The chemistry of naphthazarin derivatives

Direct oxidation of naphthazarin with manganese dioxide in conc. H₂SO₄ was found to be a simple and effective method for the synthesis of mompain. For Part 3, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1019–1021, May, 1999.     

Ab initio HF-SCF study of naphthazarin: Geometries,isomerism, hydrogen bonding,and vibrational spectrum

The structural properties and intramolecular hydrogen bonding of a series of structures of naphthazarin molecule were investigated by ab initio HF-SCF methods. The geometries of theC _2v ,C _2h ,D _2h , andC _s symmetry structures were optimized using split-valence basis sets. MP2/6-31G^*// HF/6-31G single-point energy calculations indicate that theC _2v isomer (5,8-dihydroxy-1,4-naphthoquinone) is the lowest energy structure of the molecule and that theC _2h symmetry one (4,8-dihydroxy-1,5-naphthoquinone), lying 37 kJ/mol above theC _2v form, is the other stable isomer of naphthazarin. At the HF/6-31G level, the intramolecular proton exchange between two equivalentC _2v structures is a two-step process where each proton can be independently transferred through an unsymmetrical potential having a 1,5-quinone intermediate, theC _2h symmetry structure, and two equivalent transition states ofC _s symmetry, with a barrier height equal to 38 kJ/ mol (MP2/6-31G^*//HF/6-31G). The study of naphthazarin molecule is flanked by a theoretical investigation on theC _2v andC _2h isomers of the parent naphthoquinone and dihydroxynaphthalene molecules. The SCF vibrational spectrum of the ground state of naphthazarin, harmonic frequencies, and infrared and Raman band intensities were computed at the HF/6-31G level. The results of the calculations are compared with the matrix isolation FT-IR spectroscopy measurements and with the infrared and Raman spectra of the crystal molecule.     

Direct Amination of Naphthazarin,Juglone, and Some Derivatives

Mono‐ and diamino‐derivatives of naphthazarin, 2‐methoxynaphthazarin, juglone and their methylethers were prepared by reaction with ammonia. The structure of the products was established by NMR studies. Some compounds were tested for cytotoxic activity.     

Synthesis of water-soluble N-Acetyl-L-cysteine conjugates of naphtazarin (5,8-Dihydroxy-1,4-naphthoquinone) derivatives

Base-catalytic condensation of N-acetyl-L-cysteine with substituted naphthazarins was first obtained a series of mono-, di-, tri- and tetra-substituted S-aminoacid naphthazarin conjugates bearing alkyl (hydroxy) groups. It was shown that three- and tetra-N-acetyl-L-cysteine naphthazarin derivatives are readily soluble in water.     

Cytotoxic activity of intermediates and side products of echinochrome synthesis

The cytotoxic activity of the principal intermediates and side products of echinochrome synthesis toward gametes of the sea urchin Strogylocentrotus intermedius was studied. Di-and trichloro naphthazarin derivatives with two vicinal Cl atoms were the most active. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 228–231, May–June, 2008.     

The Fourier Transform Raman and infrared spectra of naphthazarin

The FT Raman spectra of the three naphthazarin polymorphs have been recorded for the first time and compared with the FTIR spectra of the polymorphs and of naphthazarin with deuterated hydroxyl groups. It is possible to distinguish between the polymorphs, to deduce that the room temperature static symmetry point group of naphthazarin is C_2v, to assign the ν(CH), σ(OH), γ(OH) vibrations and to confirm the absence of the ν(OH) mode.     

Quinoid pigments of echinodermata V. Pigments of the sea urchinStrongy locentrotus dr?ebachiensis

Summary From a mixture of the pigments of the sea urchinStrongy locentrotus dröebachiensis, in additionto the known spinochromes A, C, D, and E, we have isolated a binaphthoquinone and its anhydro derivative. On the basis of¹³C NMR spectra the position of the ethylidene bridge symmetrically binding the two naphthazarin fragments of the binaphthoquinone has been definnitely established, and the structure of this compound has been determined as ethylidene-6,6-bis(2,3,7-trihydroxynaphthazarin).Pacific-Ocean Institute of Bioorganic Chemistry, Far-Eastern Scientific Center of the Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 438–441, July–August, 1978.     

Structure-Infrared Optical Property-Correlations of C,O,H-Polymers for Transparent Insulation and Greenhouse Applications

Summary. In this paper an understanding of the physical relationships between the material structure and the temperature dependent infrared optical properties of different transparent polymer films for solar applications is described. The infrared optical properties are relevant for the heat transport of e.g. greenhouse and transparent insulation structures. The properties were determined based on infrared transmittance measurements and the assumption of a constant index of refraction from the visible range. To establish structure-property-correlations molecular structure parameters such as the concentration of carbon-oxygen single bonds and carbon-hydroxyl groups were determined. For 50 μm thick films a good correlation between the concentration of the functional carbon-hydroxyl and the carbon-oxygen group and the infrared optical thickness as well as the hemispherical emittance was found. This correlation fits well for high and low infrared radiation absorbing polymeric materials consisting of carbon, hydrogen, and oxygen atoms. The carbon-hydroxyl group appears to be slightly more effective than the carbon-oxygen single bond. Interestingly, the correlation works for polymers with aromatic (PC, PET) and aliphatic (PMMA, CTA, ethylene copolymers) groups.     

Synthesis and near infrared properties of rare earth ionomers

Fully exchanged, anhydrous ionomers of ethylene-co-acrylic acid (EAA) copolymers and ethylene-co-methacrylic acid (EMAA) copolymers containing Dy⁺³, Er⁺³, Sm⁺³, Tb⁺³, Tm⁺³, and Yb⁺³, and mixtures of them, were synthesized and studied in the near infrared region by reflection and Fourier Transform Laser Raman spectroscopies. The EAA copolymers ranged from 1.4 to 8.7 mol % acid and the EMAA copolymers were 7.3 and 16.2 mol % acid. The ionomers were shown to be essentially free of carboxylic acid groups, water, or other forms containing O (SINGLE BOND) H groups and were characterized by infrared and other methods. They are light and heat stable, and become thermoplastic and moldable at ca. 220°C under pressure. When excited at 1.064 μ with a Nd: YAG laser, these ionomers exhibit novel, lanthanide-dependent near infrared luminescence and strong Raman scattering in the near infrared region. The strongest luminescence is observed with Sm⁺³ ionomers. The Dy⁺³ ionomer Raman-shifts this source to emit light most strongly in the 1.53–1.55 μ range where the ionomer also transmits light well. © 1996 John Wiley & Sons, Inc.     

Structure-Infrared Optical Property-Correlations of C,O,H-Polymers for Transparent Insulation and Greenhouse Applications

In this paper an understanding of the physical relationships between the material structure and the temperature dependent infrared optical properties of different transparent polymer films for solar applications is described. The infrared optical properties are relevant for the heat transport of e.g. greenhouse and transparent insulation structures. The properties were determined based on infrared transmittance measurements and the assumption of a constant index of refraction from the visible range. To establish structure-property-correlations molecular structure parameters such as the concentration of carbon-oxygen single bonds and carbon-hydroxyl groups were determined. For 50 μm thick films a good correlation between the concentration of the functional carbon-hydroxyl and the carbon-oxygen group and the infrared optical thickness as well as the hemispherical emittance was found. This correlation fits well for high and low infrared radiation absorbing polymeric materials consisting of carbon, hydrogen, and oxygen atoms. The carbon-hydroxyl group appears to be slightly more effective than the carbon-oxygen single bond. Interestingly, the correlation works for polymers with aromatic (PC, PET) and aliphatic (PMMA, CTA, ethylene copolymers) groups.     

Naphthoquinones ofLithospermum erythrorhizon

Summary 1. The roots ofLithospermum erythrorhizon Sieb. et Zucc. have yielded six naphthazarin pigments which have been characterized as shikonin itself and derivatives of it. A new quinoid pigment of nonnaphthazarin structure has also been isolated.2. The pigments of the roots ofL. erythrorhizon collected in the Maritime Territory have not been found to contain the ,-dimethylacrylic ester of shikonin which has been reported for this species in the literature.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center of the Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 726–730, November–December, 1976.     

Thioxanthone–carbazole as a visible light photoinitiator for free radical polymerization

A thioxanthone (TX) derivative with the additional carbazole chromophore, namely thioxanthone‐carbazole (TX‐C) was synthesized and characterized. The photophysical properties and its efficiency to polymerize methyl methacrylate both in the presence and absence of N,N‐dimethylaniline (DMA) as coinitiator was investigated and compared with that of the commercially available TX. TX‐C was found to display better photophysical properties and in both cases initiate polymerization more efficiently. Detailed real‐time Fourier transform infrared studies revealed that high polymerization rates can be obtained when TX‐C in conjunction with DMA was used. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Determination of the degree of N-deacetylation in chitin and chitosan as well as their monomer sugar ratios by near infrared spectroscopy

Chitin and its derivative chitosan are rapidly becoming of commercial interest in the biomedical, wastewater treatment, and fiber industries. One of the most important properties of these copolymers is the degree of N-acetylation. Presently there is no rapid accurate method to determine this value. We propose near infrared spectroscopy for such a method. Using a primary method such as hydrobromic acid titration or ¹H-NMR, standards can be established. Once a model calibration equation has been developed, unknown samples can be analyzed by near infrared spectroscopy in less than 5 min. This is demonstrated by examining representative structural monomers of chitosan, N-acetyl-D-glucosamine and D-glucosamine hydrochloride, as model compounds as well as actual chitin and chitosan samples. © 1993 John Wiley & Sons, Inc.     

Homogeneous and heterogeneous olefin epoxidation catalyzed by a binuclear Mn(II)Mn(III) complex

The synthesis and characterization of a binuclear carboxylated bridged manganese complex containing the heptadentate ligand N,N′-bis(2-hydroxybenzyl)-N,N′-bis(2-methylpyridyl)-2-ol-1,3-propanediamine (H₃bbppnol) is reported. This complex was characterized by elemental analysis; infrared, electronic (UV–vis) and EPR spectroscopy; and conductivity measurements. The complex was immobilized on silica by either adsorption or entrapment via a sol–gel route. The obtained solids were characterized by thermogravimetric analyses (TG and DSC), UV–vis and infrared spectroscopy, and X-ray diffraction. The catalytic performance of the binuclear manganese complex in epoxidation reactions was evaluated for both homogeneous and heterogeneous systems. The catalytic investigation revealed that the complex performs well as an epoxidation catalyst for the substrates cyclohexene (26–39%) and cyclooctene (29–74%). The solids containing the immobilized complex can be recovered from the reaction medium and reused, maintaining good catalytic activity.     

Preparation and properties of isomeric polyphenylacetylenes

Polyphenylacetylenes were prepared using ferric acetylacetonate and (i-Bu)₂AlH, RhCl[(C₆H₅)₃P]₃ and thermal initiation. Color, infrared spectra, softening temperatures, ultraviolet fluorescence, solubility, and crystallinity are described. A method is presented for assigning to these three macromolecular species predominantly cis, trans, and cis–trans copolymer structures, respectively. The dominantly cis polymer is believed to form in a transoid conformation which can easily be transformed to a more helical arrangement which exhibits a degree of crystallinity. Pyridine promotes the isomerization of cis to trans structure. The rhodium phosphine is thought to effect chain growth by repeated additions of the acetylenic C? H of monomer across a terminal triple bond. Phenylacetylene thus behaves as a bifunctional molecule in this system. Color, polymer conformation, and crystallinity appear to be strongly interrelated.     

A DFT and MP2 Study on the Molecular Structure and Vibrational Spectra of Halogenosubstituted Phosphoryl and Thiophosphoryl Compounds

The molecular geometrical parameters, rotational constants, dipole moments and vibrational infrared properties of a series of phosphoryl compounds (OPX _i Y _j Z _k , X, Y, Z = F, Cl, Br; i+ j + k = 3) and their thio analogs are predicted by density functional and MP2 calculations using the 6-311G(2d,2p) basis set. Both methods yielded similar results. The predicted molecular parameters and the vibrational Raman and infrared spectra agree well with the available experimental data. The Raman Scattering Activities (RSA) and depolarization ratios (Dep) of the molecules are obtained by DFT calculations. Considering the different substitution modes of various halogen atoms, the resultant changes in the geometrical and vibrational properties are discussed. Such studies permit detailed information to be obtained concerning unknown molecules and can define the guidelines for synthesizing molecules of particular characteristics.     

Synthesis,Structure, and Properties of Nonlinear Optical Crystal Na2SiF6

Nonlinear optical crystals of fluosilicate Na₂SiF₆ are synthesized via hydrothermal method and its structure is determined by single‐crystal X‐ray diffraction (XRD). The space group of Na₂SiF₆ is P321 with cell parameters a = 8.8715(3) Å, c = 5.0484(5) Å, Z = 3, V = 344.09(4) ų. The properties of the crystal are measured by powder XRD, infrared (IR) spectroscopy, ultraviolet/visible (UV/Vis) near‐infrared (NIR) diffuse reflectance spectroscopy, thermogravimetric (TG), and differential scanning calorimetry (DSC) analysis. The bandgap calculated using CASTEP is 7.41 eV, indicating that the cut‐off edge of the Na₂SiF₆ crystal can be down to deep‐UV energy region. The first‐principles studies were performed to elucidate the structure/property relationship of Na₂SiF₆.     

Structure of aromatic polyimides

With a view to understanding the structure of aromatic polyimide backbone, model compound N,N-bis(4-phenoxyphenyl)-1,2:4,5-benzenetetracarboxdiimide was synthesized by the condensation of pyromellitic dianhydride and 4-aminodiphenyl ether in solvent N,N-dimethylacetamide or N,N-dimethylformamide. Various side products formed during the reaction were isolated and identified by spectroscopical methods. This study reveals that the polymer backbone contains nearly 85% imide rings. The uncyclizable residues in the backbone are those derived by the chemical interaction of polymerization solvent or by the modification of intermediate orthoamido acid. The uncyclizable nature of the latter was explained in mass and infrared (IR) spectral studies. The role of the dipolar solvent appears to be vital to imidization.     

Contact bactericides and fungicides on the basis of amino‐functionalized poly(norbornene)s

This study is aimed at investigating the microbiocidal potential of amino‐functionalized poly(norbornenes) in the solid state. A series of norbornene‐type monomers that carry secondary or tertiary amine functions as well as hexyl and dodecyl groups were prepared. Ring‐opening metathesis polymerization was used to prepare homopolymers of the amine bearing monomers and random copolymers of amine‐ and alkyl‐substituted monomers of high average molar mass. The resulting polymers were characterized by nuclear magnetic resonance, thermogravimetry, differential scanning calorimetry, infrared spectroscopy, and contact angle measurements, and their contact biocidal potential was evaluated according to the Japanese Industry standard Z2801. Tested microorganisms comprised Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Candida albicans, and Aspergillus niger. Microbiocidal activity of selected polymer films against E. coli, S. aureus, and A. niger was found, whereas against C. albicans and P. aeruginosa microbiostatic behavior was observed. Moreover, the most potent copolymer revealed no cytotoxicity rendering a biocidal polymer with potential applications in mammalian‐, and in particular, human‐related fields. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

The base-catalyzed transformation of polyacrylonitrile

In an effort to produce high-molecular-weight, linear ladder polymer by linking the nitrile groups within the molecule of polyacrylonitrile, polyacrylonitrile homopolymers were heat treated in N,N-dimethylformamide and N,N-dimethylacetamide solutions, in the presence of tertiary alkylamine catalysts. The products were soluble in formic acid, had relatively low molecular weight, and could be cast into brittle films. The infrared spectra indicated that the polymerization of the nitrile groups is initiated by a self-initiation mechanism based on the active methine groups in polyacrylonitrile, as proposed by Grassie and Hay, and that the reaction is complicated by molecular weight degradation via reverse Michael addition, as proposed by Hamada and Takahashi. The inherent viscosities of the products increase with increasing catalyst concentration, and further increases can be achieved by the addition of anionic chain coinitiators of phenolic nature. Density measurements indicated that the ladder structures undergo rearrangement into a more stereoregular form after formation, and that some aromatization occurs when the reaction is carried out in the presence of air.