Showing papers on "Fluorenone published in 2004"

Understanding the Origin of the 535 nm Emission Band in Oxidized Poly(9,9‐dioctylfluorene): The Essential Role of Inter‐Chain/Inter‐Segment Interactions

Abstract: We present a careful study of the effects of photo-oxidation on the emissive properties of poly(9,9-dioctylfluorene) (PFO) that addresses important issues raised by a recent flurry of publications concerning the degradation of blue light-emitting, fluorene-based homo- and copolymers. The photoluminescence (PL) spectra of thin PFO films oxidized at room temperature comprise two major components, namely a vibronically structured blue band and a green, structureless component, referred to hereafter as the ‘g-band’. These are common features in a wide range of poly(fluorene)s (PFs) and whilst the former is uniformly accepted to be the result of intra-chain, fluorene-based, singlet-exciton emission, the origin of the ‘g-band’ is subject to increasing debate. Our studies, described in detail below, support the proposed formation of oxidation-induced fluorenone defects that quench intra-chain, singlet-exciton emission and activate the g-band emission. However, whilst these fluorenone defects are concluded to be necessary for the g-band emission to be observed, they are considered not to be, alone, sufficient. We show that inter-chain/inter-segment interactions are required for the appearance of the g-band in the PL spectra of PFO and propose that the g-band is attributable to emission from fluorenone-based excimers rather than from localized fluorenone π–π* transitions as recently suggested.

Fluorenone-Containing Polyfluorenes and Oligofluorenes: Photophysics, Origin of the Green Emission and Efficient Green Electroluminescence†

Abstract: A series of four new statistical copolymers of 9,9-dihexylfluorene and 9-fluorenone with well-defined structures and a new fluorene−fluorenone−fluorene trimer model compound were synthesized and used to investigate the photophysics, origin of the green emission, and electroluminescence of this class of light-emitting materials. We show that the new oligofluorene trimer with a central fluorenone moiety is an excellent model of the green-emitting chromophore in polyfluorenes. From systematic studies of the steady-state photoluminescence (PL) and PL decay dynamics of solutions of the fluorenone-containing copolymers and oligomer and thin films of the copolymers, we show that the controversial 535-nm green emission band originates from the fluorenone defects in single-chain polyfluorenes and not from intermolecular aggregates or excimers. The green emission, centered at 535 nm, was observed in dilute toluene solutions of all fluorenone-containing copolymers and oligomer; it was long-lived with a single-expone...

White Light Electrophosphorescence from Polyfluorene-Based Light-Emitting Diodes: Utilization of Fluorenone Defects†

Abstract: Poly(9,9-dioctylfluorene-co-fluorenone) with 1% fluorenone, (PFO-F(1%)), was synthesized as a model compound to investigate the optical and electrical effects of fluorenone defects in poly(9,9-dioctylfluoren2,7-diyl), PFO. Photoluminescence (PL) and electroluminescence (EL) measurements demonstrate that PFO-F(1%) emits stable green light. PL and EL studies indicate that Forster energy transfer to and charge carrier trapping on fluorenone defects (with subsequent fluorenone emission) are responsible for the color degradation typically observed with the polyfluorenes. By utilization of "fluorenone defects" in PFO-fluorenone copolymers (PFO-F), white electrophosphorescent light-emitting diodes were fabricated. Polymer blends were spin-cast from solution containing PFO, PFO-F (1%), and tris[2,5-bis(9,9-dihexylfluoren-2-yl)pyridine-κ 2 NC 3 ]iridium-(III), Ir(HFP) 3 . The white emission turns on at approximately 5 V, with a luminance (L) of 6100 cd/m 2 at 17 V. The luminous efficiency is 3 cd/A at current density of 8.5 mA/cm 2 (L = 255 cd/m 2 ). The white light exhibits stable color coordinates and stable color temperature and has a high color rendering index.

Directed metalation route to ferroelectric liquid crystals with a chiral fluorenol core: the effect of restricted rotation on polar order.

Abstract: A new series of smectic C* (SmC*) mesogens containing a chiral (R)-2-octyloxy side chain and either a fluorenone (2a−e) or chiral fluorenol (3a−e) core were synthesized using a combined directed ortho metalation−directed remote metalation strategy. The SmC* phase formed by the fluorenol mesogens is more stable and has a wider temperature range than that formed by the fluorenone mesogens, which may be ascribed to intermolecular hydrogen bonding according to variable-temperature FT-IR measurements. The C11 fluorenol mesogens (R,R)-3d and (S,R)-3d were obtained in diastereomerically pure form and gave reduced polarization (Po) values of +106 and +183 nC/cm2, respectively, at 10 K below the SmA*−SmC* phase transition temperature. The difference in Po values suggests that the chiral fluorenol core contributes to the spontaneous polarization of the SmC* phase. This is ascribed to the bent shape of the fluorenol core, which should restrict its rotation with respect to the side chains in the SmC* phase and favor ...

Electronic and Vibrational Properties of Fluorenone in the Channels of Zeolite L

Abstract: Fluorenone (C13H8O) was inserted into the channels of zeolite L by using gas-phase adsorption. The size, structure, and stability of fluorenone are well suited for studying host–guest interactions. The Fourier transform IR, Raman, luminescence, and excitation spectra, in addition to thermal analysis data, of fluorenone in solution and fluorenone/zeolite L are reported. Normal coordinate analysis of fluorenone was performed, based on which IR and Raman bands were assigned, and an experimental force field was determined. The vibrational spectra can be used for nondestructive quantitative analysis by comparing a characteristic dye band with a zeolite band that has been chosen as the internal standard. Molecular orbital calculations were performed to gain a better understanding of the electronic structure of the system and to support the interpretation of the electronic absorption and luminescence spectra. Fluorenone shows unusual luminescence behavior in that it emits from two states. The relative intensity of these two bands depends strongly on the environment and changes unexpectedly in response to temperature. In fluorenone/zeolite L, the intensity of the 300 nm band (lifetime 9 μs) increases with decreasing temperature, while the opposite is true for the 400 nm band (lifetime 115 μs). A model of the host–guest interaction is derived from the experimental results and calculations: the dye molecule sits close to the channel walls with the carbonyl group pointing to an Al3+ site of the zeolite framework. A secondary interaction was observed between the fluorenone's aromatic ring and the zeolite's charge-compensating cations.

Electrophotographic organophotoreceptors with novel charge transport materials

Abstract: This invention relates to a novel organophotoreceptor comprising: (a) at least one charge transport material comprising a fluorenone hydrazone having a combination of groups thereon, the combination of groups being selected from the group consisting of a) at least two fluorenone alkylsulfonylphenylhydrazone groups, b) at least two fluorenone pyrrolylhydrazone groups, c) at least two fluorenone benzotriazolylhydrazone groups, d) at least two fluorenone sulfolanylhydrazone groups, e) at least two fluorenone pyrazolylhydrazone groups, f) at least two fluorenone naphthylhydrazone groups, g) at least two fluorenone tetrazolylhydrazone groups, h) at least two fluorenone stilbenylhydrazone groups, and i) at least two fluorenone (9H-fluoren-9-ylidene)benzylhydrazone groups. Some of these fluorenones may be represented by the formula where n is an integer between 2 and 6, inclusive; R1 is hydrogen, an alkyl group, or an aryl group (e.g., phenyl, naphthyl, stilbenyl, benzyl, or tolanyl group); R2 is an alkylsulfonylphenyl or one of its derivatives; X is a linking group having the formula -(CH2)m-, branched or linear. The compounds may form electrostatic imaging systems in combination with (b) a charge generating compound; and (c) an electrically conductive substrate.

Factors Enhancing the Reactivity of Carbonyl Compounds for Polycondensations with Aromatic Hydrocarbons. A Computational Study

Abstract: For the first time, reactions of acetophenone, 2,2,2-trifluoroacetophenone, fluorenone, and dinitrofluorenones with diphenyl and 4,4‘-diphenoxybenzophenone in trifluoromethanesulfonic acid (TFSA) have been studied theoretically at the B3LYP/cc-pvtz(-f)//B3LYP/6-31G* level of theory as a model reaction for a superelectrophile involving polycondensation. It was found that the introduction of electron-withdrawing groups into the carbonyl compound reduces activation and total reaction energies of the aromatic electrophilic substitution reaction. The enhancement of the reactivity of carbonyl compounds bearing electron-withdrawing groups is due to lowering of LUMO energy. The electrophiles having highly delocalized LUMO are less active in the reaction of electrophilic aromatic substitution due to decreases of local LUMO density at the reaction center. General rules for the design of reactive monomer are formulated on the basis of calculational results.

Effect of keto defects on the electrical properties of fluorene-based oligomers

Abstract: The effect of ketonic defects on electrical properties, i.e., the performance of organic field-effect transistors (OFETs) was examined in fluorene end capped fused bithiophene oligomers (BFTT). The long wavelength emission at 2.1–2.3eV resulting from the ketonic defects was observed in photoluminescence spectra of BFTT films after UV irradiation in air. In addition, the peak corresponding to the carbonyl stretching mode of the fluorenone moiety at 1721cm−1 was also apparent after UV irradiation for periods longer than 6h in air. These observations confirm that ketonic defects are present in the fluorene units of BFTT after photo-oxidation. The threshold voltage (Vth), i.e., switch-on voltage, of OFETs was increased and field-effect mobility (μFET) was decreased after the formation of the ketonic defects, since these defects induce the formation of numerous trap sites in the bandgap of the semiconducting conjugated oligomer.

Developing Investigation Skills in an Introductory Multistep Synthesis Using Fluorene Oxidation and Reduction

Abstract: A two-step reaction sequence in the beginning organic laboratory provides a useful introduction to the importance of multistep synthesis. In addition to introducing several common synthetic methods and techniques, a two-step preparation can quickly establish the importance of testing alternative reactions in order to optimize intermediate yields. This article describes the preparation of 9-fluorenol in a sequence that first oxidizes fluorene to 9-fluorenone, followed by reduction of the ketone to 9-fluorenol. The entire experiment occurs over three lab periods. Air oxidation of fluorene under basic conditions is compared with an alternative oxidation using acidic chromate conditions. Students use semiquantitative TLC and product recoveries from column chromatography to determine which procedure provides the better yield of fluorenone. A final sodium borohydride reduction of the fluorenone then provides 9-fluorenol. All isolated products can be characterized using a variety of methods including melting poi...

Synthesis, Basicity, and Dynamics of a Perfluorocyclohexenyl Anion

Abstract: Electron transfer to perfluoro-1,3-dimethylcyclohexane in moist THF has yielded two quite different products. Tetrabutylammonium iodide irradiated with ultraviolet light gives a tetrabutylammonium enolate, but potassium fluorenone ketyl affords a cyclohexenyl anion. This allylic anion was isolated as its conjugate acid, a rather strong carbon acid. Ring inversion in the anion, measured by (19)F NMR line shape analysis, is characterized by these activation parameter values: DeltaH(++) = 8.84 +/-0.14 kcal/mol and DeltaS(++) = 0.81 +/- 0.6 cal mol(-1) K(-1).

Method for producing 9-spirofluorene compound

Abstract: PROBLEM TO BE SOLVED: To provide a method for efficiently producing a 9-spirofluorene compound useful as a raw material for a phenanthrene spiroindenonaphthopyran compound having excellent photochromic characteristics SOLUTION: An organometallic compound such as 4-lithiophenanthrene derived from 9-fluorenylmethanol is reacted with a fluorenone compound such as 3,7-dimethoxy-5-t-butyldimethylsilyloxybenzo[c]fluoren-7-one to produce the 9-spirofluorene compound In the process, the 9-fluorenylmethanol is mixed with an alkali metal hydride compound in an aprotic solvent and then treated with a formic ester The resultant fluorene-9-carbazole is then subjected to dehydration transformation to synthesize the 9-spirofluorene compound COPYRIGHT: (C)2004,JPO

Losses in the Energy of Low-Energy Electrons in Fluorene, Fluorenone, and Diiodofluorenone Vapors

Abstract: Electron energy loss spectra (EELS) of fluorene, fluorenone, and diiodofluorenone vapors excited by monokinetic electrons of energies 15–50 eV have been obtained. The singlet and triplet absorption bands of these molecules have been calculated. Comparison of these bands with the experimental EELSs and optical absorption spectra has shown that the forbiddenness of singlet-triplet transitions is not completely removed in the process of interaction of molecules with electrons. The presence of heavy iodine atoms in the diiodofluorenone molecule enhances singlet-triplet transitions. Bands of overtones of stretching vibrations of the CH groups of the benzene rings have been detected near the peak of elastic scattering of electrons of the molecules studied.

Thermodynamic constants for excimer formation and dissociation in oxidized poly(9,9-dioctylfluorene) (PFO)

Abstract: We have studied the temperature-dependent photoluminescence (PL) characteristics of oxidised PFO thin films at temperatures above 298K. We find the relative strength of the green emission band (g-band) to increase greatly at temperatures corresponding to the onset of crystallisation. Based on the proposal that the g-band arises from a fluorenone-based excimer, this finding would seem to indicate that a close approach of neighbouring fluorenone-containing segments may be energetically favourable. Finally, by successfully identifying diffusion-limited and dynamic equilibrium regimes within the temperature dependence of the ratio R=I D /I M , we extract an activation energy for excimer formation of ~ 0.05 eV and an excimer binding energy of ~ 0.51 eV. This is a relatively high binding energy for an excimer and lends credibility to the notion of an energetically favourable fluorenone:fluorenone coupling configuration, perhaps as a result of the considerable ground state dipole moments associated with the ketone group.

Fluorenone of high purity and manufacturing method therefor

Abstract: PROBLEM TO BE SOLVED: To simply and efficiently manufacture high-purity fluorenone by separating and removing impurities from fluorenone at a high degree. SOLUTION: By such a method as to form an insoluble matter under heating in the presence of an acid catalyst, an impurity (the one bearing hydroxy group, e.g., 9-methyl-9-fluorenol) in fluorenone is converted into a derivative having a solubility or boiling point different from that of fluorenone. The derivative is separated and removed from fluorenone, giving high-purity fluorenone. When analyzed by gas chromatography at a column temperature of 180°C by using a silica gel as a column filler, the high-purity fluorenone substantially exhibits no peak within a retention time of 16-18 min and exhibits a single peak within a retention time of 18.5-19.5 min. An ethanol solution of the high-purity fluorenone with a concentration of 20 wt.% has a transmittance of 99% or higher at a wavelength of 600 nm. COPYRIGHT: (C)2004,JPO

On the Origin of Color Degradation in Polyfluorenes – Block Copolymer Approach for Stable Blue Light Emission

Abstract: Spectroscopic studies on a series of rod-coil block copolymers with terfluorene as the rigid segment demonstrate that the main cause of color instability in fluorene oligomers and polymers is aggregate and/or excimer formation and not the presence of keto defects alone (fluorenone formation) along the molecular chain. Keto defects when are present contribute to the appearance of the undesirable ‘green’ emission band but are not the leading cause of color instability. Thus, the synthesis of materials where aggregation and/or inter-chain, inter-segment interactions are inhibited is the key approach for the production of stable polymeric light-emitting devices (PLED’s). The potential of this method is verified by the synthesis of photo-oxidative stable fluorene/styrene diblock copolymer blue emitters.

The interchain origin of the green emission band in oxidized poly(9,9-dioctylfluorene) (PFO)

Abstract: We report systematic measurements of the evolution of the emission characteristics of PFO whilst undergoing photo-oxidation. Pure PFO and highly diluted PFO/polystyrene blended films were prepared for the studies by spin-coating. Each film was oxidised by exposure to the 351 nm line of a cw Ar + laser. Both the kinetics of the various spectral components and the photoluminescence intensity for each film was monitored as a function of oxidation time and their respective behaviours were compared. Our results demonstrate that there is a strong tendency for singlet intrachain excitons initially created on pristine PFO segments to migrate to the fluorenone moieties produced by photo-oxidation. However, we conclusively show that emission from states localised at these defect sites cannot account for the appearance of the broad green emission band (g-band) that is well-known to occur in degraded polyfluorenes. Instead, it is shown that the g-band must emanate from interchain states that are formed after energy has been transferred to the fluorenone moieties (either via energy transfer from non-defective PFO segments or by direct excitation).

Photoconductor with light fatigue additives

Abstract: A photoconductor having a charge generation layer and a charge transport layer, the charge transport layer having hydrazone or aryl amine charge transport molecules and also having as room light protective additives acetosol yellow 5GLS and tetraphenylcyclopentadienone or 9-fluorenone. Preferably the amount of the acetosol yellow is 2 to 4 percent by weight of the weight of the charge transfer layer and the ratio of weight between the acetosol yellow and the dienone or fluorenone is in the range of 1:1 to 1:3.

Process for preparing fluorene derivative

Abstract: In the present invention, there is disclosed a method of producing a fluorene derivative, which comprises subjecting fluorenone and a phenolic compound (such as 2-alkylphenol containing 1 to 4 carbon atoms in the alkyl moiety) to a condensation reaction in the presence of mercaptocarboxylic acid and a hydrochloric acid aqueous solution to obtain a fluorene derivative ( such as 9,9-bis(alkylhydroxyphenyl)fluorene containing 1 to 4 carbon atoms in the alkyl moiety), wherein the fluorenone/mercaptocarboxylic acid weight ratio is approximately 1/0.05 to 1/0.3 wherein the ratio of said mercaptocarboxylic acid to hydrogen chloride comprised in said aqueous solution of hydrochloric acid is approximately 1/0.3 to 1/2. Using the preparation method according to the present invention it is possible to obtain an extremely pure fluorine derivative exhibiting excellent transparency without need of use gaseous hydrogen chloride, which is difficult to handle.

Electron receptor for color display panel light conducting layer, especially including fluorenone derivative

Abstract: PURPOSE: An electron receptor for a color display panel light conducting layer is provided to eliminate the change in the luminance of the fluorescent plane and color coordinate. CONSTITUTION: The light conducting layer electron receptor of a color display panel includes a fluorenone derivative expressed as a chemical formula including NC and CN and R4 and R5. R4 is selected from a group comprising ethoxycarbonyl group, butoxycarbonyl group, phenoxycarbonyl group, benziloxycarbonyl group, ethylcarbonyl group, propylcarbonyl group, butylcarbonyl group and t-butylcarbonyl group. And R5 is selected from a group comprising hydrogen atom, halogen atom, alkyl group, alkoxy group, cyano group, nitro group, ester group and trifluoro group.