In situ electrochemical and AFM study of thalidomide–DNA interaction

The interaction of thalidomide (TD) with double-stranded DNA (dsDNA) was studied using atomic force microscopy (AFM) at highly oriented pyrolytic graphite (HOPG), differential pulse voltammetry (DPV) at glassy carbon electrodes (GCE), UV–Vis and electrophoresis. After incubation of dsDNA with different concentrations of TD, the AFM images show the formation of thin and incomplete TD–DNA network films with a number of embedded molecular aggregates and regions of uncovered HOPG. Both the TD–dsDNA aggregates and network thickness directly depended on the TD concentration and incubation time. The voltammetric data also showed that the modifications caused by TD to the DNA double helical structure are time-dependent. In agreement with AFM, DPV, UV–Vis and electrophoresis results, a model is proposed for the TD–DNA interaction, considering that TD intercalates into the dsDNA, causing defects in the dsDNA secondary structure and DNA double helix unwinding. Moreover, both AFM and DPV show that condensation is caused to DNA by TD and occurs until 24 h of incubation, as well as DNA oxidative damage, detected electrochemically by the appearance of the 8-oxoGua and/or 2,8 oxoAde oxidation peak.     

Density functional theory study on surface-enhanced Raman scattering of 4,4′-azopyridine on silver

Surface-enhanced Raman scattering (SERS) of 4,4′-azopyridine (AZPY) on silver foil substrate was measured under 1064 nm excitation lines. Density-functional theory (DFT) methods were used to calculate the structure and vibrational spectra of models such as Ag–AZPY, Ag₄–AZPY and Ag₆–AZPY complexes with B3LYP/6-31++G(d,p)(C,H,N)/Lanl2dz(Ag) basis set. The Raman bands of AZPY were identified on the ground of analog computation of potential energy distribution. The calculated spectra of Ag₄–AZPY and Ag₆–AZPY models were much approximated to the experimental results than that of Ag–AZPY model. The DFT results showed that the angles between two pyridyl rings keep 0° from AZPY to Ag–AZPY, Ag₄–AZPY and Ag₆–AZPY model. The energy gaps between the HOMO and LUMO changed from 363 to 1140 nm for AZPY-Ag complexes according to the DFT results. An conclusion was conceived that chemical enhancement mechanism may play an important role in the SERS of AZPY on silver substrate.     

Structures and excitation energies of Zn–tetraarylporphyrin analogues: A theoretical study

The photophysical properties of β-substituted Zn–tetraarylporphyrin (ZnTAP) analogues used as dyes in dye-sensitized solar cells were studied using density functional theory (DFT). Singlet-excitation energy calculations of ZnTAP analogues were performed using time-dependent DFT with B3LYP, B3PW91, PBE0 exchange–correlation functionals at 6-31G(d) and 6-31+G(d) basis sets using B3LYP/6-31G(d) geometries. The PBE0 functional at 6-31+G(d) basis set provided a better correlation with the experimental data for both B- and Q-bands. The inclusion of solvation effect in the calculations provided a good agreement in terms of B:Q_ave ratio of the oscillator strengths for both analogues with the experimental values. Analogue 2 has a higher and a more balanced charge-carrier transport rates than analogue 1. In general, the addition of an electron-donating group in the meso-substituent (analogue 2) resulted in a narrower band gap, higher oscillator strength, a more red-shifted absorption spectra, and better charge-transfer characteristics than analogue 1.     

Tuning the optical properties of ZnTPP using carbonyl ring fusion

Zinc meso-tetraphenylporphyrin (ZnTPP) was modified in such a way to allow the effect of an asymmetric structural distortion on its optical properties to be investigated. This involved the fusion of a phenyl group to an adjacent pyrrole ring via a carbonyl bridge. With the aid of Density Functional Theory (DFT) and time-dependent DFT (TD-DFT) calculations it was found that the asymmetric distortion away from planarity induced by the carbonyl fusion resulted in a loss of degeneracy in the two lowest unoccupied molecular orbitals (LUMOs). The effect was a red shift of the electronic absorbance bands, an increased Q:B ratio from 0.046 in ZnTPP to 0.096 in the fused derivative, and the appearance of additional UV–vis peaks. This study therefore suggests that structural distortions, as well as electronic substituents may be used to alter absorbance spectra, a technique which is of interest in the design of light-harvesting dyes.     

ZnO nanorods decorated calcined Mg–Al layered double hydroxides as photocatalysts with a high adsorptive capacity

The nanocomposites of magnesium–aluminium–carbonate–layered double hydroxides (Mg–Al–CO₃–LDHs) and ZnO nanorods were prepared via a homogeneous precipitation process. The presence of ZnO nanorods made the calcined Mg–Al–CO₃–LDHs, the strong adsorptive adsorbents for anions, have a photocatalytic activity. Both Mg–Al–CO₃–LDHs and the nanocomposites with various ZnO/Mg–Al–CO₃–LDHs mass ratios from 0.5:1 to 3:1 were characterized by X-ray diffraction, transmission electron microscope and UV–vis diffuse reflectance spectra. The nanocomposites quickly adsorbed the anionic dyes such as acid red G (ARG) without the light illumination, and the adsorbed dyes on the recovered nanocomposites were then degraded in a separated photocatalytic reactor. The adsorption ability of the nanocomposites and their photocatalytic activities for the removal of ARG were evaluated by the Fourier transform infrared spectra and UV–vis extinction spectra. The sample at 3:1 ZnO/Mg–Al–CO₃–LDHs mass ratio was shown to have higher photocatalytic efficiencies.     

Synthesis, spectroscopic characterization, X-ray structure and DFT calculations of [Re(CO)3L2Cl] (L = 1,2,4-triazolo-[1,5-a]pyrimidine)

The paper presents a combined experimental and computational study of novel tricarbonyl complex – fac-[Re(CO)₃(tp)₂Cl] (tp = 1,2,4-triazolo-[1,5-a]pyrimidine). The compound has been characterized spectroscopically and structurally (by single-crystal X-ray diffraction). The absorption and emission spectra of the complex have been discussed on the basis of DFT and time-dependent (TD)DFT calculations.     

Interfacing capillary electrophoresis and surface-enhanced resonance Raman spectroscopy for the determination of dye compounds

The at-line coupling of capillary electrophoresis (CE) and surface-enhanced resonance Raman spectroscopy (SERRS) was optimized for the separation and subsequent spectroscopic identification of charged analytes (dye compounds). Raman spectra were recorded following deposition of the electropherogram onto a moving substrate. To this end a new interface was developed using a stainless steel needle as a (grounded) cathode. The outlet end of the CE capillary was inserted into this metal needle; CE buffer touching the needle tip served as the electrical connection for the CE separation. A translation table was used to move the TLC plate at a constant speed during the deposition. The distance between the tip of the fused silica column and the TLC plate was kept as small as possible in order to establish a constant bridge-flow, while avoiding direct contact. The dyes Basic Red 9 (BR9), Acid Orange 7 (AO7) and Food Yellow 3 (FY3) were used as test compounds. After CE separation in a 20 mM borate buffer at pH 10, after deposition, concentrated silver colloid was added to each analyte spot, followed by irradiation with 514.5 nm light from an argon ion laser to record the SERRS signal using a Raman microscope. Different types of silver colloids were tested: Lee–Meisel type (citrate), borate, and gold-coated silver. BR9 (positively charged) gave much more intense SERRS spectra than the two negatively charged dyes. For BR9 and AO7 the citrate-coated Lee–Meisel colloid yielded the most intense SERRS spectra. The CE–SERRS system was used to separate and detect the negatively charged dyes. Silver colloid and nitric acid (to improve adsorption) were added post-deposition. Even though their chemical structures are very similar, AO7 and FY3 could be readily distinguished based on their SERRS spectra. The limits of detection (S/N=3) of the CE–SERRS system ranged from 6.7×10^–5 M (2.6×10^–12 mol injected) for FY3 down to 1.8×10^–6 M (7.0×10^–14 mol injected) for BR9.D. Arráez Román and E. Efremov contributed equally to this work.     

Nanolayers of selected porphyrin and phthalocyanine dyes on solid substrates studied by electronic absorption and IR reflection–absorption spectroscopy

Electronic absorption and IR reflection–absorption spectra in non-polarized and in polarized light for lead porphyrin as well as magnesium and lead phthalocyanine dyes when deposited in the form of Langmuir–Blodgett (LB) nanolayers on solid inorganic surfaces (quartz, semiconductor and metal) were measured. Some IR bands of the Langmuir–Blodgett dye layers’ spectra show frequency shifts and changes in the relative intensities as well as in half widths when compared with the vibrational features of powdered dyes dispersed in KBr pellets, which were used as references. The FT-IR spectroscopic examination of the Langmuir–Blodgett layers allowed to estimate electron redistribution at the interface between dye layer and solid substrates. The Langmuir–Blodgett films of different thicknesses (3, 5, 10 layers) were studied at various angles of IR beam incidence and different light polarizations. The most spectacular results were obtained for the grazing incidence (80°) and films of 5 layers for dyes on the Au substrate. The IR spectroscopy was supported with electronic absorption studies (UV–vis) to follow interaction at interface between the dye layers and the substrates as well as to evaluate linear dichroism and to determine arrangement of molecules in the Langmuir–Blodgett films. Molecular arrangement in the Langmuir–Blodgett layers was discussed. It was shown that the dye molecular planes are rather randomly oriented in the Langmuir–Blodgett films with a tendency that the Q_y and Q_x transition moments in the phthalocyanine macroring are slightly directed along the y-axis (Langmuir–Blodgett dipping direction) and the x-axis direction, respectively.     

Charge distribution and 13C NMR spectra of cyanine dyes with bridging groupings in the chromophore

The electronic structure of cationoid and anionoid cyanine dyes was calculated by the CNDO/2 method. The calculation results were compared with the data of the ¹³C NMR spectra. It was shown that the anionoid dyes of the malonocyanine class have all the inherent properties of a polymethine state, i.e., alternation of charges and leveling of bonds, and these are also characteristic of cationic streptopolymethines. According to the calculation data, the introduction of bridging groupings causes considerable changes in the electronic structure of the cyanine dyes, as confirmed by the results of the study of their ¹³C NMR spectra.Translated from Teoreticheskaya i Ékperimental'naya Khimiya. Vol. 23, No. 6, pp. 687–692, November–December, 1987.     

Analogs of styryl dyes and the simplest AZO dyes from 2-dimethylaminothiophene

The condensation of 2-dimethylaminothiophene with the appropriate derivatives of quaternary benzothiazole salts has give the vinylene-homologous series of dyes with the structure (I). By coupling with benzenediazonium salts, the simplest azo dyes of structure (III) have been synthesized. The influence on the absorption spectra of the replacement of a dimethylaniline nucleus in polymethine and azo dyes by a 2-dimethylaminothiophene nucleus has been investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 923–925, July, 1973.     

Secondary ion mass spectra of organic cationic dyestuffs

Rules for the behavior under fast atom bombardment (FAB) have been established for 15 cationic dyes — quaternary ammonium salts of heterocyclic amines and heterocycles containing quaternary nitrogen atoms with aliphatic substituents. Intense peaks corresponding to the molecular mass of the cationic part of the dyes [M-Hal]⁺ are observed in the spectra of all the derivatives. Fragmentation of the azodyes is determined by the azo group and the heterocyle. The base peaks in the case of compounds containing a quaternary nitrogen atom with aliphatic substituents correspond to the ammonium ion and a fragment of amine type. The results obtained can be used to identify dyes of unknown structure from their secondary ion mass spectra (SIMS).DeceasedTranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, 1411–1417, October, 1992     

Spectral-luminescent and generation properties of rhodamine dyes in thin polymer films under optical excitation

A study was made of the absorption, fluorescence, and emission spectra of organic dyes Rhodamine 6Zh and Rhodamine C in thin (0.6–1.0 µm) layers based on methyl methacrylate-methacrylic acid copolymers formed by centrifugation on optically transparent glasses. The influence of a terbium salt on the properties of laser dyes in acrylic films was elucidated.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 8, 2004, pp. 1340–1345.Original Russian Text Copyright © 2004 by Vaitulevich, Eremina, Kopylova, Mokrousov, Samsonova, Svetlichnyi.     

Crown-containing styryl dyes

Novel crown ether styryl dyes containing heterocyclic residues with various substituents were synthesized. The fluorescence and absorption spectra of thetrans-isomers of crown ether styryl dyes and their complexes with metal cations were studied. Based on spectral data, the influence of the nature of a heterocyclic residue, the crown ether fragment, and the temperature on the fluorescence of dyes and their complexes with metal cations was elucidated.For Communication 13, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2003–2008, October, 1995.This study was financially supported by the Russian Foundation for Basic Research (Project Nos. 93-03-04089 and 93-03-18141) and the International Science Foundation (Grant M8Q 000).     

染料敏化太阳能电池中具有不同电子给体的吩噻嗪类有机光敏染科的理论研究

采用密度泛函理论和含时密度泛函理论方法计算了2个吩噻嗪类染料及其吸附到TiO2上后分子的基态和激发态光物理性质与热力学参数.结果表明,电子给体的改变虽未明显改变染料的光谱性质(垂直跃迁能和振子强度),但可以改变分子的前线轨道能级,进而影响染料分子的激子结合能Eb及激发态电子注入到半导体TiO2中的驱动力△Gint的大小...     

Exploration on Charge Transfer and Absorption Spectra of Spiro[fluorene-9,90-xanthene]-based Polyoxometalate Hybrids Toward High Performance Dye-sensitized Solar Cell

Based on spiro[fluorene-9,90-xanthene](SFX, dye 1), the Lindqvist-type polyoxometalate(POM) functionalized with SFX and its derivatives(dyes 2-4) used in dye-sensitized solar cells(DSSCs) were designed and investigated with the density functional theory(DFT) and time-dependent DFT(TD-DFT) calculations. The results indicate that Lindqvist-type POM is the main contribution to the lowest unoccupied molecular orbital(LUMO) and affects the LUMO energies of dyes 2-4. The maximum absorptions of the designed dyes containing POM(dyes 2-4) are red shifted comparing with that of dye 1. The introduction of electron-donating group onto SFX segment is helpful to red shift the absorption spectra. The major factors affecting the performance of DSSCs, including light harvesting and electron injection were evaluated. Considering the absorption spectra and photovoltaic parameters, dyes 3 and 4 are promising high performance dye sensitizers in n-type DSSCs.     

Plates for thin-layer chromatography with adsorption-immobilized reagents in chemical test analysis methods

The use of plates for thin-layer chromatography (TLC) with adsorption-immobilized organic reagents in chemical test methods for analysis is considered. Triarylmethane, triazine, eirodine, acridine, and rhodamine dyes are used for immobilization. The degree of retention of the reagents is 52–98%. It is found that the absorption spectra of these reagents on TLC plates exhibit a hypsochromic shift of absorption bands by 8–30 nm in comparison with their absorption spectra in solutions. The retention is higher for the reagents that exhibit a hypsochromic shift of absorption bands on TLC plates. The sorption isotherms of the reagents on TLC plates are obtained and analyzed. Test methods have been developed for the determination of 1–200 mg/L Au(III) and 0.1–5 M acids and alkalies with the use of reagent TLC plates. The relative standard deviation of the results of analysis is no larger than 10%; the time of analysis is 3–7 min.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 3, 2005, pp. 291–296.Original Russian Text Copyright © 2005 by Amelin, Tretyakov.     

Accurate theoretical prediction of optical properties of BODIPY dyes

Boron-dipyrromethene dyes (BODIPY) are of great interest nowadays mostly due to their valuable optical properties. Nevertheless, no systematic research of the optical property dependence on the structure of dyes has been performed yet. In this work, analysis of the available quantum-chemical methods for BODIPY optical property calculations has been carried out. The accuracy of eight DFT functionals has been studied. The solvation effects upon excitation have been considered within two schemes. The methods that predict the absorption and emission spectra of BODIPY derivatives with high accuracy have been proposed. Using the suggested methods, the influence of nature of substituents and their position in the BODIPY core on the optical spectra of the dyes has been studied. A complex pattern of red- and blue-shifts in optical spectra in dependence of nature and position of substituents has been revealed. The results of this work provide the way for efficient design of BODIPY derivatives with desired optical properties.     

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.     

Cationic dye dimers: a theoretical study

In this work we present a quantum-mechanical study on the structure and electronic spectra of three cationic dyes monomers and dimers: acridine orange (AO), proflavine (PF) and methylene blue (MB). The geometries were obtained from crystallographic data, the electronic properties were calculated with DFT (B3LYP functional) and the theoretical spectra were obtained with ZINDO. The solvation methodology adopted was the Integral Equation Formalism (IEF) version of the Polarizable Continuum Model (PCM). This study shows that the differences, even small, between optimized and crystal geometries are responsible for important spectral characteristics. Also, it indicates possible structures for interacting dimers.     

Hemicyanine and azahemicyanine cationic dyes containing an anthrapyridinium ring

Green dyes were, obtained by the reaction of 2,3-dimethylanthrapyridinium methyl-sulfate with N,N-disubstituted p-aminobenzaldehydes and p-nitrosoanilines. The features of the electronic spectra of the dyes are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 236–239, February, 1981.