Multifunctional Chromophores Research Articles

Photoresponsive conductive polymer network based on azobenzene bridging crosslinked polycarbazole for boosting solar thermal storage

Azobenzene is one of the most extensively researched multifunctional chromophores and azobenzene including materials has a wide variety of applications due to their photoisomerization behavior. In this study, electroactive and light-harvesting carbazole and photoresponsive azobenzene units have been combined with a special macromolecular design. In this design the azo groups can be effectively isomerized in solid state, and free-standing films can be obtained by the electrochemical method. Thermal characterizations of both monomer and polymer have been performed and isomerization kinetics and solar-thermal properties have been investigated. The half-life at 60 °C and the gravimetric energy storage density of polymer was calculated as 103 min and 179.9 j g−1, respectively. Cross-linked polycarbazole structure causes dramatically increased solar thermal storage and half-life compared to respective monomer and brought unexpected mechanical and solvatochromic properties.

Smart design of highly luminescent octupolar mesogenic tetra styryl-alkynyl bipyrimidine-based chromophores presenting non-linear optical properties

The research investigations reported in this paper focuses on the influence of rational design on the photophysical properties of new all-organic multifunctional chromophores. Nonlinear optical (NLO) behavior, optical properties and mesogenicity of several new π-conjugated octupolar chromophores, presenting alkoxy styryl-alkynyl donor groups carrying aliphatic achiral and chiral chains in the 3,4/3,5/2,4 position, connected to electron-accepting 2,2-bipyrimidine cores are investigated by various techniques (light-transmission measurements, polarized-light optical microscopy, differential scanning calorimetry measurements, two-photon excited fluorescence and Hyper Rayleigh Scattering). The mesogenic properties were investigated depending on the position of the alkoxy chain and the 3,4 derivatives were found to exhibit liquid-crystal properties with the formation columnar phases over large temperature ranges which were confirmed by small-angle X-ray scattering analysis. All the molecules exhibit exceptional high fluorescence quantum yields values around 80 % and excellent nonlinear optical properties.

Meso-borneol- and meso-carbazole-substituted porphyrins: multifunctional chromophores with tunable electronic structures and antitumor activities

Herein, a series of five C2 symmetric H2porphyrins with meso-borneol and meso-carbazole units have been synthesized and isolated. Their electronic structures, photophysical properties and anticancer activity were investigated.

Structure and luminescence investigations on the chromophore intercalated layered rare-earth hydroxides hybrids

Abstract Niflumic acid (NFC) and surfactant 1-octane sulfonic acid sodium (OS) are intercalated into the gallery of NO3 type layered europium hydroxide (NO3–LEuH) by ion-exchange method. The prepared products display XRD patterns with series of diffractions attributing to layered materials. The composites correspond to a bilayered vertical arrangement. The thermal stability of the composites are enhanced after intercalation. Tunable luminescence of the composites is realized through the synergistic effect of layered europium hydroxide (LEuH) layer and NFC with different states and different excitation wavelength. Facile one-pot delamination of the composites achieves when dispersed in formamide (FM), which contributes to a white emission. This work may be beneficial to the fabrication of multifunctional chromophore intercalated layered rare-earth hydroxides (LRHs) hybrids, which may have wide applications in white emission materials.

Library of Azabenz-Annulated Core-Extended Perylene Derivatives with Diverse Substitution Patterns and Tunable Electronic and Optical Properties.

Here, we present a collection of different azabenz-annulated perylene derivatives. By developing new synthetic strategies and improving existing protocols, we have expanded the structural diversity of these dye molecules to a multifunctional class of ligating chromophores. The Pictet-Spengler (PS) reaction of 1-amino-perylenes with different aldehydes is used to modify the terminal substitution pattern. PS transformations of 1,6- and/or 1,7-diamino perylenes result in 2-fold annulated nitrogen-containing coronene-type molecules like anti-(ab)2-PBI 15, syn-(ab)2-PBI 16, and syn-(ab)2-PTE 18. In addition, azabenz-annulated perylene bisanhydrides (ab-PBA 6 and syn-(ab)2-PBA 19) were explored as universal starting materials providing access to any desired imide functionality. Furthermore, a newly developed regioselective nitration procedure for perylene monoimide diesters (PMIDE) enables the synthesis of 1-nitro-PMIDE 10 and thus of azabenz-annulated perylene derivatives with unsymmetric peri-substitution patterns (ab-PMIDE 12 and ab-PMIMA 13). According to our spectroscopic and theoretical investigations, the optical and electrochemical properties of these multifunctional chromophores can easily be modified and adjusted to many desirable applications following the synthetic strategies presented in this work.

Tuning the Dipolar Second‐Order Nonlinear Optical Properties of Cyclometalated Platinum(II) Complexes with Tridentate N^C^N Binding Ligands

Appropriate functionalization of the cyclometalated ligand, L, and the choice of the ancillary ligand, X, allows the dipolar second-order nonlinear optical response of luminescent [PtLX] complexes--in which L is an N^C^N-coordinated 1,3-di(2-pyridyl)benzene ligand and X is a monodentate halide or acetylide ligand--to be controlled. The complementary use of electric-field-induced second-harmonic (EFISH) generation and harmonic light scattering (HLS) measurements demonstrates how the quadratic hyperpolarizability of this appealing family of multifunctional chromophores, characterized by a good transparency throughout much of the visible region, is dominated by an octupolar contribution.

Light-induced charge separation in a donor–chromophore–acceptor nanocomposite poly[TPA-Ru(tpy)2]@ZnO

The synthesis and characterisation of a new donor–chromophore–acceptor system based on poly(vinyltriphenylamine) as the electron donor and a glycine-functionalised bis(2,2′;6′,2′′-terpyridine)ruthenium(II) complex acting both as a chromophore and as an anchor group attached to ZnO nanorods as the electron acceptor are described. The TPA-containing block copolymer was synthesised by Reversible Addition Fragmentation Chain Transfer (RAFT) polymerisation and the ruthenium complex glycine conjugates prepared by Solid Phase Peptide Synthesis (SPPS) were attached via post-polymerisation esterification. GPC, NMR, IR and UV-Visible spectroscopy were used to characterise the multifunctional chromophore–donor polymer. Zinc oxide nanorods were functionalised with the block copolymer by multisite adsorption via the glycine COOH groups. The functionalised nanoparticles were well dispersible in organic solvents. Photoluminescence studies showed a complete quenching of the phosphorescence of the ruthenium chromophore (3MLCT state). Kelvin probe force microscopy (KPFM) was used to confirm that under continuous excitation of the RuII complex (1MLCT) the polymer corona develops a positive charge and thus efficient charge separation between ZnO and the polymer is achieved.

Ultra-simple hybrid white organic light-emitting diodes with high efficiency and CRI trade-off: Fabrication and emission-mechanism analysis

We present a simple hybrid white organic light-emitting diodes (WOLED) consisting of only two layers, i.e., a hole-transporting layer and an emitting layer. The emitting layer is formed by simply co-doping a green phosphor and a red phosphor in bis[2-(2-hydroxyphenyl)-pyridine]beryllium (Bepp2), which acts as the blue emitter, electron-transport material, and high triplet energy host for the phosphors, i.e., a multifunctional chromophore. This simple device exhibits a maximum power and quantum efficiency of 46.8lmW−1 and 16.5%, respectively, with a good CRI up to 90. The versatile experimental techniques are performed to gain a deep understanding of the emission mechanism. We believe that this simple design concept can provide a new avenue for achieving ultrahigh performance WOLEDs for lighting application.

Photorefractive Materials, from Polymer to Hyper-Structured Molecule

A series of amorphous polyphosphazenes containing carbazole-based multifunctional chromophores and two hyper-structured photorefractive molecular glasses with a cyclotriphosphazene core were synthesized. These photorefractive polymers and molecular glasses show low glass transition temperature (20-90oC) and can easily be fabricated into optically transparent films with long-term stability. Results of two-beam-coupling and four-wave-mixing experiments demonstrated that high gain coefficient and diffraction efficiency were achieved at zero electric field for samples fabricated with these materials.

Synthesis and Properties of Polyurethanes of Hexamethylene Di-Isocyanate with Multifunctional Chromophores in the Main Chain

Various polyurethanes containing photoactive bis(azo) and bis(o-nitrobenzyl) groups in the main chain were synthesized by polyaddition reactions of diols such as bis(4-hydroxyphenylazo)-2,2′-dinitrodiphenylmethane, 4-hydroxy-3-methylphenylazo-4′-hydroxyphenylazo-2,2′-dinitrodiphenylmethane and bis(4-hydroxy-3-methylphenylazo)-2,2′-dinitrodiphenylmethane with hexamethylene di-isocyanate (HMDI), in dimethyl acetamide (DMAc) in the presence of di-n-butyltin dilaurate (DBTDL) as catalyst. All of them were characterized by IR, UV-vis, 1H NMR and 13C NMR spectra and also by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC).

Photorefractive properties of polyphosphazenes containing carbazole-based multifunctional chromophores

A series of amorphous polyphosphazenes containing carbazole-based multifunctional chromophores were synthesized. These polymers show low glass transition temperature (20–65°C) and can easily be fabricated into optically transparent films with long-term stability. As an unambiguous evidence of photorefractive effect, preliminary two-beam-coupling experiments were performed at 633nm under room temperature. All of these single-component polymers exhibited photorefractive performance without external electric field or prepoling, and gain coefficient of 91cm−1 was observed in a polymer with the lowest glass transition temperature. The influence of the alkylene spacer length between the side group and the polymer backbone on the glass transition temperature, chromophore loading, as well as the optical gain was discussed. The steady-state photorefractive performance of a polyphosphazene with the shortest alkylene spacer was enhanced significantly by adding a photoconductive plasticizer N-ethyl-carbazole to lower the glass transition temperature and a gain of 198cm−1 and a diffraction efficiency of 46% were achieved at zero electric field.

Phosphorescent Platinum(II) Complexes Derived from Multifunctional Chromophores: Synthesis, Structures, Photophysics, and Electroluminescence

The synthesis and structural, photophysical, electrochemical, and electroluminescent properties of a novel class of trifunctional Pt(II) cyclometalated complexes are reported in which the hole-transporting triarylamine, electron-transporting oxadiazole, and electroluminescent metal components are integrated into a single molecule. These neutral metal chelates display good thermal stability (>250 degrees C under N2) and morphological stability. All of them exhibit intense ligand-centered fluorescence and phosphorescence in fluid solutions at room temperature, but the emission spectra become largely dominated by triplet emission bands in CH2Cl2 glass at 77 K. Substituents with different electronic properties were introduced into the bipolar cyclometalating ligands to fine-tune the absorption and emissive characteristics of the compounds, and the results were correlated with theoretical calculations using density functional theory. A comparison of the photophysics and electrochemistry of our multifunctional systems to those only derived from each of the constituent components was also made and discussed. These Pt complexes can be vacuum-sublimed and applied as emissive dopants for the fabrication of vapor-deposited electrophosphorescent organic light-emitting devices (OLEDs), which generally exhibit good device performance with efficiencies up to 3.6%, 11.0 cd A-1, and 5.8 lm W-1. While the electroluminescence energy resembles that recorded in fluid solutions for these Pt emitters, these monochromatic OLEDs can emit tunable colors by varying the aryl ring substituents and the level of doping. Saliently, single dopant white-light electroluminescence, triggered by the simultaneous fluorescence/phosphorescence emission of the metal complexes and a variation of applied driving voltages, has also been realized based on some of these multifunctional complexes with peak electrophosphorescence efficiencies of 6.8 cd A-1 and 2.6%.

Light Emitting Devices from Transition Metal Complexes

Transition metal complexes have emerged as promising candidates for applications in solid state electroluminescent devices. These materials serve as multifunctional chromophores, into which electrons and holes can be injected, migrate and recombine to produce light emission. Their device characteristics are dominated by the presence of mobile ions that redistribute under an applied field and assist charge injection. An efficiency of 10 lm/W –among the highest efficiencies in a single layer electroluminescent device– was recently demonstrated in an iridium complex. We present recent experimental results and discuss the issues that need to be addressed for these materials to succeed in display and lighting applications.

Second-Order Nonlinear Optical Property of Polysiloxane Containing Indole-Based Multifunctional Chromophore

A new strategy to develop polysiloxane ( P2 ) with a high density of the multifunctional indole-based chromophore is presented. Thus a polysiloxane ( P1 ) with indole as side chains was first synthesized through hydrosilylation reaction, and then the post azo coupling of p-nitrobenzenediazonium fluoroborate toward the indole ring afforded a mulifunctional indole-based chromophore-functionalized polysiloxane ( P2 ). The polymers exhibit excellent solubility in common organic solvents and are thermally stable. The poled lilm of P2 reveals a resonant d 33 value of 25 pm/V by second harmonic generation ( SHG ) measurements.

Solid-state electroluminescent devices based on transition metal complexes.

Transition metal complexes have emerged as promising candidates for applications in solid-state electroluminescent devices. These materials serve as multifunctional chromophores, into which electrons and holes can be injected, migrate and recombine to produce light emission. Their device characteristics are dominated by the presence of mobile ions that redistribute under an applied field and assist charge injection. As a result, an efficiency of 10 lm/W--among the highest efficiencies reported in a single layer electroluminescent device--was recently demonstrated. In this article we review the history of electroluminescence in transition metal complexes and discuss the issues that need to be addressed for these materials to succeed in display and lighting applications.

Synthesis and Characterization of Photorefractive Polymer containing Multifunctional Chromophore

The main chain photorefractive polymer (PUA-M) having multifunctional chromophore was synthesized by the step-growth polymerization from N-hydroxyethylcarbazole-4′-[6-(hydroxysulfonyl)]-azobenzene (Azo-2OH) and 1,6-hexamethylene diisocyanate. The molecular weight of the resulting polymer was determined to be Mw=41,300 (Mw/Mn=1.19) by the gel permeation chromatography using polystyrene as a standard, and could be processed into optical quality films. The thermal properties of PUA-M were detected by DSC and TGA. It shows a glass transition temperature of 183°C and an initial decomposition temperature of 223°C. The absorption maximum in UV/vis spectrum of PUA-M film was detected at 416 nm. The second-order nonlinear coefficient (d 33) of PUA-M was about 27 pm/V. The studies into the detailed photorefractive properties for this polymer is in progress.

Synthesis and properties of oligomeric poly(glycidyl ether)s with a carbazole-based multifunctional photorefractive chromophore

Novel photorefractive poly(glycidyl ether) oligomers of a carbazole-based multifunctional chromophore were synthesized via ring-opening cationic polymerization. This new class of materials showed good solubility in various organic solvents and thermal stability up to 400°C. Optical quality films of excellent transparency at the light wavelength above 430 nm were obtained by spin-coating or casting. Photoconductive sensitivity of the film was as high as 10 −13 S cm −1/mW cm −2 at 532 nm. Electrooptic coefficients ( r 33) of 5–7 pm V −1 were easily achieved by the contact poling of spin-coated films. As evidence of photorefractivity, an asymmetric two-beam coupling gain of 3.2 cm −1 was demonstrated at an electric field of 30 V μm −1 with a low- T g polymer blend of multifunctional poly(glycidyl ether).

%Synthesis and Properties of Photorefractive Polymers Containing Indole-Based Multifunctional Chromophore as a Pendant Group

Novel photorefractive chromophores with indole and nitrobenzene as the push and pull groups, respectively, were synthesized and subsequently reacted with methacryloyl and acryloyl chloride to give multifunctional monomers. Polymers were obtained by copolymerization of these monomers with methyl methacrylate (P1, P2) or butyl acrylate (P3). These polymers were very soluble in organic solvents to be fabricated into optically clear polymer films and showed glass transition (Tg) at ca. 150 °C for P1, P2 and at 8 °C for P3, respectively. Large nonlinear optical coefficients (d33 as high as 49 pm/V) and photoconductive sensitivity (on the order of 10-9 S·cm-1/W·cm-2) were identified with high Tg polymers P1 and P2. Preliminary investigation of photorefractivity was carried out with low Tg polymer (P3) by two-beam coupling and four-wave mixing experiments. It was observed that P3 doped with 1% TNF showed two-beam coupling gain of 2.2 cm-1 at 75 V/μm and diffraction efficiency of 0.44% at 60 V/μm. When the photoc...

Carbazole photorefractive materials

Considerable progress has been made in organic photorefractive materials, since the first observation of photorefractive phenomena from organic materials. Within recent years, a large number of organic photorefractive materials, especially amorphous materials, have been developed based on polymeric composites, fully functional polymers and the multifunctional chromophore approach. Among these organic photorefractive materials, some of them containing carbazole components as a charge transporting function have been demonstrated to exhibit high performance photorefractive effects. The carbazole building blocks with charge transporting functionality or multifunctions play a very important role in photorefraction and have been widely used in the molecular design approach to new organic photorefractive materials. Based on carbazole functional building blocks, amorphous multifunctional chromophores, amorphous monolithic chromophores and amorphous dendrimers have also been developed as new types of organic photorefractive materials. This paper reviews the recent progress of organic photorefractive materials, especially organic photorefractive materials containing carbazole functional components.

ChemInform Abstract: A Novel Approach to the Synthesis of Conjugated Carbazole Trimers as Multifunctional Chromophores for Photorefractive Materials.

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