Showing papers on "Fluorenone published in 1996"

Reactions of a Silanediyl with Carbon−Oxygen and Carbon−Nitrogen Double Bonds

Abstract: Silanediyl 2 (generated by thermolysis of cyclotrisilane 1) reacts with benzophenone, tetracyclone, and fluorenone to yield products, which may originate from highly reactive siloxiranes as intermediates. However, using adamantanone as ketone, stable siloxirane 24 is obtained. The interaction of 2 with benzophenone anil or 36 gives heterocyclic compounds 31 and 37, respectively. The involvement of silaziridines in these reactions, as well as in the reactions of 1 with 1,4-diaza-1,3-butadienes 41a and b, which yield the expected formal [4 + 1] cycloaddition products, remains questionable.

Solvent and concentration effects on the steady state fluorescence of fluorenone

Abstract: The electronic absorption and steady state fluorescence spectra of fluorenone in the regions 280–340 and 320–420 nm respectively have been obtained at room temperature for various concentrations in a series of non-polar and polar solvents. The effects of fluorenone concentration in various solvents in the range 10 −6 −10 −3 M on the spectral properties are discussed. In addition to the monomer fluorescence, we have also observed another fluorescence band at longer wavelength in the region 420–600 nm which has been ascribed to excimer formation. The monomer and excimer fluorescence lifetimes of fluorenone in typical solvents such as benzene and acetonitrile have been determined experimentally. By combining our results of steady state fluorescence and measurements of fluorescence lifetimes with previously reported studies of laser-induced fluorescence, the mechanism of excimer formation has been explained. The absence of excimer formation in hexane, cyclohexane and alcohols is discussed.

Fluorescence quenching of fluorenone by alcohols

Abstract: The absorption and fluorescence spectra of fluorenone have been observed in various solvents. The fluorescence intensity increases with increasing solvent polarity, except in alcoholic solvents. The relative fluorescence intensity of fluorenone in acetonitrile is about 14-times greater than that in methanol. There are isosbestic points in the absorption spectra of fluorenone in mixed solvents comprising ethanol–cyclohexane and ethanol–acetonitrile, indicating the formation of a 1 : 1 hydrogen-bonded complex between fluorenone and ethanol. The equilibrium constants for the complex formation are estimated to be 2.0 ± 0.5 and 0.6 ± 0.2 mol−1 dm3 in ethanol–cyclohexane and ethanol–acetonitrile solvents, respectively. The results indicate that the complex formation changes the relative energy of the singlet and triplet states, which have n–π* and π–π* characters, respectively. The complex formation causes a strong fluorescence quenching of fluorenone in the alcohols. A plot of the fluorescence quenching also s...

Production of fluorene derivative

Abstract: PROBLEM TO BE SOLVED: To provide a method for profitably producing 9,9-bis(4-(2- hydroxyethoxy)phenyl)fluorene in a high quality and in a high yield. SOLUTION: This method comprises reacting fluorenone with phenoxyethanol in the presence of sulfuric acid and a thiol to produce the 9,9-bis(4-(2- hydroxyethoxy)phenyl)fluorene. Therein, an organic solvent simultaneously satisfying the following conditions (1), (2) and (3) is used as a reaction solvent. (1) The organic solvent is slightly compatible with water. (2) The organic solvent hardly reacts with sulfuric acid. (3) The organic solvent can easily dissolve 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene.

Oligomeric bis(1,3-indandiylidene)azines: preparation, electrochemical and spectroscopic properties, and implications for the use of polyazines as conducting materials

Abstract: Four oligomeric azines of the general structure FlN(NC9H4N)nNFl, where Fl represents the 9-fluorenylidene group, C9H4 the 1,3-indandiylidene unit, and n has the values 1 to 4, have been prepared and characterised. Their electrochemical reduction has been studied by cyclic voltammetry and the results compared with the behaviour of fluorenone azine. Two reversible peaks have been observed for each of the compounds and the peak potentials observed show an unusual alternation in their values as n increases. Vibrational spectra have been recorded for all five compounds. The strong Raman lines associated with the collective stretching of the C–C bonds involved in π-delocalisation [[graphic omitted](ya) modes] have been studied. The effect of chain length on the frequency and intensity of this mode is the reverse of that found, for example, with polyacetylene. This suggests that, while polyazines are unlikely to produce materials of very high electrical conductivity, they may be candidates as materials for electroluminescence purposes in the fabrication of organic light-emitting diodes.

Characterization of 9-(p-Substituted Benzylidenehydrazono)fluorenes

Abstract: The title azine was obtained by a reaction of the corresponding fluorenone hydrazone and p-substituted benzaldehyde. The hydrazone formed from the unsymmetrical fluorenone afforded configurational isomers; the E-isomer was thermodynamically more stable than the Z-isomer. The structure of the title azines, derived from symmetrical fluorenone, was assigned to be (s-trans/E) form. The azines from unsymmetrical fluorenone gave isomeric mixtures due to the 9-iminofluorene moiety. The electronic spectra of these azines show an intramolecular charge transfer; the red shift beyond 250 nm is observed in the case of 9-[p-(diethylamino)benzylidenehydrazono]-2,4,7-trinitrofluorene, compared to the mother azine. 9-[p-(Pentyloxy)benzylidenehydrazono]-2,7-dinitrofluorene and some of the homologs possess a liquid-crystalline property; the phase-transition temperature of the dinitro compound is K (172 °C) M1 (185) M2 (187) I between the crystalline and liquid phases.

Process for making fluorenones

Abstract: A process for the oxidation of a fluorene compound to a corresponding fluorenone compound comprises treating the fluorene compound with an oxidizing gas in the presence of a solid alkali metal or alkaline earth metal oxide or hydroxide or a concentrated aqueous solution thereof in a reaction mixture containing a non-aqueous heterocyclic nitrogenous solvent, wherein the reaction mixture is free of a phase transfer agent, for a time sufficient and at a temperature sufficient to convert the fluorene compound to the fluorenone compound

Fluorenone derivative, its polymer and electrophotographic photoreceptor using the same

Abstract: PURPOSE: To obtain a new fluorenone derivative capable of providing a raw material for electron transport polymers, having the electron transport ability and useful for producing an electrophotographic photoreceptor having a high sensitivity and a low residual potential. CONSTITUTION: A fluorenone derivative of formula I [A is H, a halogen, an alkyl or an alkoxyl; B is H, a halogen, an alkyl, an alkoxyl, cyano, nitro, an ester or trifluoromethyl: Q is O, C(CN)2 , C(C02 R)2 (R is an alkyl or an aryl), C(CN)CO2 R, C(CN)COR, C(CN)COAr (Ar is an aryl), NCN or NAr], e.g. a compound of formula II. The exemplified compound is obtained by providing a dicyanomethylenefluorenone derivative from fluorenonecarboxylic acid and malononitrile and reacting the resultant derivative with chloromethylstyrene.

Indolopyridines with a bridging heteroatom. 9. Synthesis, structure, and thermolysis of 5-hydroxy-5-(2-pyridyl)-fluorene and 4-azafluorene

Abstract: Treatment of fluorenone or 4-azafluoren-9-one with 2-pyridyllithium gives 45-hydroxy-5-(2-pyridyl)fluorene and its aza analog. The structure of the former has been studied by x-ray crystallography. It was found that, in contrast to the non-condensed diaryl-2-pyridylcarbinols, these alcohols do not undergo acid catalyzed dehydration and heterocyclization. Under pyrolytic conditions. 5-pyridylfluorenol undergoes fission to form fluorenone.

Microscale Preparation of Difluorenylidene and trans-2,3-Dibenzoylspiro[cyclopropane-1-99-fluorene]

Abstract: The synthetic sequence involving the oxidation of fluorene to fluorenone and the reduction of fluorenone to fluorenol can be extended by preparing the title compounds via the intermediate 9-chlorofluorene. The latter is obtained by heating fluorenol in methanol with conc. hydrochloric acid.

Economical, ecologically friendly prepn. of fluorene-bisphenol(s)

Abstract: In the prepn. of fluorene-bisphenols (I) by reacting fluorenone (II) with phenols in the presence of strongly acid ion exchange resin (III) based on styrene with SO3H gps., (a) gelatinous (II) crosslinked with 1-6 wt.% DVB is used; and (b) the mother liquor contg. isomers, oligomers and by-prods., obtd. by sepg. most of (I), is treated with (III) and the by-prods. are converted to (I).

Hydrogen Bonding Interactions With Cyclodextrins: Utilization of Fluorenone as a New Probe

Abstract: The interaction of fluorenone with cyclodextrins (CD) was studied by fluorescence lifetime, fluorescence quantum yield and triplet yield measurements. In aqueous solutions, the fast internal conversion of the singlet excited inclusion complexes indicates that fluorenone, while embedded in the CD cavity, still retains hydrogen bonded water. In organic media, the dynamic quenching of fluorescence and singlet-triplet transition was attributed to formation of a short lived, non- or very weakly fluorescent excited fluorenone/CD hydrogen-bonded complex since the methylation of the glycosidic OH-groups significantly decreased the quenching rates.

Friedel-Crafts Reaction of Toluene with Oxalyl Chloride

Abstract: By the Friedel-Crafts reaction of toluene with oxalyl chloride, three kinds of fluorene derivatives (c, d, e), naphthalene derivative f, fluorenone derivative g, were obtained in addition to 4,4′-dimethyl benzophenone b. In the compounds (c, d, e, f, g), c shows thermochromism above 135°C in solution, while e emits phosphorescence and f exhibits fluorescence at room temperature in the solid states.