Magnetic field induced Freedericksz transition of a planar aligned liquid crystal doped with metalloporphyrins FeTPPCl, MnTPPCl and ZnTPP

We observed that the planar aligned nematic liquid crystal (5CB) doped with a volume fraction of 1% of FeTPPCl [5,10,15,20-tetraphenylporphyriniron(III)chloride] or MnTPPCl [5,10,15,20-tetraphenylporphyrinmanganese(III)chloride] dramatically decreased the critical magnetic field for the magnetic field induced Freedericksz transition, while 5CB doped with ZnTPP [5,10,15,20-tetraphenylporphyrinzinc(II)] revealed no such effect, when compared with pure 5CB. In the guest-host (5CB) system, FeTPPCl and MnTPPCl as guests are both strong paramagnetic materials with an interaction through coordination of the -CN group in 5CB onto the metal ion of the porphyrin. As a result, the 5CB molecules are dragged to reorientate under a static magnetic field, while ZnTPP is a diamagnetic material without such a property. This phenomenon concerning magneto-optical components could be useful in liquid crystal displays.     

Preliminary communication: Magnetic-field-induced Freedericksz transition of a planar aligned liquid crystal doped with porphyrinatozinc(II): influence of the substituent of the porphyrin ring

The magnetic-field-induced Freedericksz transition of a planar aligned nematic liquid crystal doped with 1.0 wt % of a diamagnetic porphyrinatozinc(II) has been studied. It was observed that 5CB doped with 1.0 wt % of derivatives of Zn(II)TPP-5,10,15,20-tetraphenyl-porphyrinatozinc(II) - which have different substituents in one phenyl ring display sharp Freedericksz transition curves and dramatically decrease the critical magnetic field compared with pure 5CB.     

Preliminary communication: Magnetic-field-induced Freedericksz transition of a planar aligned liquid crystal doped with porphyrinatozinc(II): influence of the substituent of the porphyrin ring

The magnetic-field-induced Freedericksz transition of a planar aligned nematic liquid crystal doped with 1.0 wt % of a diamagnetic porphyrinatozinc(II) has been studied. It was observed that 5CB doped with 1.0 wt % of derivatives of Zn(II)TPP-5,10,15,20-tetraphenyl-porphyrinatozinc(II) - which have different substituents in one phenyl ring display sharp Freedericksz transition curves and dramatically decrease the critical magnetic field compared with pure 5CB.     

Synthesis, characterization, and electrochemical studies of beta,beta'-fused metallocenoporphyrins

Beta,beta'-Fused monoruthenocenylporphyrins, Cp*Ru(III)[1,2-[M(II)-5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)-porphyrinato]-3-methyl-cyclopentadienide] (M = Ni (20), Cu (21), Zn (22)), and bisferrocenoporphyrins, Fe(II) bis[1,2-[M(II)-5,10,15,20-tetraphenylporphyrinato]-3-methyl-cyclopentadienide] (M = Ni (24), Cu (25), Zn (26)), were synthesized and characterized. A novel synthetic approach to beta,beta'-fused porphyrins through Pd(0)-catalyzed [3 + 2] cycloaddition was implemented in this work. UV-vis spectra of these compounds show largely broadened and red-shifted bands (relative to their precursors) indicating potential electronic communication between the attached organometallic moiety and the porphyrin core. The electrochemistry of these molecules suggests significant electronic interactions between the metallocene and metalloporphyrin in molecules 20 and 24. The crystal structure of the bisferrocenoporphyrin 26, Fe(II) bis[1,2-[Zn(II)-5,10,15,20-tetraphenylporphyrinato]-3-methyl-cyclopentadienide], was determined: [Cp2Fe[ZnTPP(THF)]2][Cp2Fe[ZnTPP(THF)ZnTPP(MeOH)]].3MeOH.6THF, M = 3804.35, monoclinic, space group P21/c, a = 33.327(5) A, b = 19.145(3) A, c = 29.603(5) A, beta = 106.309(2) degrees , V = 18128(5) A3, Z = 4. In this molecule, one porphyrin ring is rotated by about 72 degrees with respect to the other in the 5-fold axis of the Cp ring.     

Temperature-driven luminescence switching of europium(III) in a glass dispersed liquid crystal film

Glass dispersed liquid crystal films doped with the tris(β-diketonato)europium(III) complex [Eu(dbm)₃(gly)] (Hdbm=dibenzoylmethane, gly=1,2-dimethoxyethane) were prepared. The liquid crystal host was 4-pentyl-4'-cyanobiphenyl (5CB); a mixed silica-titania glass with a refractive index close to that of 5 CB was chosen as the glass matrix. The photoluminescence intensity was measured as a function of temperature. A strong intensity change was observed at the nematic-to-isotropic transition.     

Temperature-driven luminescence switching of europium(III) in a glass dispersed liquid crystal film

Glass dispersed liquid crystal films doped with the tris(β-diketonato)europium(III) complex [Eu(dbm)₃(gly)] (Hdbm=dibenzoylmethane, gly=1,2-dimethoxyethane) were prepared. The liquid crystal host was 4-pentyl-4′-cyanobiphenyl (5CB); a mixed silica–titania glass with a refractive index close to that of 5 CB was chosen as the glass matrix. The photoluminescence intensity was measured as a function of temperature. A strong intensity change was observed at the nematic-to-isotropic transition.     

The first lanthanide(III) monoporphyrin complex liquid crystal

Hydroxy [5,10,15,20-tetra[ p -decyloxy- m -methyloxy)phenyl]porphyrin Yb(III) exhibits a discotic hexagonal columnar phase, it is the first example of a monoporphyrin rare earth complex liquid crystal.     

The first lanthanide(III) monoporphyrin complex liquid crystal

Hydroxy [5,10,15,20-tetra[P-decyloxy- ^m -methyloxy)phenyl]porphyrin Yb(III) exhibits a discotic hexagonal columnar phase, it is the first example of a monoporphyrin rare earth complex liquid crystal.     

Self-assembled nanoporphyrins in the presence of gold bio-nanoparticles as heterogeneous nano-biocatalyst for green production of aldehydes and ketones

We report a simple and facile self-assembly method for the successful fabrication of a biological macromolecule, MnTPPCl (manganese(III) chloride 5,10,15,20-tetraphenylporphyrin), intercalated into gold nanoparticles using the cooperative effects of Sesbania sesban plant. This biohybrid was characterized using various techniques for further investigation. The catalytic activity of this biological hybrid was considered in the production of aldehydes and ketones from primary and secondary alcohols, respectively. Excellent conversions and selectivties were obtained applying Au@MnTPPCl colloidal nanocomposite and NaIO₄ as an oxygen donor in ethanol.     

Phase behavior of nanoparticles in a thermotropic liquid crystal

In this work, we describe the outstanding behavior of a nanocomposite system composed of the thermotropic liquid crystal 5CB doped with nanoparticles of the magnetic iron oxide maghemite (gamma-Fe(2)O(3)). We show that the I-N transition is associated with a reversible gathering of nanoparticles inside droplets of the ferronematic phase coexisting with a nonmagnetic nematic host phase.     

金属卟啉的直接电化学合成及其固体微粒伏安行为研究

用固体微粒伏安法在电极表面直接获得了铜卟啉、铁卟啉及钴卟啉,在氯化钾支持电解质溶液中用循环伏安法对meso四苯基卟啉(H₂TPP)及现场合成的金属卟啉的固体电化学行为进行了表征.作为电荷补偿,实验证明在固体金属卟啉还原及氧化过程中同时伴随有钾离子在晶胞中的迁移,文中对金属卟啉的形成机理及其电极反应机理进行了详细探讨.     

Crystallographic identification of a series of manganese porphyrin complexes with nitrogenous bases

Studying the axial ligation behavior of metalloporphyrins with nitrogenous bases helps to better understand not only the biological function of heme‐based protein systems, but also the catalytic properties of porphyrin‐based reaction sites in other biomimetic synthetic support environments. Unlike iron porphyrin complexes, little is known about the axial ligation behavior of Mn porphyrins, particularly in the solid state with Mn in the +3 oxidation state. Here, we present the syntheses and crystal and molecular structures of three new high‐spin manganese(III) porphyrin complexes with the different amine‐based axial ligands imidazole (im), piperidine (pip), and 1,4‐diazabicyclo[2.2.2]octane (DABCO), namely bis(imidazole)(5,10,15,20‐tetraphenylporphyrinato)manganese(III) chloride chloroform disolvate, [Mn(C₄₄H₂₈N₄)(C₃H₄N₂)₂]Cl·2CHCl₃ or [Mn(TPP)(im)₂]Cl·2CHCl₃ (TPP = 5,10,15,20‐tetraphenylporphyrin), (I), bis(piperidine)(5,10,15,20‐tetraphenylporphyrinato)manganese(III) chloride, [Mn(C₄₄H₂₈N₄)(C₅H₁₁N)₂]Cl or [Mn(TPP)(pip)₂]Cl, (II), and chlorido(1,4‐diazabicyclo[2.2.2]octane)(5,10,15,20‐tetraphenylporphyrin)manganese(III)–1,4‐diazabicyclo[2.2.2]octane–toluene–water (4/4/4/1), [Mn(C₄₄H₂₈N₄)Cl(C₆H₁₂N₂)]·C₆H₁₂N₂·C₇H₈·0.25H₂O or [Mn(TPP)Cl(DABCO)]·(DABCO)·(toluene)·0.25H₂O, (IV). A fourth complex, chlorido(pyridine)(5,10,15,20‐tetraphenylporphryinato)manganese(III) pyridine disolvate, [Mn(C₄₄H₂₈N₄)Cl(C₅H₅N)]·2C₅H₅N or [Mn(TPP)Cl(py)]·2(py), (III), acquired using different crystallization methods from published data, is also reported and compared to the previous structures.     

Structure and properties of [Cr(III)F(NCMe)5](BF4)2.MeCN: a nonaqueous source of Cr(III)F2+ and a building block for new Prussian-blue-like magnetic materials

[Cr (III)F(NCMe) 5](BF 4) 2.MeCN ( 1) was synthesized from a prolonged dissolution of [Cr (III)(NCMe) 6](BF 4) 3 in MeCN via fluoride abstraction from BF 4 (-). Complex 1 exhibits a crystal field splitting, Delta o, of 17 470 cm (-1) and is a nonaqueous source of Cr (III)F (2+). The reaction of 1 with (NEt 4) 3[Cr (III)(CN) 6] formed a new Prussian-blue-like magnetic material of (NEt 4) 0.04[Cr (III)F] 1.54[Cr (III)(CN) 6](BF 4) 0.12.0.10(MeCN) ( 2) composition. Complex 2 magnetically orders at a critical temperature, T c, of 85 K and at 2 K exhibits magnetic hysteresis with a coercive field, H cr, of 60 Oe and a remanent magnetization, M rem, of 1880 emuOe/mol.     

New class of potent catalysts of O2.-dismutation. Mn(III) ortho-methoxyethylpyridyl- and di-ortho-methoxyethylimidazolylporphyrins

Three new Mn(III) porphyrin catalysts of O2.-dismutation (superoxide dismutase mimics), bearing ether oxygen atoms within their side chains, were synthesized and characterized: Mn(III) 5,10,15,20-tetrakis[N-(2-methoxyethyl)pyridinium-2-yl]porphyrin (MnTMOE-2-PyP(5+)), Mn(III)5,10,15,20-tetrakis[N-methyl-N'-(2-methoxyethyl)imidazolium-2-yl]porphyrin (MnTM,MOE-2-ImP(5+)) and Mn(III) 5,10,15,20-tetrakis[N,N'-di(2-methoxyethyl)imidazolium-2-yl]porphyrin (MnTDMOE-2-ImP(5+)). Their catalytic rate constants for O2.-dismutation (disproportionation) and the related metal-centered redox potentials vs. NHE are: log k(cat)= 8.04 (E(1/2)=+251 mV) for MnTMOE-2-PyP(5+), log k(cat)= 7.98 (E(1/2)=+356 mV) for MnTM,MOE-2-ImP(5+) and log k(cat)= 7.59 (E(1/2)=+365 mV) for MnTDMOE-2-ImP(5+). The new porphyrins were compared to the previously described SOD mimics Mn(III) 5,10,15,20-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE-2-PyP(5+)), Mn(III) 5,10,15,20-tetrakis(N-n-butylpyridinium-2-yl)porphyrin (MnTnBu-2-PyP(5+)) and Mn(III) 5,10,15,20-tetrakis(N,N'-diethylimidazolium-2-yl)porphyrin (MnTDE-2-ImP(5+)). MnTMOE-2-PyP(5+) has side chains of the same length and the same E(1/2), as MnTnBu-2-PyP(5+)(k(cat)= 7.25, E(1/2)=+ 254 mV), yet it is 6-fold more potent a catalyst of O2.-dismutation , presumably due to the presence of the ether oxygen. The log k(cat)vs. E(1/2) relationship for all Mn porphyrin-based SOD mimics thus far studied is discussed. None of the new compounds were toxic to Escherichia coli in the concentration range studied (up to 30 microM), and protected SOD-deficient E. coli in a concentration-dependent manner. At 3 microM levels, the MnTDMOE-2-ImP(5+), bearing an oxygen atom within each of the eight side chains, was the most effective and offered much higher protection than MnTE-2-PyP(5+), while MnTDE-2-ImP(5+) was of very low efficacy.     

Formation of 6-formyl-7-hydroxy-8-methoxycoumarin and 5,8-dioxopsoralen by reaction of 8-methoxypsoralen with H2O2 and potassium superoxide (KO2) catalyzed by halogenated or perhalogenated 5,10,15,20-tetraarylporphyrinatoiron(III) chlorides

The oxidation of 8-methoxypsoralen (2) with hydrogen peroxide and potassium superoxide catalyzed by 5,10,15,20-(2,4,6-trimethylphenyl)porphyrinatoiron(III) chlorides [Me12TPPFe(III)Cl] (1a) and 5,10,15,20-(2,6-dichlorophenyl)porphyrinatoiron(III) chlorides [Cl8TPPFe(III)Cl] (1b) in dichloromethane gives 6-formyl-7-hydroxy-8-methoxycoumarin (3) in moderate yields, whereas the oxidation of (2) with H2O2 catalyzed by 5,10,15,20-(2,6-dichlorophenyl)-beta-octahaloporphyrinatoiron(III) chlorides [Cl8betaX8TPPFe(III)Cl] (X=Cl, Br) (1c, 1d) gives specifically 5,8-dioxopsoralen (4) in moderate yields.     

Magnetocaloric effect and heat capacity of high-spin manganese complexes in a disperse state

Magnetothermal properties of high-spin chloro(2,3,7,8,12,13,17,18-octaethylporphyrinato)manganese(III), chloro(5,10,15,20-tetraphenylporphyrinato) manganese(III), bromo(5,10,15,20-tetraphenylporphyrinato)manganese(III), and (acetato)(5,10,15,20-tetraphenylporphyrinato)manganese(III) complexes as 6% water suspensions were determined by the microcalorimetric method at 298 K in a magnetic field of 0–1.0 T. It was established that when the magnetic field was applied, the temperature of the systems increases, leading to positive values of the magnetocaloric effect: the higher the magnetic field induction, the higher the values. It is shown that the dependences of the heat capacity of the complexes’ solid particles on the magnetic field induction are of an extreme nature with a heat capacity in the area above 0.6 T less than that in the zero field. The regularities of the dynamics of the numerical values of the change in enthalpy and magnetic entropy of the manganese complexes when a growing magnetic field was applied and the regularities of the influence of the acidoligand in pentacoordinated complexes on their magnetothermal properties were considered.     

Glycosylated metalloporphyrins as neutral carriers for PVC membrane electrodes.

In this paper, the synthesis of a novel ionophore, chloro[5,10,15,20-tetrakis[2-(2,3,4,6-tetraacetyl-beta-D-glucopyranosyl)-1-O-phenyl]porphinato]manganese (MnT(o-glu)PPCl), and its application as a neutral carrier for a PVC membrane electrode are described. The MnT(o-glu)PPCl-based PVC membrane electrode shows a potentiometric responses to SCN- over a concentration range of 3.4 x 10(-7) - 1.0 x 10(-1) mol L(-1) with a Nernstian slope and a response time of 20 s. The electrode exhibits an anti-Hofmeister selectivity toward SCN- with respect to common coexisting anions. As active materials, MnT(o-glu)PPCl shows better selectivity toward SCN- than chloro(tetraphenylporphinato)manganese (MnTPPCl). The effect of the electrode membrane compositions has been studied and the experimental conditions were optimized. The electrode was applied to the determination of SCN- in body fluids with satisfactory results.     

Holmium porphyrin compound liquid crystals: Synthesis and properties

5,10,15,20-Tetra-[(p-alkoxy-m-ethyloxy)phenyl]porphyrin and [5-(p-alkoxy)phenyl-10,15,20-tri-phenyl]porphyrin and their holmium(III) complexes are reported. They display a hexagonal columnar discotic columnar (Col_h) liquid crystal phase and were studied by cyclic voltammetry, surface photovoltage spectroscopy (SPS), electric-field-induced surface photovoltage spectroscopy (EFISPS) and luminescence spectroscopy. Within the accessible potential window, all these compounds exhibit two one-electron reversible redox reactions. Quantum yields of Q band are in the region 0.0045–0.21 at room temperature. The SPS and EFISPS reveal that all the compounds are p-type semiconductors and exhibit photovoltaic response due to π–π^* electron transitions.     

Characterisation of polymerisation-induced phase separation process in polymer-dispersed liquid crystals based on hydroxyalkyl-methacrylate matrices

Hydroxyalkyl-methacrylates are very well-known hydrogel-forming biocompatible polymers. In this work, polymer-dispersed liquid crystals (LCs) based on hydroxyethyl- and hydroxypropyl-methacrylate (HEMA and HPMA) matrices are synthesised and characterised. Two different LCs from the cyano-biphenyl family (4?-pentyl-4-cyanobiphenyl [5CB] and 4?-octyl-4-cyanobiphenyl [8CB]) are used. Polymerisation kinetics, phase transitions, and morphologies generated during the polymerisation-induced phase separation process are analysed. Phase separation is observed at very low conversions, where a polymer-rich phase is initially segregated and this produces an increase in the low-conversion polymerisation rate (ascribed to the auto-acceleration effect of free-radical polymerisations in the polymer-rich phase). The liquid crystalline transition temperature decreases as the concentration of LC decreases, indicating that this phase is impurified. The liquid crystal 8CB is found to be less miscible than 5CB with the polymer matrices, so the LC-rich phase for 5CB is more impurified and its total volume in the material is smaller.     

Ising wall instability in a nematic liquid crystal

A new instability for a splay-bend Ising wall was found in a 5CB nematic liquid crystal layer. This instability, which occurs in the presence of an external horizontal magnetic field, is driven by the elastic anisotropy of the liquid crystal material. Depending on the homogeneity of the magnetic field, the unstable straight interface evolves towards a new steady state or undergoes a spinodal decomposition into facets. Energy arguments are given in order to explain these physical phenomena.