Showing papers on "Fluorenone published in 1999"

Electrical and Photoinduced Degradation of Polyfluorene Based Films and Light-Emitting Devices

Abstract: Degradation-induced changes in the structural and optical properties of the polyfluorene-based blue emitting films and LEDs are examined using spectroscopic (FTIR, UV−vis, photo- and electroluminescence), analytical (FTIR and ESCA), and scanning probe microscopy techniques. The materials studied are oligomers (DP ∼ 10) of 9,9-di-n-hexylfluorene and its random copolymer with anthracene. In situ FTIR monitoring is used to characterize chemical changes in the active layer of operating LED devices. Two primary mechanisms of degradation are identified. In the first, photooxidation of the polymer matrix leads to the formation of an aromatic ketone, most likely fluorenone at the chain terminating monomer units, which quenches the fluorescence. The second process promotes aggregate formation, which then leads to loss of luminous intensity by exciton transfer and relaxation through excimers.

2,7-Disubstituted amidofluorenone derivatives as inhibitors of human telomerase.

Abstract: Telomerase is a major new target for the rational design of novel anticancer agents. We have previously identified anthraquinone-based molecules capable of inhibiting telomerase by stabilizing G-quadruplex structures formed by the folding of telomeric DNA. In the present study we describe the synthesis and biological evaluation of a series of analogous fluorenone-based compounds with the specific aims of, first, determining if the anthraquinone chromophore is a prerequisite for activity and, second, whether the conventional cytotoxicity inherent to anthraquinone-based molecules may be reduced by rational design. This fluorenone series of compounds exhibits a broad range of telomerase inhibitory activity, with the most potent inhibitors displaying levels of activity (8-12 microM) comparable with other classes of G-quadruplex-interactive agents. Comparisons with analogous anthraquinone-based compounds reveal a general reduction in the level of cellular cytotoxicity. Molecular modeling techniques have been used to compare the interaction of fluorenone- and analogous anthraquinone-based inhibitors with a human G-quadruplex structure and to rationalize their observed biological activities.

Effects of molecular structure and hydrogen bonding on the radiationless deactivation of singlet excited fluorenone derivatives

Abstract: Substituent effects on intramolecular radiationless deactivation and hydrogen-bonding-induced quenching have been examined for various fluorenone derivatives. In toluene, triplet formation is the dominant process from the singlet excited state when an electron-withdrawing group is attached to the fluorenone moiety, whereas an electron-donating substituent promotes internal conversion. There is a clear correlation between the internal conversion rate constant and the lowest excited singlet state energy, which can be explained in terms of the energy gap law. It is shown that both the electron-donating character of the substituent in the excited fluorenone and the hydrogen-bonding power of alcohol play important roles in determining the rate of dynamic quenching by alcohols. The intermolecular hydrogen bonding with alcohols in the singlet excited state acts as an effective accepting mode of radiationless deactivation for fluorenones substituted with an electron-donating group. However, 2-NO2− and 2-COOCH3− d...

A Precursor Route to 2,7-Poly(9-fluorenone)

Abstract: 2,7-Poly(9-fluorenone) (PF) (1), a unique electron-deficient conjugated polymer, was prepared via a precursor route, using 2,7-poly(spiro[4‘,4‘-dioctyl-2‘,6‘-dioxocyclohexane-1‘,9-fluorene]) (10b) (POFK) as precursor polymer. Ketalization of 2,7-dibromo-9-fluorenone (6) with the diol 2,2-dioctyl-1,3-propanediol (8b) afforded a dibrominated ketal derivative of fluorenone (9b) which after Ni(0)-induced coupling provided the well-processable, structurally defined precursor polymer 10b with a polyphenylene backbone. Conversion to PF (1) proceeded smoothly by treating a POFK (10b) film with dichloroacetic acid. The cyclic voltammogram of PF (1) exhibits a reversible reduction with a E1/20 of −1.48 V vs Fc/Fc+ which qualifies 1, together with its facile accessibility, e.g., as electron transport material in multilayer LED.

Complexation of Fluorenone and Xanthone to Cyclodextrins: Comparison of Theoretical and Experimental Studies

Abstract: The structural aspects for the complexation of xanthone and fluorenone to α- as well as β-cyclodextrins (CDxs) were explored by combining absorption, fluorescence, and induced circular dichroism studies with theoretical calculations of the optimized structures for the ketone−CDx complexes and their predicted ICD spectra. Detailed information on the similarities and differences for the complexes of these ketones with CDxs was obtained. For both CDxs, the ketones are bound to the rim of the cavity, and deeper penetration is observed for the complexes with β-CDx. In addition, a 1:2 complex involving α-CDx was only observed in the case of fluorenone. Although the two ketones have similar structures, their molecular recognition properties and the resulting structures of the CDx complexes show distinct differences.

Models of Nitric Oxide Synthase: Iron(III) Porphyrin-Catalyzed Oxidation of Fluorenone Oxime to Nitric Oxide and Fluorenone

Abstract: Nitric oxide synthase (NOS) is a heme-containing monoxygenase that catalyzes the oxidation of l-arginine to l-citrulline and NO in two steps. In the second step of the NOS reaction, citrulline and NO are generated from the heme-catalyzed 3-electron oxidation of l-N-hydroxyarginine. To model this unusual reaction, iron porphyrin-catalyzed oxygenations of oximes with O2 were investigated. The oxidation of fluorenone oxime and a stoichiometric amount of hydroxoiron(III) porphyrin (Fe(OH)P, P = TMP and TPFPP) with O2 in benzene generated Fe(NO)P, fluorenone, and O-(9-nitro-9-fluorenyl)fluorenone oxime. The X-ray crystal structure of the oxime ether product suggests that it originated from the dimerization of the fluorenyl iminoxy radicals. Detailed analysis of this reaction showed that the oxime reacted first with Fe(OH)P to generate a 5-coordinate, high-spin oximatoiron(III) porphyrin species [Fe(oximate)P]. The X-ray crystal structure of oximatoiron(III) tetrakis(2,6-dichlorophenyl)porphyrin [Fe(oximate)TDC...

Complexes containing redox-active fluorenone-based ligands linked to redox-active tris(pyrazolyl)boratomolybdenum fragments: assignment of ligand-centred and metal-centred redox processes by EPR and UV/VIS/NIR spectroelectrochemistry †

Abstract: The dinuclear complex [{Mo(TpMe,Me)(NO)Cl}2(µ-L2)] 2 [L2 is the new bridging ligand 2,7-bis{2-(4-pyridyl)ethen-1-yl}fluorenone] contains two redox-active molybdenum(I) centres linked by a bridging ligand which is itself redox-active by virtue of the fluorenone spacer unit. The complex undergoes four one-electron reductions of which two are metal-centred Mo(0)/Mo(I) couples and two are reductions of the fluorenone unit. Also studied were the mononuclear analogue [Mo(TpMe,Me)(NO)Cl(L1)] [L1 is 2-bromo-7-{2-(4-pyridyl)ethen-1-yl}fluorenone], and the dinuclear complex [{Mo(TpMe,Me)(NO)Cl}2(µ-L3)] 3 [L3 is the bridging ligand 2,7-bis{2-(4-pyridyl)ethen-1-yl}fluorene] which lacks the ligand-centred redox activity. A combination of EPR and UV/VIS/NIR spectroelectrochemical techniques was used and showed how the separate metal-centred and ligand-centred reduction processes lead to quite distinct and characteristic spectroscopic signatures, such that it was possible to assign the sequence of reduction sites as ligand–metal–metal–ligand. The initial reduction of the bridging ligand in 2 results in a much larger separation between the two Mo(0)/Mo(I) couples (240 mV) than occurs in complexes where the bridging ligand is not redox-active.

Production of 9,9-bis(4-(2-hydroxypropoxy)phenyl)fluorene

Abstract: PROBLEM TO BE SOLVED: To produce the subject compound by an economically advantageous process suitable for industrial production by reacting fluorenone with phenoxypropanol using sulfuric acid and a thiol as catalysts. SOLUTION: The objective compound of the formula is produced by reacting fluorenone with phenoxypropanol in the presence of a catalyst comprising 10-500 ml of sulfuric acid (having a concentration of >=75%, preferably >=95%) and 0.01-100 ml of a thiol (e.g. a 1-10C mercaptan or 2-11C mercaptocarboxylic acid) based on 1 mol of fluorenone preferably in a water-immiscible organic solvent such as toluene at 30-150 deg.C, preferably 40-100 deg.C for 1-10 hr, preferably 3-6 hr in the case of performing the reaction by batch process.

A Short Route to Multiply Substituted Fluorenones.

Abstract: We report a two-step synthesis of polysubstituted fluorenones by condensation of malononitrile with aromatic aldehydes and methylketones or with β-aryl-α,β-unsaturated carbonyl compounds, aldehydes or ketones. The yields of the fluorenone systems depend on the nature of the substitution on the aromatic rings.

Production of fluorenone derivative

Abstract: PROBLEM TO BE SOLVED: To obtain a high-purity fluorenone derivative industrially safely and simply under mild conditions in a high yield without requiring a complicated separating means, by subjecting a biphenyl derivative to ring formation in the presence of methanesulfonic acid and dealkylating the obtained fluorenone derivative. SOLUTION: A biphenyl derivative of formula I (R is H or a lower alkoxy; R is H, a lower alkenyl or the like; R is a lower alkyl; R is H, a lower alkenyl or the like; (p) and (q) are each 1-3) is subjected to ring formation in the presence of methanesulfonic acid in a solventless state generally at a temp. of room temperature to 150 deg.C for 1-5 hours. The obtained fluorenone derivative of formula II is heat-treated and dealkylated in a mixture of an acid and a solvent usually at a temp. of 30-150 deg.C for 1-15 hours to give the objective compound of formula III (e.g. 2,5-dihydroxy-1,3,6,8-tetrapropyl-9- fluorenone or the like).

Method for purifying charge transfer material for electrophotographic photoreceptor

Abstract: PROBLEM TO BE SOLVED: To provided the purifying method capable of obtaining a charge transfer material for electrophotographic photoreceptor having excellent characteristics. SOLUTION: In this method, a charge transfer material(CTM) is purified by dissolving the CTM in an organic solvent, adding an activated clay in the solution to suspend them and filtering them with a membrane filter >=90 KPa in isopropyl alcohol having a bubble point stipulated by JIS K3832 or >=249 KPa in water. As an electron attractive materiel used as the CTM, diphenoquinone, naphthoquinone, anthraquinone and an aromatic carbonyl compound such as fluorenone or the like are exemplified. As an electron donating material, one low in ionization potential is preferably used and a compound having nitrogen atom in the molecule is particularly suitable.

Magnetic and Electrochemical Investigations on Anions Derived from Oligoketones Containing Fluorenone and Benzophenone Units. An Approach to the Design of Stable Multiradical Organic Materials.

Abstract: The mono- and poly-anions of some mono-, di- and tetra-ketones containing fluorenone and benzophenone moieties have been studied by NMR and cyclic voltammetry. Alkali metal anion radicals of fluorenone, generated by electron transfer from an alkali metal naphthalene radical anion exhibit markedly lower molar paramagnetic solvent shifts than those generated by direct reduction with an alkali metal. Evidence is provided for the involvement of hyperfine interactions between the naphthalene and the paramagnetic solute. The dianion of the diketone 9 is paramagnetic as are the dianions of the tetraketones 6 and 7. The NMR data, combined with those obtained by cyclic voltammetry, indicate that polyketones possessing fluorenone moieties connected through isophthaloyl ‘spacers’ are promising systems for the preparation of high-spin organics and electrophores.

Photochemical Pinacol Rearrangement.

Abstract: Irradiation of 9,9‘-bifluorene-9,9‘-diol (1) gave 9-fluorenone and spiro[9H-fluorene-9,9‘(10‘-H)-phenanthren]-10‘-one (4), the latter arising from a pinacol rearrangement. The distribution of fluorenone and ketone 4 was solvent dependent with the latter being the major product in trifluoroethanol, a solvent known to stabilize carbocation intermediates. Laser flash photolysis of diol 1 in 2,2,2-trifluoroethanol or hexafluoro-2-propanol showed two transients absorbing at 350 and 505 nm with a weak band at 700 nm. The latter two peaks are assigned to the corresponding substituted 9-fluorenyl cation (5) formed from photoheterolysis of diol 1. Comparison of the decay kinetics between cation 5 and other 9-fluorenyl cations, the parent 9-fluorenyl and 9-phenyl-9-fluorenyl cations, showed that the decay of 5 was relatively insensitive to the nature of the solvent as compared to the latter two carbocations suggesting that unimolecular rearrangement in 5 competes with nucleophilic quenching.