Phenylenevinylene Units Research Articles

Rapid Methods of Synthesis of Stilbene and Phenylethynylstilbene Arms

Stilbene and phenylethynylstilbene units are excellent candidates for fluorescent sensor synthesis. In this paper we show a fast and efficient method for the preparation of fluorophores based on biphenyl nuclei with phenylene-vinylene units functionalized by donor groups. Using pallado catalysed coupling reactions of Sonogashira types and Wittig or Wittig-Horner reaction, the stilbene and phenylethylsilbene arms functionalized with O-alkyl and N-alkyl donor groups were synthesized.

Novel benzimidazole-based conjugated polyelectrolytes: synthesis, solution photophysics and fluorescent sensing of metal ions

Abstract Two benzimidazole-based conjugated polyelectrolytes (+)-PPBIPV and (-)-PPBIPV which have opposite charges on their side chains were synthesized via Heck coupling reaction and characterized by 1H-NMR, UV-vis and PL spectroscopy. These two polyelectrolytes are both consisted of benzimidazole derivatives and phenylenevinylene units. The absorption and emission spectra reveal that the polymers both have solvent-dependency and concentration-dependency, and they exhibit aggregation effect in aqueous solution. In the respect of ion detection, the aqueous solution of (+)-PPBIPV has excellent selectivity and sensitivity for Fe3+. Moreover, Pd2+ can almost completely quench the fluorescence of (+)-PPBIPV in methanol solution, and its quenching constant K SV is 5.93×104 M-1. For (-)-PPBIPV, Sn2+ can double the fluorescence intensity of its aqueous solution, while (-)-PPBIPV has good identification for Fe3+ in methanol with a K SV = 3.44×105 M-1. Hence, two polyelectrolytes have considerable potential to become effective fluorescent sensing materials for some specific metal ions. All of the stoichiometric relationships between metal ions and conjugated polyelectrolytes were calculated using Benesi-Hildebrand equation.

Toward rational design of metal-free organic dyes based on indolo[3,2-b]indole structure for dye-sensitized solar cells

Three organic dyes containing a nitrogen-bridged phenylenevinylene (NPV: indolo[3,2-b]indole) unit were synthesized and applied in dye-sensitized solar cells, where NPV was employed as a donor itself or as a π-spacer with the extra-donor diphenylamine. The photophysical, electrochemical and photovoltaic properties of the dyes were investigated. All dyes displayed broad absorption spectra and high molar extinction coefficient, resulting in high light harvesting efficiency. The results showed that the dye with two cyanoacrylic acid as the acceptors exhibited photovoltaic performance of 7.39% under standard global AM 1.5 solar condition, better than the other two with only one acceptor. These results indicate that the NPV-based organic dye is a promising candidate for efficient DSSCs.

Synthesis, characterization, and properties of new 3‐hexyl‐2,5‐diphenylthiophene: Phenylene vinylenes copolymers as colorimetric sensor for iodide anion

ABSTRACTFour new conjugated copolymers P1‐P4 have been prepared by the Horner‐Emmons and Knoevenagel polymerization reactions. P1‐P4 were characterized by NMR, FTIR, cyclic voltammetry (CV), diffuse reflectance UV–vis spectroscopy (DR UV–vis), and thermal gravimetric analysis (TGA). The optical band gaps of these polymers, calculated from the onset absorption edge, were found between 2.15 and 2.34 eV. The band gaps calculated by CV were ranged between 1.94 and 2.57 eV. The presence of nitrile moiety on the phenylene vinylene unit is believed to influence the optical properties of these polymers, i.e., P3 and P4 have shown lower band gaps than P1 and P2. All polymers possess good iodide anion sensing property over a wide range of other anions (F−, Cl−, Br−, , CN−), indicating their promise in fabricating selective iodide sensors. The initial colorless solution of polymers in THF changed to deep yellow upon the addition of aqueous solution of iodide salts along with significant changes in the UV–vis spectra of the polymers. The limit of detection (LOD) for P1‐P4 were found between 0.43 and 2.54 mM. These polymers constitute long alkoxy and alkyl side chains, bearing excellent solubility in most common organic solvents which warrants their suitability for photovoltaic devices application. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44948.

Density Functional Study of Stacking Structures and Electronic Behaviors of AnE-PV Copolymer.

In this work, we report an in-depth investigation on the π-stacking and interdigitating structures of poly(p-anthracene-ethynylene)-alt-poly(p-phenylene-vinylene) copolymer with octyl and ethyl-hexyl side chains and the resulting electronic band structures using density functional theory calculations. We found that in the π-stacking direction, the preferred stacking structure, determined by the steric effect of the branched ethyl-hexyl side chains, is featured by the anthracene-ethynylene units stacking on the phenylene-vinylene units of the neighboring chains and vice versa. This stacking structure, combined with the interdigitating structure where the branched side chains of the laterally neighboring chains are isolated, defines the energetically favorable structure of the ordered copolymer phase, which provides a good compromise between light absorption and charge-carrier transport.

Cationic Main‐Chain Polyelectrolytes with Pyridinium‐Based p‐Phenylenevinylene Units and Their Aggregation‐Induced Gelation

Cationic polyelectrolytes find potential applications in electronic device fabrication, biosensing as well as in biological fields. Herein, a series of cationic main‐chain polyelectrolytes with pyridinium‐based p‐phenylenevinylene units that are connected via alkylene spacers of varying lengths are synthesized by a base‐catalyzed aldol‐type coupling reaction. Their mean average molecular weights range from 15 000 to 32 000 g mol‐1, corresponding to about 16–33 repeat units. Due to the presence of alkyl side‐chains and alkylene spacers as well as cationic hard‐charges the polymers are endowed with amphiphilic character and hence, aggregation of these polyelectrolytes at high concentration leads to thermoreversible physical gel formation in dimethyl sulfoxide accompanied by interchain interactions. Morphological analysis shows spherical aggregates in case of C16‐Poly‐S12 in dimethyl sulfoxide. Dependence of gelation behavior on the length of alkyl side‐chains and alkylene spacers of the polyelectrolytes are addressed. image

The effect of cross-linking yield of PVK on the vibrational and emissive properties of new copolymer based on vinylcarbazole and phenylene-vinylene units

The Phenylene-Vinylene (PV) unit’s was successfully incorporated in the Vinylarbazole (VC) skeleton using the oxidative way via an anhydrous FeCl3. Dramatic changes in the vibrational and emissive properties are founded by varying the FeCl3 amount in the synthesis way due to the cross-linking of PVK units. SEM analysis showing a modified morphology structures of three compounds. However the percentage of the oxidant account induces the modulation of copolymer properties particularly theirs emissive proprieties. A red shifting of the maximum of photoluminescence, a quenching of luminescence and a fast decay time was observed with increasing of the oxidation yields.

Synthesis and characterization of alternating copolymers containing bipyridine and phenylene vinylene for fluorescent chemosensors

ABSTRACTAlternating copolymers containing bipyridine and phenylene vinylene were synthesized through a Wittig condensation reaction of their corresponding diphosphonium salts and dialdehydes. The molecular weights of the resulting polymers were relatively low because of the low solubility in the reaction solvents. The optical properties of the polymers were substantially affected by the repeating units of phenylene vinylene. The absorption spectra of the copolymers in the solid state exhibited a bathochromic shift compared to those carried out in solution. The effective conjugation length could be extended with the addition of Cu2+, Ni2+, and Zn2+ ions into the polymer solutions in a 1 : 1 ratio of the bipyridine to the phenylene vinylene units. All of the polymer solutions behaved as a turn‐off fluorescent chemosensor upon the addition of a variety of the metal ions. The sensing behavior to various metal ions revealed that the polymers were highly sensitive to the Cu2+, Ni2+, and Zn2+ ions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42795.

Conjugated donor–acceptor copolymers derived from phenylenevinylene and trisubstituted pyridine units

Copolymers having intramolecular donor–acceptor systems encompassing trisubstituted pyridine derivatives as acceptor and phenylenevinylene (PPV) unit as a donor segment were synthesized. In addition, thiophene-containing random terpolymer PPVPYT via palladium-catalyzing Heck coupling reaction is reported. The novel-substituted pyridine monomers (PYBr) are synthesized by adopting a one-pot synthesis method using p-toluenesulfonic acid as catalyst in ethanol medium, which results in an excellent yield of about 95%. All the copolymers Poly phenylenevinylene-co-Pyridine derivatives (PPVPY) and terpolymers of Polyphenylenevinylene-co-Pyridine and Thiophene (PPVPYT) are found to be soluble in organic solvents, such as tetrahydrofuran, chloroform, and N, N-dimethylformamide. The molecular weights of the synthesized polymers were characterized by gel permeation chromatography (GPC), and their chemical structures were confirmed by infra red and nuclear magnetic resonance spectroscopies. The electrochemical band gaps of PPVPY-1, PPVPY-2, and PPVPY-3 copolymers are estimated to be 2.55, 2.48, and 2.0, respectively. Similarly, the band gap of PPVPY75T25, PPVPY50T50, and PPVPY25T75 random copolymers are estimated as 2.31, 1.95, and 2.23, respectively. These polymers also show excellent optical and thermal properties.

Layer-Block Dendrimers with Alternating Thienylenevinylene and Phenylenevinylene Units

A series of new hybrid, layer-block π-conjugated dendrons and dendrimers with alternating thienylenevinylene and phenylenevinylene units has been prepared by means of an orthogonal and convergent-growth methodology that made use of the Horner-Wadsworth-Emmons (HWE) reaction. The placement of the thiophene and benzene rings can be accurately controlled to afford a large variety of dendritic structures, although access to compounds of high generation proved difficult. The optical properties of the synthesized dendrimers were determined by UV/vis and fluorescence spectroscopy, and the influence of the generation and nature of the core on the behavior of these materials was evaluated.

Structure–properties correlation of copolymers derived from poly(phenylene vinylene) (PPV)

Bond lengths and Mullikan charges distribution as well as optoelectronic properties including electronic structure and simulated optical and emission spectra on ground and excited states of modified PPV containing a random repetition of PV and ether's units, model structure, are examined by the use of density functional theory (DFT). Accordingly, the effect of ether inserting on the phenylene vinylene units at single or both sides and those of terminal groups are carried out. Findings are correlated with time transient photoluminescence decays (TR-PL) of standard PPV structure. Then, introduction of ether's segment on PPV backbone induces exciton confinement ant trapping process.

Synthesis and double doping behavior of a poly(p-phenylenevinylene)s bearing conjugated side chains

A poly(p-phenylenevinylene) derivative bearing conjugated side chains (polyCPV) was synthesized by Migita-Kosugi-Stille type coupling polycondensation reaction. This polymer contains phenylenevinylene units in both the main chain and the side chains. UV–vis absorption and fluorescence emission spectroscopies revealed a well-developed π-conjugation of the polyCPV. The absorption band of the polymer was extended to long wavelengths. A fluorescent emission maximum of polyCPV is located at considerably longer wavelengths than that of the conjugated side chain monomer. Electron spin resonance measurements of polyCPV confirmed generation of charge species in both the main chain and the side chains via iodine doping. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Density functional theory studies of new bipolar carbazole–benzothiazole: Electronic and vibrational properties

An intramolecular donor–acceptor compound containing carbazole as a donor group and two benzothiazole rings as electron acceptors, has been theoretically studied using the density functional theory (DFT) with the hybrid B3LYP exchange correlation function and the split valence 6-31G* basis set. The ground-state geometries’ optimization was carried out, showing a reduction in the band gap when going from the bicarbazole ((Cz)2) to the carbazole attached to benzothiazole rings in both sides (Cz–(Bzt)2). Structural parameters, electronic and vibrational properties have been analyzed and discussed in terms of conjugative pathway between the electron-donating and electron-accepting moieties. It is predicted that benzothiazole systems exhibit large optical responses based on intramolecular charge transfer (CT) process. Optical properties may be altered by changing the compound’s molecular structure by a series of π-bridges, such as ethylene (eth) and phenylene-vinylene (PV) units. These modifications lead to obtain a resulting compound having better optoelectronic properties, through the redistribution of its HOMO and LUMO energy levels. On the other hand and in order to check the real properties of the resulting compound, calculations have also been performed for all compounds in solvated media (chloroform). The obtained results reveal a significant influence of solvation on optical properties, due to the change of the spectral response caused by the increase of ground state CT process.

Spectroscopic and electrochemical sensing of lanthanides with π-extended chromophores incorporating ferrocenes and a coordinative end

In this study, we report the synthesis and characterization of three novel "push-pull" chromophores, in which multiple phenylenevinylene units are endcapped by ferrocene as donor units and malonate moieties as acceptor units. These chromophores have spectroscopic and electrochemical characteristics which consistently change according to the extension of the conjugated bridge, thus to the variation of the HOMO-LUMO band gap. The 1,3-dicarbonyl units, directly incorporated into the conjugated molecular structures, are able to coordinate Lewis acid-like cations, such as lanthanides, as confirmed by UV/Vis, (1)H NMR and cyclic voltammetry studies. The UV/Vis spectroscopic response upon complexation with Sc(3+) or Eu(3+) as the triflate salts is rather unselective and nonlinear in going from the least to the most π-extended chromophore. Binding studies in MeCN, analyzed via equilibrium-restricted factor analysis, give values between log K(a) = 1.21 and 3.07 and affirm a 1 : 1 stoichiometry of the host:guest complexes in all cases. On the other hand, cyclic voltammetry reveals a selectivity in the response to Sc(3+) coordination over Ln(3+) (Eu(3+), but also Lu(3+) and Er(3+) were tested) for the two shorter chromophores, whereas the ligand with the longest π-bridge is able to sense Er(3+) (ΔE(1/2) complexed/uncomplexed chromophore = 20 mV) selectively over the other lanthanides.

Anisotropic carrier transport properties of highly aligned oligophenylenevinylenes in organic field-effect transistors

Organic field-effect transistors (OFETs) based on highly aligned oligo-p-phenylenevinylenes (5P4Vs) were fabricated and their anisotropic carrier transport properties were investigated to compare intermolecular charge transport via the π–π interaction of phenylenevinylene units and intramolecular charge transport via the conjugated oligomeric chains of 5P4V. The absorption spectra of the 5P4V layer, under irradiation of parallel and perpendicularly polarized light along the rubbing direction, showed that the dichroic ratio was 6.2 at the peak wavelength of 346 nm. The strong optical-absorption anisotropy indicates the production of well-aligned 5P4Vs along the rubbing direction. The field-effect mobility in a current flow perpendicular to the rubbing direction is larger by a factor of 2.7 compared to that parallel to the rubbing direction. These results indicate that the charge transport via π–π interaction of phenylenevinylene units is greater than the charge transport via conjugated oligomeric chains of 5P4V.

Synthesis of a New Water-Soluble Oligo(phenylenevinylene) Containing a Tyrosine Moiety for Tyrosinase Activity Detection

A new water-soluble oligo(phenylenevinylene) containing a tyrosine unit (OPV-Tyr) was synthesized as a fluorescent probe to optically detect tyrosinase activity. Upon the addition of tyrosinase, the tyrosine moiety was oxidized to quinone, which quenched the fluorescence of OPV-Tyr via intramolecular electron transfer from the phenylenevinylene unit to the quinone site. OPV-Tyr was elaborated to detect tyrosinase activity both in aqueous buffer solution and in agarose gel.

Molecular Engineering of Organic Sensitizers Containing p-Phenylene Vinylene Unit for Dye-Sensitized Solar Cells

Three organic sensitizers containing bis-dimethylfluorenyl amino donor and a cyanoacrylic acid acceptor bridged by p-phenylene vinylene unit were synthesized. The power conversion efficiency was quite sensitive to the length of bridged phenylene vinylene groups. A nanocrystalline TiO2 dye-sensitized solar cell was fabricated using three sensitizers. The maximum power conversion efficiency of JK-59 reached 7.02%.

Effect of 3D π−π Stacking on Photovoltaic and Electroluminescent Properties in Triphenylamine-containing Poly(p-phenylenevinylene) Derivatives

Poly(p-phenylenevinylene) (PPV) derivatives containing the 3D π−π stacking structures of the triphenylamine moieties as two side chains have been synthesized by the Wittig−Horner reaction. The presence of 2,5-bis(4-(N,N-diphenylamino)phenylenevinylene units along these π-conjugated polymer backbone lowered the band gap, and thus the resulting polymers exhibited strong and broad absorption in the visible region. Triphenylamine groups effectively extended the conjugation length through 3D π−π stacking and enhanced the hole-transporting properties of the polymers. Furthermore, the 3D π−π stacking effects of the triphenylamine moieties on the properties of the polymer light-emitting devices (PLEDs) and photovoltaic solar cells were also investigated in detail. The maximum electroluminescence (EL) brightness of the single-layer light emitting devices for P1 and P2 achieved 3003 and 1697 cd/m2, respectively. The bulk heterojunction polymer photovoltaic cells (PPVCs) based on P1 or P2 and PCBM (1:1, w/w) showed ...

Excited-State Dynamics of Polyfluorene Derivatives in Solution

The excited-state dynamics of two polyfluorene copolymers, one fully conjugated containing phenylene vinylene units alternated with 9,9'-dihexylfluorenyl groups and the other segmented by -(CH2)8- spacer, were studied in dilute solution of different solvents using a picosecond single-photon timing technique. The excited-state dynamics of the segmented copolymer follows the Förster resonant energy-transfer model which describes intrachain energy-transfer kinetics among random oriented chromophores. Energy transfer is confirmed by analysis of fluorescence anisotropy relaxation with the measurement of a short decay component of about 60 ps. The fluorescence decay surface of the fully conjugated copolymer is biexponential with decay times of about 470 and 900 ps, ascribed to deactivation of chain moieties containing trans and cis isomers already in a photostationary condition. Thus, energy transfer is very fast due to the conjugated nature and rigid-rod-like structure of this copolymer chain.

Heterocyclic polycatenar liquid crystals

We report the synthesis of polycatenar liquid crystals incorporating 2,5‐disubstituted 134‐oxadiazole and 134‐thiadiazole rings joined by a combination of carbon–carbon single and double bonds (–CH = CH–). The ratio of the aromatic core to the aliphatic chains was varied systematically by changing the number of the aliphatic chains, from two to six, and their length, from short to very long, i.e. from methoxy to hexadecyloxy. The shape anisotropy of the core was varied by exchanging the oxygen atom in the 134‐oxadiazole for a sulfur atom to form the corresponding 134‐thiadiazole ring with a smaller deviation from coaxiality of the bonds in the 2,5‐positions. The shape anisotropy of the core was increased by the presence of an additional phenylenevinylene unit in a series of tetracatenar oxadiazoles. We report the synthesis, physical properties and polymerization of a polycatenar reactive mesogen in a columnar phase to form a polycatenar polymer network.