Synthesis and properties of new polyazines—III

Polycondensations of 1,2- and 1,4-naphthoquinones with hydrazine hydrate and disulphinylhydrazine under various conditions were carried out. The optimum parameters for the disulphinylhydrazine synthesis were established. The thermal stabilities and electrical conductivities of the polynaphthoquinoneazines were determined.     

Synthesis and properties of a functionalized heterobimetallic Re(I)–Gd(III) complex as a potential dual-contrast agent for molecular imaging

In the design of dual-imaging probes, the first functionalized and neutral heterobimetallic Re(I)–Gd(III) complex, highly soluble in aqueous solutions, has been prepared. This system exhibits interesting photophysical properties (λ_em = 578 nm, ? = 1.4%) for optical imaging and substantial higher relaxivity (r₁ = 6.6 mM⁻¹ s⁻¹ at 0.47 T and 37 °C) than the clinically used MRI contrast agents. Moreover, this system incorporates an aromatic ester functionality suitable for bioconjugation.     

Synthesis and properties of poly(amide–imide)s containing a N-methylcarbazole group

A new dicarboxylic acid monomer containing the N-methylcarbazole and imide structures, 3,6-bis(trimellitimido)-N-methylcarbazole (I), was prepared from the condensation of 3,6-diamino-N-methylcarbazole (c) and trimellitic anhydride. The diamine c was synthesized in three steps starting from the methylation of carbazole, followed by nitration and catalytic hydrazine reduction. A series of N-methylcarbazole-containing poly(amide–imide)s were synthesized by direct polycondensation from the diimide–diacid I with various aromatic diamines. These poly(amide–imide)s had inherent viscosities of 0.66–1.47 dl/g and were readily soluble in a variety of organic solvents, including N-methyl-2-pyrrolidone and N,N-dimethylacetamide (DMAc). Transparent, flexible, and tough films of these polymers could be cast from DMAc solutions, and these films exhibited excellent mechanical strength. The glass-transition temperatures of these poly(amide–imide)s were in the range 317–362 °C. All the poly (amide–imide) did not degrade noticeably below 480 °C in nitrogen, and the 10% weight loss temperatures and char yields at 800 °C were above 520 °C and 60% in nitrogen, respectively, indicating high thermal stability. Received: 8 February 2000/Accepted: 23 March 2000     

Synthesis,structure and properties of a series of scorpionate oxovanadium(IV)–carboxylate complexes

A series of oxovanadium(IV) complexes: TpVO(pzH)(2,4-Cl–C₆H₃–OCH₂COO) (1), TpVO(pzH)(C₆H₅–OCH₂COO) (2), TpVO(pzH)(p-Cl–C₆H₄–COO) (3), TpVO(pzH)(3,5-NO₂–C₆H₃–COO) (4), Tp∗VO(pzH∗)(p-Cl–C₆H₄–COO) (5) and Tp∗VO(pzH∗)(p-Cl–C₆H₄–COO) · CH₃OH (6) (Tp = hydrotris(pyrazolyl)borate, pzH = pyrazole, Tp∗ = hydrotris(3,5-dimethylpyrazolyl)borate, pzH∗ = 3,5-dimethylpyrazole) were synthesized and their crystal structures were determined by X-ray diffraction. In all the complexes, the vanadium ions are in a distorted-octahedral environment with a N₄O₂ donor set. Hydrogen bonding interaction exists in each complex. Complexes 1 and 2 are hydrogen-bonded dimers. Dimeric units of 2 are connected to one another via weak inter-molecular C–H···O interactions to form a 2D network on the bc-face. In 3–6 there exist intramolecular N–H···O hydrogen bonds between the neutral pyrazole/3,5-dimethylpyrazole and the uncoordinated carboxyl oxygen atom. In addition, the catalytic activity of complex 2 in a bromination reaction in phosphate buffer with phenol red as a trap was evaluated by UV–Vis spectroscopy. Furthermore, the elemental analyses, IR spectra and thermal stabilities were recorded.     

Cyanide-bridged bi- and trinuclear heterobimetallic Fe(III)–Mn(III) complexes: Synthesis,crystal structures and magnetic properties

By employing trans-dicyano or pentacyanometalate as building block and using a bicompartimental Schiffbase based manganese(III) compound as assemble segment, two new cyanide-bridged heterometallic Fe(III)–Mn(III) complexes {[Mn(L)(H₂O)][Febpb(CN)₂]}·2CH₃OH (1) and {[Mn(L)(H₂O)]₂··[Fe(CN)₅NO]} (2) (bpb^2– = 1,2-bis(pyridine-2-carboxamido)benzenate, L = N,N'-ethylene-bis(3-ethoxysalicylideneiminate) have been synthesized and characterized by elemental analysis, IR spectroscopy and X-ray structure determination. Single X-ray diffraction analysis reveals binuclear FeMn and trinuclear FeMn₂ structure, respectively, in which the cyanide precursor acts as mono- or bidentate ligand to connect the Mn(III) Schiff-base unit(s). Furthermore, these two complexes are self-complementary through coordinated aqua ligands from one complex and the free O₄ compartments from the neighboring complex, giving dimeric and 1D single chain supramolecular structure. Investigation of the magnetic susceptibility of 1 reveals weak antiferromagnetic coupling between the adjacent Mn(III) ions. Based on the binuclear FeMn model, best fit of the magnetic susceptibilities of 1 leads to the magnetic coupling constants J =–1.37 cm^–1 and zJ′ =–0.72 cm^–1 (1).     

Synthesis,characterization, and biocide activity of new dithiocarbamate-based complexes of In(III), Ga(III), and Bi(III) – Part III

In this work, we describe the syntheses, characterization, and antifungal activity of [In{S₂CNR(R¹)}₃] (1), [Ga{S₂CNR(R¹)}₃] (2), [Bi{S₂CNR(R¹)}₃] (3), [In{S₂CNR(R²)}₃] (4), [Ga{S₂CNR(R²)}₃] (5), and [Bi{S₂CNR(R²)}₃] (6) {R?=?Me; R¹?=?CH₂CH(OMe)₂; and R²?=?2-methyl-1,3-dioxolane}. All complexes have been characterized using infrared and ¹H and ¹³C spectroscopy, and the structures of 1, 3, 4, and 6 have been authenticated by X-ray diffraction. The In(III)–dithiocarbamate bonding scheme depicts a distorted octahedral with asymmetric In(III)–S bonds and S–In–S angles. A pentagonal bipyramid is observed for the corresponding Bi(III) complexes with intermolecular Bi–S associations through the lone pair of electrons. The antifungal activities of 1–6 have been screened against Aspergillus niger, Aspergillus parasiticus, and Penicillium citrinum, and the results have been compared with those of nystatin and miconazole nitrate, as control drugs.     

Synthesis,crystal structure and other properties of the complexes of Er(III), Yb(III) and Lu(III) with 4,4′-bipyridine and dichloroacetates

A novel mixed-ligand complexes of Er(III), Yb(III) and Lu(III) with title ligands were prepared and characterized by chemical and elemental analysis and IR spectroscopy, conductivity (in methanol, dimethyloformamide and dimethylsulphoxide). The thermal properties of complexes in the solid state were studied. The mode of metal–ligand coordination was discussed. The title compounds are isomorphic and isostructural in solid state. All atoms in studied compounds lie in general positions but occurrence of inversion on the midpoint of the bond linking two pyridine rings leads to existence in asymmetric unit one complex molecule and half of outer coordination sphere 4-bpy molecule. All chelating carboxylate groups are symmetrically bonded to the metal cations. The molecules of studied compounds are connected to the three dimensional network via O–H···O and O–H···N intermolecular hydrogen bonds. In the structures also exist C–H···O, C–H···Cl weak hydrogen bonds and π····π stacking interactions.     

Synthesis and properties of double copper(I)–nickel(II) sulfite

Pourbaix diagrams of Cu–H₂SO4–H₂O and Ni–H₂SO₄–H₂O systems have been refined, and stability regions of the sulfite phases have been determined. State diagrams of double copper(I)–copper(II) and copper(I)–nickel(II) sulfites have been constructed. Double copper(I)–nickel(II) sulfite has been isolated from aqueous solutions saturated with sulfur dioxide. The solutions at different ratios of the metals have been studied by spectrophotometry; the isolated double sulfite has been studied by X-ray diffraction, IR spectroscopy, dispersion analysis, and thermal analysis. Fundamentals of thermodynamic prognostication of the Cu₂SO₃·MSO₃ double sulfites synthesis have been elaborated.     

Synthesis and mesomorphic properties of new azine-type liquid crystals

A series of symmetrical azine-type liquid crystals were synthesized. The characteristic of these liquid crystals is that they had high clearing point ( ～320 ℃) and broad thermal range of nematic phase ( ～154 ℃). It was also found that the end groups of the liquid crystals had effect on the mesomorphic properties.     

Synthesis and Photoluminescence of a New Red PhosphorescentIridium(III) Quinoxaline Complex

Much attention has been paid to the phosphorescent materials in recent years for their potential application as highly efficient electroluminescent (EL) emitters in organic light emitting diodes (OLEDs) 1-2. Heavy metal complexes, particularly those containing Pt and Ir, where strong spin orbit coupling leads to singlet-triplet state mixing, can result in high efficiency electrophosphorescence in OLED 3-5. Among the many kinds of metal complexes, iridium complexes are the most effective …     

Synthesis of a π-extended TTF-perylenediimide donor-acceptor dyad

A donor-acceptor dyad containing perylenediimide as the electron acceptor and π-extended tetrathiafulvalene as electron donor has been successfully synthesized by means of a Wittig reaction. Cyclic voltammetry and absorption spectroscopy show that both electroactive units preserve their nature, whereas preliminar photophysical investigations show a strong fluorescence quenching.     

Synthesis and luminescence properties of Eu(III)-doped silica nanorods based on the sol–gel process

Uniform Eu³⁺-doped SiO₂ nanorods were synthesized through a simple sol–gel method using cetyltrimethylammonium bromide (CTAB) as surfactant template and tetraethylorthosilicate as silicon source. X-ray diffraction, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectrum, scanning electron microscope (SEM), transmission electron microscopy, and photoluminescence spectra were employed to characterize the products in detail. The nanorods have good uniformity and their diameters and lengths are in the range of 200–300 and 500–700 nm through the SEM images, respectively. The formation of the nanorods was studied by taking SEM images after different aging time. The experimental results indicate that CTAB plays a crucial role in the formation of the silica nanorods. The luminescence of Eu³⁺-doped SiO₂ nanorods is dominated by red-emission around 612 nm due to intra-atomic 4f → 4f (⁵D₀ → ⁷F₂₎ transition of Eu³⁺ ions. Furthermore, the effect of doping concentrations of Eu³⁺ ions on the luminescence was investigated.     

Synthesis,thermal study and some properties of Gd(III), Tb(III), Dy(III) and Er(III) complexes with 4,4′-bipyridine and dibromoacetates

Journal of Thermal Analysis and Calorimetry - New complexes with formulae: Ln(4-bpy)(CBr2HCOO)3·3H2O (where Ln(III) = Gd, Tb, Dy) and Er(4-bpy)1.5(CBr2HCOO)3·3H2O, were...     

Synthesis,crystal structure,and properties of a μ3-oxo-trichromium(III) propionate cluster with pyrazole

A new μ₃-oxo trinuclear chromium(III) propionate cluster, [Cr₃(μ₃-O)(O₂CCH₂CH₃)₆(pyr)₃]NO₃·0.25(H₂O) (1), has been synthesized by reaction of a μ₃-oxo trinuclear chromium(III) propionate precursor [Cr₃(μ₃-O)(O₂CCH₂CH₃)₆(H₂O)₃]NO₃ with a pyrazol ligand (pyr) and characterized by IR spectroscopy, single-crystal X-ray structure determination, and thermal analysis. Magnetic susceptibility and magnetization studies revealed antiferromagnetic exchange interactions within the trinuclear Cr(III) cluster (J = ?11.9 cm^?1) and determined the electronic ground state (S = ½) of the compound.     

Synthesis and structure of iron(III) complexes with a new ligands based on Girard’s reagent

Condensation of 5-bromosalicylaldehyde with Girard’s reagent T yields a new ligand in the form of a salt, 5-bromosalicylaldehyde (carboxymethyl)trimethylammonium chloride hydrazone (5-BrH₂SalGT)Cl (I). Ligand I is readily soluble in water and reacts with iron chloride to give the complex [Fe(5-BrSalGT)Cl₂] (II). Treatment of II with KCNS leads to the compound [Fe(5-BrSalGT)(NCS)₂(H₂O)] (III). At any ratio of the initial reagents, only complexes with the ratio metal: ligand = 1: 1 are isolated. Comparison of the structural data for compounds I–III shows that ligand I is deprotonated in the course of complex formation and is coordinated in the anionic form. Its conformational rearrangement is minimal and involves only a change in the orientation of the terminal group N(CH₃)₃. In complexes II and III, ligand I is coordinated to the metal ion through the ONO donor atoms. The structures of the complexes with different acido ligands are significantly different. Although the complexes contain each two inorganic anions, their coordination polyhedra differ from each other. In II, the iron atom is at the center of a trigonal bipyramid, whereas in III the iron atom has a tetragonal-bipyramidal environment due to the extra coordination of a water molecule. In both complexes, the iron atom is in the high-spin state: at room temperature, μ_eff is 5.86 and 5.81 μ_B for II and III, respectively. Complexes II and III are ordinary paramagnets down to 2 K.     

Synthesis and characterization of a monomeric and a dihydroxo-bridged dimeric complexes of iron(III) with α-benzoinoxime

The reaction of α-benzoinoxime, H₂BNO with FeCl₃ in the presence of Et₃N as a base gives the mononuclear Fe(III) complex, Fe(HBNO)₃ (1). Treatment of 1 with a methanolic solution of KOH at room temperature leads to a dinuclear Fe(III)–Fe(III) complex, [Fe(HBNO)₂OH]₂ (2). The complexes were initially characterized on the basis of their elemental, mass and thermal analyses. The IR studies were useful in assigning the coordination mode of the benzoinoxime ligand to the iron metal. In addition, the presence of a hydroxo-bridge in the dimeric complex 2 is inferred from the IR spectral studies. Room-temperature Mössbauer studies indicated octahedral, high-spin iron(III). Variable-temperature magnetic susceptibility measurements supported the existence of the μ-dihydroxo-bridging structure core, Fe^III(μ-OH)₂Fe^III in the dinuclear complex 2. Theoretical modelling of the magnetic data indicated a weak antiferromagnetic spin exchange between the iron(III) centers (J = −8.35 cm⁻¹, g = 2.01, ρ = 0.02 and TIP = 1.7 × 10⁻⁴ cm³ mol⁻¹ for H = −2JS₁ · S₂). The electronic spectra of the complexes revealed two bands due to d–d transitions and one band assignable to an oxygen (p_π) → Fe(d_π∗) LMCT transition observed in each complex. An additional charge-transfer transition, assignable to μ-hydroxo(p_π) → Fe(d_π∗), was observed for the dimeric complex 2. The structural and vibrational behaviors of these complexes have been elucidated with quantum mechanical methods.     

Synthesis and spectral properties of new 3,3’-bis(dipyrrolylmethene) with acetylene spacer

Bis(2,4,7,9-tetramethyl-8-ethyldipyrrolylmethen-3-yl)acetylene dihydrobromide (H₂L·2HBr), new bis(dipyrrolylmethene), in whose molecule dipyrrolylmethene domains were connected through 3,3′-carbon atoms of internal pyrrole nuclei by acetylene spacer, were synthesized by original procedure. The compound was characterized by element analysis, IR, ¹H NMR, and electronic spectroscopy. The comparative analysis of spectral properties shows the reduction of the basicity of H₂L ligand in comparison with the structural analogs, which contain internal methylene spacer. The quantum-chemical simulation showed that the rigid acetylene spacer gives linear structure to the H₂L molecule in contrast to the spiral-shaped geometry of structural analogs with -CH₂- spacer.