The development of polar discotic metallomesogens Vanadyl 1,3-diketonate complexes

The dependence of mesomorphism of 1,3-diketonate vanadium-oxo (vanadyl) complexes on the number of side chains was investigated. These complexes have a large dipole normal to the disc plane and are under investigation in an effort to generate discotic phases with polar order. Relatively complex phase behaviour is observed when the vanadyl 1,3-diketonate complexes are appended with four phenyl groups with two octyloxy or decyloxy side chains each for a total of eight side chains. These complexities are most likely related to the order/disorder associated with the polar vanadyl group. Vanadyl 1,3-diketonate complexes with four side chains were prepared by replacement of two of the phenyl groups with methyl or trifluoromethyl groups, and these complexes displayed only crystal phases. Complexes with two trialkyloxy phenyls and two dialkyloxy phenyls were synthesized and found to display a very stable D_hd phase. The presence of additional alkyloxy groups was found also to promote a linear chain structure, (i.e. --V=O--V=O--), in the crystal phase.     

Thermal behavior of some uranyl bis-(1,3-diketonate) complexes

Thermal gravimetric (TG) and differential thermal (DTA) analyses were performed to characterize the thermal behavior and the stoichiometry of uranyl bis-1,3-diketonate complexes (R₁COCR₂COR₃)₂ UO₂ x H₂O, where R_1,3=CH₃; C₂H₅; C₆H₅; CF₃; pNO₂−C₆H₄; pCl−C₆H₄; pMe−C₆H₄; NH−C₆H₅; R₂=H, C₆H₅ andx=1; 2. Based on the data obtained, a thermal degradation mechanism for each complex was proposed. The final degradation product for all studied complexes was U₃O₈ oxide. The temperature of the first organic fragment rupture including the U-O (ligand) bond was taken as criterion for the thermal stability of the metal-oxygen donor bond in these complexes. The observed stability order is in good agreement with the IR determined constant force values,k, of the U-O (ligand) bond.     

A new form of discotic metallomesogens: the synthesis of metal-bridged triphenylene discotic dimers

Discotic metallomesogens are becoming increasingly important due to their electronic and optoelectronic properties. Preliminary results on the synthesis and characterization of a new form of discotic metallomesogens in which a Hg atom is covalently linked with two substituted triphenylene moieties are presented.     

A new form of discotic metallomesogens: the synthesis of metal-bridged triphenylene discotic dimers

Discotic metallomesogens are becoming increasingly important due to their electronic and optoelectronic properties. Preliminary results on the synthesis and characterization of a new form of discotic metallomesogens in which a Hg atom is covalently linked with two substituted triphenylene moieties are presented.     

Discotic metallomesogens: Synthesis and properties of square planar metal bis(β-diketonate) complexes

Discotic β-diketonate liquid crystals containing palladium(II), and oxovanadium(IV), (V≡0), analogous to known copper complexes (which display discotic lamellar and columnar mesophases), have been prepared and characterized. These are the first enantiotropic discotics containing Pd(II) and among the earliest examples containing VO(IV). The best-behaved Pd(II) complex is [Pd(DK 10, 10)₂], and it also is probable that the complexes [Pd(DKn,n)₂] (n = 7-9) are mesomorphic, however their characterization is difficult due to decomposition in the isotropic phase. The mesophase of [Pd(DK 10²,10²)₂], which appears below 100°C, is suggested to be an example of the rare N_d phase on the basis of optical microscopy. The complex [VO(DK8,8)₂] is an enantiotropic discotic vanadyl complex; the monotropic behaviour of [VO(DK 10,10)₂] was also confirmed. It is suggested that the discotic phase which occurs for [VO(DK 8,8)₂] is more organized than that of [Cu(DK 8,8)₂].     

The first columnar discotic liquid crystalline anthraquinone metal complexes

In this communication we present the synthesis and characterization of the first two members of a new class of metallomesogen. The Pd and Cu complexes of 1-hydroxy-2,3,5,6,7-pentakis(dodecyloxy)anthra-9,10-quinone were prepared by reacting the respective metal(II) acetate with the ligand. Preliminary mesophase characterization by DSC and polarizing optical microscopy indicates the formation of columnar mesophases in both the complexes.     

Structural and near-IR photophysical studies on ternary lanthanide complexes containing poly(pyrazolyl)borate and 1,3-diketonate ligands

The ligands tris[3-(2-pyridyl)pyrazol-1-yl]hydroborate (L1, potentially hexadentate) and bis[3-(2-pyridyl)pyrazol-1-yl]dihydroborate (L2, potentially tetradentate) have been used to prepare ternary lanthanide complexes in which the remaining ligands are dibenzoylmethane anions (dbm). [Eu(L1)(dbm)2] is eight-coordinate, with L1 acting only as a tetradentate chelate (with one potentially bidentate arm pendant) and two bidentate dbm ligands. [Nd(L1)(dbm)2] was also prepared but on recrystallization some of it rearranged to [Nd(L1)2][Nd(dbm)4], which contains a twelve-coordinate [Nd(L1)2]+ cation (two interleaved hexadentate podand ligands) and the eight-coordinate anion [Nd(dbm)4]- which, uniquely amongst eight-coordinate complexes having four diketonate ligands, has a square prismatic structure with near-perfect O8 cubic coordination. Formation of this sterically unfavourable geometry is assumed to arise from favourable packing with the pseudo-spherical cation. The isostructural series of complexes [Ln(L2)(dbm)2](Ln = Pr, Nd, Eu, Gd, Tb, Er, Yb) was also prepared and all members structurally characterised; again the metal ions are eight-coordinate, from one tetradentate ligand L2 and two bidentate dbm ligands. Photophysical studies on the complexes with Ln = Pr, Nd, Er, and Yb were carried out; all show the near-IR luminescence characteristic of these metal ions, with longer lifetimes in CD3OD than in CH3OH. For [Yb(L2)(dbm)2], two species with different luminescence lifetimes were observed in CH3OH solution, corresponding to species with zero or one coordinated solvent molecules, in slow exchange on the luminescence timescale. For [Nd(L2)(dbm)2] a single average solvation number of 0.7 was observed in MeOH. For [Pr(L2)(dbm)2] a range of emission lines in the visible and NIR regions was detected; time-resolved measurements show a particularly high susceptibility to quenching by solvent CH and OH oscillators.     

Structure and chromotropic properties of mono- and binuclear mixed-ligand nickel(II) complexes containing 1,3-diketonate and polyamine ligands

Abstract  

Mixed-ligand Ni^II complexes have been synthesized with 1,3-diketonate and bulky tri- or tetra-amine ligands. Their structures were determined by X-ray crystallography, and solvatochromic behavior was examined by UV–vis–NIR spectroscopy. Steric effects of the bulky ligands on the coordination distances and spectral properties are discussed.     

Structure and chromotropic properties of mono- and binuclear mixed-ligand nickel(II) complexes containing 1,3-diketonate and polyamine ligands

Abstract  Mixed-ligand Ni^II complexes have been synthesized with 1,3-diketonate and bulky tri- or tetra-amine ligands. Their structures were determined by X-ray crystallography, and solvatochromic behavior was examined by UV–vis–NIR spectroscopy. Steric effects of the bulky ligands on the coordination distances and spectral properties are discussed. Graphical Abstract  

Emissive metallomesogens based on 2-phenylpyridine complexes of iridium(III)

Preparation of Ir(III) complexes using anisotropic 2,5-di(4-alkoxyphenyl)pyridine ligands leads to emissive, liquid-crystalline complexes containing bound Cl and dimethyl sulfoxide. Using analogous poly(alkoxy) ligands allows the preparation of bis(2-phenylpyridine)iridium(III) acac complexes, which are also mesomorphic. The observation of liquid crystallinity in octahedral complexes of this type is without precedent.     

Quenching of the triplet state of benzophenone by lanthanide 1,3-diketonate chelates in solutions

The phosphorescence of benzophenone in benzene and acetonitrile was quenched by several lanthanide (Sm, Eu, Gd, Tb and Dy) acetylacetonate chelates. The results ofStern-Volmer analysis including the quenching of benzophenone triplet and sensitization of lanthanide emission indicate that the quenching process occurs by the energy transfer mechanism via the excited triplet state of the ligand.

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Löschung des Triplettzustandes von Benzophenon mittels Lanthanid-1,3-Diketonat-Chelatverbindungen in Lösung

Zusammenfassung Die Phosphoreszene von Benzophenon in Benzophenon in Benzen und Acetonitril wurde durch 1,3-Diketonat-Chelatverbindungen von einigen Lanthaniden (Sm, Eu, Gd, Tb und Dy) gelöscht. Die Resultate derStern-Volmer-Analyse einschließlich der Auslöschung des Benzophenon-Tripletts und die Sensibilisierung der Lanthanid-Emission zeigen, daß der Löschprozeß mittels Energieübertragungsmechanismus via angeregtem Triplettzustand des Liganden stattfindet.

     

Synthesis and properties of some chromium(III) β-diketonate complexes

Summary Equimolar quantities of CrCl₃ · 3THF and-diketones, -dkH, react to yield CrCl₂(-dk) · 2THF and CrCl₂(-dk) · THF complexes in coordinating and noncoordinating solvents respectively. For 1 : 2 and 1 : 3 molar ratios of reactants, derivatives of general formulae CrCl(-dk)₂ and Cr(-dk)₃ (where-dkH = acerylacetrrnc, benzoylacetonc and dibenzoylmethane) have been isolated. All complexes have been characterized by elemental analysis, molecular weights and by i.r. spectra.     

Structural investigations of copper(II) complexes containing fluorine-substituted β-diketonate ligands

The crystal structures of the β-diketonate complexes Cu(pta)₂, Cu(pta)₂·EtOH, and Cu(F₆-thd)₂ (where pta is the anion of 1,1,1-trifluoro-5,5-dimethylhexane-2,4-dione and F₆-thd is the anion of 2,2-bis(trifluoromethyl)-6,6-dimethylheptane-3,5-dione) were determined. The solid-state structures of Cu(pta)₂ and Cu(F₆-thd)₂ are square planar, while Cu(pta)₂·EtOH is approximately square pyramidal with the EtOH ligand occupying the apical position. In each case, only one geometrical isomer (cis or trans) was observed in the crystals; arguments are presented that both isomers are present in bulk samples. Calculations of molecular volumes for structurally related Cu(II) complexes containing non-fluorinated versus fluorinated ancillary ligands show that fluorine substitution does not significantly affect packing efficiency in the solid-state; however, solvent coordination decreases packing efficiency slightly. [Cu(tdf)(py)(μ-C₃F₇CO₂)]₂ (where tdf is the anion of 1,1,1,2,2,3,3,7,7,8,8,9,9,9-tetradecafluorononane-4,6-dionate), a derived impurity from preparations of Cu(tdf)₂, was isolated in low yield. The copper coordination geometries in the centrosymmetric structure are intermediate between square pyramidal and trigonal bipyramidal, with two unsymmetrically bridging μ,η¹:η¹-C₃F₇CO₂ ligands.     

Luminescence of europium(III) β-diketonate complexes in a Nafion membrane

EuL₃ · phen complex compounds (L is benzoylacetone, dibenzoylmethane, or thenoyltrifluoroacetone; phen is 1,10-phenanthroline) were synthesized in a perfluorosulfonic membrane. The results of adsorption measurements suggest that the complexes experience steric hindrances in the membrane pores. The luminescence from intercalates is sensitized due to the increase in the degree of population of the ⁵ D ₀ excited state of europium(III) caused by the transfer of energy from the ligands. Depending on the type of β-diketonate ligand, the adsorption of water on the modified membrane can enhance or suppress the luminescence from the complex.     

First nucleophilic addition of acetylide to 1,3-diketonate anions: reaction of 1-aryl-4,4,4-trifluorobutane-1,3-diones with sodium acetylide

The nucleophilic addition of sodium acetylide to 1,3-diketonates derived from 1-aryl-4,4,4-trifluorobutane-1,3-diones is reported. Tertiary 1,4-alkynediols containing CF₃ and aroylmethyl groups are synthesized. 5,5′-Diaryl-3,3′-bis(trifluoromethyl)-2,2′-bifurans are prepared via a novel double cyclization of these alkynediols.     

Spontaneous copolymerization of 1,3-cyclohexadiene with polar vinyl monomers

In the reactions of 1,3-cyclohexadiene(1,3-CHD) with polar vinyl monomers, CH₂?C(X)Y (X is -? CN and ? CO₂CH₃; Y is ? CI, ? H, and ? CH₃), the two α-chlorosubstituted monomers underwent rapid spontaneous copolymerization, accompanied by the formation of a small amount of cycloadduct. Both polar monomers also gave predominantly copolymers in the reaction with 1,3-cycloheptadiene(1,3-CHpD) in lower yield. 1,3-Cyclooctadiene (1,3-COD) reacted only with α-chloroacrylonitrile (CAN) to give a copolymer, while only cycloaddition took place in systems involving cyclopentadiene(CPD) as diene. The charge–transfer (CT) complex formation of 1,3-CHD with CAN and methyl α-chloroacrylate(MCA) was confirmed by ultraviolet spectroscopic studies and the equilibrium constants estimated were 0.18 and 0.07 liter/mole, respectively, at 25°C in chloroform as solvent. The activation energies for the copolymerizations of 1,3-CHD with CAN and MCA in benzene were determined to be ca. 6.6 and 9.6 kcal/mole, respectively. In the system composed of 1,3-CHD and CAN, only the copolymerization was affected by solvents used and oxygen. Although addition of ZnCl₂ to the system resulted in the acceleration of the both reactions, the variation in the product ratio of copolymer to cycloadduct with ZnCl₂ concentration showed a maximum. Based on the results in the present and preceding studies for systems involving 1,3-cyclodienes and acceptor monomers, the relationship between the cycloaddition and the spontaneous copolymerization is discussed.     

氧钒（Ⅳ）离子与G－肌动蛋白的相互作用

用凝胶色谱法以及荧光光谱和ＣＤ谱研究ＶＯ￣（２＋）与Ｇ－肌动蛋白的作用。结果表明，在一个Ｇ－肌动蛋白分子上有一个ＶＯ￣（２＋）的强结合部位和几个弱结合位点。随ＶＯ￣（２＋）与肌动蛋白的摩尔比增加，ＶＯ￣（２＋）先结合在强结合位点上，使α－螺旋含量增加，蛋白质构象变得更为紧密。更多的ＶＯ￣（２＋）结合在弱结合位点上，使α－螺旋含量降低，构象变得更为开放。用光散射法测定Ｇ－肌动蛋白缔合动力学，发现在低浓度ＶＯ￣（２＋）影响下，ＶＯ￣（２＋）和Ｍｇ￣（２＋）一样，促进缔合，而在浓度高时，缔合反而受到抑制。但是都未改变线性缔合本质。结果提示ＶＯ￣（２＋）与Ｍｇ￣（２＋）相似，可能结合在钙的强结合部位上。     

Metal complexes of 2-hetarylindandiones-1,3

The chelate and molecular complexes of 2-(2-benzazolyl, perimidyl)-indandiones-1,3 were synthesized for the first time. The structures of the ligands (tautomeric forms) and complex compounds were determined from the X-ray diffraction, ¹H, ¹³C NMR, and IR data and the quantum-chemical calculations (RHF SCF in 6-31 G** basis).