Theoretical Studies on the Molecular Structures and Thermodynamic Properties of Polychlorinated Fluorenes

Geometric structures of 135 polychlorinated fluorene （PCFR） molecules were optimized using density functional theory （DFT） at the B3LYP/6-311G＊＊ level and their thermodynamic properties in the ideal gas state were calculated. The relations of these thermodynamic properties with the number and position of chlorine atoms were also explored, from which the relative stability of PCFR congeners was theoretically proposed according to the magnitude of the relative standard Gibbs free energy of formation （Δr,fGθ）. The results show that the geometric configuration of PCFR isomers is determined by the position of chlorine atoms. There exist two types of intramolecular weak interactions, i.e., C–H···Cl and Cl···Cl interactions in PCFR molecules. The change of ΔfHθ and ΔfGθ of most stable PCFR isomers with increasing the number of chlorine atoms is different from that in most unstable PCFR congeners. The values of ΔfHθ and ΔfGθ for PCFR isomers with the same number of chlorine atoms strongly depend on the position of chlorine atoms and the relative stability of PCFR congeners is mainly determined by intramolecular delocalized π bond and Cl···Cl nuclear repulsive interaction.

A Comparative Kinetic Study on the Efficacious Permanganate Oxidation of Fluorenes in Perchloric and Sulfuric Acid Media

Oxidation kinetics of fluorene (Fl) and its halogenated derivatives, namely, 2,7-dichlorofluorene (Fl-Cl), 2,7-dibromofluorene (Fl-Br) and 2,7-diiodofluorene (Fl-I), by permanganate ion in both perchloric and sulfuric acid media have been investigated using conventional spectrophotometric technique. In both acidic media, the reactions manifested first order kineticsin [permanganate] and less than unit order each in [reductants] and [acid]. Increasing ionic strength had no effect on the oxidation rates. Oxidation rates of fluorenes in perchloric acid were higher than those in sulfuric acid and the order of the oxidation rates was: Fl > Fl-I > Fl-Br > Fl-Cl. Final oxidation products were identified by GC/MS and FT-IR analyses in all cases as 9H-fluorenone derivatives. Reaction constants as well as activation parameters of the second order rate constants were also evaluated.

Synthesis and Characterization of 9,9-diethyl-1-phenyl-1,9-dihydrofluoreno[2,3-d]imidazole-ended Fluorophores

A series ofπ-conjugated compounds ending with 9,9-diethyl-1-phenyl-1,9-dihydrofluoreno[2,3-d]imidazole were conveniently synthesized by condensation of the key intermediate9,9-diethyl-N^(2)-phenyl-9H-fluorene-2,3-diamine with the corresponding symmetric aryl phthalaldehydes under very mild conditions.The structures of these compounds were confirmed by^(1)H NMR,^(13)C NMR,and HRMS.Their UV-Vis spectroscopy data,fluorescent spectroscopy data,and further details of the electronic properties from cyclic voltammetry measurements and theoretical calculations were studied.Most compounds possess good fluorescence-emitting ability with quantum yield of fluorescence values in the region of 0.36-0.92 and display emission within 449-513 nm depending on the molecular nature.

Synthesis of Fluorene Derivatives Via TfOH-catalyzed Intramolecular Friedel-Crafts Alkylation Reactions

We devoloped an efficient and simple method to synthesize fluorene derivatives via intramolecular Friedel-Crafts alkylation of chalcones.The transform is catalyzed by TfOH in CH_(3)NO_(2)at 80℃and the yield is up to 99%.

Synthesis and Crystal Structure of 10-(3,4-Dichlorophenymethylidyne)-9,10-dihydrofluorene

A novel compound of 10-（3,4-dichlorophenymethylidyne）-9,10-dihydrofluorene （C20H12Cl2, Mr = 323.20） was synthesized via Knoevenagel reaction under microwave irradiation （500 w） within short reaction time （8 min）, giving a high yield of product （87%）. Its structure was determined by IR, 1H NMR, MS, elemental analysis and X-ray diffraction. The crystal of the new compound is of monoclinic system, space group P21/c with a = 12.8781（13）, b = 16.5067（16）, c = 7.4656（7）, β = 103.567（2）o, V = 1542.7（3）3, Z = 4, Dc = 1.392 g/cm3, μ = 0.413 mm-1, F（000） = 664, R = 0.0569 and wR = 0.1342 for 3355 observed reflections with I 2σ（I）. The crystal structure involves a conjugated system which shows an olefin structure.

Experimental Study on the Solubility of Fluorene in Different Solvents

The solubilities of fluorene in Exxsol D30, Exxsol D40, and crude dimethyl ethylbenzene(DME) from 299.25 to 356.85 K were investigated using the gas chromatography(GC) observation technique. Solubility curves were obtained based on the results and correlated with the modified Apelblat and λh equations to provide a valid model to predict the dissolution thermodynamic properties of fluorene at different temperatures, which is important in separating fluorene by crystallization.

Synthesis, Crystal Structure and Properties of 2,7-Bis[4-(diphenylamino)phenyl]fluorene

A novel fluorene derivative containing triphenylamine groups, 2,7-bis[4-（diphe- nylamino）-phenyl]fluorene （C49H36N2, Mr = 652.80）, was synthesized via Suzuki coupling reaction （yield： 19%） and its crystal structure was determined by single-crystal X-ray diffraction. It crystallizes in triclinic, space group P1 with a = 9.320（4）, b = 11.250（6）, c = 17.369（6） A, a = 88.035（3）, β = 86.450（5）, γ = 73.524（5）°. V= 1742.8（13）A3, Z = 2, Dc = 1.244 g/cm3, p（MoKa） = 0.072 mm-1, F（000） = 688, S = 1.095, the final R = 0.0616 and wR = 0.1878. It presents a linear framework constituted by a linkage of fluorene as a bridge and two triphenylamine groups. Its spectral and electrochemical properties were studied by UV-Vis absorption, fluorescence spectroscopy and cyclic voltammetry （CV）. This compound can emit intense blue fluorescence with a peak wavelength of 446 nm and a full width at half maximum （FWHM） of 38 nm under UV excitation at 350 nm in film. The highest occupied molecular orbital （HOMO） energy level, the lowest unoccupied molecular orbital （LUMO） energy level and optical band gap （Eg） of the title compound are -5.46, -2.57 and 2.89 eV, respectively.

Distribution and Geochemical Implication of Aromatic Hydrocarbons across the Meishan Permian-Triassic Boundary

Aromatic compounds extracted from sedimentary rocks can reflect environmental conditions, organic sources and maturity. The aromatics, identified in association with mass extinction in particular, would provide a signature assisting our understanding of the causes of the biotic crisis. Aromatic hydrocarbons were fractionated from the total lipid extracts of 37 samples taken from the PermianTriassic boundary （beds 23 to 34） of section B at Meishan （煤山）, Zhejiang （浙江） Province in South China. These aromatics were analyzed by using gas chromatography-mass spectrometry （GC-MS）. Main compounds identified include naphthalene, phenanthrenes, fluorene, dibenzothiophene, dibenzofuran, fluoranthene, pyrene and some of their methyl homologues. The indices of methyl phenanthrene distribution fraction indicate the comparable maturity （within the oil window, 0.7%-1.0% of the mean vitfinite reflectance） of the organic matter throughout the whole profile analyzed. The ratio of dibenzothiophene to phenanthrene （DBT/PHN） varies generally at a comparable pace with lithology. Significantly, a gradual decrease of this ratio was observed within bed 24 limestone, which is probably due to the variation of sedimentary environment. This change is in line with the drop in the carbon isotope composition of carbonate, the loss of the Changhsingian reef ecosystem, and the decrease of cyanobacteria abundance within the bacteria population. The coincidence of these records suggests a close relation between the biotic crisis and marine environmental conditions, and these records clearly show the onset of the biotic crisis prior to event bed 25.

Synthesis and characterization of X-shaped oligo(para-phenylene) derivatives functionalized with fluorene ethynylene

A series of linear and X-shaped oligo（para-phenylene） derivatives functionalized with fluorene ethynylenes 1,3 and 4 were synthesized through sequent Sonogashira coupling and Suzuki-Miyaura reaction in high yield.The electron-donating group-OCH3 and electron-withdrawing counterparts-CF3 were introduced to tune the spectra properties of compounds 3 and 4.The detail investigation of their photophysical properties in solution and film indicated that the introduction of both -OCH3 and -CF3 makes maximum emission distinct red-shift in comparison with parent compound 1,but the latter more prominently.

Synthesis and Crystal Structure of 2-Nitro-9,9-bis(methylpropionate)fluorine

The title compound of 2-nitro-9,9-bis（methylpropionate）fluorine （C21H21NO6, Mr = 383.39） was synthesized for the first time. Complete assignments were achieved by 1H NMR, IR, EI-MS, elemental analysis and single-crystal X-ray diffraction technique. The crystal belongs to monoclinic, space group P21/c with a = 11.4581（15）, b = 10.3624（14）, c = 16.573（2） A.,/？ = 96.629（2）°, V = 1954.6（5） A3, Z = 4, Dc = 1.303 g/cm3, p = 0.096 mm-1, F（000） = 808, R = 0.0493 and wR = 0.1499 for 3107 observed reflections with I 〉 2tr（/）. X-ray analysis reveals that three fused rings of the fluorene system are almost coplanar and the two ester groups are nearly perpendicular to the fused-ring system. Weak C-H...O hydrogen bonding connects the molecules into centrosymmetric dimmers.

SYNTHESIS,CHARACTERIZATION AND PHOTOLUMINESCENT PROPERTIES OF NEW PLATINUM-CONTAINING POLY(FLUORENYLENEETHYNYLENE) ANCHORED WITH CARBAZOLE PENDANTS

A new luminescent and thermally stable platinum(Ⅱ) polyyne polymer trans-[-Pt(PBu_3)_2C=CArC=C-]_n(P1) containing the 2,7-fluorene chromophoric spacer substituted by pendant carbazolyl group via long alkyl bridges. The regiochemical structures of these compounds were studied by various spectroscopic analyses.We report the photophysical properties of this group 10 polymetallayne and a comparison was made to its binuclear model complex trans-[Pt(Ph)(PEt_3)_2C≡CArC≡CPt(Ph)(PEt_3)_2](M1) as well as to those wit...

FLUORENE-BASED LIGHT-EMITTING POLYMERS

Several series of fluorene-based light-emitting polymers with the emphasis on achieving efficient and stable bluelight emission are reported. Spiro-functionalization may narrow the emission spectra (with smaller tail at Ionger wavelengths)of fluorene homopolymers to provide purer blue emission. The thermal spectral stability of the polymers could also beimproved because of the elevation of the glass transition temperature caused by the spiro-functionalization. However, theexcimer emission in fluorene homopolymers is not suppressed by the spiro-functionalization. Alternate copolymers of 9,9-dihexylfluorene and substituted phenylenes may emit efficient blue ligh both in solution and in film. The optical propertiesare dependent on the substituion on the phenylene ring. The alkoxy-substituted polymers displayed efficient PL and EL andgood thermal spectral stability. The HOMO and LUMO energy levels of the polymers based on the backbone structure couldbe tuned in a wide range by attaching different functional groups on the phenylene ring. By attaching europium(III) complexat the ends of the side chains in the alternate copolymers, we have demonstrated a new approach to achieving red emissionwith a very narrow spectrum. The copolymers of 9,9-dihexylfluorene and thiophene and bithiophene with differentsubstitutions were also synthesized to study the effect of substitution and regioregularity on the optical and other physicalproperties of the polymers.

SYNTHESIS AND PROPERTIES OF POLY(AROMATIC DIACETYLENE)S CONTAINING FLUORENE

Novel fluorene-based poly(aromatic diacetylene)s have been synthesized by CuCl-catalyzed oxidative coupling of aromatic diynes.New aromatic diynes 2,7-diethynyl-9,9-bis(triphenylamine)fluorene(M_1)is synthesized by multistep reactions.The structures and properties of the polymers are characterized and evaluated by IR,NMR,TGA,UV, photoluminescence(PL),and cyclic voltammetry analyses.These polymers possess good thermal stability.All the polymers are completely soluble in coammon solvents such as toluene,THF,c...

Exciplex elimination in an organic light-emitting diode based on a fluorene derivative by inserting 4,4'-N,N'-dicarbazole-biphenyl into donor/acceptor interface

Organic light-emitting diodes （OLEDs） composed of a novel fluorene derivative of 2,3-bis（9,9-dihexyl-9H-fluoren- 2-yl）-6,7-difluoroquinoxaline （F2Py） were fabricated, and exciplex emission was observed in the device. To depress the exciplex in an OLED for pure colour light emission, 4, 4＇-N,N＇-dicarbazole-biphenyl （CBP） was inserted as a separator at the donor/acceptor interface. It was found that the device without the CBP layer emitted a green light peaking at 542 nm from the exciplex and a shoulder peak about 430 nm from F2Py. In contrast, the OLED with CBP layer emitted only a blue light peak at about 432 nm from F2Py. Device efficiencies were calculated by a simulative mode in an injection controlled type mechanism, and the results showed that exciplexes yield much lower quantum efficiency than excitons. The device with CBP has a higher power efficiency as no exciplex was present.

Syntheses,Structures,and Properties of Two Cobalt(Ⅱ)Coordination Complexes Based on(Fluorene-9,9-diyl)dipropanoic Acid and 1,3-Bis(imidazol-1-yl)butane Ligands

Two new cobalt（II） coordination complexes, namely [Co（HL）2（biim）（H2O）2]n·n H2O（1） and [Co（Et L）2（biim）]n·3 n（H2O）·2 n（Et HL）（2）（H2L =（fluorene-9,9-diyl）dipropanoic acid, biim = 1,3-bis（imidazol-1-yl）butane）, have been synthesized using the same starting reactants but different solvent medium. The two complexes exhibit distinctly different structures. Compound 1 exhibits a one-dimensional linear chain structure. However, complex 2 reveals a one-dimensional zigzag chain structure. Thermogravimetric analyses（TGA） and luminescent properties of these two complexes have been discussed.

Polypyrrole Chitosan Cobalt Ferrite Nanoparticles Composite Layer for Measuring the Low Concentration of Fluorene Using Surface Plasmon Resonance

Fluorene is a polycyclic aromatic hydrocarbon, which is a hazardous toxic chemical in the environment. The measurement of low concentrations of fluorene is a subject of intense interest in chemistry and in the environment. Polypyrrole chitosan cobalt ferrite nanoparticles are prepared using the electrochemical method. The prepared layers are characterized using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy. The layers are used to detect fluorene using the surface plasmon resonance technique at room temperature. The composite layer is evaluated after detection of fluorene using atomic force microscopy. The fluorene is bound on the layer, and the shift of the resonance angle is about 0.0052°, corresponding to the limitation of 0.01 ppm.

Synthesis and Photophysical Properties of Fluorene or Carbazole-Based Alternating Copolymers Containing Si and Ethynylene Units in the Main Chain

Alternating copolymerization of 9,9-dihexyl-2,7-dibromofluorene, N-hexyl-2,7-dibromocarbazole (HCz) with diethynyldimethylsilane, diethynyldiphenylsilane, has been investigated using Sonogashira coupling reaction. Photophysical properties of the resulting copolymers were investigated with UV-Vis absorption and photoluminescence spectroscopy. All the copolymers in chloro-form solution showed absorption peaks at 270 - 280 nm with shoulder peaks at around 380 nm derived from π-π* transition or intra-molecular charge transfer through σ-π moiety, respectively. The chloroform solutions of the copolymers showed broad emission peaks at 415 - 425 nm. The emission wave lengths of the copolymers in the solid state (cast film) detected at 360 - 385 nm were remarkably blue-shifted in comparison with those in the chloroform solutions. Hydrosilylation reaction of the copolymers with 1,4-bis(dimethylsilyl)benzene yielded networked copolymers soluble in chloroform, indicating formation of branching polymers. The chloroform solutions of the HCz-based networked copolymers showed bimodal emission derived from new highly energy states in the σ-π conjugation.

Synthesis and Solvatochromic Behavior of Hexaphenylbenzenes and Indeno[1,2-<i>b</i>]fluorene Derivatives with Hydroxy Groups

Hexakis(4-methoxyphenyl)benzene (HPB-OMe(1)) and hexakis(2,6-dimethyl-4-methoxyphenyl)benzene (HPB-OMe(2)) were synthesized via organometallic complex catalysis. The treatment of HPB-OMe(1) with FeCl3 caused cyclodehydrogenation at two positions to yield an oligophenylene with an indeno[1,2-b]fluorene structure (IF-OMe). Deprotection of the methoxy groups of these compounds was conducted by treatment with BBr3. Deprotonation of the OH groups of HPB-OH(1), HPB-OH(2), and IF-OH through treatment with NaH caused a bathochromic shift in the absorption and photoluminescence (PL) peaks. The bathochromic shift of the deprotonated species increased with the donor number (DN) of the solvents. These observations can be explained as the consequence of intramolecular charge transfer (ICT) from the ONa groups to the inner benzene rings.

Fluorene pendant-functionalization of poly(N-vinylcarbazole)as deep-blue fluorescent and host materials for polymer light-emitting diodes

π-Electron coupling of pendant conjugated segment inπ-stacked semiconducting polymers always causes the formation of defect trapped sites and further quenched high-band excitons,which is harmful to the performance and stability of deep-blue polymer light-emitting diodes(PLEDs).Herein,considerate of“defect”carbazole(Cz)electromers in poly(N-vinylcarbazole)(PVK),a series of fluorene units are introduced into pendant segments(PVCz-DMeF,PVCz-FMeNPh and PVCz-DFMeNPh)to suppress the strongπ-electron coupling of pendant Cz units and enhance radiative transition toward fabricating sable PLEDs.Compared to PVCz-FMeNPh and PVCz-DFMeNPh,PVCz-DMeF spin-coated films show a relatively efficient deep-blue emission,completely similar to its single pendant chromophore,confirmed an extremely weak charge-transfer and electron coupling between adjacent pendant segments.Therefore,PLEDs based on PVCz-DMeF present stable and deep-blue emission with a high color purity(0.17,0.08),associated with extremely weak defect emission at 600∼700nm(induced by carbazole electromers).Finally,PLEDs based on PVCz-DMeF/F8BT blended films(1:1)also present the high maximum luminance(Lmax)of 6261 cd/m2 and current efficiency(CE_(max))of 2.03 cd/A,confirmed slightly trapped sites formation.Therefore,precisely control the arrangement and packing model of pendant units inπ-stacked polymer is an essential prerequisite for building efficient and stable emitter for optoelectronic devices.

One-Pot Synthesis of Spiro[fluorene-9,9'-xanthene]Derivatives

As a novel class of spirofluorenes,spirobifluorene(SBF)and spiro[fluo-rene-9,9'-xanthene]derivatives(SFXs)have orthogonal geometric config-uration,spiro-conjugation effect,and rigid steric hindrance,which can be widely used in the fields of synthetic chemistry,materials chemistry and supramolecular chemistry.Due to their facile one-pot synthetic route,and to the variety of molecular designs,SFXs are expected to become new spiro functional materials that replace SBF.In this review,we present the history,development and expansion of SFXs synthesis in one-pot methods,and the advantages and limitations of one-pot synthesis are also dis-cussed.