = tetra-(15-crown-5)-phthalocyaninate dianion) is studied. Double-decker [An₄P]La[(15C5)₄Pc] complex is shown to be susceptible to effective concentration-driven assembly determined by the deviation from the Beer-Lambert-Bouguer law up to a concentration of 10⁻⁶ M. Triple-decker [An₄P]La[(15C5)₄Pc]La[An₄P] complex is not inclined to the concentration-driven assembly up to a concentration of 10⁻⁴ M. The interaction between the receptors and sodium or potassium salt is determined by the receptor structure and independent of the salt anion. When interacting with potassium salts, the double-decker complex can form a supramolecular cofacial dimer. In the case of the triple-decker complex, the crown-phthalocyanine deck of the molecule is sterically blocked, and supramolecular aggregates do not form. Sodium cations can be encapsulated in the crown ether rings of both receptors.     

Octa- and tetra-(benzo-15-crown-5)phthalocyanines in surfactant-containing solutions

The behavior of octa-(benzo-15-crown-5)phthalocyanine (H₂cr₈Pc), as well as cobalt octa- and tetra-(benzo-15-crown-5)phthalocyaninates (Cocr₈Pc and Cocr₄Pc), in aqueous solutions containing cationic or anionic surfactants, such as cetyl trimethylammonium bromide (CTAB), sodium carboxymethyl cellulose (Na-CMC), and sodium dodecyl sulfate (SDS), is studied using electronic spectroscopy. The presence of eight benzo-15-crown-5 ether fragments on the periphery of the phthalocyanine ring is shown to facilitate the dissolution of Pc in an aqueous environment. The interactions between CTAB and crown-containing Pc promotes the dissolution of H₂cr₈Pc; Cocr₈Pc; and, to a lesser degree, Cocr₄Pc, which is accompanied by the appearance of molecular aggregates, including heteronuclear cofacial dimers. The presence of a metal in the ring is not the necessary condition of the process. In microscopically heterogeneous medium, such as an aqueous SDS-containing solution, H₂cr₈Pc is present in monomeric form at SDS concentrations close to C _cr and in dimeric form at SDS content below C _cr. Under similar conditions (environment, surfactant), Cocr₄Pc can exist in monomeric form at SDS concentrations much high than C _cr. The effect of the size of cation on the form of the crown-containing Pc in an aqueous solution is illustrated by an example of H₂cr₈Pc. Na-CMC promotes the dissolution of Pc and enables one to produce K⁺/Mcr₈Pc-modified films from aqueous solutions.     

The effect of aggregate state of octa-(benzo-15-crown-5)-substituted phthalocyanines in aqueous solutions on the structure of self-organized composites of ultrathin ion layers

The method of layer-by-layer (LbL) deposition from aqueous solutions was used to obtain electrostatic self–organized composites consisting of cationic fragments of octa-[(4′-benzo-15-crown-5)oxy]phthalocyaninates of metals (Mcr8Pc)/K⁺ and anionic fragments of sodium polystyrenesulfonate or 4,4′,4″,4?-[cobalt phthalocyaninate-2,(3),9,(10),16,(17),23,(24)-tetrayl-tetrakis(oxy)]-tetrabenzoic acid. The electronic absorption spectra of composite coatings indicate preservation of structures formed in aqueous solutions of Mcr₈Pc: coaxial associates, noncoaxial associates, and high-order aggregates. An increase in the content of noncoaxial associates and the possible presence of suspension particles in the composite are observed.     

Magnesium Octa[(4'-Benzo-15-Crown-5)-Oxy]Phthalocyaninate in Low-Molecular Hydrogels: Spectral Properties and Release under Stimulation

This work is dedicated to low-molecular hydrogels based on biodegradable sodium deoxycholate (SDC) and lysine hydrochloride (lys × HCl) with magnesium octa-[(4'-benzo-15-crown-5)-oxy]phthalocyaninate (Mgcr₈Pc) as the active component, namely, their synthesis, spectral properties of gel-solubilized Mgcr₈Pc, its release from the gel etc. Addition of Mgcr₈Pc occurs both via the mixing of the components and via its diffusion from the aqueous solution into the phase of the formed SDC/lys × HCl gel. Mgcr₈Pc-containing hydrogels are thermoreversible. The state of Mgcr₈Pc in the SDC/lys × HCl/NaCl gel at the room temperature and in the melt is studied using spectral methods. Gel melting releases Mgcr₈Pc in the form of a micelle-bound monomer. The presence of the Mgcr₈Pc monomer phase in the phthalocyanine-carrying supramolecular hydrogel causes fluorescent activity of the latter.     

Heteroleptic triple-decker terbium(III) (porphyrinato)(crownphthalocyaninate) as an efficient receptor of alkaline metal cations

Peculiarities of the interaction between a heteroleptic triple-decker terbium(III) complex of a general type [Br₄TPP]Tb[(15C5)₄Pc]Tb[(15C5)₄Pc] (Tb-TD*, where Br₄TPP = 5,10,15,20-tetra-(4-bromophenyl)-porphyrin and (15C5)₄ Pc = tetra-(15-crown-5)-phthalocyanine) and potassium cations in different solvents are studied. The interaction between Tb-TD* and potassium acetate is found to proceed via either the supramolecular dimerization of the complex or the inclusion of the cations between the crown-containing molecular decks depending on the polarity of the media. From the analysis of the titration curves, the stability constant of Tb-TD* × 4K⁺ adduct in a chloroform : methanol = 1 : 1 mixture was estimated. The stability constant of the aggregate was found to exceed the known values of similar compounds by over ten orders.     

Potassium-promoted anionic selectivity of lanthanide bis(tetra-15-crown-phthalocyaninate) complexes

The interaction between neutral, lanthanide bis(tetra-15-crown-5-phthalocyaninate) complexes Ln[(15C5)₄Pc]₂⁰, (Ln = La, Tb, and Tm) and potassium bromide, picrate, or tetraphenylborate in chloro-form-acetonitrile solutions is studied using the spectrophotometric titration. The architecture of the supramolecular aggregates formed is shown to depend on the size of the lanthanide ion introduced into crown-phthalocyaninate and the nature of potassium salt anion.     

Photorefractive and nonlinear optical properties of indium(III) tetra(15-crown-5)phthalocyaninate-based composites

Photoelectric, nonlinear optical, and photorefractive properties of hybrid composite materials based on polyvinylcarbazole (PVK) and indium(III) 2,3,9,10,16,17,23,24-tetra(15-crown-5)phthalocyaninate [(15C5)₄Pc]In(OH) are studied in detail. Field dependence of the quantum efficiency in a 7.8 μm-thick layer containing 5 at % [(15C5)₄Pc]In(OH) is measured. The best approximation of the quantum efficiency with Onsager’s equation corresponds to a quantum yield of thermalized electron-hole pairs φ₀ = 0.01 at initial separation r ₀ = 9.8 Å. Z-scan measurements in a nanosecond range showed that the electric susceptibility of [(15C5)₄Pc]In(OH) solution in tetrachloroethane (TCE) with a concentration of 7 × 10^?4 mol/L is χ⁽³⁾ = 1.34 × 10^?9 esu. The maximum coupling gain coefficient found for the material composed of PVK and 5 wt % [(15C5)₄Pc]In(OH) at an electric-field intensity of 200 V/μm is Γ = 80 cm^?1, and the difference between the coupling gain and absorption coefficients is Γ ? α = 70 cm^?1. The dependence of the coupling gain coefficient on the intensity ratio of interfering beams 1 and 2 (β = I ₁(0)/I ₂(0)) in a composite containing 3 wt % [(15C5)₄Pc]In(OH) is measured. An increase in β was attained by decreasing intensity of the signal beam I ₂(0) at constant intensity of the pump beam I ₁(0) = 0.15 W/cm² and E ₀ = 214 V/μm. Within the initial segment of the curve, the coupling gain coefficient increases from 30 to 60 cm^?1; then, the coefficient drops almost to the initial value. The data obtained show that the composite materials studied can be used in practice for correcting faded images. The combined analysis of the results obtained and similar data for gallium and ruthenium tetra-15-crown-5-phthalocyaninate complexes revealed the regularities in the change of the quantum yield of thermalized electron-hole pairs and the photorefractive coupling gain coefficient in a series of complexing metals: gallium(III), ruthenium(II), and indium(III). An increase in the molecular weight of the central metal atom is found to result in a substantial decrease in Γ and φ₀ due to the increase in the spin-orbit coupling constant.     

Bridged polysilsequioxane adsorption materials containing phosphonic acid residues

Reactions of hydrolytic polycondensation of bis(triethoxysilane) [(C₂H₅O)₃Si]₂C₂H₄ (or [(C₂H₅O)₃Si]₂C₆H₄) and functional agent (C₂H₅O)₃Si(CH₂)₂P(O)(OC₂H₅)₂ (alkoxysilanes molar ratio of 2: 1 and 4: 1, fluoride ion catalyst and ethanol solvent) yielded powder-like xerogels that contained phosphonic acid residues in the surface layer. Their treatment with boiling concentrated hydrochloric acid resulted in transformation of functional groups ≡Si(CH₂)₂P(O)(OC₂H₅)₂ into acid groups ≡Si(CH₂)₂P(O)(OH)₂. The methods of IR, ¹H MAS NMRm and ¹³C, ²⁹Si, ³¹P MAS NMR spectroscopy showed the following (1) The surface layer in the initial xerogels contains not only phosphorus functional groups, but also some non-hydrolyzed ethoxysilyl groups as well as silanol groups. (2) The hydrochloric acid treatment of the initial xerogels causes the hydrolysis of not only ethoxy groups in the phosphonic acid residues, but also most residual ethoxysilyl groups. (3) Vacuum drying of xerogels after acid treatment forms ≡Si(CH₂)₂P(O)(OH)-OSi≡ links in their surface layer (not more than 20% of phosphorus-containing groups). (4) According to ²⁹Si CP MAS NMR spectroscopic data, boiling acid treatment relatively enriches the xerogel structure T² and T³ units and accounts for the higher rigidity of the hybrid framework. These units also account for retention of the porous structure in these xerogels over time, while most initial xerogels have porous structures that collapse in 12–18 months of storage. The acid-treated xerogels were attributed to microporous adsorbents (having specific surface area of 620 to 760 m²/g). According to the AFM data, both initial and acid-treated xerogels contain almost spherical aggregates of the primary particles (globules).     

High resolution solid-state 13C CPMAS study of neutral and partially oxidized aluminium polyfluorophthalocyanines

This paper reports a high resolution solid-state ¹³C CPMAS study of the low dimensional phthalocyanine (Pc = C₃₂H₁₆N₈) conductors (PcAlF)-(MoF₆)_0.38, (PcAlF)(IF₅)_0.43 and (PcAlF)(XeF₂)_0.35 as well as the precursor (PcAlF)_n. This study confirms that the stacking configuration of Pc rings along polymeric chains of neutral polymer is eclipsed. The four inequivalent carbon sites resulting from this structure are clearly separate and identified. From this study it is concluded that intrachain disorder is more extended in MoF₆- and IF₅-doped compounds than in the XeF₂-doped one.     

Studies of galvanised steel atmospheric corrosion in Saudi Arabia

Abstract

This paper summarises the results obtained for galvanised steel specimens exposed in Saudi Arabia region for four years at four pure marine and five mixed marine (SO₂ polluted) sites. The atmospheres at these sites were characterised climatologically and in terms of their pollution level so that their corrosivity could be expressed in accordance with ISO standards. Chemical characterisation of the galvanised steel corrosion product layers was performed using X-ray diffraction. The main phases determined were zincite (ZnO), simonkolleite [Zn₅(OH)₈Cl₂.H₂O], smithsonite (ZnCO₃), magnetite (Fe₃O₄), gordaite [NaZn₄(SO₄)Cl(OH)₆Cl.6(H₂O)], hematite (Fe₂O₃), zinkosite (ZnSO₄), zinc chloride (ZnCl₂), zinc hydroxide sulphate hydrate [(Zn(OH)₂)₃(ZnSO₄)(H₂O)₃] and zinc sulphate hydroxide hydrate [ZnSO₄(OH)₂.5H₂O] was found on the specimens. The results obeyed well with the empirical kinetics equation of the form C?=?Ktⁿ, where K and C are the corrosion losses in mg cm^?2 after 1 and ‘t’ years of the exposure respectively, and ‘n’ is constant. Based on ‘n’ values, the corrosion mechanism of galvanised steel is predicted. The results obtained show that the corrosion rate of galvanised steel is a function of both the chloride, SO₂ pollution level and the humidity. Corrosion rate of galvanised steel specimens have been obtained by loss of weight after each year of exposure.     

Electrically conductive,processable polymeric materials constructed from metallophthalocyanines

This contribution describes an approach to producing new classes of macromolecular/macromolecular and molecular/macromolecular hybrid materials which can be spun into environmentally stable, flexible, oriented, electrically conductive fibers. Solutions of a phthalocyanine-containing macromolecular (e.g., [Si(Pc)O]_n) or molecular(e.g., Ni(Pc)) ‘metal’ precursor and a host polymer (e.g., Kevlar) are wet-spun to yield, after halogen or electrochemical doping, strong, air-stable fibers with thermally activated electronic conductivities as high as 5 ω^?1 cm^?1. X-ray diffraction and resonance Raman studies of the fibers reveal the presence of preferentially oriented Kevlar and {[Si(Pc)O]I_1.1}_n (or M(Pc)I) crystalline regions, the latter regions with the metallophthalocyanine stacking directions preferentially parallel to the longitudinal fiber axis.     

One-step chemical synthesis of doped polythiophene by use of copper(II) perchlorate as an oxidant

A reaction of 2,2′-bithiophene with copper(II) perchlorate in acetonitrile achieved polymerization and doping in one step, and yielded polythiophenes, [(C₄H₂S)(ClO₄)_x·yH₂O]_n. The polymers with x ∼ 0.17 and y ∼ 0.3 exhibited a high electrical conductivity in the range 3 – 8 S cm⁻¹ at 300 K and a small activation energy of 0.04 eV. The i.r. and e.s.r. spectra showed the characteristics of doped polythiophenes.     

Dopant-polymer interaction: MoCl5-doped polyacetylene

Polyacetylene is doped with MoCl₅. The doping levels determined using the method of neutron activation analysis indicate that the atom ratio [Cl]/[Mo] varies from 5 to 1.6, depending on doping time. The C_1s XPS (X-ray photoelectron spectroscopy) binding energy (BE) decreases from 283.7 eV for the pristine PA to 282.9 eV, similar to that of WCl₆-doped PA as reported in our previous work, but opposite to that of I_2- and AsF₅-doped PA. The lowering of the BE means that the outer shell electron densities of carbon increase after the doping. The Cl_2p XPS of the doped PA shows that there is only one type of chlorine in the adducts. Mo_3d XPS shows that there are two states of Mo existing in the doped PA, being state A (MoCl₂(CC)₄) and state B (Mo(CC)_n), quite different from those in the WCl₆-doped PA. The level created at 1.72 eV related to state B is closer to the HOMO π orbital (BE 1.8 eV) of the pristine PA, and is therefore a more shallow level than the state created at 1.24 eV (due to state A Mo). Several olefins from more than one PA chain can interact with one Mo atom, allowing electron transfer from one PA chain to another.     

Corrosion behavior of AZ91D magnesium alloy in sodium sulfate solution

The corrosion behavior of as‐cast AZ91D magnesium alloy in 0.1M sodium sulfate solution at the corrosion potential (E_corr) was investigated by using electrochemical impedance spectroscopy (EIS), environmental scanning electron microscopy (ESEM), energy dispersive X‐ray spectroscopy (EDS) and X‐ray diffraction (XRD). The results showed that the corrosion of AZ91D started at both the primary α‐Mg and the eutectic α‐Mg. The surface first was covered by a film (MgO, Mg(OH)₂) which became thicker with time. Due to the dissolution of the eutectic α‐Mg, the concentration of aluminum increased, MgAl₂(SO₄)₄ · 2H₂O precipitated at the primary α‐Mg and progressively spread to the eutectic α‐Mg areas. The surface film changed from two‐layer to three‐layer structure with the increase of immersion time.     

Corrosion behaviour of die-cast AZ91D magnesium alloy in aqueous sulphate solutions

The corrosion behaviour of die-cast AZ91D magnesium alloys in sulphate solutions was investigated by SEM, FTIR and polarization measurements. For immersion times less than 48 h, no pitting corrosion occurred and only generalized corrosion was apparent. According to the polarization curves, the corrosion rate order of the die-cast AZ91D Mg alloy in three aqueous solutions was: NaCl > MgSO₄ > Na₂SO₄. The main corrosion products were Mg(OH)₂ and MgAl₂(SO₄)₄·22H₂O in the sulphate solutions and the product film was compact. Precipitation of MgAl₂(SO₄)₄·22H₂O required a threshold immersion time.     

X-ray photoelectron spectroscopy of chromium layers electroplated from oxalate-sulfate solutions

The chemical composition of chromium deposits obtained from acidic (pH 1.5 to 1.7) chromium (III) oxalate-sulfate solutions was studied with the use of x-ray photoelectron spectroscopy. From the solutions containing more than 100 g/l Cr₂(SO₄)₃·6H₂O, an amorphous carbide close to Cr₂₃C₆ with inclusions of metallic chromium clusters is deposited on the cathode. From less acidic solutions poorer in chromium, metallic chromium is deposited. The work was financially supported by the Russian Foundation for Basic Research (projects nos. 99-03-32058 and 96-15-97368).     

Effects of additives on synthesis of vanadium carbide (V8C7) nanopowders by thermal processing of the precursor

Vanadium carbide (V₈C₇) nanopowders can be synthesized by thermal processing of the precursor of ammonium vanadate (NH₄VO₃) and nanometer carbon black. Effects of additives (CaF₂, CeCl₃·7H₂O and LaCl₃·7H₂O) on the phase composition and microstructure of the synthesized powders were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that additives (CaF₂, CeCl₃·7H₂O and LaCl₃·7H₂O) can accelerate the solid state reaction during synthesis of V₈C₇, and these additives play a vital role in determining the phase composition and microstructure. V₈C₇ powders with basically single phase can be synthesized at 1100 °C for 0.5 h with the addition of additives (CaF₂, CeCl₃·7H₂O and LaCl₃·7H₂O), and the powders show good dispersion and are mainly composed of uniformly-sized spherical particles with a mean diameter of 50 nm. Further experiment shows that V₈C₇ powders can be prepared at 950 °C for 1 h with 1.0 wt% CaF₂ as additive.     

Corrosion and electrochemical behavior of Mg–Y alloys in 3.5% NaCl solution

The corrosion mechanism of Mg–Y alloys in 3.5% NaCl solution was investigated by electrochemical testing and SEM observation. The electrochemical results indicated that the corrosion potential of Mg–Y alloys in 3.5% NaCl solution increased with the increase of Y addition. The corrosion rate increased with the increase of Y addition because of the increase of Mg₂₄Y₅ intermetallic amounts. The corrosion gradually deteriorated with the increase of immersion time. The corrosion morphologies of the alloys were general corrosion for Mg–0.25Y and pitting corrosion for Mg–8Y and Mg–15Y, respectively. The main solid corrosion products were Mg(OH)₂ and Mg₂(OH)₃C1.4H₂O.