Absorption and luminescence spectra of electroluminescent liquid crystals with triphenylene,pyrene and perylene units

New derivatives of triphenylene, perylene, and pyrene are described, some of which form columnar mesophases. The absorption spectra are investigated both experimentally and theoretically. The spectra calculated using the density functional tight binding (DFTB) theory are in good agreement with experimental results. The investigated compounds show photoluminescence of violet-blue (triphenylene), yellow-green (pyrene), and orange-red (perylene) colours. In addition, electroluminescence is observed in thin films of these compounds between a positively charged ITO electrode and a negatively charged aluminium electrode. The brightness of the electroluminescence decreases in the order perylene > pyrene > triphenylene. Threshold voltages below 20 V and a luminance up to 100 cd m^-2 were observed.     

Error propagation as a factor in selection of measurement intervals for the determination of polycyclic aromatic hydrocarbons by second-derivative spectrofluorimetry

The most suitable wavelength intervals were selected for the determination of 4 polycyclic aromatic hydrocarbons (PAHs; benzo[g,h,i]perylene, dibenzo[a,h]anthracene, pyrene, and triphenylene) in very complex mixtures of 11 PAHs: anthracene, benz[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[g,h,i]perylene, benzo[k]fluoranthene, chrysene, dibenz[a,h]anthracene, phenanthrene, pyrene, and triphenylene. The multiple linear regression algorithm was applied to measurements made in several wavelength intervals previously selected on the basis of sensitivity and minimum number of interfering compounds. Of the different models obtained, those displaying minimum error propagation in the analytical result were selected. By applying the models proposed in this study, we precisely and accurately determined benzo[g,h,i]perylene, dibenz[a,h]anthracene, pyrene, and triphenylene in complex mixtures--a feat that could not be achieved by the use of constant-wavelength spectrofluorimetry in combination with second-derivative techniques.     

NMR relaxation of rigid molecules in the nematic phase of a discotic liquid crystal

Abstract

Frequency and temperature dependent NMR relaxation measurements were performed on deuteriated benzene, pyrene and triphenylene dissolved in the nematic phase of a discotic liquid crystal. The results show a strong frequency dependence of the spectral densities. Based on the symmetries of the system and the usual model for director fluctuations this frequency dependence should be equal for J ₁ and J ₂. From fitting the commonly used model of rotational diffusion and director fluctuations to the data we see that this is not the case for benzene and triphenylene, even though the fits themselves are satisfactory. Values for the elastic constants, effective viscosity and translational diffusion in similar discotic liquid crystals do not account quantitatively for the frequency dependence of benzene. For both pyrene and triphenylene quantitative comparison was impossible due to lack of translational diffusion data. We also find that the so-called cut-off wave-length is of the order of the dimensions of the liquid crystal molecules, just as in ordinary nematics.     

A Gas Liquid Chromatographic Fluorescent Procedure for the Analysis of Benzo(A)Pyrene in 24 Hour Atmospheric Particulate Samples

Abstract

This paper describes a selective method for the assay of benzo(a)pyrene (BaP) in 24 hour particulate samples. Benzo(a)pyrene is partially separated from the other polynuclear aromatic hydrocarbons via gas chromatography and then is completely resolved optically from traditionally difficult to resolve compounds (benzo(e)pyrene, perylene, benzo(k)fluoranthene) by means of a gas phase fluorescent detector. Ambient air concentrations as low as 20 picograms per cubic meter of air can be assayed with this gas chromatographic - gas phase fluorescent detection system.     

Admicelle-enhanced synchronous fluorescence spectrometry for the selective determination of polycyclic aromatic hydrocarbons in water

A simple and rapid method for the highly sensitive determination of polycyclic aromatic hydrocarbons (PAHs) in water was developed. Benzo[a]pyrene, benzo[k]fluoranthene, perylene, and pyrene in water were concentrated into sodium dodecyl sulfate (SDS)-alumina admicelles. The collection was performed by adding SDS and alumina particles into the sample solution at pH 2. After gentle mixing, the resulting suspension was passed through a membrane filter to collect the SDS admicelles containing highly concentrated PAHs. The filter was placed on a slide glass and then covered admicellar layer with a fused silica glass plate before setting in a fluorescence spectrometer. Benzo[a]pyrene, benzo[k]fluoranthene, perylene, and pyrene were selectively determined by the synchronous fluorescence scan (SFS) analysis with keeping wavelength intervals between excitation and emission to 98, 35, 29, and 45 nm, respectively. Because of the minimum spectral overlapping, 1-40 ng l⁻¹ of benzo[a]pyrene, benzo[k]fluoranthene, and perylene as well as 10-150 ng l⁻¹ of pyrene were selectively determined with eliminating the interferences of other 12 PAHs. The detection limits were 0.3 ng l⁻¹ for benzo[a]pyrene, benzo[k]fluoranthene, and perylene, and 1 ng l⁻¹ for pyrene. They were 2-3 orders of magnitude lower than the detection limits in normal aqueous micellar solutions. The application to water analysis was studied.     

Resolution of overlapped chromatograms by means of the kalmam filter : Data Processing of Liquid Chromatographic Signals without Solvent Peaks

If several samples are injected successively at short intervals into a liquid chromatograph, overlapped chromatograms of the samples will result. This paper describes an application of this successive-injection method to determination of samples without solvent peaks. Twenty peaks in the overlapped chromatograms resulting from five successive injections of samples with four components (phenetole, biphenyl, pyrene and perylene) were resolved and quantified by a reduced four-dimensional Kalman filter. The period of the single chromatogram of the four components is ca. 14 min, and the period of the five overlapped chromatograms ca. 26 min, for injection intervals of 3 min. The calibration lines for the four components are all straight and satisfactory; the slope, A, of every line was 1.005>A>0.9996 with correlation coefficients better than 0.999992. This successive-injection method with the reduced Kalman filter is time-saving for trivial routine work.     

Supercritical fluid extraction of polycyclic aromatic hydrocarbons from liver samples and determination by HPLC-FL

An extraction/clean-up procedure by SFE was developed for isolating PAHs from liver samples for subsequent HPLC-FL determination of ten PAHs in the enriched extract. Recoveries (90–115%) and RSD % (≤ 7.7) were satisfactory. When applied to 11 samples of bird of prey (Tyto alba) protected species and classified of special interest, from the Galicia (Northwest to Spain), benzo[ghi]perylene and indeno[1,2,3-cd]pyrene were undetectable; chrysene and benzo[a]pyrene are only detected in one sample; benzo[a]anthracene and benzo[k]fluoranthene are only quantified in one sample and benzo[b]fluoranthene in two samples. The other PAHs, anthracene, fluoranthene and pyrene are present in almost all the samples.     

Simultaneous Determination of Phenanthrene and Benzo(a)pyrene in Water Samples by Synchronous Fluorescence Spectroscopy

Abstract

A simple and sensitive method was developed to simultaneously determine phenanthrene and benzo(a)pyrene in water samples using synchronous fluorescence spectroscopy with a 56-nm Δλ. The method was used to simultaneously determine both compounds in samples of spiked surface water. Analytical recoveries were 96.9–101.1% for phenanthrene and 95.8–103.5% for benzo(a)pyrene. Analytical results were checked for precision with 15 measurements for each compound. Relative standard deviations were 1.9% for phenanthrene and 2.9% for benzo(a)pyrene, which shows that the proposed method is quite precise.     

Micelle-sensitized constant-energy synchronous fluorescence spectrometry for the simultaneous determination of pyrene, benzo[a]pyrene and perylene.

The use of micellar media in constant-energy synchronous fluorescence spectrometry has been proposed. The influence of some aqueous micellar systems on the determination of pyrene, perylene and benzo[a]pyrene has been investigated. The presence of these micellar systems allows their determination in aqueous media, thus avoiding the use of an organic solvent, and greatly enhances the fluorescence signals. The combination of a constant-energy synchronous scanning technique and a micellar system provided a single spectrum for the simultaneous identification and quantitative determination of the three polycyclic aromatic hydrocarbons (PAHs). Further there was no energy transfer among them, making the measurement simple and fast. A constant-energy difference of 2800 cm(-1) was selected. The analytical characteristics of the proposed method in the presence of anionic micelles of sodium dodecylsulfate (SDS) were studied. The detection limits were at a level of ng ml(-1). Analysis of water samples from two different origins spiked with known amount of pyrene, perylene and benzo[a]pyrene also gave satisfactory results, and total average recoveries were greater than 97.1%.     

Flow-through sensor based on derivative synchronous fluorescence spectrometry for the simultaneous determination of pyrene, benzo(e)pyrene and benzo(ghi)perylene in water

A flow-through/first derivative synchronous spectrofluorimetric sensor for the determination of PAH has been described. This sensor has been used for the simultaneous determination of PAH mixtures (pyrene, benzo(e)pyrene and benzo(ghi)perylene). Linear calibration ranges between 10 and 500 ng/ml with acceptable precision (repeatability, expressed as relative standard deviation, smaller than 4.6%, and sampling frequency of 12 h^–1) have been obtained. The method has been applied to the determination of the target analytes in spiked water samples with excellent results (recoveries between 94 and 108%).     

水中痕量有机污染物质富集技术的发展──聚氨酯类泡沫富集回收水中的多环芳烃

用聚氨酯类泡沫（PUF）富集回收蒸馏水、自来水与河水中的多环芳烃，方法简便，回收率高，适于现场采集各种不同类型的水样．GC／MS分析中，氘化芘在IL蒸馏水中的检出限为26ng／L；而在HPLC／FLD分析中，苯并（k）荧蒽、苯并（a）芘、二苯并（a，h）蒽、苯并（ghi）在IL蒸馏水中的检出限分别为0.86、0.51、2.1和3.0ng／L.     

Supercritical fluid extraction of polycyclic aromatic hydrocarbons from liver samples and determination by HPLC-FL

An extraction/clean-up procedure by SFE was developed for isolating PAHs from liver samples for subsequent HPLC-FL determination of ten PAHs in the enriched extract. Recoveries (90-115%) and RSD % (< or =7.7) were satisfactory. When applied to 11 samples of bird of prey (Tyto alba) protected species and classified of special interest, from the Galicia (Northwest to Spain), benzo[ghi]perylene and indeno[1,2,3-cd]pyrene were undetectable; chrysene and benzo[a]pyrene are only detected in one sample; benzo[a]anthracene and benzo[k]fluoranthene are only quantified in one sample and benzo[b]fluoranthene in two samples. The other PAHs, anthracene, fluoranthene and pyrene are present in almost all the samples.     

Novel hexasubstituted triphenylene discotic liquid crystals having three different types of peripheral substituent

The synthesis and mesomorphic properties of a variety of novel hexasubstituted triphenylene derivatives having three different types of peripheral substitutions are described. Monobromination of 2,3,6,7-tetrakis(pentyloxy)triphenylene 4, prepared by Suzuki coupling of 2-iodo-3′,4,4′,5-tetrakis(pentyloxy)biphenyl 2 and phenylboronic acid followed by cyclization, yields 10-bromo-2,3,6,7-tetrakis(pentyloxy)triphenylene 5. Nucleophilic aromatic displacement of the bromine with the potassium salt of pentanethiol, followed by bromination, yields 2-bromo-6,7,10,11-tetrakis(pentyloxy)-3-(pentylsulphanyl)triphenylene 7 having a bromo, thioalkyl and alkoxy-substituted periphery of the triphenylene nucleus. The reaction of 7 with copper(I) cyanide gives the cyanotriphenylene derivative 8, while palladium-copper catalysed alkynylation of 7 results in the synthesis of the substituted alkyne derivative 9. The deprotected alkyne 10 was converted to dimer 11 where two molecules of a monothioalkyl-tetra-alkoxytriphenylene are connected via a rigid π-conjugated diacetylene bridge. Compounds 7,8,9,10 form hexagonal columnar phases while the dimer 11 shows a discotic nematic phase.     

Pyrene dimerization into 1,1′-dipyrenyl

Treatment of pyrene and some its derivatives with Cu(II) tetrafluoroborate or perchlorate in CH₃CN cleanly led to the formation of 1,1′-dipyrenyls. The other polycyclic hydrocarbons (anthracene, perylene) under the same conditions provide cation-radicals. 1,1′-Dipyrenyl strongly differs from pyrene in the chemical behavior: it does not undergo either formylation by Vilsmeier reaction, neither acylation (AcCl, ZnCl₂) or nitration (by pyridinium nitrate in boiling pyridine whereas the pyrene is easily involved into these reactions.     

Determination of Polycyclic Aromatic Hydrocarbons in Airborne Particulate by High Performance Liquid Chromatography

This paper presents a trisolvent ultrasonic extraction and HPLC analysis method for the determination of 11 polycyclic aromatic hydrocarbons in air particulate collected on an air filter by a commercial high volume air sampler. A reverse phase column, Vydac 201 TP, and a gradient mobile phase, acetonitrile/water, were used. The 11 PAHs, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a, h]anthracene, benzo[ghi]perylene, indeno[1,2,3-cd]pyrene, and coronene were completely resolved under experimental conditions. All the PAHs except coronene were monitored by fluorescence with λ_ex=270 nm, λ_em>389 nm. Coronene was monitored by UV with λ=300 nm. The methodology was evaluated by spiking SRM 1649 with a PAH standard and then going through different extraction procedures and analyzing the PAH concentrations without clean-up. An external standard method was used for quantitation. The recovery yields for fluoranthene, benz[a]anthracene, benzo[a]pyrene, benzo[ghi]perylene and indeno[l,2,3-cd]pyrene were above 90%. The detection limits of PAH with fluorescence at λ_ex=270 nm, λ_em>389 nm ranged from 5.7 pg to 69.5 pg.     

NMR relaxation of rigid molecules in the nematic phase of a discotic liquid crystal

Frequency and temperature dependent NMR relaxation measurements were performed on deuteriated benzene, pyrene and triphenylene dissolved in the nematic phase of a discotic liquid crystal. The results show a strong frequency dependence of the spectral densities. Based on the symmetries of the system and the usual model for director fluctuations this frequency dependence should be equal for J₁ and J₂. From fitting the commonly used model of rotational diffusion and director fluctuations to the data we see that this is not the case for benzene and triphenylene, even though the fits themselves are satisfactory. Values for the elastic constants, effective viscosity and translational diffusion in similar discotic liquid crystals do not account quantitatively for the frequency dependence of benzene. For both pyrene and triphenylene quantitative comparison was impossible due to lack of translational diffusion data. We also find that the so-called cut-off wave-length is of the order of the dimensions of the liquid crystal molecules, just as in ordinary nematics.     

Detection and quantification of PAH in drinking water by front-face fluorimetry on a solid sorbent and PLS analysis

The direct determination in drinking water of perylene, chrysene, pyrene, benzo[a]pyrene, and benzo[k]fluoranthene, by front-face synchronous fluorimetry on a commercial SPE disk, has been evaluated. Sorbent treatment, influence of humic substances, and pH effect are discussed. In pure water the detection limits were estimated to be in the range 0.03–0.01 g L^–1. A working pH in the range 10–11 was found to minimize the fluorescence quenching effect of humic substances. The proposed method combined with a partial-least-square (PLS) treatment was tested for quantitative analysis of mixtures of four PAH in a spiked drinking water.     

不同氟取代基对苝酰亚胺电子迁移率的影响

利用空间电荷限制电流(SCLC)法测试了二种氟代苝酰亚胺的电子迁移率, 一种是N,N'-二(五氟代苯基)-3,4,9,10-苝四羧基二酰亚胺(1), 另一种是N,N'-二(1,1-二氢十五氟代辛基)-3,4,9,10-苝四羧基二酰亚胺(2). 结果发现, 化合物2的电子迁移率要比1高1～2个数量级. UV-Vis, XRD, SEM和AFM等表征手段证明, 这一现象可以用不同的氟取代基导致不同的聚集态结构来解释: 对于化合物1而言, 苯环平面与苝环平面之间存在大的夹角, 破坏了苝酰亚胺分子的平面性, 再加上刚性的氟代苯环大的空间位阻作用, 化合物1分子无法依靠相邻苝环之间的重叠排列而结晶, 只能无序堆积形成非晶膜; 与之相反, 在化合物2分子中苝环上的端基是柔性的锯齿状氟代烷基链, 空间位阻小, 化合物2分子能通过相邻苝环之间相互接近而形成的π-π偶合作用而结晶, 因此有利于电子在苝酰亚胺分子间的跳跃传输.     

Synthesis and optical properties of perylene diimide derivatives with triphenylene-based dendrons linked at the bay positions through a conjugated ethynyl linkage

A number of groups including trimethylsilyl, phenyl, triphenylene, and triphenylene-based dendron have been linked to the bay positions of a perylene diimide (PDI) core through an ethynyl bridge. The photophysical properties of the resulting bay-substituted PDI derivatives have been carefully studied in different solvents and as thin films. Without any capping group, the two ethynyl bay-substituted PDI derivates PAT and PRT both aggregate strongly even in dilute solutions but in different perylene-perylene π–π stacking modes; PRT aggregates through slipped (or longitudinal) stacking while PAT self-assembles by rotational (or cross) stacking. With capping groups, the perylene core stacking is completely blocked for PATS in both solution and solid film. For PRTS, the slipped stacking is observed only for its film sample, while for PTB, association only occurs after excitation (excimer formation). When triphenylene or triphenylene-based G1 dendron is attached to the acetylene bridge, the resulting donor–acceptor systems (PTG0 and PTG1) exhibit strong electronic coupling between the dendritic donors and the PDI acceptor, leading to significantly red-shifted absorption bands. The conjugated linkage also facilitates photoinduced electron transfer from the triphenylene or triphenylene dendron to the PDI core, effectively quenching fluorescence emissions of both the donor and the acceptor. The significantly red-shifted absorption bands and the efficient photoinduced electron transfer observed on PTG0 and PTG1 indicate that these new PDI derivatives may find applications in solar cells.     

Second-derivative constant-wavelength synchronous scan spectrofluorimetry for determination of benzo[b]fluoranthene, benzo[a]pyrene and indeno[1,2,3-cd]pyrene in drinking water

The use of derivative constant-wavelength synchronous scan fluorimetry is reported for the determination of three polycyclic aromatic hydrocarbon pollutants in drinking water (linearity range 0.4-4 mug 1(-1)). The limits of detection (LD) and quantification (LQ) (mug 1(-1)) are 0.01 and 0.07 for benzo[b]fluoranthene, 0.03 and 0.12 for benzo[a]pyrene and 0.19 and 0.57 for indeno[1,2,3-cd]pyrene in the presence of three other pollutants, benzo[k]fluoranthene, benzo[ghi]perylene and fluoranthene. The precision (RSD /= 85%) were satisfactory.