Fluorenone

About: Fluorenone is a research topic. Over the lifetime, 1067 publications have been published within this topic receiving 17162 citations. The topic is also known as: Diphenylene ketone & 9-Oxofluorene.

One-step construction of five successive rings by rhodium-catalyzed intermolecular double [2+2+2] cycloaddition: enantioenriched [9]helicene-like molecules.

Abstract: Helicenes and helicene-like molecules have long attracted much attention because of their potential applications to optical or electronic functional materials. Therefore, flexible as well as convenient methods for their syntheses are highly desired for structural alterations and supply of sufficient quantities. The most frequently employed method for the synthesis of helicenes is the oxidative photocyclization of stilbene-type precursors, however this procedure cannot be conducted on a large scale because of the highly dilute reaction conditions. Several non-photochemical methods for the synthesis of [6]and [7]helicenes and helicene-like molecules have been developed to date. As such, transition metal mediated intramolecular [2+2+2] cycloadditions of triynes are useful methods for the synthesis of [6]and [7]helicene-like molecules through the formation of three successive rings. 6] Star and co-workers pioneered this strategy by using cobaltor nickel-mediated or catalyzed [2+2+2] cycloadditions. Following this pioneering work, we recently reported a cationic rhodium(I)/chiral bisphosphine complex, which catalyzed the intramolecular [2+2+2] cycloadditions of 2-naphthol-linked triynes, leading to enantioenriched [7]helicene-like molecules (Scheme 1). 7] Notably, non-photochemical methods that can furnish higher ordered ( [8]) helicenes and helicene-like molecules are rare. To access sterically more demanding [9]helicene-like molecules starting from commercially available 2-naphthol, we designed an intermolecular double [2+2+2] cycloaddition between a 2-naphthol-linked tetrayne and a dialkynylketone, which forms five successive rings (Scheme 2). This method would furnish various [9]helicene-like molecules, containing a densely substituted fluorenone core, by changing substituents of each cycloaddition partner. The 2-naphthol-linked tetraynes 4 were readily prepared by a three-step sequence starting from a known terminal alkyne 1 as shown in Scheme 3. A copper-mediated Scheme 1. Rhodium-catalyzed intramolecular [2+2+2] cycloaddition leading to enantioenriched [7]helicene-like molecules.

One-Electron Reduction of Aromatic Ketones by Low-Valent Lanthanides. Isolation, Structural Characterization, and Reactivity of Lanthanide Ketyl Complexes

Abstract: In this paper we report on the isolation, structural characterization, and reactivity of a series of lanthanide ketyl complexes, which are generated by reactions of benzophenone and fluorenone with several different types of lanthanide reducing agents including Ln(OAr)2(L)x (Ar = C6H2-tBu2-2,6-Me-4; 1a: Ln = Sm, L = THF, x = 3; 1b: Ln = Yb, L = THF, x = 3; 1c: Ln = Sm, L = HMPA, x = 2; 1d: Ln = Yb, L = HMPA, x = 2), (C5Me5)2Ln(THF)2 (Ln = Sm, Yb), (C5Me5)Sm(OAr)(HMPA)2, Sm(N(SiMe3)2)2(THF)2, and Ln/HMPA (Ln = Sm, Yb) (HMPA = hexamethylphosphoric triamide). Reactions of 1a−d with 1 equiv of fluorenone in THF afforded the corresponding ketyl complexes Ln(OAr)2(ketyl)(L)2 (3a−d) in 85−90% isolated yields. Hydrolysis of 3a (Ln = Sm, L = THF) gave the corresponding pinacol-coupling product, 1,2-bis(biphenyl-2,2‘-diyl)ethane-1,2-diol (4), while air oxidation of 3a yielded fluorenone almost quantitatively. Reaction of 3a with 1 equiv of 1a followed by hydrolysis afforded fluorenol quantitatively. When 3a was dis...

Monodisperse Oligofluorenes with Keto Defect as Models to Investigate the Origin of Green Emission From Polyfluorenes: Synthesis, Self-Assembly, and Photophysical Properties

Abstract: Oligofluorenes (a trimer, pentamer, and heptamer) with one fluorenone unit in the center (OFnK: n=3, 5, or 7) were synthesized and used as models to understand the origin of the low-energy emission band in the photoluminescence and electroluminescence spectra of some polyfluorenes. All compounds form glasses with T(g) at 30 degrees C (OF3 K), 50 degrees C (OF5 K) and 57 degrees C (OF7 K). Oligomers OF5 K and OF7 K exhibit smectic liquid crystal phases that undergo transition to isotropic melts at 107 and 205 degrees C, respectively. Oligomer OF5 K could be obtained in form of single crystals. The X-ray structure analysis revealed the helical nature of the molecule and a helix reversal defect located at the central fluorenone unit. The packing pattern precludes formation of excimers. Electrochemical properties were investigated by cyclic voltammetry. The ionization potential (I(p)) and electron affinity (E(a)) were calculated from these data. Studies of the photophysical properties of OFnK in solution and thin film by steady-state and time-resolved fluorescence spectroscopic measurements suggest efficient funneling of excitation energy from the photoexcited fluorene segments to the low-energy fluorenone sites by both intra- and intermolecular hopping events whereby they give rise to green emission. Intermolecular energy transfer was investigated by using a model system composed of a highly defect free polyfluorene PF2/6 doped by OFnK. Forster-type energy transfer takes place from PF2/6 to OFnK. The energy-transfer efficiency increases predictably with increasing concentration of OFnK.

Ultrafast intermolecular hydrogen bond dynamics in the excited state of fluorenone

Abstract: Steady-state fluorescence and time-resolved absorption measurements in pico- and femtosecond time domain have been used to investigate the dynamics of hydrogen bond in the excited singlet (S 1 ) state of fluorenone in alcoholic solvents. A comparison of the features of the steady-state fluorescence spectra of fluorenone in various kinds of media demonstrates that two spectroscopically distinct forms of fluorenone in the S 1 state, namely the non-hydrogen-bonded (or free) molecule as well as the hydrogen-bonded complex, are responsible for the dual-fluorescence behavior of fluorenone in solutions of normal alcoholic solvents at room temperature (298 K). However, in 2,2,2-trifluoroethanol (TFE), a strong hydrogen bond donating solvent, emission from only the hydrogen-bonded complex is observed. Significant differences have also been observed in the temporal evolution of the absorption spectroscopic properties of the S 1 state of fluorenone in protic and aprotic solvents following photoexcitation using 400 nm laser pulses. An ultrafast component representing the solvent-induced vibrational energy relaxation (VER) process has been associated with the dynamics of the S 1 state of fluorenone in all kinds of solvents. However, in protic solvents, in addition to the VER process, further evolution of the spectroscopic and dynamical properties of the S 1 state have been observed because of repositioning of the hydrogen bonds around the carbonyl group. In normal alcohols, two different kinds of hydrogen-bonded complex of the fluorenone-alcohol system with different orientations of the hydrogen bond with respect to the carbonyl group and the molecular plane of fluorenone have been predicted. On the other hand, in TFE, formation of only one kind of hydrogen-bonded complex has been observed. These observations have been supported by theoretical calculations of the geometries of the hydrogen-bonded complexes in the ground and the excited states of fluorenone. Linear correlation between the lifetimes of the equilibration process occurring because of repositioning of the hydrogen bonds and Debye or longitudinal relaxation times of the normal alcoholic solvents establish the fact that, in weakly hydrogen bond donating solvents, the hydrogen bond dynamics can be described as merely a solvation process. Whereas, in TFE, hydrogen bond dynamics is better described by a process of conversion between two distinct excited states, namely, the non-hydrogen-bonded form and the hydrogen-bonded complex.

Photochemical insolubilisation of polymers

Abstract: Light-sensitive compositions are produced by homogeneously mixing (A) a soluble, light-sensitive polymer being (i) a polymer carrying side substituents possessing unsaturation of the acryl or alkylacryl type, or (ii) a polycondensation product of an aliphatic or aromatic diol with an aliphatic dicarboxylic acid possessing side-chain unsaturation, and (B) a synergistic activating mixture consisting of two different activating agents of which one is benzophenone, p,p1 - bis - (dialkylamino) benzophenone or fluorenone, and the other is benzoin, benzoin methyl ether, anthraquinone, 2-methylanthraquinone, benzophenone, benzyl, xanthone, 1,3,5-triacetylbenzene, fluorenone, fluorene, biacetyl, propiophenone or benzaldehyde. Polymers (A) (i) specified are the reaction products of acrylic acid chloride or alkylacrylic acid chloride with polymers containing hydroxyl or thiol groups such as cellulose, starch and dextrin and their partial ethers and esters, polyvinyl alcohol and its partial acetals and ethers, vinyl alcohol copolymers, polyhydroxy polyethers derived from epichlorohydrin and 2,2 - bis - (4 - hydroxyphenyl) propane, thiolated gelatin, polythiolstyrene, polyvinyl mercaptan, and the condensation product of poly-(isophthalylidene - hexamethylenediamine) and thioglycolic acid. The compositions may also contain organic solvents.