Theoretical study of the valence π → π* excited states of polyacenes: anthracene and naphthacene

The valence π → π ^* excited states of anthracene and naphthacene are studied with multireference perturbation theory with complete active space self-consistent field reference functions. The predicted spectra provide a consistent assignment of all one- and two-photon spectra and T-T spectra of low-lying valence π → π ^* excited states of anthracene and naphthacene. The present theory predicts the valence π → π ^* excitation energies with an accuracy of 0.15 eV for anthracene and of 0.25 eV or better for naphthacene. The excited states of anthracene and naphthacene are compared with those of benzene and naphthalene studied previously. The present calculations predict that, going from anthracene to naphthacene, there is a symmetry reversal of the two lowest singlet state transitions, but not for the triplet, just as indicated by the experimental data. Some general trends of polyacene excited states are discussed based on the calculated results for benzene to naphthacene. Conclusive results obtained for anthracene and naphthacene can be used as a model for understanding the excited states of larger polyacenes. Received: 22 April 1998 / Accepted: 6 July 1998 / Published online: 28 September 1998     

Emission spectra of naphthalene,anthracene and naphthacene oriented in stretched polyethylene and in shpolskii matrices

Emission spectra of naphthalene, anthracene and naphthacene, oriented in stretched polyethylene sheets, have been studied. Absolute polarization of the bands and symmetry assignments of the vibrational modes are deduced and progressions of bands are drawn up. A comparison with other polarization investigation is given.To support the interpretation of the film spectra the molecules have also been measured (20 K) in suitable crystalline solvents (Shpolskú matries). Discrepancies with the literature are discussed. The anomalous behavior of the environment multiplet structure of naphthacene in n-nonane is described.     

Fluorescence spectra and their temperature dependence of amorphous anthracene films doped with naphthacene

Fluorescence spectra and their temperature dependence of amorphous anthracene films doped with naphthacene were observed. An amorphous film was prepared by vacuum evaporation technique on a quartz plate cooled down to 30–40°K. The obtained results were discussed in relation to the structural change in the amorphous film.     

Photoelectron measurements of naphthacene polycrystal by using NeII and HeII resonance radiation

Photoelectron spectra of naphthacene polycrystals excited with NeII and HeII resonance radiation have been measured. The spectra are compared with that excited with HeI resonance radiation. It is found that the corresponding peak positions of these three spectra are in good agreement with each other, while the peak intensity depends on the energy of the incident photon. The origin of the peak width in the photoelectron spectrum is discussed.     

Some characteristic features of shpolskii spectra. The key and hole rule for shpolskii systems

The key and hole rule for Shpolskii systems has been re-examined by studying fluorescence spectra of naphthalene, anthracene and naphthacene in several n-alkane polycrystals (20 K). It is demonstrated that the key and hole rule has no significance for the systems under study. From our results and literature data the Shpolskii effect appears to be a rather general phenomenon for aromatic hydrocarbons in frozen n-alkanes, provided a correct concentration is chosen and a proper cooling rate is applied.     

Electron emission from naphthacene crystal due to the impact of argon and krypton metastable atoms

Energy distributions of electrons emitted from polycrystalline naphthacene due to the impact of metastable argon or krypton atoms were measured. The energy distribution peaks, except for large peaks appearing near zero eV, correspond to the kinetic energies estimated from photoelectron spectra on the assumption that the excitation energies of the metastable atoms are transferred to the electrons in the valence bands. The results are interpreted as the occurrence of Penning ionization (Auger de-excitation) on the naphthacene surface.     

Near and vacuum ultraviolet absorption spectra of polycrystalline and amorphous evaporated films of naphthacene,pentacene, perylene and coronene

The near- and vacuum-ultraviolet absorption spectra of polycrystalline and amorphous films of naphthacene, pentacene, perylene evaporated on substrate at room and low temperatures have been measured at room temperature. The changes in the spectra are explained in terms of the loss of molecular orientation and the change in Davydov splitting. The spectra for coronene evaporated at room temperature are also reported.     

Component recognition with three‐dimensional fluorescence spectra based on non‐negative matrix factorization

Non‐negative matrix factorization (NMF) is a widely used approach in signal processing. In this work, we apply it to the component recognition of mixtures with multicomponent three‐dimensional fluorescence spectra. Compared with the popular PARAFAC for component recognition, NMF has the following advantages: on one hand, the decomposed spectra are three dimensional, and thus, more information can be obtained, which is beneficial for component recognition; on the other hand, the decomposed spectra are non‐negative and thus have a certain physical significance. More importantly, we propose a type of integrated similarity indices for the three‐dimensional fluorescence spectra, which, by construction, is good at component recognition from overlapping fluorescence spectra. Experiment results demonstrate that NMF combined with integrated similarity index provides an effective method for component recognition of multicomponent three‐dimensional overlapping fluorescence spectra. Copyright © 2011 John Wiley & Sons, Ltd.     

交替最小化协变矩阵误差算法与三维荧光分析法相结合同时分辨利尿类药品

氨苯喋啶、呋塞米和阿米洛利是3种常用的利尿药,被广泛用来治疗多种疾病。近来这3种药物被用作兴奋剂提高运动员在比赛中的成绩,因此,国际奥林匹克委员会(IOC)将其列为违禁药品[1]。因此对这3种物质进行同时分辨和测定具有极其重要的现实意义。然而这3种物质具有相似的理化性质     

Principal component and decomposition analysis of multicomponent mixtures of carcinogenic fluorophores

A series of binary and tertiary mixtures of polycyclic aromatic hydrocarbons is analyzed by using principal component and decomposition analysis of molecular fluorescence spectra. The results demonstrate the ability to determine the number and identity of species that are present. Failures caused by high correlation among spectra are considered.     

THE PRIMARY REACTION IN THE PHOTOREDUCTION OF PROTOCHLOROPHYLLIDE MONITORED BY NANOSECOND FLUORESCENCE MEASUREMENTS

Abstract— Time resolved fluorescence measurements, carried out on protochlorophyllide reductase enriched membranes from oat ( Avena sativa ), are described. A fast (1 ns at 293 K) decaying fluorescence component is assigned to the photoactive NADPH-protochlorophyllide-enzyme complex, while a slower (5 ns) component is ascribed to non-photoactive protochlorophyllide. The results are interpreted in terms of a new fast primary step in the light requiring step of chlorophyll synthesis. The temperature dependence of the rate of this reaction has been studied by measuring the decay time of the fast fluorescence component at various temperatures from 77 to 293 K. Complete spectra of the kinetic fluorescence components have been measured at 293, 160 and 77 K.     

Heterocyclic triptycenes : Synthesis and ultraviolet spectroscopy

The synthesis of some heterocyclic triptycenes is reported. A study of the UV spectra of these and analogous compounds was undertaken. Two series of compounds were prepared: 9,10-bridged anthracene compounds and 5,12-bridged naphthacene compounds. The results from these studies alone are inconclusive. However if calculations are made, based on interannular π-π interactions between the aromatic rings in these systems, the calculated N → V₁ transitions and longest wavelength absorption maxima give a straight line when plotted.     

An Improved Algorithm of Resolution of Fluorescence Spectra into Quencher Accessibility-Associated Components

Abstract— A novel algorithm (QUENCH) is described that resolves fluorescence spectra into components differing in the accessibility (the Stern-Volmer constants) for small quencher molecules. In contrast to the known algorithms, QUENCH first evaluates Stern-Volmer constants of the components using the total set of intensities in spectra measured at several quencher concentrations and then calculates contributions of each component in the emission intensities at every wavelength value. The component spectra, revealed with QUENCH in the tryptophan fluorescence of ribosomal S7 protein, are very similar to the log-normal components calculated using the SIMS program (Abornev, S. M. and E. A. Burstein Mol. Biol. [Engl, transl.] 26, 890-897 1992). The QUENCH method is applicable for the component resolution of fluorescence spectra of any liquid system containing fluorophores of different accessibility to small quenchers.     

Classification of edible and lampante virgin olive oil based on synchronous fluorescence and total luminescence spectroscopy

Total luminescence and synchronous fluorescence spectroscopies were tested as regards their ability to differentiate edible from lampante virgin olive oils. Total luminescence spectra were recorded by measuring the emission spectra in the range 350-720 nm at excitation wavelengths from 320 to 535 nm. The synchronous fluorescence spectra of 41 edible and 32 lampante virgin olive oils were acquired by synchronous scanning the excitation and emission monochromator maintained at an offset value of 80 nm. Classification of virgin olive oils based on their synchronous fluorescence spectra was performed by hierarchical cluster analysis and principal component analysis using the spectral range of 429-545 nm. Principal component analysis provided better discrimination between the two classes, without any classification error, while hierarchical cluster analysis allowed 97.3% correct classification. These results indicate the capability of fluorescence techniques to differentiate virgin olive oils according to their quality.     

Spectroscopic properties of Cs2NaLa1−xNdxCl6 crystal. Concentration quenching of fluorescence

The results of the absorption, infrared, Raman and fluorescence spectra of the title compound are reported. An assignment of the vibronic peaks of the fluorescence spectra is proposed. It was found that the concentration dependence of the fluorescence decay times was temperature dependent. The mechanism of concentration quenching of Nd³⁺ fluorescence is discussed in terms of resonant and non-resonant cross relaxation.     

Spectroscopic determination of solvation shell composition of fluorenone and 4-hydroxyfluorenone in binary solvent mixtures

Preferential solvation of fluorenone (9Fl) and 4-hydroxyfluorenone (4HOFl) in binary solvent mixtures (cyclohexane-tetrahydrofuran (CH-THF) and cyclohexane-ethanol (CH-EtOH)) has been studied using steady-state spectroscopic measurements. The solvation of the fluorenones, both in the ground and in the excited states, exhibits a non-linear solvatochromic shifts as a function of polar component in the binary solvent mixtures. The results of spectroscopic measurements were used to calculate, according to Bakhshiev's and Kiselev's theory, the fluorescence spectra of solvates having different number of polar component in the first solvation shell. The different features of fluorescence spectra of molecule under study in CH-THF and CH-EtOH are explained by the absence and presence of specific solute-solvent interactions (hydrogen bond).     

Criteria of asymmetry of the electron density distribution of polymethine dyes with several chromophores

The absorption and fluorescence spectra of 6-B-thia- and 6-B-imidathiadimethinemerocyaninocyanines were investigated. It was established that the transition from absorption spectra to fluorescence spectra leads to an underestimation of the deviations. The influence of resonance interaction of the chromophores on the value of the deviations of the long-wave absorption and fluorescence bands of dyes with two chromophores is discussed. It was shown that resonance interaction leads to a decrease in the contribution to the deviation from alternation of the bonds in the polymethine chromophore and an increase in the topologic component of the deviation. A new criterion of asymmetry of the electron density distribution in dyes with several chromophores is proposed.Translated from Teoreticheskaya i Éksperimental'naya, Khimiya, Vol. 21, No. 6, pp. 641–650, November–December, 1985.     

Fluorescence lifetimes of protochlorophyllide in plants with different proportions of short-wavelength and long-wavelength protochlorophyllide spectral forms

Dark-grown leaves of maize (Zea mays), wheat (Triticum aestivum), wild-type pea (Pisum sativum) and its light-independent photomorphogenesis mutant (lip1) have different proportions of protochlorophyllide (Pchlide) forms as revealed by low-temperature fluorescence emission spectra. Four discrete spectral forms of Pchlide, with emission peaks around 633, 640, 656 and 670 nm, could be distinguished after Gaussian deconvolution. In maize and wheat the 656 nm component was the most prominent, whereas for wild-type pea and its lip1 mutant, the 633 and 640 nm components contributed mostly to the fluorescence emission spectra. For the fluorescence lifetimes measured at 77 K a double exponential model was the most adequate to describe the Pchlide fluorescence decay not only for the Pchlide(650-656) form but also for the short-wavelength Pchlide forms. A fast component in the range 0.3-0.8 ns and a slow component in the range 5.1-7.1 ns were present in all samples, but the values varied, depending on species. The long-wavelength Pchlide(650-656) form had a slow component with a lifetime between 5.1 and 6.7 ns, probably reflecting the fluorescence from aggregated Pchlide. The short-wavelength Pchlide(628-633) form had values of the slow component varying between 6.2 and 7.1 ns. This represents a monomeric but probably protein-bound Pchlide form because the free Pchlide in solution has a much longer lifetime around 10 ns at 77 K. The contribution of different Pchlide forms to the measured lifetime values is discussed.     

Absorption and emission spectroscopic characterisation of 8-amino-riboflavin

The flavin dye 8-amino-8-demethyl-d-riboflavin (AF) in the solvents water, DMSO, methanol, and chloroform/DMSO was studied by absorption and fluorescence spectroscopy. The first absorption band is red-shifted compared to riboflavin, and blue-shifted compared to roseoflavin (8-dimethylamino-8-demethyl-D-riboflavin). The fluorescence quantum yield of AF in the studied solvents varies between 20% and 50%. The fluorescence lifetimes were found to be in the 2–5 ns range. AF is well soluble in DMSO, weakly soluble in water and methanol, and practically insoluble in chloroform. The limited solubility causes AF aggregation, which was seen in differences between measured absorption spectra and fluorescence excitation spectra. Light scattering in the dye absorption region is discussed and approximate absorption cross-section spectra are determined from the combined measurement of transmission and fluorescence excitation spectra. The photo-stability of AF was studied by prolonged light exposure. The photo-degradation routes of AF are discussed.     

完全未知混合体系的纯物种光谱辨析

基于因子分析的迭代目标转换算法,本文提出一种从完全未知混合物体系中获取纯物种光谱的解析方法。该法简单明了,不增加任何困难即可拓广至含n组份的混合体系,对光谱峰形状亦无任何附加限制要求。先采用计算机模拟技术对该法进行了校验,继用于紫外可见与荧光光谱的实际混合体系的解析,均获满意结果。