A novel method for the synthesis of coumarin laser dyes derived from 3-(1H-benzoimidazol-2-yl) coumarin-2-one under microwave irradiation

We want to achieve the synthesis of 3-(1H-benzoimidazol-2-yl)-7-(diethylamino) coumarin-2-one (1), 3-(1H-benzoimidazol-2-yl)-7-(dimethylamino) coumarin-2-one (2), 3-(1H-benzoimidazol-2-yl) coumarin-2-one (3) that are important dyes in industries (Soko owska et al., 2001). Methods for the synthesis of some of these compounds have been the title in some pervious patents, but enough information about separation and purification of them was not clearly indicated. We carried out several methods for the synthesis of the mentioned compound and purification with different yields. Now, we can synthesise these dyes under microwave irradiation in solid phase and solvent free methods with 80% yield, which is a high and remarkable percentage.     

Synthesis and evaluation of a series of symmetrical hot brand bis azo reactive dyes using 4,4′-methylene-bis-metanilic acid on various fibre

4,4′-Methylene-bis-metanilic acid (A) was synthesized by the reaction between metanilic acid and formaldehyde. The compound (A) was used as a bifunctional middle component in the preparation of several symmetrical hot brand bis azo reactive dyes. The compound (A) was tetrazotized and coupled with various m-nitro anilino cyanurated coupling component to give various hot brand bis azo reactive dyes. The entired compounds have been identified by IR, ¹H NMR spectra and elemental analysis. The dyes were applied on silk, wool and cotton fabrics and their fastness properties were evaluated. All the dyes give good fastness properties. The percentage dye bath exhaustion was also been studied.     

Use of poly(N,N-dimethylacrylamide-co-sodium acrylate) hydrogel to extract cationic dyes and metals from water

Poly(N,N-dimethylacrylamide-co-sodium acrylate) hydrogel, which bears negatively charged –COO⁻ groups was used to extract organic or inorganic solutes from water. Some model dyes and metal ions have been studied. Cationic dyes are strongly adsorbed and retained by the polymer while adsorbance of hydrophobic dyes was very low and that of anionic dyes was negligible. Both maximum adsorption and equilibrium binding constant varied from one cationic species to the other depending on the chemical structure of the dye, the presence of functional chemical groups and the hydrophobic–hydrophilic balance. In the case of metal cations, adsorption depended on valence. The hydrogel can be regenerated in an aqueous phase of low pH and thus be reused in several adsorption procedures.     

Sequential injection analysis with second-order treatment for the determination of dyes in the exhaustion process of tanning effluents

A sequential injection (SI)-DAD spectrophotometric method to control the exhaustion of dyes in a mixture of three dyes from a tanning industry process has been developed. It is based on an interdiffusion process of the sample and reagents which leads to a gradual fall in pH through the channel to the detector recording a data matrix. The aim of this paper is to develop a second-order calibration model that is unaffected by interferents by applying multivariate curve resolution with alternating least squares (MCR-ALS). We obtained a linear calibration in the 5-30 mg l⁻¹ range with a correlation coefficient of 0.999 for each dye with detection limits of 2.6, 3.9 and 2.1 mg l⁻¹ for Acid Red, Acid Brown and Acid Orange, respectively. The simultaneous determination of the three dyes from tanning samples showed a satisfactory precision for the three analytes. The method has been validated comparing the concentration of some spiked samples with the expected concentration using a t-paired test. When we used this method to study the exhaustion of dyes, we found that there were several stages in this process. These data may be the key to optimising the exhaustion process.     

A structural remedy toward bright dipolar fluorophores in aqueous media

The donor–acceptor (D–A) type dipolar fluorophores, an important class of luminescent dyes with two-photon absorption behaviour, generally emit strongly in organic solvents but poorly in aqueous media. To understand and enhance the poor emission behaviour of dipolar dyes in aqueous media, we undertake a rational approach that includes a systematic structure variation of the donor, amino substituent of acedan, an important two-photon dye. We identify several factors that influence the emission behaviour of the dipolar dyes in aqueous media through computational and photophysical studies on new acedan derivatives. As a result, we can make acedan dyes emit bright fluorescence under one- and two-photon excitation in aqueous media by suppressing the liable factors for poor emission: 1,3-allylic strain, rotational freedom, and hydrogen bonding with water. We also validate that these findings can be generally extended to other dipolar fluorophores, as demonstrated for naphthalimide, coumarin and (4-nitro-2,1,3-benzoxadiazol-7-yl)amine (NBD) dyes. The new acedan and naphthalimide dyes thus allow us to obtain much brighter two-photon fluorescent images in cells and tissues than in their conventional forms. As an application of these findings, a thiol probe is synthesized based on a new naphthalimide dye, which shows greatly enhanced fluorescence from the widely used N,N-dimethyl analogue. The results disclosed here provide essential guidelines for the development of efficient dipolar dyes and fluorescence probes for studying biological systems, particularly by two-photon microscopy.     

Viscosity dependent radiationless relaxation rate of cyanine dyes. A picosecond laser spectroscopy study

The viscosity dependent radiationless relaxation of several cyanine dyes has been studied by picosecond laser spectroscopy. It was found that the relaxation rate is proportional to η^?α. The value of α, however, is not constant for a certain dye molecule, but is strongly dependent on the kind of solvent used. In n-alcohols for instance α is typically about 1. In glycerol/methanol or glycerol/water mixtures on the other hand α ≈ 0.5. A comparison is made with literature data on orientational relaxation lifetimes of some dyes in similar solvents. It is shown that the radiationless relaxation of cyanine dyes and the orientational relaxation of for instance xanthene dyes changes in roughly the same way as the solvent is changed. This is taken as proof of the proposal that a torsional motion of the heterocyclic quinolyl rings is the main course of the viscosity dependent relaxation of the cyanine dyes studied.     

Fluorescence lifetime and electron transfer in cyclobutenediylic dyes

Fluorescence lifetimes in different solvents of several cyclobutenediylic dyes and electron-transfer rate constants from excited S₁ states of the dyes to p-methylbenzendiazonium tetrafluoroborate were measured. Inter- and intra-molecular hydrogen bonding probably plays the most important role in the relaxation processes of the excited dyes.     

A Raman spectroscopic study of photochromic benzothiazolium dyes

Resonance Raman spectra using several excitation wavelengths have been obtained in the region 300–1750 cm⁻¹ for two photochromic benzothiazolium dyes containing a crown ether ring. Bands arising from both cis- and trans-isomers have been distinguished by comparing the spectra observed at different resonances and under different sample conditions. Preliminary assignments of the bands have been made, allowing insight into the changes in structure and bonding which occur on photoisomerization.     

Investigation of the colourants used in icons of the Cretan School of iconography

The red shades of 13 icons (15th-17th century) of the Cretan School of iconography are investigated in detail to identify the inorganic and organic colouring materials comprising the paint layers. Examination of sample cross-sections is performed with optical microscopy. Micro-Raman spectroscopy and high performance liquid chromatography (HPLC) coupled to a photodiode array detector are employed for the identification of the inorganic and organic colouring materials, respectively. The results reveal the extensive use of coccid dyes by the Cretan painters: kermes (Kermes vermilio Planchon) is found in icons dated before the middle 16th century and cochineal in icons created several decades after the discovery of the New World. Other dyestuffs detected in the historical samples are madder (possibly Rubia tinctorum L., according to HPLC profiles), soluble redwood and indigoid dyes. Organic dyes were used by the painters as exclusive colouring matters (or glazes) or in mixtures with inorganic pigments, such as red ochre, cinnabar, minium, azurite lead white and carbon black.Liquid chromatography with mass spectrometry (LC-MS) coupled to a negative electrospray ionization mode is employed to provide information on the identity of some unknown colouring components, of the aforementioned dyes, detected in the historical samples. The results suggest that (i) the type B compound (also known as Bra′) is a dehydro-brazilein product and (ii) the deprotonated molecular ion of the type C compound corresponds to m/z = 243. Both compounds are commonly used as markers for the identification of soluble redwood in historical samples. LC-MS analysis of cochineal shows that the dcIV and dcVII components are isomeric with carminic acid, as it has been recently suggested. Finally, LC-MS is employed to identify and record kermesic and flavokermesic acid in kermes and rubiadin in wild madder.     

Convenient one-pot procedure for synthesizing 4,4′-dimethoxy-boradiaza-s-indacene dyes and their application to cell labeling

We succeeded in developing a convenient one-pot pathway for synthesizing 4,4′-dimethoxy-boradiaza-s-indacene dyes 4a-d. The structures feature two methoxy groups in place of the fluorine atoms in 4,4′-difluoro-4-boradiaza-s-indacene. These novel dyes emitted green fluorescence and possessed moderate to high fluorescence quantum yields (Φ=0.32-0.93). We demonstrated that these dyes have applicability to cell labeling.     

Organic Electronics from Nature: Computational Investigation of the Electronic and Optical Properties of the Isomers of Bixin and Norbixin Present in the Achiote Seeds

Organic compounds have been employed in developing new green energy solutions with good cost-efficiency compromise, such as photovoltaics. The light-harvesting process in these applications is a crucial feature that still needs improvements. Here, we studied natural dyes to propose an alternative for enhancing the light-harvesting capability of photovoltaics. We performed density functional theory calculations to investigate the electronic and optical properties of the four natural dyes found in achiote seeds (Bixa orellana L.). Different DFT functionals, and basis sets, were used to calculate the electronic and optical properties of the bixin, norbixin, and their trans-isomers (molecules present in Bixa orellana L.). We observed that the planarity of the molecules and their similar extension for the conjugation pathways provide substantially delocalized wavefunctions of the frontier orbitals and similar values for their energies. Our findings also revealed a strong absorption peak in the blue region and an absorption band over the visible spectrum. These results indicate that Bixa orellana L. molecules can be good candidates for improving light-harvesting in photovoltaics.     

“Xanthene” is a premium bridging group for xanthenoid dyes

Novel xanthenoid dyes by replacing the central oxygen atom of the xanthene dyes with less electron-rich bridging groups have been intensively sought after primarily for their long spectral wavelengths. However, the new scaffolds are likely prone to nucleophilic attack at their central methane carbon, as the result of the reduced electron density of the fluorochromic scaffolds. We envisage that the bridging group may be harnessed to sterically shield the central methane carbon from incoming nucleophiles and render high stability and synthesized xantheno-xanthene dyes. Additionally, the xantheno-bridging group can be modified via electrophilic aromatic substitution to introduce functionalities, e.g., sulfonate groups.     

Green synthesis,characterization and photocatalytic application of silver nanoparticles synthesized by various plant extracts

Recently, the discharge of effluent containing dyes and other chemicals into river, lakes, and land has become a serious problem which increases the pollution level drastically. The dyes in the effluent are very difficult to be removed by conventional water treatment methods. Thus, there is a great need for more advanced methods that are cost-effective and more efficient. In this study, silver nano particles (AgNps) were synthesized by green method using extracts of onion (O), tomato (T), acacia catechu (C) alone, and mixed COT extracts. The reduction and formation of AgNps and its ions have been characterized by using several techniques, Ultra visible spectroscopy (UV–vis), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM)-energy dispersive X-ray spectrometer (EDX), Fourier transmission infrared spectroscopy (FTIR), and dynamic light scattering (DLS). These techniques revealed that the particle sizes of synthesized AgNps in all the extracts were ranged in between 5 and 100 nm with a crystalline nature. The synthesized AgNps were used as catalysts for the degradation of three different types of dyes, methyl orange (MO), methyl red (MR), and congo red (CR) in the liquid state. The excellent catalytic application of all the synthesized AgNps on the degradation of the studied dyes was confirmed via UV–visible results by studying the reduction in the absorbance maxima value within a very short interval of time. COT synthesized products were found to achieve the best performance for all dyes degradation among all products.     

Improving fast atom bombardment mass spectra: The influence of some controllable parameters on spectral quality

The relative effects of adjustable fast atom bombardment (FAB) parameters (choice of matrix, primary atom flux, and primary atom energy) on the appearance of FAB spectra (including signal-to-noise, signal-to-background, and signal-to-matrix ratios) of several organic dyes have been investigated. Beam-induced chemical damage is minimized by lowering the primary atom flux, by raising the primary atom energy, and by selecting a matrix with radical scavenging properties (e.g., m-nitrobenzyl alcohol). The relative importance in minimizing this chemical damage is choice of matrix > primary atom flux > (nominal) primary atom energy, but optimization of the parameters involves a trade-off between sensitivity and damage. The effect of these parameters on thermal damage (fragmentation) is much less. It can be concluded from comparison of the dyes that the extent of beam damage does not depend simply on the standard reduction potential of the analyte.     

Application of newly synthesized bisazo dichloro-s-triazinyl reactive dyes bearing 1,3,4-oxadiazole molecule

Novel bisazo dichloro-s-triazinyl (DCT) reactive dyes (5a–h) containing 1,3,4-oxadiazole molecule as a tetrazo component were synthesized and applied on silk, wool and cotton fibers by exhaust dyeing method. The structures of these dyes were confirmed by UV–vis, FT-IR, ¹H and ¹³C NMR and elemental analyses. The exhaustion, fixation and fastness properties of the dyed fabric were assessed and the results demonstrated that these dyes showed moderate to very good light and good to excellent washing and rubbing fastness properties. The colorimetric data (L¹, a¹, b¹, C¹, H¹, K/S) of these dyes have also been studied in detail.     

The synthesis and characterization of novel coumarin-containing cyanine dyes via “Click” chemistry

Four novel cyanine dye derivatives (C-Cy(1–4)) in which a coumarin moiety is attached to benzoindole ring of asymmetric trimethine cyanine dyes or hemicyanine dye by 1,2,3-triazole have been successfully synthesized via “Click” reaction between the corresponding alkyl-end cyanine dyes and 3-azidocoumarin. Six reaction systems were employed to find the suitable “Click” conditions of cyanine dyes. It was found that the combination of DMF, CuI and di-i-propylethylamine (DIPEA) was the most excellent system for “Click” reaction. All of the compounds were characterized by ¹H-NMR, MS, UV and FL.     

Synthesis and spectroscopic properties of ring-fused thiophene bridged push–pull dyes and their application in dye-sensitized solar cells

Bisdimethylfluorenylamino-based push–pull dyes bearing one or two benzo[c]thiophene and its precursor bicyclo[2.2.2]octadiene (BCOD) fused thiophene as π bridge have been synthesized. The effect of fused-ring on thiophene bridge for the spectroscopic and electrochemical properties of these dyes has been investigated. Dye-sensitized solar cells fabricated with these dyes show moderate photovoltaic properties.     

Electrogenerated chemiluminescence: Part XXVII. E.C.L. and electrochemical studies of selected laser dyes

The electrogenerated chemiluminescence (e.c.l.) and electrochemistry of the laser dyes, coumarin-2, coumarin-30, rhodamine-6G (perchlorate), rhodamine-B (perchlorate), oxazine-1 (perchlorate), and Nile Blue (perchlorate) were studied in acetonitrile using 0.1 M tetra-n-butylammonium perchlorate (TBAP) as a supporting electrolyte. Rather low intensity e.c.l. was obtained for all dyes except Nile Blue. A study of the electrochemical oxidation and reduction of coumarin-30, oxazine-1 and rhodamine-6G using cyclic voltammetry and controlled potential coulometry demonstrated that chemical side reactions of the electrogenerated reactants are responsible for the low e.c.l. efficiency. In several cases the one-electron transfer reaction at the electrode is followed by a dimerization reaction. The neutral free radical formed on reduction of oxazine-1 was investigated by electron spin resonance spectroscopy and coupling constants for it are reported. Some experiments in which the e.c.l. of mixtures of the dyes with rubrene or 9,10-diphenylanthracene were determined are also described.     

Modeling and optimization of simultaneous photocatalysis of three dyes on ceramic-coated TiO2 nanoparticles using chemometrics methods: phytotoxicological assessment during degradation process

In this paper, ceramic plates were used as a support of TiO₂ nanoparticles for photocatalytic decolorization of a mixture of three dyes. The three textile dyes (C.I. Basic Red 46, C.I. Basic Blue 3 and Malachite Green) were quantified simultaneously during the photocatalytic degradation process. The partial least squares modeling was successfully applied for the multivariate calibration of the spectrophotometric data. Also, the central composite design has been applied to the optimization of photocatalytic decolorization of the dye solution containing three dyes using an immobilized UV/TiO₂ process. The optimum initial concentration of three dyes, reaction time, and UV light intensity were found to be 5 mg/L, 240 min, and 47.2 W/m², respectively. The chronic phytotoxicity of mixture of dyes was evaluated using aquatic species Spirodela polyrhiza (S. polyrhiza) prior to and after photocatalysis. The phytotoxicity results revealed that the photocatalysis process could effectively reduce the phytotoxicity of the dyes from their aqueous solutions.     

Microbial decolourization of textile waste water

Six fungal isolates belong to Aspergillus niger, Penicillium spp., and Pleurotus osstreatus were used for decolourization activities of some acid and reactive dyes, after they screened for optimum efficiency and the condition for temperature and pH were optimized The results obtained indicated that Pleurotus osstreatus and Aspergillus niger 1 and 2 are more efficient than Penicillium spp., with the two kinds of dyes used. The results also revealed that, the maximum degradation activities of these isolates for acid dyes was at pH 5 after 9 days incubation period and at pH 5-6, for reactive dyes. Simulated and actual waste water samples were used in the experiments. Fungi decolourization of synthetic dyes according to their life state group 1: (living cells) to biodegradation and biosorb dyes. The major mechanism is biodegradation because they can produce the lignin modifying enzymes, lactose, manganese peroxides (Lip) to mineralize synthetic lignin of dyes. Group 2: dead cells (Fungal biomass) to adsorb dyes.