Showing papers on "Fluorenone published in 2002"

Green emission from poly(fluorene)s: The role of oxidation

Abstract: Poly(fluorene)-type materials are widely used in polymer-based light emitting devices. In their pristine state, they emit in the deep blue spectral region. During operation there appears, however, an additional emission peak at around 2.3 eV. This observation has usually been attributed to aggregate or excimer formation. Recently, it has been shown that photo- and/or electro-oxidation of poly(fluorene) chains resulting in ketonic defects (i.e., formation of fluorenone groups) can also be held responsible for emission in that spectral region. In this contribution, we apply quantum-chemical techniques to gain a detailed understanding of the optical properties of poly(fluorene)s containing ketonic defects. In particular, we compare model systems for poly(fluorene) with their ketone-containing counterparts, focusing on the influence of excited-state localization effects. The results of the theoretical calculations are confirmed by experimental investigations on statistical copolymers of fluorene and 9-fluorenone.

Bichromophoric Perylene Derivatives: Energy Transfer from Non‐Fluorescent Chromophores

Abstract: The energy of excitation at non-fluorescent chromophores such as fluorenone and anthraquinone has been trapped by a fast energy transfer to the highly fluorescent perylene bisimides. To this end, anthraquinone, fluorenone and anthracene derivatives have been linked to the perylene bisimides by non-conjugating spacers and fluorescence quantum yield of such assemblies have been determined as a function of the wavelengths of excitation. Energy transfer in such assemblies is strongly influenced by the orientation of the two chromophores. This is of interest for the construction of fluorescence switches.

Fluorene–fluorenone copolymer: Stable and efficient yellow-emitting material for electroluminescent devices

Abstract: We have synthesized and characterized a new fluorene copolymer exhibiting bright yellow luminescence. In order to ensure a complete π-stacking of the active layer, a 9-fluorenone monomeric unit (FOne) has been used as comonomer in conjunction with the more classical 9,9-di-n-nonylfluorene unit. As expected with fluorene-based materials, when excited at 370 nm, the corresponding dilute copolymer solution photoluminescence spectra exhibit a main peak centered at 450 nm in the blue part of the visible spectrum. However, in the solid state, immediate structural reorganization of the layer occurs, leading to a red-shifted emission (bright yellow emission) centered at 550 nm. The origin of the emitted light has been attributed to excimers and/or aggregates based on short FOne segments and involves mainly exciton transfer between nonaggregated fluorene segments and aggregated ones. It is noteworthy that organic light-emitting devices based on these new materials exhibit no spectral evolution upon device operatio...

Method for producing fluorene derivative

Abstract: Fluorenone and a phenolic compound (eg, a 2-C1-4alkylphenol) is subjected to a condensation reaction in coexistence with a thiol compound and a hydrochloric acid aqueous solution to produce a fluorene derivative [eg, 9,9-bis(C1-4alkylhydroxyphenyl)fluorene] The proportion (weight ratio) of fluorenone relative to the thiol compound [fluorenone/the thiol compound] is about 1/001 to 1/05, and the proportion (weight ratio) of the thiol compound relative to hydrochloric acid (HCl) in the hydrochloric acid aqueous solution [the thiol compound/hydrochloric acid] is about 1/01 to 1/3 As the thiol compound, a mercaptocarboxylic acid (β-mercaptopropionic acid) may be used According to the method, a highly purified fluorene derivative excellent in transparency can be obtained inexpensively and simply without using a hydrogen chloride gas having handling difficulty

Use of 9-Methylfluorene as an Indicator in the Titration of Common Group IA and Group IIA Organometallic Reagents

Abstract: 9-Methylfluorene was tested as an indicator in the titration of commonly used organometallic reagents. This indicator is readily prepared in three steps from fluorenone. In THF solution the deprotonated indicator is red and exhibits a sharp endpoint. The highly basic reagents sec-butyllithium and tert-butyllithium can be titrated in ether solution, where the color of the deprotonated indicator is yellow.

Process for producing fluorene derivative

Abstract: Fluorenone is condensed with a phenol [e.g., 2-(C1-4 alkyl)phenol] in the presence of both of a thiol and an aqueous hydrochloric acid solution to produce a fluorene derivative {e.g., 9,9-bis[(C1-4 alkyl)hydroxyphenyl]fluorene}. The proportion (by weight) of the fluorenone to the thiol is about from 1/0.01 to 1/0.5. The proportion (by weight) of the thiol to the hydrochloric acid (HCl) contained in the aqueous hydrochloric acid solution is about from 1/0.1 to 1/3. The thiol may be a mercaptocarboxylic acid (s-mercaptopropionic acid). Thus, a high-purity fluorene derivative having excellent transparency can be easily produced at low cost without using hydrogen chloride gas, which is difficult to handle.

Production method for bisphenolfluorenes

Abstract: PROBLEM TO BE SOLVED: To provide a method for easily and efficiently producing uncolored high-purity bisphenolfluorenes with a high clarity. SOLUTION: Fluorenone is condensed with a phenol [e.g. 2-(1-4C)alkylphenol] in the presence of a thiol compound (e.g. β-mercaptopropionic acid) and sulfuric acid; then, the resultant reaction mixture is neutralized and is freed of an aqueous phase to give an organic layer; and a crystallization solvent comprising a hydrocarbon (e.g. toluene) and a polar solvent [e.g. a ketone (e.g. acetone), an alcohol, or a nitrile] is added to the organic layer to precipitate crystals, giving a bisphenolfluorene [e.g. 9,9-bis(1-4C-alkylhydroxyphenyl)fluorene]. COPYRIGHT: (C)2003,JPO

(9,9-Dialkylfluorene-co-fluorenone) copolymers containing low fluorenone fractions as model systems for degradation-induced changes in polyfluorene-type semiconducting materials

Abstract: Abstract This short communication describes synthesis, optical and electronic properties of novel 9,9-dialkylfluorene-co-fluorenone copolymers which function as model systems for degradation-induced changes in polyfluorene-type semiconducting materials. Only very small fractions of incorporated fluorenone building blocks lead to a dramatic change of the solid state properties (photo- and electroluminescence). The results are discussed in terms of intra- vs. intermolecular excitation energy transfer.

Process for preparation of spirofluorenols

Abstract: Spirofluorenols (for example, 3',9'-dimethoxy-5'- hydroxyspiro[(1H-cyclopento[d,e,f]phenanthrene)-1,7'-benzo-[c]fluorene]) are prepared by a process which comprises protecting the hydroxyl group of a specific fluorenone compound (for example, 3,9-dimethoxy -5-hydroxybenzo[c]fluoren-7-one) with a substituted silyl group wherein the substituents bonded directly to the silicon atom have 5 to 12 carbon atoms in total (for example, t-butyldimethylsilyl), reacting the protected fluorenone compound with a specific organometallic compound (for example, 1-lithiophenanthrene) to form a spiro compound, and then deblocking the spiro compound. According to this process, spirofluorenols useful as raw materials of photochromic compounds can be efficiently prepared.

Photocatalytic oxidation of selected fluorenols on TiO2 semiconductor

Abstract: Photocatalytic oxidation of the title compounds 1 and 2 in nonaqueous oxygen saturated TiO 2 suspension was carried out. The corresponding ketones were formed in a high yield, in addition to minor amount of the corresponding hydrocarbon and other decomposition products. Interestingly, photocatalytic oxidation of the parent fluorene ( 3 ) afforeded fluorenone under the same conditions. Also, compound 4 as an acyclic simulant gave the corresponding ketone and hydrocarbon. Furthermore, the effect of solvent polarity has been tested. An electron–hole pair generated on the irradiated TiO 2 surface is suggested for the semiconductor-mediated photocatalysis.

Bisthiophenolfluorene compounds and method for producing the same

Abstract: PROBLEM TO BE SOLVED: To provide a new compound which has excellent performances as a heat-resistant material having a high refractive index and is useful as a resin raw material, an antioxidant, a curing agent, and the like. SOLUTION: This bisthiophenolfluorene compound represented by general formula (I) [R to R are the same as or different from each other and each H, a 1 to 6C alkyl or phenyl; (n) is an integer of 0 to 10]. The method for producing the bisthiophenolfluorene compound comprises azotizing the amino group of a bisanilinefluorene compound, reacting the reaction product with sulfate anion, and then hydrolyzing the product. The method for producing the bisthiophenolfluorene compound comprises reacting fluorenone with a thiophenol compound whose mercapto group is protected with a protecting group, in an acidic condition, and then removing the protecting group with an acid. The method for producing the bisthiophenolfluorene compound also comprises reacting a bisphenolfluorene compound with a compound represented by the formula: (R )2 N(C=S)-X' (X' is a halogen), thermally rearranging the compound to obtain the fluorene thioester compound, and then hydrolyzing the fluorene thioester compound.

Method for preparing bromofluorenes

Abstract: A method for preparing bromofluorenes includes a step of dispersing a compound selected from the group consisting of fluorene, fluorenone, and derivatives of fluorene and fluorenone in water to prepare a disperse system. Bromination is initiated by adding bromine Br2 into the disperse system. Thus, bromofluorenes can be efficiently and economically prepared without using any environmentally harmful organic solvent requiring a high cost to dispose of.

The red-edge effect in the spectra of fluorenone and 4-hydroxyfluorenone alcohol solutions

Abstract: Photophysical parameters of fluorenone and 4-hydroxyfluorenone have been studied in various solvents using steady state and time-resolved spectroscopic measurements. The fluorescence spectrum of both molecules in hydrogenbonding solvents is inhomogeneously broadened and strongly red shifted in comparison to that determined in nonploar and polar media. At 77 K the fluorescence spectra of the protic solvents are blue shifted (posses a changed intensity distribution) whereas in polar and nonploar one they are red shifted. In H-bond solvents at 77 K the fluorescence spectra of both molecules show an excitation wavelength dependence - the red-edge effect. The observed changes of the spectra are confirmed by the results of fluorescence decay measurements. The obtained results are explained by taking into consideration the statistical distribution of the solute-solvent interaction energies and the correlations between the fluorescence rate k F , solvent-cage relaxation rate τ - 1 R and the vibronic relaxation rate τ - 1 V .

Method for producing hydrocarbon group-substituted fluorenone

Abstract: PROBLEM TO BE SOLVED: To provide an industrially advantageous method for producing an alkylfluorenone useful as an intermediate for various organic products. SOLUTION: This method for producing a hydrocarbon group-substituted fluorenone is to oxidize a fluorene having at least one hydrocarbon group on an aromatic ring with molecular oxygen in the presence of a caustic alkali and a phase transfer catalyst.

Study on Preparation of Fluorenone by Liquid-Phrase Oxidation

Abstract: Fluorenone is got from fluorene by liquid_phrase oxidation.In this process pyridine is used as solvent and KOH as catalyst.By experiment some factors such as the quantity of solvent,catalyst and reaction time that have effects on reaction are determined.Finally the optimum conditons are found which can make the yield of fluorenone above 98% and the percent conversion of fluorine above 99%.

Rhodium‐Catalyzed Activation and Functionalization of the C—C Bond of Biphenylene.

Abstract: Biphenylene reacts with the rhodium(I) dimer [(dtbpm)RhCl]2 (1) (dtbpm = bis(di-tert-butylphosphino)methane) to yield (dtbpm)Rh(2,2‘-biphenyl)Cl (2). Lewis bases react with compound 2 at room temperature, displacing the chelating phosphine. A new five-coordinate complex, (PPh3)2Rh(2,2‘-biphenyl)Cl (3), is formed when the base is triphenylphosphine. Fluorenone and fluorenimine are formed when the base used is carbon monoxide and isonitrile, respectively. The dimer 1 and compound 2 are catalysts for coupling reactions of biphenylene with unsaturated organic substrates. Substituted phenanthrenes and benzenes are formed using alkynes with simple alkyl or aryl substituents. Substituted phenanthrenes and fluorenes are produced using alkynes with trimethylsilyl substituents. Olefinic substrates yield vinylbiphenyls. The production of vinylbiphenyls is hindered by steric substitution on the olefin. α-Olefins with substituents that block double-bond migration yield the cleanest product ratios.

The influence of interchain interactions on the photophysics of conjugated polymers

Abstract: This thesis presents findings on the photoluminescence properties of two conjugated polymers with special interest paid to interchain interactions and chemical degradation. The delayed luminescence of thin films of poly(3-methyl-4-octyl-thiophene) (PMOT) has been observed via time-resolved photoluminescence spectroscopy (TRS) in different temperature regimes. While at 15 K the emission consists of delayed fluorescence (DF) and phosphorescence (Ph) originating from radiatively decaying singlet and triplet excitons, room temperature emission is red-shifted with respect to the DF and originates from excimers. Supportingly, photo-induced absorption experiments detect very long-lived excitations allocated to the triplet counterparts of the emitting excimers. Furthermore, the influence of the photo-oxidisation of polyfluorenes on their luminescence is investigated. A series of polyfluorene/polyfluorenone co-polymers (PFO/PFl) with varying percentages of fluorenone repeat units was analysed via TRS as well as steady-state absorption, photoluminescence and photoexcitation spectroscopy in solid state and solution. Fluorenone repeat units (or keto defects) arising from polyfluorene photo-oxidation are the origin of the green luminescence band affecting the colour purity and quantum yield of polyfluorene devices. Fluorenone triplets play a major role and can be directly photo-excited. Moreover, they form upon polyfluorene degradation. Efficient energy transfer takes place from PFO singlets to fluorenone triplets entailing two types of triplet-triplet interaction processes, which lead to the formation of fluorenone excimers as well as polyfluorene-fluorenone exciplexes. Two types of the green emission can be assigned to emission from these states. This could be confirmed by the decay kinetics, thermal behaviour and keto level dependence of the emissions.