A versatile copper-induced synthesis of fluorinated oligo(para-phenylenes)

Ullmann-like reductive coupling of 1,4-diiodo-2,3,5,6-tetrafluorobenzene, promoted by copper(I) thiophene-2-carboxylate in N-methylpyrrolidinone at room temperature, followed by treatment with lithium aluminum hydride in THF, allowed us to obtain fluorinated poly(para-phenylene) oligomers containing up to five aromatic rings with hydrogen atoms as terminal groups. (C) 1998 Elsevier Science Ltd. All rights reserved

Synthesis of conjugated polymers by coupling between arenediazonium tetrafluoroborates and vinyl silanes

A new and general methodology for the synthesis of conjugated polymers presenting a variety of structural features is described. The methodology is based upon the palladium-catalyzed coupling reaction of a bis(1-trimethylsilylethenyl)benzene with arenebisdiazonium tetrafluoroborates. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2002)

A synthetic strategy leading to monodisperse PPV oligomers by coupling reactions of vinyltrimethylsilanes

A novel strategy for the synthesis of well-defined oligo(phenylenevinylene)s was developed. The procedure is entirely based upon two coupling processes, both involving vinyltrimethylsilanes. Bis-(styryl)benzenes 2a-g bearing two octyloxy groups in the central aromatic ring and various substituents on the external aromatic rings were prepared in good yield by a regio- and stereoselective coupling reaction of 1 with different arenediazonium tetrafluoroborates. Oligomers with a more extended conjugated system, 4a-c, and with m-phenylene subunits 13a,b, were also readily obtained by conversion of the unsaturated trimethylsilyl derivatives 3a,c,d to the corresponding boron derivatives and a subsequent coupling reaction with compounds 2a and 2c

Synthesis, characterization and properties of a soluble polymer with a poly(phenylenevinylene) structure

Soluble poly(2,5-dialkoxy-1,4-phenylenevinylene) has been prepared via Stille coupling reaction between 2,5-dialkoxy-1,4-diiodobenzene and E-1,2-bis(tributylstannyl)ethene in the presence of palladium complexes. Characterization of this material by means of H-1 and C-13 nuclear magnetic resonance (NMR), ultraviolet/visible (UV/VIS) and infrared (IR) spectra is described. Molecular weights, determined by means of gel-permeation chromatography (GPC) analysis and referred to standard polystyrene, were in the range number-average molecular weights <(M)over bar (n)> = 2061-2544 and weight-average molecular weights <(M)over bar (w)> = 3347-3878. X-ray diffraction (XRD) analysis of the polymer showed semicrystalline structure. T-g = 57 degrees C, transition to a stable smectic mesophase at 115 degrees C and clearing point at 210 degrees C were revealed by differential scanning calorimetry analysis, optical microscopy observation and XRD of the annealed polymer

Chiroptical Properties of Glucose-Substituted Poly(p-phenyleneethynylene)s in Solution and Aggregate State

The aggregation behavior of two D-glucose-substituted phenyleneethynylenes, an alternate copolymer (AP) and a homooligomer (HO), has been investigated by means of UV-vis absorption, circular dichroism (CD) and fluorescence spectroscopy. CD reveals superior capability to detect the early stages of aggregation and to provide information about aggregate geometries. The multiband CD spectrum of the AP and of analogous chiral PPEs is rationalized on the basis of the exciton coupling between vibronic transitions localized on proximate portions of the chromophoric chains

Silicon-substitued PPV for LED preparation

The photoluminescence and electroluminescence of a novel kind of soluble poly(phenylenevinylene) containing silyloxy groups (PPV-OSi) have been studied PL is not detectable in the solid state for the pure material while is present in solution and in thin film of blend with polystyrene and polymethylmethacrilate. Electroluminescence was found only in the case of LEDs formed with blends

Investigation of luminescence in new blue-emitting poly(2 ',5 '-dioctyloxy-4,4 ',4 ''-terphenylenevinylene)s

The dependence of the linear optical properties of some soluble poly (terphenylenevinylene)s on the relative amount of cis- and trans-vinylene units has been investigated. A regular blue-shift of the absorption spectra in solution has been observed upon the addition of cis double bonds. Luminescence spectra show a vibronic structure which accounts for the reduced inter-ring torsion in the excited state with respect to the ground state. Moreover, an increased electron-phonon coupling for cis-rich polymers has been observed. (C) 2003 Elsevier Science B.V. All rights reserved

A phosphorescent iridium complex as a probe for diatom cells' viability

Diatoms are unicellular photosynthetic algae that autonomously fabricate a porous organized biosilica shell refined in billion years of evolution. They represent an inexhaustible source of low cost, biocompatible mesoporous silica. Despite the major advances in the genomic field, studies on diatom cell biology are still hampered by a lack of cellular tools. In particular, cell staining assays of diatoms viability are still limited or not well performant. Here we provide a phosphorescent organometallic iridium complex (Ir-Fcx) suitable to act as staining agent to detect diatoms viability

Nanostructuring poly-[2-methoxy-5-(2 '-ethyl-hexiloxy)-p-phenylenevinylene] thin films by high-temperature soft lithography

Sub micron patterning of the conjugated polymer, poly-[2-methoxy-5-(2'-ethyl-hexiloxy)-p-phenylenevinylene] (MEH-PPV) has been achieved by high-temperature soft lithography. The process has been carried out by placing a spin-coated polymer film in conformal contact with elastomeric replicas of master structures fabricated by electron beam lithography. The system is then heated to decrease the polymer viscosity, allowing the pattern transfer with resolution down to 300 nm. The well-preserved photoluminescence spectrum and efficiency of the emissive polymer clearly indicate that high-temperature soft lithography can be successfully applied for the one-step realization of organic-based devices. (C) 2003 Elsevier B.V. All rights reserved

Deposition and application in gas sensors of thin films of a bridged chain dialkoxy PPV derivative

Films of a dialkoxy poly(p-phenylenevinylene) (PPV) derivative bearing a bridged chain dialkoxy substituent on the aromatic rings (Bridged Dialkoxy PPV: BDA-PPV) were prepared via solvent casting and Langmuir-Blodgett (LB) techniques for applications in gas sensing devices. A description of the LB deposition of the sensing layers starting from an equimolar mixture of the polymer and arachidic acid is reported. Silicon substrates equipped with gold interdigitated electrodes have been used for both deposition procedures. In particular, the samples deposited by solvent casting evidence variation of the electrical conductivity when exposed to NO2 oxidising agent at a working temperature of about 75 degreesC. They also exhibit selectivity towards NO2 with respect to other different gases like carbon monoxide, nitrogen monoxide, ammonia and sulphur dioxide. On the contrary, LB multilayers, containing arachidic acid, have not shown any sensitivity towards all analysed gases. (C) 2002 Elsevier Science B.V. All rights reserved