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PubMed1986

1H NMR study of self-association and restricted internal rotation of the C8-substituted deoxyguanosine 5'-monophosphate adduct of the carcinogen 2-(acetylamino)fluorene.

The high-field 1H NMR spectra of a nucleotide-carcinogen adduct formed from 2-(acetylamino)fluorene (8-(N-fluoren-2-ylacetamido)-2'-deoxyguanosine 5'-monophosphate) have been examined in aqueous solution as a function of concentration at high and low temperatures. An anomalous concentration dependence of NMR spectra was observed at concentration levels over 1 mM. These spectral characteristics have been analyzed in terms of changes in self-association and in the interconversions between torsional diastereomers associated with the central nitrogen. Association constants have been computed. Stacking interactions, which involve both the fluorene and guanine rings, are strong, cooperative and highly temperature-dependent. Deacetylation alters the mode of stacking. Several effects of solvent and aggregation on the conformation at the central nitrogen are discussed.

2-Acetylaminofluorene↗
PubMed1982

Effects of prolonged oral treatment with N-fluoren-4-ylacetohydroxamic acid on rat liver fine structure.

Inbred male Leeds strain rats were given a diet containing 0.05% N-fluoren-4-ylacetohydroxamic acid for up to 7 months. A modified method for the synthesis of this compound is described. Rats were killed at intervals during and after treatment and their liver tissues examined by light and electron microscopy. The treated rats developed a very low incidence of (non-hepatic) tumours and hepatic clear cell foci appeared during the late stages of the experiment. The only significant fine structural changes observed were glycogenosis and alterations in the morphology of the rough endoplasmic reticulum, both of which developed only after prolonged treatment and affected a minority of hepatocytes. These changes are discussed in relation to the fine structural changes elicited by the strongly carcinogenic N-fluoren-2-ylacetamide and the non-carcinogen, N-fluoren-4-ylacetamide.

2-Acetylaminofluorene↗
PubMed2001

9-(1-Acetoxyethylidene)fluorene ("diacetylfluorene"), a by-product from the acetylation of 9-fluorenyllithium.

Treatment of 9-fluorenyllithium with acetyl chloride produces 9-acetylfluorene, (I), and several by-products, among which is "diacetylfluorene", now characterized definitively as 9-(1-acetoxyethylidene)fluorene [IUPAC name: (1-fluoren-9-ylidene)ethyl acetate], (II), C(17)H(14)O(2), derived from acetylation of initially formed (I). Various parameters disclose substantial structural distortion within (II) emanating from A((1,3)) strain associated with the 9-(acetoxyethylidenyl)fluorene system.

Journal Article↗
PubMed2004

Nonlinear transmission and excited-state absorption in fluorene derivatives.

The nonlinear transmission and the excited-state absorption spectra of three fluorene derivatives exhibiting large two-photon absorptivity were measured by the third harmonic of a picosecond Nd:YAG laser. We analyzed their capability for exhibiting stimulated emission in polar solvents and found that asymmetrical fluorene compounds with a diphenylamino substituent exhibited large Stokes shifts (approximately 8000 cm(-1)), high quantum yields (approximately 0.9-1.0), and no optical gain over their entire fluorescence spectral region. In contrast, a symmetrical fluorene derivative with vinylphenylbenzothiazole substituents in positions 2 and 7 underwent lasing under one-photon excitation by use of picosecond pulsed irradiation.

Journal Article↗
PubMedDate not supplied

[Experimental study of the new medicinal form of the antiviral preparation fluorenal].

Repository forms of a 0.1% fluorenal solution prepared with buffered polyglucin and a 1% polyacryamide were found to be curatively effective in experimental herpetic keratitis in rabbits. When stored in small tube-droppers for not less than 12 months (observation time) the repository fluorenal eye drops retain their therapeutic activity. In its new presentation the drug is highly effective, stable and convenient in use. This medicinal preparation of fluorenal permits reduce its concentration and the number of instillations.

Acrylamides↗
PubMed2006

Two-photon photochromism of a diarylethene enhanced by Förster resonance energy transfer from two-photon absorbing fluorenes.

Resonance energy transfer from two-photon absorbing fluorene derivatives to the photochromic compound 3,4-bis-(2,4,5-trimethyl-thiophen-3-yl)furan-2,5-dione (PC 1) is investigated in hexane under one- and two-photon excitation. The quenching of the steady-state fluorescence of donor molecules in the presence of the diarylethene acceptor is used to study the nature of resonance energy transfer. The Förster distances and critical acceptor concentrations are determined for nonbound donor-acceptor pairs in homogeneous molecular ensembles. Quite significantly, up to a two-fold enhancement in the velocity of the photochromic transformation of 1, in the presence of two-photon absorbing fluorene derivatives, is demonstrated.

Ethylenes↗
PubMed2007

One- and two-photon singlet oxygen generation with new fluorene-based photosensitizers.

The spectral properties of new fluorene-based photosensitizers for efficient singlet oxygen production are investigated at room temperature and 77 K. Two-photon absorption (2PA) cross-sections of the fluorene derivatives are measured by the open aperture Z-scan method. The quantum yields of singlet oxygen generation under one- and two-photon excitation (phi(delta) and 2PAphi(delta), respectively), are determined by the direct measurement of singlet oxygen luminescence at approximately 1270 nm. The values of phi(delta) are independent of excitation wavelength, ranging from 0.6-0.9. The singlet oxygen quantum yields under two-photon excitation are 2PAphi(delta) approximately 1/2 phi(delta), indicating that the two processes exhibit the same mechanism of singlet oxygen production, independent of the mechanism of photon absorption.

Fluorenes↗
PubMed1990

Degradation of phenanthrene, fluorene and fluoranthene by pure bacterial cultures.

Bacterial mixed cultures able to degrade the polycyclic aromatic hydrocarbons (PAH) phenanthrene, fluorene and fluoranthene, were obtained from soil using conventional enrichment techniques. From these mixed cultures three pure strains were isolated: Pseudomonas paucimobilis degrading phenanthrene; P. vesicularis degrading fluorene and Alcaligenes denitrificans degrading fluoranthene. The maximum rates of PAH degradation ranged from 1.0 mg phenanthrene/ml per day to 0.3 mg fluoranthene/ml per day at doubling times of 12 h to 35 h for growth on PAH as sole carbon source. The protein yield during PAH degradation was about 0.25 mg/mg C for all strains. Maximum PAH oxidation rates and optimum specific bacterial growth were obtained near pH 7.0 and 30 degrees C. After growth entered the stationary phase, no dead end-products of PAH degradation could be detected in the culture fluid.

Alcaligenes↗
PubMed2006

Singlet oxygen quantum yield determination for a fluorene-based two-photon photosensitizer.

The quantum yield, Phi(Delta), of singlet oxygen generation under two-photon excitation has been determined for a fluorene derivative. A photochemical method was developed using 1,3-diphenylisobenzofuran (DPBF), a chemical quencher of 1O2, and 2-(9,9-didecyl-7-nitrofluoren-2-yl)benzothiazole (1) as a two-photon photosensitizer (PS). The photochemical kinetics of the quencher was measured by two different fluorescence methods. Fluorene 1 exhibited relatively high singlet oxygen quantum yield, Phi(Delta) approximately 0.4 +/- 0.1, and had a two-photon absorption cross-section of 28 +/- 5 GM. Thus, 1 may have potential for use as a two-photon PS in the near-IR spectral region for biomedical applications.

Benzofurans↗
PubMed2006

Synthesis and characterization of new fluorene-based singlet oxygen sensitizers.

The synthesis, photophysical characterization, and determination of singlet oxygen quantum yields (Phi(Delta)) for a class of fluorene derivatives with potential application in two-photon photodynamic therapy (PDT) is reported. It has been demonstrated that these compounds possess the ability to generate singlet oxygen (1O2) upon excitation. A photochemical method, using 1,3-diphenylisobenzofuran (DPBF) as 1O2 chemical quencher, was employed to determine the singlet oxygen quantum yields (Phi(Delta)) of the fluorene-based photosensitizers in ethanol. Phi(Delta) values ranged from 0.35 to 0.75. These derivatives may have potential application as two-photon photosensitizers when pumped via two-photon excitation in the near-IR spectral region.

Benzofurans↗
PubMed1986

Binding of trifluoperazine and fluorene-containing compounds to calmodulin and adducts.

Calmodulin can be specifically acylated with a fluorene-containing hydrophobic spin-labeling reagent at just Lys 75 or at Lys 75 and Lys 148. The binding of trifluoperazine to calmodulin and the two adducts was determined using a Hummel-Dreyer procedure, and binding of the phenothiazine was found to be characterized by apparent positive cooperativity and an apparent limiting stoichiometry of about seven binding sites per protein molecule. Two non-reactive fluorene-containing compounds were synthesized, and both reagents exhibited far less binding to calmodulin than did trifluoperazine. One of these was also assayed for binding to the monolabeled adduct, and this binding was about half that observed with calmodulin and was non-cooperative. Thus, the qualitative and quantitative binding parameters of hydrophobic groups to calmodulin can be quite different.

Calmodulin↗
PubMed1979

Mutagenicity of fluorene derivatives: a proposed mechanism.

Several derivatives of fluorene, a tricyclic, organic molecule, have been found to induce both frameshift mutations and base-pair substitutions in Salmonella typhimurium strains developed by Ames. Comparisons of the mutagenic potency of these derivatives for several strains of Salmonella suggest the importance of a carbonyl group substituted at the carbon-9 position of mutagenic derivatives, with respect to mutagenic potency. In this study, we present a feasible mechanism for the interaction of mutagenic fluorene derivatives with deoxyribonucleic acid. This mechanism requires the interaction of the mutagenic molecule with carbon-8 of guanine and a second concurrent interaction with the C-4 amino group of an adjacent cytosine residue.

DNA, Bacterial↗
PubMed1981

Nitrated fluorene derivatives are potent frameshift mutagens.

Nitrated derivatives if fluorene are potent frameshift-type mutagens. A reduction of the nitro function is required for the expression of mutagenicity. Hydroxylamines are the presumed key intermediates, which following esterification to electrophiles are capable of forming adducts with cellular DNA. Evidence in support of this mechanism is obtained by the use of tester strains having a functional uvrB gene product or lacking specific nitroreductases. The mutagenic potency of nitrated fluorenes increases upon successive addition of nitro groups reaching a peak at the trisubstituted state. Addition of a 4th nitro group leads to decreased activity.

Fluorenes↗
PubMed1991

Clastogenicity of 1-nitropyrene, dinitropyrenes, fluorene and mononitrofluorenes in cultured Chinese hamster cells.

The chromosomal aberration test using a Chinese hamster lung cell line (CHL) was carried out on 1-nitropyrene (NP), 3 dinitropyrenes (DNPs), fluorene and 4 mononitrofluorenes with and without metabolic activation (rat S9 mix). The 3 DNPs (1,3-, 1,6- and 1,8-DNP) induced chromosomal aberrations in the absence of S9 mix. The frequencies of cells with aberrations after treatment for 48 h were 43% at 2 micrograms/ml of 1,3-DNP, 55% at 0.1 microgram/ml of 1,6-DNP and 45% at 0.025 microgram/ml of 1,8-DNP, indicating the order of clastogenic potency as 1,8- greater than 1,6- greater than 1,3-DNP. On the other hand, 1-NP, which is known to be a direct-acting mutagen in bacteria, was negative in the chromosomal aberration test without S9 mix, but clearly positive with S9 mix. This effect was dependent on the concentration of the S9 fraction in the reaction mixture. High-pressure liquid chromatography analysis showed that 1-NP was converted by S9 mix to several metabolites, including 1-aminopyrene (AP). The clastogenic activity of 1-AP, however, was equivocal without S9 mix, suggesting that active clastogens other than 1-AP exist. Fluorene induced chromosomal aberrations only in the presence of S9 mix (61.8% at 25 micrograms/ml). 1-, 2-, 3- and 4-nitrofluorene (NF) were more clastogenic in the presence of S9 mix than in the absence of S9 mix, suggesting that NFs were converted to more active clastogens by S9 mix.

Animals↗
PubMed2004

Photophysical processes of a fluorene derivative containing 1,3,4-oxadiazole.

The photophysical processes of 9,9-bis[4'-[2''-phenyl-5''-(3'''-(methacryl-amido)phenyl)]-1'',3'',4''-oxadiazolylphenyl]fluorene (F-MAOP) formed by Heck reaction of 9,9-bis(4'-iodophenyl)fluorene (F-IP) and 2-phenyl-5-[3'-(methacrylamido)phenyl]-1,3,4-oxadiazole (OXD) have been carefully studied. The results show that the compound emits blue and blue-violet light and the emission spectra exhibit obvious solvent effect. With the increase of polarity of solvents, the fluorescence spectra change obviously and appear blue shift at room temperature. In addition, the light-emitting can be quenched by both electron donor (N,N-dimethylaniline, DMA) and electron acceptor (C60). When N,N-dimethylaniline is gradually added into the solution of F-MAOP, the emission intensities of fluorescence are unusually increased. But when the concentration of DMA beyond a certain scope, the emission intensities of fluorescence are gradually decreased. The dimolecular exciplex between F-MAOP and C60 are formed and the quenching effect follows the Stern-Volmer equation. Moreover, interaction between F-MAOP and carbon nanotubes (CNTs) is also studied by fluorescent quenching.

Absorption↗
PubMed2005

Photophysical processes of a fluorene derivative containing carbazole unit.

The photoluminescence properties of 9,9-bis[4'-(9''-carbazovinylene)phenyl]fluorene (F-CZV) formed by Heck reaction of 9,9-bis(4'-iodophenyl)fluorene (F-IP) and N-vinylcarbazole have been carefully studied. The results show that the compound emits blue light and the dimolecular excimer is formed with gradual increase in concentration of F-CZV. The results also indicate the interaction between F-CZV and electron donors (N,N-dimethylaniline) or electron acceptors (dimethylterephthalate, fullerene carbon nanotubes) can be efficiently generated where the processes follow the Stern-Volmer equation. Moreover, when dimethylterephthalate (DMTP) or carbon nanotubes (CNTs) is gradually added into the solution of F-CZV, the emission intensities of fluorescence are unusually increased. But when concentration of dimethylterephthalate or carbon nanotubes beyond a certain scope, the emission intensities of fluorescence are gradually decreased.

Carbazoles↗
PubMed2004

Synthesis, characterization and photophysical processes of fluorene derivative containing naphthalene nucleus.

A novel luminescent compound, 9,9-bis[4'-(beta-naphthyl-methacrylate)phenyl]fluorene (F-NMAP) is synthesized by Heck reaction of beta-naphthyl methacrylic ester (NMAE) and 9,9-bis(4'-iodophenyl)-fluorene (BIPF). The structure is characterized by MS, 1H NMR, IR, and UV-vis spectroscopy. The photophysical processes of F-NMAP have been carefully investigated by UV-vis absorption and fluorescence spectra. The results show that the compound emits blue and blue-violet light. The luminescence quantum yield is 0.652 in ethanol and the emission spectra exhibit obvious solvent effect. With the increase in polarity of solvents, the fluorescence spectra change obviously and appear blue shift at room temperature. The light emitting can be quenched by both electron donor, N,N-dimethylaniline (DMA), and electron acceptor, dimethylterephthalate (DMTP). On adding gradually, DMA or DMTP into the solution of F-NMAP, the emission intensities of fluorescence are unusually increased. But when the concentration of DMA or DMTP goes beyond a certain scope, the emission intensities of fluorescence are gradually decreased. Simultaneously, the maximum emission peaks of F-NMAP-added DMA are blue-shifted and the maximum emission peaks of F-NMAP-added DMTP are red-shifted, respectively. Moreover, interactions between F-NMAP and fullerene (C60), or carbon nanotubes (CNTs) are also studied by fluorescent quenching where the processes follow the Stern-Volmer equation.

Aniline Compounds↗
PubMed2006

Photoinduced intermolecular electron transfer process of fullerene (C60) and amine-substituted fluorenes studied by laser flash photolysis.

Photoinduced intermolecular electron transfer process of fullerene (C60) with 9,9-bis(4-triphenylamino)fluorene (BTAF) and 9,9-dimethoxyethyl-2-diphenylaminofluorene (DAF) in toluene and benzonitrile has been investigated by nanosecond laser photolysis technique in the visible/near-IR regions. By the selective excitation of C60 using 532 laser light, it has been proved that the electron transfer takes place from the ground states BTAF and DAF to the triplet excited state of C60 ((3)C60*) by observing the radical anion of C60 and radical cation of BTAF and DAF. It was observed that the electron transfer of BTAF/(3)C60* is more efficient than DAF/(3)C60* reflecting the effect of amine-substitutents of the fluorene moiety on the efficiency of the electron transfer process. On addition of a viologen dication (OV(2+)), the electron of the anion radical of C60 mediates to OV(2+) yielding the OV(+). These results proved that the photosensitized electron-transfer/electron-mediating processes have been confirmed by the transient absorption spectral method.

Amines↗