CyanobenzeneTTF-type donors; synthesis and characterization

Two cyanobenzeneTTF-type electron donors, which are also dithiolene ligand precursors, cyanobenzenedicyanoethylthiotetrathiafulvalene, (cbdc-TTF) and dicyanobenzenedicyanoethylthiotetrathiafulvalene, (dcbdc-TTF), were obtained through cross-coupling reactions with triethyl phosphite between 4,5-bis(2-cyanoethylthio)-1,3-dithiole-2-one and 4,cyanobenzene-1,3-dithiole-2-thione or dicyanobenzene-1,3-dithiole-2-thione, respectively. These reactions also yield 2,3,6,7-tetrakis(2-cyanoethylthio)-TTF and the corresponding symmetric cyanobenzene TTF derivatives dicyanodibenzenetetrathiafulvalene (dcdb-TTF) and tetracyanodibenzotetrathiafulvalene (TCN-DBTTF) resulting from the self-coupling reactions of the ketone and the thiones. Compound dcdb-TTF was also synthesized by homo-coupling reaction of the cyanobenzene-1,3-dithiole-2-ketone with triethyl phosphite. These compounds were characterized namely by single crystal X-ray diffraction and cyclic voltammetry.     

Photocyclization of norbornadienes fused with quinone units

On irradiation with visible light, norbornadienes fused with naphthoquinone units (1) isomerized to the corresponding quadricyclanes (2) quantitatively. Methyl or methoxy substituents in the quinone unit do not affect the quantum yields (Φ∼0.2) for the isomerization, but increase the absorbance in the visible region. The photoproducts 2 undergo easy one-electron oxidation and reduction.     

Efficient regioselective heterocyclisation leading to fluorescent fused pyrazine derivatives

The regioselective syntheses of substituted pyrrolo[2,3-b]quinoxaline, pyrido[2,3-b]pyrrolo[2,3-e]pyrazine, pyrido[2,3-b]pyrrolo[3,2-e]pyrazine and pyrido[3,4-b]pyrrolo[3,2-e]pyrazine are reported. Differential reactivity between two amino groups in ortho-diaminopyridine can be exploited to obtain new regio-defined unsymmetrical pyridopyrrolopyrazine derivatives. Weak electron-donating methyl or moderately electron-withdrawing carboxylic groups attached to the aromatic ortho-diamines reduce the regioselectivity of obtaining unsymmetrical substituted pyrrolo[2,3-b]quinoxaline. The fluorescence properties of the resultant 1-alkyl pyridopyrrolopyrazine and substituted pyrrolo[2,3-b]quinoxaline derivatives are presented.     

Polyfluorenes containing pyrazine units:Synthesis,photophysics and electroluminescence

A series of conjugated copolymers of 9,9-dioctylfluorene and symmetrical pyrazine unit (BY) were synthesized by Suzuki copolymerization and were used as novel light-emitting materials in PLEDs.Efficient energy transfer was observed in both thin film and solution.Compared with the lowest occupied molecular orbital (LUMO) energy level of the polyfluorenes homopolymer (PFO),the lower LUMO energy levels of copolymers indicated that the introduction of the BY unit would be benefit to electron injection.The turn-...     

The synthesis and characterization of novel non-symmetric dimers with rod-like and disc-like mesogenic units

Theory predicts that a compound whose structure possesses both rod-like and disc-like characteristics should exhibit a biaxial nematic phase. With this in mind we have synthesized and characterized two new series of non-symmetric dimers containing rod-like and disc-like mesogenic units linked by a flexible spacer. The two series differ in that in one the perimeter of the disc-like unit is decorated with alkyl chains, whereas for the other it is not. The liquid crystalline properties of the two series were investigated both as pure systems and in their equimolar binary mixtures with an electron acceptor. The nematic phase formed by the equimolar binary mixtures is monotropic. However, a small entropy change at the nematic-isotropic transition could be determined. The nature and structure of the monotropic nematic phase is discussed.     

Synthesis and characterization of TTF-type precursors for the construction of conducting and magnetic molecular materials

New TTF precursors for the construction of conducting and magnetic materials have been synthesized by using the palladium-catalyzed cross-coupling reaction between a mono- or a bis(trialkylstannyl)tetrathiafulvalene and a series of heteroaryl halides. The redox potential and some crystallographic data of these new building blocks are presented and discussed.     

Shape-persistant macrocycles with terpyridine units: synthesis,characterization, and structure in the crystal

The synthesis of a variety of shape-persistent macrocycles with either one (1a-d, 2) or two (opposing) terpyridine units (3, 4, 5a-c) and inner diameters of up to 2 nm is described. The sequences are mainly based on transition metal cross-coupling reactions and, whenever appropriate, compared with one another regarding their respective efficiency. Typical overall yields and amounts prepared range from 8% (4) to 27% (3) and 25 mg (1a) to 290 mg (1b), respectively. For solubility and processing of the targeted cycles, all precursors have already been decorated with flexible side chains (hexyloxy or hexyloxymethyl). The cycles' characterization is based on MALDI-TOF mass spectrometry, 2D NMR spectroscopy, and/or low-temperature single-crystal X-ray diffraction. Their packing in the crystal is discussed in terms of both number and length of side chains. Cycle 1d was physisorbed into an ordered structure at the solution-HOPG interface and investigated by scanning tunneling microscopy (STM).     

Preparation and optical and electrochemical properties of octaethylphthalocyanines fused with several tetrathiafulvalene units

3,6‐Diethylphthalonitrile ( 3 ) with a tetrathiafulvalene (TTF) unit at 4,5‐positions was prepared from 4,5‐xylylenedithio‐3,6‐diethylphthalonitrile ( 1a ) via elimination of the xylylene group, connection of a carbonyl group to benzenedithiolate generated, and condensation of 4,5‐bis(methylthio)‐1,3‐dithiole‐2‐thione with benzo‐1,3‐dithiole‐2‐one ( 2‐O ) produced. A 1:1 mixture of phthalonitrile ( 3 ) and 4,5‐bis(benzylthio)‐3,6‐diethylphthalonitrile ( 1b ) was treated with lithium in n‐hexanol at 120°C to produce hexakis (benzylthio)mono(tetrathiafulvaleno)phthalocyanine ( 5 ), tetrakis(benzylthio)bis(tetrathiafulvaleno)phthalocyanine ( 6 ), and bis(benzylthio)tris(tetrathiafulvaleno)phthalocyanine ( 7 ). The structures of 5 , 6 , and 7 were determined by ¹H NMR, FAB MS, MALDI‐TOF MS (matrix assisted laser desorption ionization time‐of‐flight mass spectrometry), and UV‐‐vis spectroscopy. Compound 6 is a mixture of trans and cis isomers ( 6‐ trans and 6‐ cis ). The UV‐‐vis spectrum of 5 measured in chloroform changed by addition of trifluoroacetic acid (TFA). The Q band absorption at λ_max = 755 nm (chloroform) decreased in intensity and resulted in a new absorption at λ_max = 740 nm (chloroform/TFA). The electrochemical properties of 5 , 6 , and 7 were determined by cyclic voltammetry using Ag/AgNO₃ as a reference electrode. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:605–611, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20694     

Synthesis,structure and in vitro biological evaluation of new lupane and dammarane triterpenoids fused with pyrazine heterocycle

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Hydrothermal synthesis and characterization of two cobalt phosphates based on double-four-ring units with fluorine-occlusion and phosphite-substitution modifications

Two new fluorinated microporous cobalt phosphates, (H2en)0.5[F(0.25)Co(H(0.5)PO4)0.5(PO4)0.5].0.25H2O (1) and (H2en)0.5[Fx(H2O)0.25(-x)Co(HPO3)x(PO4)1-x].0.25H2O (x = 0.17; 2), have been synthesized from different P sources, H3PO4 and H3PO3, in the presence of ethylenediamine and F ions. Both structures of 1 and 2 are based on the similar secondary building unit of a double four ring (D4R). 1 crystallizes in the orthorhombic space group Cmcm with a = 14.895(1) A, b = 9.7133(9) A, c = 13.688(1) A, V = 1980.4(3) A(3), and Z = 16 and is built up from fully F-occluded double-four-ring units via corner-sharing Co and P polyhedra and edge-sharing Co polyhedra. 2 crystallizes in the tetragonal space group /42m with a = 10.2033(4) A, c = 9.5545(9) A, V = 994.7(1) A(3), and Z = 8 and adopts an ACO-type framework with strict alternation of corner-sharing Co and P polyhedra. On the basis of the evidence from ion chromatography studies and elemental analyses, 2 contains both phosphate and phosphite ions, and the amount of F ions in 2 is the same as the amount of phosphite ions. This implies that some PO4(3-) groups in 2 are substituted by HPO3(2-) groups with the same amount of F(-) occlusion in the center of D4R as charge compensation. Magnetic susceptibility measurements of both 1 and 2 appear that they contain mainly antiferromagnetic interaction (theta = -27.8 K for 1 and -35.0 K for 2). However, the magnetic coupling is much more complicated in compound 1 because of the Co-O-Co linkages in it. Low-field temperature-dependent magnetization curves of 1 showed spontaneous magnetization in the form of two continuous bumps, one sharp and one broad. This may be related to the temperature dependence of two related but different types of spin canting. At 2 K, 1 also showed a large coercive field of about 5000 Oe.     

Push-pull structures with a pyrazine core and hexatriene chain: synthesis and light-emitting properties

In this paper, we describe the synthesis of various push-pull molecules with a central pyrazine unit connected to a hexatriene chain terminated by various p-substituted phenyl groups. The key steps involve metallation and subsequent transmetallation of 2-chloro and 2,6-dichloropyrazine followed by a Negishi cross-coupling reaction of the intermediate organozinc derivative with (2E,4E)-5-bromopentadienal. The aldehydes are then submitted to a Wittig reaction with the appropriate phosphonium salts readily obtained from various substituted benzyl alcohols. The light-emitting properties of the so obtained molecules are then investigated in terms of absorption and emission spectra and non-linear optics experiments have been carried out in two cases.     

A selective colorimetric and fluorometric ammonium ion sensor based on the H-aggregation of an aza-BODIPY with fused pyrazine rings

The synthesis of a novel aza-BODIPY dye functionalized with fused pyrazine rings, suitable for use as a selective colorimetric and fluorometric sensor for NH(4)(+), is outlined. In addition to significant fluorescence quenching, an obvious colorimetric change from green to red-pink is observed enabling facile "naked-eye" detection of NH(4)(+).     

Selective synthesis of fused cyclooctatetraenes by [4 + 4] coupling between two different diene units

In the presence of CuCl and 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, the [4 + 4] coupling between zirconacyclopentadienes and 1,3-diiodobutadienes fused through an oxygen or nitrogen five-membered ring proceeded at ambient temperature to afford fully substituted polycyclic cyclo-octatetraenes in good yields. The fused ring moiety of the diiodides plays a critical role. The corresponding acyclic diiodide and a cyclohexane-fused analogue gave no coupling product, and a cyclopentane derivative showed only moderate reactivity. Correlation of the structures of the diiodides and their reactivity was established by an X-ray and density functional study.     

Cyclic and linear liquid crystalline functionalized polyesters with main-chain ortho-linked units. synthesis and characterization of cyclic lc unimers and dimers with “u”-shaped rigid mesogenic units with alkyl side chains

Although ortho-diphenols had not been extensively used in the synthesis of LC esters, a great variety of molecular structures of low and high molecular weight LC esters containing high proportions of these units can be synthesized. In this paper we describe the synthesis and characterization of new series of low and high molecular weight cyclic and linear LC esters with mesogenic “U”-shaped rigid units with terminal groups which are alkyl chains. Cyclic oligoesters and linear polyesters were formed by the polycondensation of 4,4'-[1,10-decamethylenebis(oxy)]bis(cinnamic acid) with monosubstituted catechols which are the alkyl esters of 3,4-dihydroxybenzoic acid. Although the great importance that concomitant cyclization reactions have in polyesterifications involving high proportions of ortho-diphenols does not seem to have been considered until now, we have found mat these polyesterifications produced linear polyesters along with high proportions of cyclic oligoesters even when reaction conditions disfavored cyclization. Copolymerization with p-hydroxybenzoic acid decreased the amount of cyclic oligomers, however it was necessary to copolymerize with proportions of PB higher than 50 mol-% to get copolyesters with low proportions of cyclic oligomers. As far as we know we describe the first examples of cyclic LC oligoesters and cyclic LC unimers and dimers which display enantiotropic LC mesophases stable over broad ranges of temperature. Cyclic dimers display mesophases whose isotropization temperatures ( > 300°C) are much higher than that of their linear high molecular mass homologues. Cyclic LC unimers and dimers, linear LC polyesters and model compounds were characterized by FAB-MS, GPC, ¹H NMR, DSC and hot-stage polarized microscopy. All these compounds contain reactive C=C double bonds and can be crosslinked thermally and photochemically. Cyclic unimers and dimers can be polymerized termally to produce high molecular mass polymers.     

Design and synthesis of fused cyclic sulfamides-oxazolidinones

An efficient protocol for the synthesis of a new series of oxazolidin-2-ones containing sulfamide moieties is described. The synthesis was achieved in two reaction steps. The first was carried out under anhydrous conditions at 0?°C through a selective addition of an alcohol and primary amines to chlorosulfonylisocyanate to produce N-carboxylsulfamides in good yields. Under appropriate conditions of solvent, base and temperature, these intermediates underwent subsequent intramolecular cyclizations, giving exclusively the corresponding sulfamoyloxazolidinones.     

Subphthalocyanine fused dimers-C60 dyads: synthesis, characterization, and theoretical study

A donor-acceptor covalently linked dyad consisting of a subphthalocyanine fused dimer unit doubly-connected to a [60]fullerene has been prepared through double cycloaddition of the fused dimer, previously functionalized with aldehyde groups in the axial positions, to the fullerene (1,3-dipolar cycloaddition of azomethine ylides). The compound, isolated in several fractions, has been characterized and studied employing photophysical and electrochemical techniques. Molecular modeling of the distinct possible isomers was carried out using semiempirical methods.