Showed Absorption Maxima Research Articles

Photophysical and electrochemical characterization of new poly(arylene vinylene) copolymers containing quinoline or bisquinoline segments

AbstractFour new fluorescent conjugated vinylene‐copolymers incorporating quinoline or bisquinoline segments along the backbone were synthesized by Heck coupling. Three of them were fluorenevinylene‐copolymers and contained quinoline (PQFV, PQFVT) or bisquinoline segments (PBQFV). One of them (PBQPV) was phenylenevinylene‐copolymer and contained bisquinoline segments. All the copolymers were soluble in common organic solvents and had relatively low glass transition temperature (Tg = 50–56 °C for fluorenevinylenes and Tg < 25 °C for phenylenevinylene). In THF solutions, the quinoline‐containing copolymers showed absorption maxima at 411–420 nm while the bisquinoline‐containing ones exhibited maxima at 357–361 nm. The emission maxima of solutions were 465–490 nm. The copolymers showed high quantum yields up to 64%. The films exhibited absorption and emission maxima in the range of 371–437 nm and 480–521 nm, respectively. All copolymers revealed reversible reduction with electron affinity of 2.66–3.53 eV and irreversible oxidation scans with ionization potential of 5.39–5.53 eV. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3370–3379, 2009

Color Tuning of Polyfluorene Emission with BODIPY Monomers

Three fluorescent conjugated copolymers, comprised of alternating fluorene and BODIPY units in the main chain, have been prepared by palladium-catalyzed Suzuki polymerization of 9,9-dihexylfluorene-2,7-diboronic acid with each of three different 2,6-diiodo-substituted BODIPY monomers. The copolymers were characterized using FT-IR spectroscopy, UV−vis spectroscopy, photoluminescence (PL), and molecular weight studies. Low-band gap BODIPY comonomers are effective in expanding the emission wavelength to the orange region because of significant extension of π-conjugation and have significantly enhanced fluorescent intensity with fluorescent quantum yield of up to 85% in methylene chloride solution. The copolymers show absorption maxima between 547 and 557 nm and emission maxima between 585 and 588 nm in methylene chloride solutions. The copolymers possess high molecular weight, good solubility and readily dissolve in common organic solvents such as THF, CH2Cl2, CHCl3, and toluene. The copolymers display sensitive fluorescent responses to fluoride and cyanide anions through their multivalent interactions while they do not respond to chloride, bromide, and iodide anions.

The presence of sinapyl lignin in Ginkgo biloba cell cultures changes our views of the evolution of lignin biosynthesis

Suspension cell cultures (SCCs) from one of the oldest seed plants, Ginkgo biloba, show unpredictable alterations in the nature of the lignins, such as is the recruitment of sinapyl alcohol for lignin biosynthesis, compared with the woody tissues of the same species, which lack syringyl (S) lignins. These results show that, in this gymnosperm, the genes involved in sinapyl alcohol biosynthesis are latent and that their regulatory regions respond, by initiating gene expression, to the developmental signals and the environmental clues, which condition its in vitro culture. G. biloba SCCs not only synthesize S lignins but also their extracellular proteome contains both class III peroxidases capable of oxidizing sinapyl alcohol and enzymes involved in H2O2 production, observation which suggests that the peroxidase branch for the oxidative coupling of sinapyl alcohol units into lignins is operative. The incomplete knowledge of the G. biloba peroxidase-encoding genes led us to purify, characterize and partially sequence the peroxidase responsible for monolignol oxidation. When the major peroxidase from G. biloba SCCs (GbPrx) was purified to homogeneity, it showed absorption maxima in the visible region at 414 (Soret band), and at 543 and 570 nm, which calls to mind those shown by low-spin ferric peroxidases. However, the results also showed that the paraperoxidase-like character of GbPrx is not an obstacle for oxidizing the three monolignols compared with high-spin ferric peroxidases. Taken together, these results mean that the time at which the evolutionary gain of the segment of the route that leads to the biosynthesis of S lignins took place in seed plants needs to be revised.

Direct and Derivative Spectrophotometric Determination of Copper(II) with 5-Bromosalicylaldehyde Thiosemicarbazone

A rapid and sensitive spectrophotometric method is developed for the determination of Copper (II) in aqueous DMF medium. The metal ion forms a light greenish yellow coloured complex with 5-bromo salicylaldehyde thiosemicar- bazone (5-BSAT) in acidic medium. The complex shows absorption maximum at 390nm. Beer's law is obeyed in the range 0.31 - 6.35 � gml -1 of Copper (II). The molar absorptivity (� ) and Sandell's sensitivity are found to be 1.08 X 10 4 l mole -1 cm -1 and 0.062 � gcm -2 respectively. A method for the determination of copper by third derivative spectrophotome- try is also proposed. The methods have been employed successfully for the determination of copper in grape leaves and aluminum based alloy samples.

Spectrophotometric estimation of ketotifen fumarate from tablet formulations

Two simple and sensitive visible spectrophotometric methods have been developed for the quantitative estimation of ketotifen fumarate from its tablet formulation. The developed methods are based on formation of chloroform extractable colored complex of with 2-nitroso- napthol-4- sulphonic acid and rhodizonic acid. The extracted complex of drug with 2-nitroso- napthol-4- sulphonic acid (method-I), showed absorbance maxima at 436.5 nm and with rhodizonic acid (method-II), showed absorbance maxima at 489.5 nm. The linearity range for both the developed methods was observed in the concentration range of 50-250 µg/ml of drug. Results of analysis for both the developed methods were validated statistically and by recovery studies.

UV Spectrophotometric Method for Determination of Cinitapride in Pure and its Solid Dosage Form

A new, rapid, precise, accurate and sensitive analytical method was developed for the UV spectrophotometric assay of cinitapride (CTP). The drug obeyed the Beer′s law and showed good correlation. It showed absorption maxima at 260 nm in methanol. The linearity was observed between 5‐40 µg mL-1. The results of analysis were validated by recovery studies. The recovery was more than 99%. The proposed method is the only method available for spectrophotometric determination of the drug. It is simple, precise, sensitive and reproducible and can be used for the routine quality control testing of the marketed formulations.

Studies on interaction of molybdenum(VI) with modified lignocellulosics using a novel spectrophotometric method

A new adsorbent (PGPEP-COOH) bearing carboxylate functional group was prepared through graft co-polymerization of acrylic acid onto pulverized Phyllanthus emblica planks using ferrous sulphate/H 2 O 2 redox initiator system. The adsorbent obtained was tested for the uptake of molybdenum(VI) from aqueous solutions. The efficiency of the PGPEP-COOH to remove Mo VI ions at different time of contact, initial adsorbate concentration, adsorbent dose, pH, ionic strength and temperature was studied by batch experiments. The amount of molybdeitum(VI) in aqueous system was determined using a very simple and sensitive method of estimation using potassium hexacyanoferrate(II). Reddish brown solution of the molybdenum complex at pH 3.2 shows absorption maximum at 390 nm. To establish the most appropriate correlation for adsorption equilibrium, isotherm studies were performed using Langmuir, Freundlich and Redlich-Peterson models. The suitability of isotherm models was compared using linear least square fitting. Experimental kinetic data were described using a diffusion controlled first order reversible model and diffusion coefficient was evaluated at different temperatures. Applying Eyring equation thermodynamic parameters were calculated. PGPEP-COOH adsorbed 99.2% Mo VI from a solution of 10 μmol dm -3 concentration at 303 K. Desorption and regeneration studies of the adsorbent under different conditions were also studied.

Isolasi dan Karakterisasi Senyawa Kimia dari Kulit Batang Manggis (Garcinia mangostana Linn) Isolation and Characterization of Chemical Compound from Bark of Mangosteen (Garcinia mangostana Linn)

The purpose of this research is to isolate and characterize chemical compound from bark of mangosteen. Bark of mangosteen was macerated with methanol. The extract from that process was fractionated with n -hexane, methylen chloride, and ethyl acetate. Ethyl acetate fraction was separated and purified by vacuum column chromatography, gravitation column chromatography, and preparative thin layer chromatography. The relative pure compound was afforded from ethyl acetate fraction of mangosteen bark (8.5 mg) resulting from 1.5 kg of mangosteen bark. The yellow amorphous powder of compound melts at 114 ~ 116oC (uncorrected). The purity of compounds was tested by 1 and 2 dimension thin layer chromatography which gave one spot on TLC plate. The ultraviolet-visible (in CH 3 OH solvent) spectrum showed absorption maximum at 318 nm (sinamoyl group/band I), 258 (shoulder), and 243 nm (benzoyl group/band II). Addition of NaOH caused batochromic shift of band I and band II predicted as two hydroxyl at C-4’ and C-7, respectively. The infrared spectrum displayed absorption bands of OH stretching at 3436 cm -1 , C-H stretching at 2920 cm -1 , C=O stretching at 1631 cm -1 , C-O-C stretching at 1094 cm -1 , and C-H aromatics bending at 970-800 cm -1 . A molecular ion in the FABMS at m/z 271.36 [M+H] + was consistent for the molecular formula C 15 H 10 O 5 . The 1 H NMR spectrum showed characteristic resonances of a flavone. Based on the result of phytochemical test and analysis of the spectrum, it is predicted that the compound belongs to flavone, a kind of flavonoids which has hydroxyl at C-5, C-7, and C-4.

Simple UV Spectrophotometric Method for the Determination of Fluvastatin Sodium in Bulk and Pharmaceutical Formulations

A simple and cost effective spectrophotometric method is described for the determination of fluvastatin sodium in pure form and in pharmaceutical formulations. When the drug reacts with sodium hydroxide shows absorption maximum at 304 nm and obeys beer′s law in the concentration range 5‐25 µg mL-1. The absorbance was found to increase linearly with increasing concentration of FVS, which is corroborated by the calculated correlation coefficient value of 0.9999 (n=5). The apparent molar absorptivity and sandell sensitivity were 1.1905×104 and 0.0368844 µg cm-2 cm respectively. The slope and intercept of the equation of the regression line are 0.027112 and 0.003539 respectively. The limit of detection and limit of quantification was found to be 0.0811 µg mL-1 & 0.2460 µg mL-1. The validity of the described procedure was assessed. Statistical analysis of the result has been carried out revealing high accuracy and good precision. The proposed method was successfully applied to the determination of FVS in pharmaceutical formulations without any interference from common excipients. The relative standard deviations were ≤ 0.937%, with recoveries of 98.60% ‐101.70%.

The Fungal Phytochrome FphA from Aspergillus nidulans

The red light-sensing photoreceptor FphA from Aspergillus nidulans is involved in the regulation of developmental processes in response to light. Here we present extended biochemical and spectroscopic characterization of recombinant FphA using a synthetic gene with host-adapted codon usage. The recombinant photosensory domain FphAN753 was shown to display all features of a bona fide phytochrome. It covalently binds biliverdin as chromophore and undergoes red/far-red light-inducible photoconversion with both parent states being protonated. The large N-terminal variable extension of FphA exerts a stabilizing effect on the active Pfr state. Upon substitution of the highly conserved histidine 504, involved in the hydrogen-bonding network of the protein moiety and the chromophore, chromophore attachment and photoreversibility were completely impaired. FphA is a functional sensor histidine kinase with a strong red-light-dependent autophosphorylation activity. Furthermore, intermolecular trans-phosphorylation to the response regulator domain of a second monomer could be demonstrated. Interestingly, co-incubation of FphA and FphA variants led to enhanced autophosphorylation, including the "inactive" Pr form. The latter observed phenomenon might suggest that auto- and trans-phosphorylation activity is modulated by additional interaction partners leading to variable phosphorylation events that trigger a specific output response.

Nanosized starlike molecules. Synthesis and optical properties of tris- and tetrakis[oligo(disilanylenebithienylene)dimethylsilyl]benzene

The syntheses of two types of starlike molecules with the arms that extend to three and four directions have been reported. The molecules with the arms consisting of a regular alternating arrangement of a silicon–silicon bond and bithienylene unit that extend to three directions were synthesized by the reactions of 1,3,5-tris(chlorodimethylsilyl)benzene, which was chosen as a core, with the lithio[oligo(disilanylenebithienylene)] derivatives. The starlike molecules with extended arms to four directions were prepared by the reaction of 1,2,4,5-tetrakis(fluorodimethylsilyl)benzene used as a core, with lithio[oligo(disilanylenebithienylene)]s. UV–Vis absorption and fluorescence properties of these starlike molecules have been investigated in a dioxane solution. The present molecules showed absorption maxima in a range of 321–337 nm, and revealed higher fluorescence quantum yields than that of the corresponding linear polymer, poly[(tetraethyldisilanylene)bithiophene].

Extractive spectrophotometric method for determination of metribuzin herbicide and application of factorial design in optimization of various factors

A simple extractive spectrophotometric method has been described for the determination of metribuzin herbicide. Metribuzin was reacted with copper and a stable complex in the presence of ammonia (0.2 M) at pH 10.5 was formed. The resulting yellow coloured complex was extracted in chloroform and showed absorption maxima at 340 nm. Beer’s law was obeyed in the range of 0.8–25 μg mL −1 with molar absorptivity of 5.67 × 10 3 L mol −1 cm −1. The composition of the complex was studied by Job’s method of continuous variation and the results indicated that the mole ratio of metribuzin:Cu 2+ is 2:1. The optimum reaction conditions for complexation and other analytical parameters were evaluated. A two-level factorial design was also used to determine the effect of different parameters and their interaction on metribuzin:Cu 2+ complex formed. The method was successfully applied for the determination of metribuzin in commercial formulations and real samples.

Carbazolevinylene‐based polymers and model compounds with oxadiazole and triphenylamine segments: Synthesis, photophysics, and electroluminescence

Two new soluble alternating carbazolevinylene-based polymers POXD and PTPA as well as the corresponding model compounds MOXD and MTPA were synthesized by Heck coupling. POXD and MOXD contained 2,5-diphenyloxadiazole segments, while PTPA and MTPA contained triphenylamine segments. All samples displayed high thermal stability. The polymers had higher glass transition temperature (Tg) than their corresponding model compounds. The samples showed absorption maximum at 364–403 nm with optical band gap of 2.62–2.82 eV. They emitted blue-green light with photoluminescence (PL) emission maximum at 450–501 nm and PL quantum yields in THF solution of 0.15–0.36. The absorption and the PL emission maxima of PTPA and MTPA were blue-shifted as compared to those of POXD and MOXD. The electroluminescence (EL) spectra of multilayered devices made using four materials exhibited bluish green emissions, which is well consistent with PL spectra. The EL devices made using poly(vinyl carbazole) doped with MOXD and MTPA as emitting materials showed luminances of 12.1 and 4.8 cd m−2. POXD and PTPA exhibited 25.4, and 96.3 cd m−2, respectively. The polymer containing the corresponding molecules in the repeating group showed much higher device performances. Additionally, POXD and MOXD exhibited better stability of external quantum efficiency (EQE) and luminous efficiency with current density resulting from enhancing the electron transporting properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5592–5603, 2008

A Novel Yellow Pigment, Furpipate, Derived from Lysine and Furfural

Furfural is an important intermediate compound of the Maillard reaction of pentose or ascorbic acid. We examined the browning of furfural and lysine by heating these compounds in solution and found two yellow compounds. The first, furpipate, is a novel pipecolic acid derivative and was (Z)-3-(2-furylmethylidene)-3H, 4H, 5H, 6H-pyridine-2-carboxylic acid. The second was decarboxylated-furpipate. Furpipate shows absorption maxima at 370 nm and 310 nm under acidic and alkaline conditions, respectively. This compound was the major colored compound of the heated solution containing lysine and furfural.

Laser flash photolysis study of the triplet reactivity of β-lapachones

The photochemical reactivity of beta-lapachone (1), nor-beta-lapachone (2) and beta-lapachone 3-sulfonic acid (3) has been examined by laser flash photolysis. Excitation (lambda = 266 nm) of degassed solutions of , in acetonitrile or dichloromethane, resulted in the formation of detectable transients with absorption maxima at 300, 380 and 650 nm. These transients, with lifetimes of 5.0 micros, were quenched by beta-carotene at a diffusion-controlled rate constant and assigned to the triplet excited states of 1-3. Addition of hydrogen donors, such as 2-propanol, 1,4-cyclohexadiene, 4-methoxyphenol or indole led to the formation of new transients, which were assigned to the corresponding ketyl radicals obtained from the hydrogen abstraction reaction by the triplets 1-3 . In the presence of triethylamine it was observed the formation of the long-lived anion radical derived from , which shows absorption maxima at 300 and 380 nm. The low values observed for the hydrogen abstraction rate constants for the beta-lapachones 1-3 using 2-propanol and 1,4-cyclohexadiene as quenchers led us to conclude that their triplet excited states show pi pi* character.

Cloning and Expression of Soluble Cytochrome c and Its Role in Polyvinyl Alcohol Degradation by Polyvinyl Alcohol-Utilizing Sphingopyxis sp. Strain 113P3

The gene encoding cytocrome c in the pva operon of Sphingopyxis sp. strain 113P3 was cloned, on the basis of the sequence of the gene for cytochrome c (GenBank accession no. AB190288). The deduced amino acid sequence of the gene showed homologies (37% and 47% identities) with two cytochromes c of different origins. The recombinant cytochrome c tagged with hexahistidines was expressed in the periplasm of Escherichia coli BL21(DE3) harboring pT-GroE, which was in accordance with the localization of cytochrome c in strain 113P3; the protein was purified to homogeneity. The purified recombinant cytochrome c was a monomeric protein with a molecular weight of 16.5 kDa. The oxidized and reduced forms of the protein showed absorption maxima at 409 nm and at 414, 520 and 550 nm, respectively. The recombinant cytochrome c was fully reduced by polyvinyl alcohol (PVA), coupled with a catalytic amount (1/10 molar concentration) of the recombinant PVA dehydrogenase (PVADH) of the same origin, suggesting that the cytochrome c involved in the pva operon is a physiological primary electron acceptor for PVADH and that PVA dehydrogenation is linked with the respiratory chain in Sphingopyxis sp. strain 113P3.

Preparation and characterization of thermally stable poly(amide‐urea)s functionalized with anthraquinone chromophore

AbstractTwo new diamines containing bulky anthraquinone pendant units were prepared via reactions of 1‐ and 2‐aminoanthraquinone with 3,5‐dinitrobenzoylchloride and a subsequent reduction of their nitro groups. A novel series of highly organosoluble poly(amide‐urea)s were synthesized from the reactions of the prepared diamines with various commercially available diisocyanates via a step‐growth addition reaction process in N‐methyl‐2‐pyrrolidone (NMP). The effects of two factors (time and temperature) on the reaction were studied to optimize the conditions for the preparation of high molecular weight polymers. All poly(amide‐urea)s were characterized by Fourier Transform Infrared (FTIR) and 1H‐nuclear magnetic resonance (NMR) spectroscopies and elemental analysis. The resulting poly(amide‐urea)s had inherent viscosities in the range of 0.54–0.73 dl/g. They exhibited excellent solubility in polar solvents. The temperature for 10% weight loss of the polymers in air was all above 285°C, their residues were more than 36% at 700°C in air, and their Tg values were in the range of 148–190°C. According to the wide‐angle X‐ray diffraction (WAXD), the polymers were almost amorphous. The optical properties of poly(amide‐urea)s measured by ultraviolet–visible (UV–Vis) spectroscopy showed absorption maxima at 303–429 nm. Copyright © 2008 John Wiley & Sons, Ltd.

Spectrophotometric Estimation of Abacavir Sulphate in Pharmaceutical Formulations

Two simple, accurate, rapid and sensitive methods (A and B) have been developed for the estimation of abacavir sulphate in its pharmaceutical dosage form. The method A and B are based on the formation of chloroform extractable complex of abacavir sulphate with bromophenol blue (method A) and bromocresol green (method B), which shows absorbance maxima at 460 nm and 469 nm respectively. The absorbance‐concentration plot is linear over the range of 1‐10 mcg/mL for method A and B respectively. Results of analysis for all the methods were validated statistically and by recovery studies. The proposed methods are economical and sensitive for the estimation of abacavir sulphate in bulk drug and in its tablet dosage form.

Simple Extractive Colorimetric Determination of Oxaprozin by Acid‐Dye Complexation Methods in Solid Dosage Form

A simple and sensitive extractive spectrophometric method has been described for the assay of oxaprozin (OXA) either in pure form or in pharmaceutical solid dosage form. The developed method involves formation of colored chloroform extractable ion‐pair complex of OXA with bromocresol green in aqueous acidic medium. The extracted complexes showed absorbance maxima at 421 nm. Beer′s law is obeyed in the concentration range of 10‐50 μg mL-1. This method has been applied to the determination of drug in commercial tablets. Results of analysis were validated statistically. The excipients present in the formulations do not interfere with the assay procedure.

Synthesis and electroluminescence properties of zinc(2,2′ bipyridine)8-hydroxyquinoline

New electroluminescent material, namely zinc(2,2′ bipyridine)8-hydroxyquinoline [Zn(Bpy)q] has been synthesized and characterized. A solution of Zn(Bpy)q showed absorption maxima at 382 nm and 342 nm in toluene solution attributed to π − π ⁎ transition. The photoluminescence spectrum in toluene solution showed peak at 545 nm. The material was stable up to 350 °C. Organic light emitting diode (OLED) fabricated with the structure ITO/α-NPD/Zn(Bpy)q/Alq 3/LiF/Al exhibits a broad electroluminescence peak at 548 nm. The maximum current efficiency of OLED was 1.34 cd/A at 5 V and the maximum power efficiency 0.84 lm/W at 5 V.