New conjugated azomethine oligomers obtained from bis-(hydroxyphenyl)methylenediamine via oxidative polycondensation and their complexes with metals

A new conjugated aromatic oligo(azomethine) derivative was synthesized by oxidative polycondensation of 1,4-bis[(2-hydroxyphenyl)methylene]phenylenediamine (HPMPDA) by air, H₂O₂ and NaOCl oxidants in an aqueous alkaline medium. The structures of 1,4-bis[(2-hydroxyphenyl)methylene]phenylenediamine and oligo-1,4-bis[(2-hydroxyphenyl)methylene]phenylenediamine (OHPMPDA) were confirmed by FT-IR, UV–vis, ¹H NMR, ¹³C NMR and elemental analysis. The characterization was made by TGA–DTA, size exclusion chromatography (SEC), magnetic moment and solubility tests. The ¹H NMR and ¹³C NMR data showed that the polymerization was proceeded by C–C coupling according to ortho and para positions of –OH group of 1,4-bis[(2-hydroxyphenyl)methylene]phenylenediamine. Metal complex compounds of OHPMPDA were synthesized with metal salts of Fe, Co, Ni, Cu, Zn, Cd, Mn, Cr, Pb and Hg. Elemental analyses of oligomer–metal complexes suggested that the ratio of metal to oligomer is 1:1. Thermal stabilities of the oligomer–metal complexes were determined by thermogravimetric analyses (TGA). According to TG analyses, oligomer–metal complexes were fairly stable against temperature and thermal decomposition. Also, electrical conductivities of OHPMPDA and oligomer–metal complexes were measured by four-point technique. The results of this study showed that aromatic oligoazomethine and its metal complexes were an interesting class of conjugated compounds of which electronic structure and the other properties can be regulated over a wide range by using different oxidation reagents.     

Synthesis,characterization, conductivity,band gap and thermal analysis of poly-2-[(4-mercaptophenyl) imino methyl] phenol and some of its polymer–metal complexes

The oxidative polycondensation reaction conditions of 2-[(4-mercaptophenyl) imino methyl] phenol (4-MPIMP) was studied in an aqueous alkaline medium between 30 and 90 °C by using oxidants such as air O₂, NaOCl and H₂O₂. Polymer–metal complex compounds were synthesized from the reactions of poly-2-[(4-mercaptophenyl) imino methyl] phenol (P-4-MPIMP) with Cr³⁺, Co²⁺, Ni²⁺, Cu²⁺, Mn²⁺, Zn²⁺, Pb²⁺, Cd²⁺ and Zr⁴⁺ ions. The structures of these monomer and polymer were identified from UV–vis, FT-IR, ¹H NMR, ¹³C NMR and elemental analysis. While thermal analysis of P-4-MPIMP and polymer–metal complexes were made by TGA–DTA, the number-average molecular weight (M_n), weight-average molecular weight (M_w) and polydispersity index (PDI) values of this polymer were determined by size exclusion chromatography (SEC). According to TG–DTA analyses, P-4-MPIMP–Cu was found to be higher stable than other synthesized polymer and polymer–metal complexes. While conductivity measurements of polymer and polymer–metal complexes were done by electrometer using four point probe techniques, electrochemical and optical band gap values of 4-MPIMP, P-4-MPIMP and polymer–metal complexes were determined by using cyclic voltammetry and UV–vis measurements. Conductivity and band gap values show that this polymer and polymer–metal complexes are a typical semiconductor.     

Investigations in the field of synthetic metals. VI. Synthesis and properties of dibenzotetrathiafulvalene halides

Direct oxidation of dibenzotetrathiafulvalene (DBTTF) by halogens in acetonitrile and nitrobenzene yielded DBTTF₂I₃, DBTTF·I₃, DBTTF·Cl_x (x = 0.7 ? 1), DBTTF·Br_x (x = 0.8 ? 1), and DBTTF·Br_1.2 complexes. Ir-, u.v.-, and e.p.r.-spectra of these compounds have been studied. X-ray data for the complex DBTTF·I₃ are discussed. Conductivities of the above mentioned complexes lie in the range 10^?2 – 10^?4 ohm^?1 cm^?1.     

Color-tunable and white-light emitting lanthanide complexes based on (CexEuyTb1−x−y)2(BDC)3(H2O)4

Ce³⁺, Eu³⁺ and Tb³⁺ complexes were synthesized through facile and mild approaches with terephthalic acid (H₂BDC) as the ligand. Their chemical compositions were determined as (Ce_xEu_yTb_1−x−y)₂(BDC)₃(H₂O)₄ by elemental analysis (EA), Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD) measurements. Fluorescent properties of the as-synthesized complexes were investigated by changing the molar ratio of Ce³⁺, Tb³⁺ and Eu³⁺ ions, and the optimized ratio of 3.0:2.0:0.15 for Ce³⁺:Tb³⁺:Eu³⁺ in the complex was determined for white-light emission. Tuning on the emitting color was realized by adjusting the ratio among lanthanide ions, indicating the energy transfer process inside the complex. It was found that Tb³⁺ could sensitize the fluorescence of Eu³⁺ while its own fluorescence was quenched by the latter ion, and concentration quenching of Ce³⁺ was also observed. Fairly good thermal stability and oxidation resistance of the as-synthesized complexes were also demonstrated.     

Syntheses and cofluorescence of complexes of Eu（Ⅲ）/Y（Ⅲ） with terephthalic acid, 2-thenoyltrifluoroacetone and trioctylphosphine oxide

A series of Eu（ Ⅲ）/Y（Ⅲ） complexes of terephthalic acid（TPA） with 2-thenoyltrifluoroacetone（HTTA） and trioctylphosphine oxide（TPPO） were synthesized. Compositions of these complexes are revealed to be Eu2（1-x）Y2x（TPA）（TTA）4- （TPPO）4 or EU1-xYx（TPA）（TTA）（TPPO）2. Their 1R spectra, fluorescent spectra and the thermal and optical stability were studied. The fluorescent excitation spectra of these complexes show more broad excitation bands than those of Eu2（TPA）3（TPPO）4 and Eu（TTA）3（TPPO）2 corresponding to their formations. In addition, both the binuclear complex EuY（TPA）（TTA）4（TPPO）4 and the chain complex EU0.4Y0.6（TPA）（TTA）（TPPO）2 present higher thermal stability and better optical stability than the mononuclear complex Eu（TTA）3（TPPO）2 does. And their thermal and optical stabilities are preferably interpreted from the binuclear structure together with the chain polynuclear structure of the complexes. The fluorescence enhancement of cofluorescence Y^3＋ ions to the Eu（Ⅲ） complexes is clear. The optimum content of Y^3＋ is 0.6 （molar fraction） for the chain complexes Eu1-xYx（TPA）（TTA）- （TPPO）2 and 0.5 for the binuclear complexes Eu^2（1-x）Y2x（TPA）（TTA）4（TPPO）4. The formation of polynuclear structure of the complex Eu1-xYx（TPA）（TTA）（TPPO）2 appears to be responsible for the good cofluorescence effect of Y^3＋ ions.     

Preparation and fluorescent properties of europium (III) complexes with β-diketone ligand and 2,2-dipyridine or 1,10-phenanthroline

The β-diketone ligand, 1-(4-methoxyphenyl)-3-phenylpropane-1,3-dione (MPPD), and its binary Eu(III) complexes Eu(MPPD)₃, ternary complexes Eu(MPPD)₃·Bipy with 2,2-dipyridine (Bipy) and Eu(MPPD)₃·Phen with 1,10-phenanthroline (Phen) were prepared. The complexes were characterized with by elemental analysis, FT-IR, ¹H NMR, UV–vis absorption, thermogravimetric analysis (TGA), ESI-MS and fluorescence spectroscopic techniques. TGA results showed that these complexes have good thermal stability. The emission spectra for complexes 2–4 exhibited the characteristic emission bands that arise from the ⁵D₀ → ⁷F_J (J = 0–4) transitions of the europium ion in solid state and chloroform solution. Based on the emission spectra in solid state, the Eu(III) ion could be sensitized efficiently by the ligands to some extent, in particular, in the ternary system, the secondary ligands Bipy and Phen acting as a light-harvesting center was involved in the highly efficient energy transfer process. In addition, the experimental intensity parameters, Ω₂ and Ω₄ were calculated from the fluorescence emission spectra. The radiative decay rate A_rad, the nonradiative rates A_nrad, the lifetime (τ) and the luminescent quantum yield (η) were determined and analyzed.     

Influence of the composition of the liquid phase and the concentration of benzohydrazide on its effectiveness during cadmium electrodeposition from water-acetone perchlorate electrolytes

Cadmium-benzohydrazide complexes (2 : 1) were found to be the main electroactive species in cadmium electrodeposition from water-acetone perchlorate baths. The discharge of these complexes is preceded by their dissociation at the cathode (zone of water structure stabilization) or in the bulk of the solution (zone of acetone structure stabilization). In the microheterogeneity zone of the mixed solvent, the complexes can be reduced from the adsorbed state. The process is best inhibited at low concentrations of benzohydrazide ((c _L ^o = 10^?4 mol/l), when the electrode is covered with a very dense layer of adsorbed benzohydrazide and acetone molecules. With an increase in c _L ^o , perchlorate anions become more adsorbable, which is accompanied by increasing facilitation of the discharge reaction (Ψ′-effect). The strongest depolarizing effect of ClO ₄ ^? anions is observed in the zone of acetone structure stabilization, which is due to selective solvation of the anion and the desalting effect of the mixed solvent.     

Investigation of crown-containing styrylthiophene derivatives which are optically and electrochemically sensitive to the presence of metal cations

The analysis of complex formation of crown-containing styryl and bisstyryl thiophene derivatives with alkaline earth metal cations and the investigation of optical and electrochemical responses induced by metal cations are reported. The monostyryl derivative forms weakly fluorescent inclusion complexes with Mg²⁺ cations and weakly fluorescent anti-sandwich complex with Ba²⁺ cations. In case of bisstyryl thiophene compounds the Mg²⁺ complexes are fluorescent, whereas, the sandwich complex with composition (1b)₂·(Ba²⁺)₂ or (1b)₂·(Ba²⁺)₃ are weakly fluorescent. The results of the investigations showed that the crown-containing mono- and bisstyryl thiophene derivatives are optically and electrochemically sensitive to the presence of metal cations.     

Deterioration and film forming abilities of the slurries used for preparing La0.8Sr0.2MnO3 films through composite sol-gel method

The slurries, used for preparing La_1−xSr_xMnO₃ (LSM) films through composite sol-gel method with citric acid, were made up of LSM particles and precursor sol with different pH values. The reasons and key factors for the deterioration of the acidic slurry were analyzed by XRD, SEM and TG/DSC. Furthermore, the LSM films were fabricated with different slurries for studying their film forming abilities. It has been found that the deterioration of the acidic slurry is determined by the abundant H⁺ ions, generated from ionization of the citric acid. Discoloration of the alkaline sol and slurry is considered as a result of complicated complexes of Mn²⁺ ions, which have a good effect on the film forming ability of the alkaline slurry, together with the complexes of La³⁺ and Sr²⁺ ions. The alkaline slurry has better long-term stability than the acidic slurry, and the films made from it are more homogeneous, thicker and have lower sheet resistance.     

Ru(II) complexes containing dihydro-1,1,3,3-tetramethyl-7,8-diazacyclopenta[1]phenanthren-2-ol ligand: Synthesis and their electrochemiluminescent characteristics

A series of new ruthenium(II) complexes containing dihydro-1,1,3,3-tetramethyl-7,8-diazacyclopenta[1]phenanthren-2-ol (DTDP-OH) ligand, such as [Ru(DTDP-OH)_n(L)_3−n]²⁺ (L = 2,2′-bipyridyl (bpy), o-phenanthroline (o-phen), 2,2′-bipyridine-4,4′-dicarboaldehyde (bpy-(CHO)₂), 1,3-dihydro-1,1,3,3-tetramethyl-7,8-diazacyclopenta[1]phenanthren-2-one(DTDP), n = 1, 2, 3) were synthesized and their electrochemical and photophysical properties were studied. The synthesized Ru(II) complexes containing the DTDP-OH ligand showed strong MLCT absorptions at 420–487 nm. All the synthesized Ru(II) complexes containing the DTDP-OH ligand exhibited more intensive ECL emissions than the well-known [Ru(o-phen)₃]²⁺ does. In particular, the ECL intensities of [Ru(DTDP-OH)₂(o-phen)]²⁺ and [Ru(DTDP-OH)₂(bpy-(CHO)₂)]²⁺ were observed to be more than 2-fold greater than that of [Ru(o-phen)₃]²⁺.     

Two-sectional struvite formation process for enhanced treatment of copper–ammonia complex wastewater

Mg²⁺ and PO₄³⁺ were added into the synthetic wastewater, leading to the dissociation of the complex ions in the wastewater, and resulting in removal of copper and ammonia therein. The effects of agents addition amount, pH, and reaction time on the removal efficiency of copper and ammonia were investigated. In particular, two-sectional struvite formation (TSSF) process was established for copper and ammonia removal. MgCl₂ and Na₂HPO₄ were added by following 90% addition in the first section and remained 10% in the second during the TSSF process. Compared with one sectional struvite formation, TSSF possessed much better performance. Under condition of n(NH₃-N):n(Mg):n(P)=1:1.2:1.5 (molar ratio), pH=9, and reaction time of 30 min, the removal efficiencies of copper and ammonia were 98.9% and 99.96%, respectively. The enhanced performance of TSSF is explained by the competition of ammonia by copper–ammonia complexes and struvite. The dissociation of copper–ammonia complexes is further demonstrated by thermodynamic equilibrium analysis, on the basis of calculations and establishment of predominance phases diagram. Moreover, XRD and EDS analyses further confirmed the formation of struvite and precipitation of copper, which prove the transmission of copper and ammonia from liquid phase into solid phase.     

Hyper-Rayleigh scattering of trans-tetraammineruthenium(II) complexes

A novel series of tetraammineruthenium complex salts trans-[Ru^II (NH₃)₄(L^D)(L^A)][PF₆]₃ has been investigated by using the hyper-Rayleigh scattering technique. These complexes exhibit very large and tunable static first hyper-polarizabilities in the range 10×10⁻³⁰ to 410×10⁻³⁰ esu. These high second-order non-linear optical responses are associated with intense, visible metal-to-ligand charge-transfer excitations. Further, changing the structure of the acceptor-substituted ligand going from a 4,4′-bipyridinium to a [trans-2-(4-pyridyl)ethenyl]pyridinium conjugated bridge leads to the notable conclusion that the extension of the conjugated bridge in these complexes neither significantly alters the metal-to-ligand charge-transfer energies nor leads to an increase in the static first hyperpolarizabilities.The non-linear optical responses of these dipolar complexes show a great sensitivity towards the oxidation state of the metal. It is proven that chemical oxidation of the ruthenium is an excellent tool to reversibly switch the molecular first hyper-polarizabilities.     

Theoretical studies on electronic structures,spectra and charge transporting properties of a series of Pt(CN)2 complexes

We report a quantum-chemical study of electronic, optical and charge transporting properties of four platinum (II) complexes, Pt(C^ΛN)₂ (C^ΛN = phenylpyridine or thiophenepyridine). The lowest-lying absorptions at 442, 440, 447 and 429 nm are all attributed to the mixed transition characters of metal-to-ligand charge transfer (MLCT) and ligand-centered (LC) π → π* transition. While, unexpectedly, the lowest-lying phosphorescent emissions at 663, 660, 675 and 742 nm are mainly from metal-to-ligand charge transfer (³MLCT) ligand-centered (LC) π → π* transition. Ionization potential (IP), electron affinities (EA) and reorganization energy (λ_{hole/electron}) were obtained to evaluate the charge transfer and balance properties between hole and electron. The calculated results reveal that the small structure changes of the charged states relative to the neutral ones, and the smaller IP and EA values indicate that they exhibit a relatively high structural stability versus the injection of one charge and have better holes than electron-injection abilities. The smaller λ values and the smaller differences (within 0.06 eV) between λ_hole and λ_electron indicate the better transfer balance between holes and electrons. Moreover, the attached methyl groups slightly improve the hole-injection ability and deduce the electron-injection ability. The strong phosphorescence emission and the favorable transporting properties compared with other reported complexes indicate their potential applications in as emitters OLEDs.     

Synthesis and conductivities of (μ-cyano)phthalocyaninatometal compounds

A review of the synthesis and characterization of a new type of stacked, bridged macrocyclic metal complexes, the (μ-cyano)phthalocyaninatometal compounds [PcMCN]_n (2) is given. By using the routes described in Fig. 3 the polymers were synthesized with M = Co³⁺, Fe²⁺, Fe³⁺, Mn³⁺ and Cr³⁺ as the central metal ion. The compounds were characterized by IR, far-IR, UV, thermal and elemental analysis, and partly by ¹H NMR and FD (field desorption) mass spectroscopy.[PcCoCN] (2a) and [PcFeCN]_n (2b) exhibit d.c. room temperature conductivities around 10^?2 S/cm without doping, thereby showing conductivities which are in the same range as the iodine-doped phthalocyaninatosiloxanes [PcSiO]_n.     

Conducting polymers synthesized by dopant-induced polymerization of insulating charge-transfer crystals

Conductive polymer complexes are formed by a one-step process resulting in successive doping and dopant-induced solid-state polymerization of insulating molecular complexes involving the donor biphenyl or terphenyl and acceptors such as TCNQ (7,7,8,8-tetracyano-p-quinodimethane) and DDQ (2,3-dichloro-5,6-dicyano-p-benzoquinone). The conductor resulting from the gas-phase doping of the terphenyl/TCNQ complex with AsF₅ contains low molecular weight poly(p-phenylene) chains complexed with AsF₆^? ions. Results are consistent with the presence of neutral TCNQ molecules as ‘molecular spacers’ within the conducting phase. The solid-state reaction and resulting conducting polymer are examined using spectroscopic and diffraction techniques, as well as anisotropic conductivity measurements.     

Cobalt(III) complexes of macrocyclic-bidentate type as a new group of corrosion inhibitors for iron in perchloric acid

A new class of corrosion inhibitors for iron demonstrated by group of cobalt complex compounds, of the general formula [Co^III(Rdtc)cyclam](ClO₄)₂ (1)-(4) where cyclam is 1,4,8,11-tetraazacyclotetradecane and Rdtc⁻ refer to piperidine-, 2-, 3- or 4-methylpiperidine-dithiocarbamates, respectively, has been studied. Investigation of inhibiting properties of the ligands themselves as well as their corresponding complexes with Co(III) ion, was performed in 0.1 M HClO₄ by potentiodynamic polarization and EIS measurements. Cobalt complexes inhibit the corrosion of iron better than the uncomplexed ligands. Polarization curves suggest that complexes and amino-ligands are mixed-type and cathodic-type inhibitors, respectively. The impedance of the inhibited substrate increased with increasing concentration of inhibitor. An equivalent circuit is suggested, based on the analysis of EIS spectra. Using molecular modeling calculations, the complex compounds were characterized in terms of their structural properties and inhibition activity.     

Structure and conductivity of poly(acetylene)

Poly(acetylene), (CH)_x, synthesized under different polymerization conditions, was investigated by means of IR and ¹³C NMR spectroscopy, X-ray diffraction, and conductivity measurements. The molecular structure is strongly influenced by the polymerization temperature and the catalyst system. The polymerization temperature mainly governs the cis to trans ratio. In low temperature Shirakawa (CH)_x the cis crystals consist cis-transoid chains, whereas in Luttinger (CH)_x the cis crystals contain cis-transoid as well as trans-cisoid chain configurations. The catalyst systems affect the degree of distortion of the conjugated (CH)_x chains by sp³ hybridized carbon atoms. In Shirakawa (CH)_x the sp³ content is very low. (CH)_x prepared after the procedures of Luttinger and Reppe is characterized by an increasing content of sp³ hybridized carbon atoms. Hatano (CH)_x exhibits the highest sp³ content of all samples under investigation. A linear relationship exists between the relative sp³ content and the X-ray crystallinity. The higher the sp³ content, the lower is the crystallinity and the less perfect are the crystals. The sp³ content and the crystallinity determine the electrical conductivity of trans (CH)_x and iodine complexed (CH)_x. Low sp³ content and high crystallinity of (CH)_x are the preconditions for high conductivity of the corresponding iodine complexes.     

Optical spectroscopy and scanning tunneling microscopy of thin films of the metal-tetracyanoquinodimethane derivatives

Semiconducting thin films of charge-transfer complexes which exhibit a novel field-induced phase change have been examined by optical spectroscopy and scanning tunneling microscopy (STM). We have demonstrated a field-induced, charge-transfer reaction driven by the electric field at the microscope tip when the field generated by the microscope exceeds the switching threshold of the organic charge-transfer complex: CuTCNQCl₂ (TCNQ = tetracyanoquinodimethane). The threshold of phase transition induced by the scanning tunneling microscope for CuTCNQCl₂ is 7.5 ×10⁵ V/cm, whereas for the parent compound CuTCNQ it is 1.0 × 10⁵ V/cm. These threshold values are proportional to the strength of the acceptor, i.e., the first half-wave reduction potential E₁ of the acceptor molecule. We used an acetonitrile-vapor-assisted film preparation method to deposit weak donor-acceptor complexes (such as 2,5-dialkyl- and 2,5-dialkoxy-substituted TCNQ derivatives). These complexes do not react with copper metal by the conventional post-heating method. These deposited films have been analyzed by UV-Vis and FT-IR spectroscopy and the surfaces have been imaged using STM. This STM-induced solid-state chemical reaction is being explored for possible development as a high-density molecular-based information storage media.     

Crystallite-conjugation regions and adjacent lattice regions in polycrystalline iridium: III. Enthalpies of formation of vacancies and the energies of interaction of partners in vacancy complexes with oxygen formed in the cores of crystallite-conjugation regions in polycrystalline iridium

The interatomic spacings in the cores of crystallite-conjugation regions (CCRs) and adjacent lattice regions (ALRs) of polycrystals either decrease or increase upon alloying of nominally pure metals with oxygen and vacancy complexes with oxygen (mVacO, where m is the number of vacancies in the complex) that are formed during annealing. These changes in the interatomic spacings lead to an increase or decrease in the isomer shifts δ of the components of the Mössbauer spectra of atomic probes ⁵⁷Fe that are localized in the CCR cores and ALRs of polycrystals [1–6]. The enthalpies Q _mcmpl1, of formation of vacancy-oxygen complexes mVacO in the CCR cores have been measured for Ir and Cr polycrystals, and the enthalpies Q _Vac,1 of formation of vacancies in CCR cores have been determined for Ta, W, Ir, and Cr polycrystals. The enthalpies E _mcmpl of the interaction between the partners of the complexes increase with increasing number m of vacancies in the complexes.     

Photoelectric, nonlinear optical, and photorefractive properties of polymer composites based on supramolecular ensembles of Ru(II) and Ga(III) complexes with tetra-15-crown-5-phthalocyanine

Techniques of the production of polymer nanocomposites based on tetrapyrrole compounds with photoelectric, nonlinear optical, and photorefractive properties are considered. Supramolecular ensembles of Ru(II) and Ga(III) complexes with tetra-15-crown-5-phthalocyanine are found to form upon the deposition of thin films from tetrachloroethane solutions that have undergone several cycles of heating followed by slow cooling. The surface formation of supramolecular ensembles is studied with the use of atomic force microscopy. The assemblage is found to give rise to photoelectric and photorefractive sensitivity in the near-infrared range (measurements were carried out at 1064 and 1550 nm). The quantum yield of thermalized electron-hole pairs at 1064 nm in composites of polyvinyl carbazole and assembled Ga(III) complexes is 20 times as high as that in composites based on Ru(II) complexes. The largest two-beam coupling gain coefficient at 1064 nm (Γ = 120 cm^?1 at E ₀ = 120 V/μm) was also observed for the Ga(III)-complex-containing composite. The third-order dielectric molecular susceptibility measured in tetrachloroethane solutions of the complexes weakly depends on the nature of the central atom and its axial neighborhood and falls in a range of γ = 4?5.2 × 10^?32 esu.