A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

Synthesis of Light-Emitting Conjugated Polymers for Applications in Electroluminescent Devices

4. Survey of Novel Multiphoton Active Materials 1257 4.1. Multiphoton Absorbing Systems 1257 4.2. Organic Molecules 1257 4.3. Organic Liquids and Liquid Crystals 1259 4.4. Conjugated Polymers 1259 4.4.1. Polydiacetylenes 1261 4.4.2. Polyphenylenevinylenes (PPVs) 1261 4.4.3. Polythiophenes 1263 4.4.4. Other Conjugated Polymers 1265 4.4.5. Dendrimers 1265 4.4.6. Hyperbranched Polymers 1267 4.5. Fullerenes 1267 4.6. Coordination and Organometallic Compounds 1271 4.6.1. Metal Dithiolenes 1271 4.6.2. Pyridine-Based Multidentate Ligands 1272 4.6.3. Other Transition-Metal Complexes 1273 4.6.4. Lanthanide Complexes 1275 4.6.5. Ferrocene Derivatives 1275 4.6.6. Alkynylruthenium Complexes 1279 4.6.7. Platinum Acetylides 1279 4.7. Porphyrins and Metallophophyrins 1279 4.8. Nanoparticles 1281 4.9. Biomolecules and Derivatives 1282 5. Nonlinear Optical Characterizations of Multiphoton Active Materials 1282

Multiphoton Absorbing Materials : Molecular Designs, Characterizations, and Applications

Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging, optical data storage, and lithographic microfabrication. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures.

Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication

Construction of organic semiconducting materials with in-plane π-conjugated structures and robustness through carbon-carbon bond linkages, alternatively as organic graphene analogs, is extremely desired for powerfully optoelectrical conversion. However, the poor reversibility for sp2 carbon bond forming reactions makes them unavailable for building high crystalline well-defined organic structures through a self-healing process, such as covalent organic frameworks (COFs). Here we report a scalable solution-processing approach to synthesize a family of two-dimensional (2D) COFs with trans-disubstituted C = C linkages via condensation reaction at arylmethyl carbon atoms on the basis of 3,5-dicyano-2,4,6-trimethylpyridine and linear/trigonal aldehyde (i.e., 4,4″-diformyl-p-terphenyl, 4,4′-diformyl-1,1′-biphenyl, or 1,3,5-tris(4-formylphenyl)benzene) monomers. Such sp2 carbon-jointed-pyridinyl frameworks, featuring crystalline honeycomb-like structures with high surface areas, enable driving two half-reactions of water splitting separately under visible light irradiation, comparable to graphitic carbon nitride (g-C3N4) derivatives. Semiconducting covalent organic frameworks (COF) with conjugated structures are desired for optoelectric conversion but poor reversibility of bond forming reactions hampers the formation of crystalline structures. Here, the authors synthesise COFs with disubstituted C = C linkages which enable water splitting under visible light irradiation.

/pdf/two-dimensional-semiconducting-covalent-organic-frameworks-ms6o17paan.pdf

Two-dimensional semiconducting covalent organic frameworks via condensation at arylmethyl carbon atoms.

We report on two-photon fluorescence excitation (TPE) action
cross sections for five widely used molecular
fluorophores. Measurements were performed by use of ultrashort
(∼100-fs) Ti:sapphire pulsed excitation over the range 690–960
nm. TPE spectra were obtained by comparison with a fluorescein
calibration standard. Large cross sections were found for the
cyanine reagent Cy 3 (∼140 GM) and for Rhodamine 6G (∼150
GM), both at 700 nm [1 GM = 10-50
(cm4 s)/photon]. Several fluorophores show
interesting and desirable blue shifts with respect to twice the
one-photon absorption wavelength. Fluorophore fluorescence
intensities showed no significant departure (±4%) from quadratic
illumination power dependence, indicating genuine two-photon
processes. Implications of these measurements for two-photon
laser-scanning microscopy are discussed.

Two-photon fluorescence excitation cross sections of biomolecular probes from 690 to 960 nm

This paper reports the synthesis of a series of donor-substituted 3,5-dicyano-2,4,6-tristyrylpyridine derivatives, having two-dimensional branched D-π-A structures, as new two-photon absorption (TPA) chromophores. These chromophores are stilbene-type chromophores containing the same acceptor group but end-capped with different aromatic groups as the donors. Measured as the two-photon-induced fluorescence in chloroform solvent, using a femtosecond multipass Ti∶sapphire amplifier as the irradiation source, the TPA cross section values of some compounds are on the order of 10−48 cm4 s photon−1. These chromophores also have relatively high two-photon-excited fluorescence (TPEF) action cross sections. Pumped by the laser at 800 nm, these chromophores show efficient two-photon-induced orange-red fluorescence emission. The experimental results indicate that the different end-capped functional electronic donors and the number of branches of these chromophores affect their one-photon properties, two-photon up-conversion emission behavior and TPA cross section values. Especially, with increasing numbers of branches, λabsmax and λspfmax exhibit bathochromic shifts, while their two-photon absorption cross sections also increase. Compared with the two-branched chromophore 6, the tribranched chromophore 4 shows a larger TPA cross section, and the cooperative enhancement of the TPA cross section from 6 to 4 is 1.2-fold at 800 nm.

Synthesis and properties of new two-photon absorption chromophores containing 3,5-dicyano-2,4,6-tristyrylpyridine as the core

Two new orange red light-emitting hyperbranched and linear polymers, poly(pyridine phenylene)s P1 and P2, were prepared by the Heck coupling reaction. In particular, an A2 + B3 approach was developed to synthesize conjugated hyperbranched polymer P2 via one-pot polycondensation. The polymers were characterized by NMR, Fourier transform infrared, ultraviolet–visible, and elemental analysis. They showed excellent solubility in common solvents such as tetrahydrofuran, CH2Cl2, CHCl3, and N,N-dimethylformamide and had high molecular weights (up to 6.1 × 105 and 5.8 × 105). Cyclic voltammetry studies revealed that P2 had a low-lying lowest unoccupied molecular orbital energy level of −3.22 eV and a highest occupied molecular orbital energy level of −5.43 eV. The thin film of P2 emitted strong orange-red photoluminescence at 595 nm. A double-layer light-emitting diode fabricated with the configuration of indium tin oxide/P2/tris(8-hydroxy-quinoline)aluminum/Al emitted orange-red light at 599 nm, with a brightness of 662 cd/m2 at 7 V and a turn-on voltage of 4.0 V; its external quantum efficiency was calculated to be 0.19% at 130.61 mA/cm2. This indicated that this new electroluminescent polymer (P2) based on 3,5-dicyano-2,4,6-tristyrylpyridine could possibly be used as an orange-red emitter in polymer light-emitting displays. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 493–504, 2005

Synthesis and properties of new orange red light‐emitting hyperbranched and linear polymers derived from 3,5‐dicyano‐2,4,6‐tristyrylpyridine

Three donor–acceptor conjugated polymers P1–P3 derived from 3,5-dicyano-2,4,6-tristyrylpyridine (PY) have been synthesized through the Knoevenagel reaction. The polymers are characterized by 1H NMR, FTIR, UV–vis and elemental analysis. P1 and P2 have high molecular weight up to 2.3 × 105 and 29.5 × 105 and show excellent solubility in common solvents such as THF, CH2Cl2, CHCl3 and DMF. They all have relatively good thermal stability with the 5% weight loss temperature at 402, 264 and 364 °C in argon, respectively. The fluorescence spectrum of P1 displayed the maximum at 588 nm in chloroform solution and at 596 nm in thin film. Two bilayer light-emitting diodes, with 5% or 10% of P1 fabricated in poly (N-vinylcarbazole) (PVK), emitted light at 549 or 552 nm, respectively, and with the increasing content of P1, the electroluminescence efficiencies of the blend devices increased. The optical limiting performance of P1 had been measured at 532 nm with nanosecond pulse, the limiting threshold of P1 was 728 mJ/cm2, and the throughput of P1 was limited to 344 mJ/cm2 for incident fluence as high as 1.1 J/cm2. The preliminary electroluminescent results and optical limiting effect of P1 suggested that P1 may be promising as light-emitting polymer and optical limiting material.

Synthesis, light-emitting and optical limiting properties of new donor-acceptor conjugated polymers derived from 3,5-dicyano-2,4,6-tristyrylpyridine

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Synthesis and properties of new two-photon absorption chromophores containing 3,5-dicyano-2,4,6-tristyrylpyridine as the core

Synthesis and properties of new orange red light‐emitting hyperbranched and linear polymers derived from 3,5‐dicyano‐2,4,6‐tristyrylpyridine

Synthesis, light-emitting and optical limiting properties of new donor-acceptor conjugated polymers derived from 3,5-dicyano-2,4,6-tristyrylpyridine