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

Abstract

Discotic β-diketonate liquid crystals containing palladium(II), and oxovanadium(IV), (V[tbnd]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].     

Magnetic properties of rare-earth β-enaminoketone metallomesogens

Reaction of β-enaminoketones with lanthanide salts leads to mesomorphic complexes displaying an S_A mesophase. The mesophase was characterized using X-ray scattering, EPR and magnetic susceptibility. A very high magnetic anisotropy was deduced for a complex containing dysprosium.     

Group 2 element β-diketonate complexes: synthetic and structural investigations

An overview of the Group 2 element β-diketonates is presented, including their synthesis, structural characteristics, physical properties, and some potential applications.     

Photophysical properties of novel fluorescent poly(oxyethylene phosphate) tris(β-diketonate) europium (III) complexes

In the present study, photophysical properties of fluorescent poly(oxyethylene phosphate) tris(β-diketonate) europium (III) complexes have been studied by means of stationary and time-resolved fluorescence spectroscopy (in ethanol at room temperature). The luminescent quantum yields and efficiency for the energy transfer from β-diketonate ligands to Eu(III) ion have been determined for the studied complexes by using diffusion-enhanced fluorescence resonance energy transfer. Obtained results show effect of the polymer ligands upon photophysical properties of the complexes and a relation has been established with length of the oxyethylene spacer between two phosphonate groups. The Förster radiuses of the synthesized compounds with SulfoRhodamine 101 as acceptor have been calculated. Measured distances between molecules of the donors and acceptor at identical acceptor/donor molar ratios have been illustrated the difference in structure of the ternary and polymer complexes in solution even at low concentration.     

Copolymerization of ethylene and cyclopentene with bis(β‐enaminoketonato) titanium complexes

The copolymerizations of ethylene and cyclopentene with bis(β‐enaminoketonato) titanium complexes {[(Ph)NC(R₂)CHC(R₁)O]₂TiCl₂; R₁ = CF₃ and R₂ = CH₃ for 1a , R₁ = Ph and R₂ = CF₃ for 1b ; and R₁ = t‐Bu and R₂ = CF₃ for 1c } activated with modified methylaluminoxane (MMAO) as a cocatalyst were investigated. High‐molecular‐weight copolymers with cis‐1,2‐cyclopentene units were obtained. The catalyst activity, cyclopentene incorporation, polymer molecular weight, and polydispersity could be controlled over a wide range through the variation of the catalyst structure and reaction parameters, such as the Al/Ti molar ratio, cyclopentene feed concentration, and polymerization reaction temperature. The complex 1b /MMAO catalyst system exhibited the characteristics of a quasi‐living ethylene polymerization and an ethylene–cyclopentene copolymerization and allowed the synthesis of polyethylene‐block‐poly(ethylene‐co‐cyclopentene) diblock copolymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1681–1689, 2005     

The interaction of triplet excited state ketones with copper(II) complexes: effects of β-diketonate ligands

The copper(II) complexes of acetylacetone, 1,1,1-trifluoroacetylacetone and 1,1,1,5,5,5-hexafluoroacetylacetone quench the triplet excited state benzophenone efficiently with about equal rate constants. However, the limiting quantum efficiency of the photoreduction increases with increasing number of CF₃ groups in the complexes or with increasing hydrogen-atom-donating ability of the solvent.     

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.     

Ru catalyzed cyclodimerization of bis(2‐thienyl)acetylene and bis(3‐thienyl)acetylene. Synthesis properties of 4,5,6‐tris(2‐thienyl)benzo(b)thiophene and 5,6,7‐tris(3‐thienyl)benzo[b]thiophene

Activated dihydridocarbonyltris(triphenylphosphine)ruthenium catalyzes the cyclodimerization of both bis(2‐thienyl)acetylene and bis(3‐thienyl)acetylene to yield, respectively, 4,5,6‐tris(2′‐thienyl)‐benzo[b]thiophene and 5,6,7‐tris(3′‐thienyl)benzo[b]thiophene. These fluoresce in the blue. Both undergo irreversible one electron oxidation at & sim1.1 mV versus Ag/Ag⁺ electrode, consistent with oxidation of the benzo[b]thiophene nuclei rather than the substituent thiophene rings.     

Novel polymer-supported β-diketonate nickel catalysts for α-olefin activation

Styrene–divinylbenzene resins were used for the synthesis of different polymer-bound β-diketones, obtained by anchoring the chelating group through either the central or the lateral position. The heterogenized diketone ligand was subsequently reacted with Ni(COD)₂ analogously to the corresponding homogeneous catalysts active in α-olefin oligomerization. The heterogenized catalysts showed a good activity only when the central position of the chelate moiety was free. Heterogenization caused a significant change of selectivity: olefin oligomerization was accompanied by the formation of a large amount of polymeric products. This behavior is discussed in terms of steric effects caused by the bulky polymeric ligand. © 1998 John Wiley & Sons, Ltd.     

Ethylene/α‐olefin copolymerization with bis(β‐enaminoketonato) titanium complexes activated with modified methylaluminoxane

Copolymerizations of ethylene with α‐olefins (i.e., 1‐hexene, 1‐octene, allylbenzene, and 4‐phenyl‐1‐butene) using the bis(β‐enaminoketonato) titanium complexes [(Ph)NC(R₂)CHC(R₁)O]₂TiCl₂ ( 1a : R₁ = CF₃, R₂ = CH₃; 1b : R₁ = Ph, R₂ = CF₃; and 1c : R₁ = t‐Bu, R₂ = CF₃), activated with modified methylaluminoxane as a cocatalyst, have been investigated. The catalyst activity, comonomer incorporation, and molecular weight, and molecular weight distribution of the polymers produced can be controlled over a wide range by the variation of the catalyst structure, α‐olefin, and reaction parameters such as the comonomer feed concentration. The substituents R₁ and R₂ of the ligands affect considerably both the catalyst activity and comonomer incorporation. Precatalyst 1a exhibits high catalytic activity and produces high‐molecular‐weight copolymers with high α‐olefin insertion. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6323–6330, 2005     

Crystalline polymers of bis(β-chloroethyl) vinylphosphonate

The polymerization of bis(β-chloroethyl) vinylphosphonate to a crystalline solid was carried out with a Ziegler-Natta catalyst. A confirmation of the crystalline nature of the polymers was carried out by x-ray diffraction. The polymers would not melt even at temperatures up to 620°C., but instead began to char. However, they were soluble in dimethylformamide and acrylonitrile.     

Synthesis and luminescent properties of polymeric metal complexes containing bis(8-hydroxyquinoline) group

A novel ligand: 4,4′-bis(8-hydroxyquinoline-5-propenyl)-biphenyl (B8QPB) (1), has been synthesized by Witting-Horner reaction, and the corresponding two polymeric metal complexes were also prepared by polynuclear of the ligand with aluminium (III) (2) and zinc (II) (3) halides, respectively. The structure of the ligand was characterized by ¹H NMR, FT-IR and elemental analysis techniques; polymeric metal complexes were characterized by FT-IR, UV-vis, elemental analysis techniques, conductivity measurements and gel permeation chromatography (GPC). The results indicate that the stoichiometry of polymeric metal complexes is [(C₃₄H₂₄O₂N₂)₁₁Al₁₂Cl₂₈] and [(C₃₄H₂₄O₂N₂)₃₂(ZnCl₂)₃₃]. B8QPB coordinated with metal ions to form polymers. The luminescence properties of the complexes 1-3 were investigated by UV-vis and fluorescence spectra at room temperature. The experimental results show that polymeric metal complexes 2 and 3 emit blue/green luminescence at 514 and 504 nm in the solid state and at 470 and 507 nm in DMSO solution. Thermal properties measurement and analysis show that they have good thermal stabilities.     

Diastereoisomeric β‐ethyl aspartate–cobalt(III) complexes: Λ(+)578‐ and Δ(−)578‐bis(ethane‐1,2‐diamine)[β‐ethyl (S)‐aspartato]cobalt(III) bis(perchlorate) monohydrate

The structures of the diastereoisomers Λ(+)₅₇₈‐, (I), and Δ(−)₅₇₈‐bis(ethane‐1,2‐diamine)[β‐ethyl (S)‐aspartato‐κ²N,O¹]cobalt(III) bis(perchlorate) monohydrate, (II), both [Co(C₆H₁₀N₂O₄)(C₂H₈N₂)₂](ClO₄)₂·H₂O, are compared. In both structures, the ester group of the amino acid side chain is engaged only in intramolecular hydrogen bonding to coordinated amine groups. This interaction is stronger in (I) and correlates with previously observed diastereoisomeric equilibrium ratios for related metal complex systems in aqueous media. The two perchlorate anions of (II) are located on twofold axes. Both perchlorates in (I) and one of the perchlorates in (II) are affected by disorder. Both structures exhibit extensive three‐dimensional hydrogen‐bonding networks.     

LAMMA mass spectra of β-diketone,bis(benzoylacetone)ethylenediimine and bis(salicylidene)ethylenediimine complexes of some transition metals

Complexes of 2,4-pentanedione (acetylacetone, acac), [Cu(acac)₂], [VO(acac)₂] and [CO(acac)₃], and the chromium(III) derivative of 3-methyl-2,4-pentanedione (methylacetylacetone, meac), [Cr(meac)₃], the ligands bis(benzoylacetone)ethylenediimine and bis(salicylidene)ethylenediimine, and their cobalt(II), nickel(II) and copper(II) chelates were analysed by laser desorption mass spectrometry (LAMMA) and compared to electron impact (EI) results. The positive ion LAMMA spectra generally reveal mostly small fragments, although metal cationization peaks are seen for most complexes. Negative ion LAMMA produce carbon clusters and some structurally important fragments.