Vibrational spectra and ab initio computations of sarcosinium oxalate monohydrate

Single crystals of sarcosinium oxalate monohydrate (SOM) are grown by the slow-evaporation technique at ambient temperature, and vibrational spectroscopic analysis is carried out using NIR-FT Raman, FT-IR, and SERS spectra. The normal mode frequencies and corresponding vibrational analysis of SOM are examined theoretically using the Gaussian’98 set of quantum chemical codes. The two bands present in the SOM ν C=O region, clearly observed in the Raman spectrum, are assigned to “free” and “bonded” carbonyl groups with the hydrogen atom. Vibrational analysis indicates the presence of C-H—O hydrogen bonding interaction producing a blueshift of the C-H stretching frequency.     

Studies on calcium‐containing poly(urethane ether)s

The calcium salt of mono(hydroxyethoxyethyl)phthalate [Ca(HEEP)₂] was synthesized by the reaction of diethylene glycol, phthalic anhydride, and calcium acetate. Calcium‐containing poly(urethane ether)s (PUEs) were synthesized by the reaction of hexamethylene diisocyanate (HMDI) or tolylene 2,4‐diisocyanate (TDI) with a mixture of Ca(HEEP)₂ and poly(ethylene glycol) (PEG₃₀₀ or PEG₄₀₀) with di‐n‐butyltin dilaurate as a catalyst. A series of calcium‐containing PUEs of different compositions were synthesized with Ca(HEEP)₂/PEG₃₀₀ (or PEG₄₀₀)/diisocyanate (HMDI or TDI) molar ratios of 2:2:4, 3:1:4, and 1:3:4 so that the coating properties of the PUEs could be studied. Blank PUEs without calcium‐containing ionic diols were also prepared by the reaction of PEG₃₀₀ or PEG₄₀₀ with HMDI or TDI. The PUEs were well characterized by Fourier transform infrared, ¹H and ¹³C NMR, solid‐state cross‐polarity/magic‐angle‐spinning ¹³C NMR, viscosity, solubility, and X‐ray diffraction studies. The thermal properties of the polymers were also studied with thermogravimetric analysis and differential scanning calorimetry. The PUEs were applied as top coats on acrylic‐coated leather, and their physicomechanical properties were also studied. The coating properties of PUEs, such as the tensile strength, elongation at break, tear strength, water vapor permeability, flexing endurance, cold crack resistance, abrasion resistance, color fastness, and adhesive strength, were better than the standard values. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2865–2878, 2003     

Magnetic behaviour of TbMnFe

Neutron diffraction and M?ssbauer measurements have been carried out on the cubic Laves phase intermetallic TbMnFe. The magnetic moment on the transition metal atom is found to be low, 0.2μ _B, at room temperature. This moment is temperature independent down to 10 K. Magnetic moment on the rare earth atom varies from 2.5μ _B at 296 K to 7.27μ _B at 10 K. M?ssbauer spectra recorded at 298 K and 78 K have magnetic character but there is a large distribution of hyperfine field values. Both these features arise due to magnetic frustration created in the sample due to the competing ferro and antiferromagnetic interactions between the transition metal atoms.     

Ion chromatography–inductively coupled plasma mass spectrometry determination of arsenic species in marine samples

Arsenic speciation analysis in marine samples was performed using ion chromatography (IC) with inductively coupled plasma mass spectrometry (ICP‐MS) detection. The separation of eight arsenic species, viz. arsenite, monomethyl arsonic acid, dimethylarsinic acid, arsenate, arsenobetaine, tetramethylarsine oxide, arsenocholine and tetramethylarsonium ion was achieved on a Dionex AS4A (weaker anion exchange column) by using a nitric acid pH gradient eluent (pH 3.3 to 1.3). The entire separation was accomplished in 12 min. The detection limits for the eight arsenic species by IC–ICP‐MS were in the range 0.03–1.6 µ g l^?1, based on 3σ of the blank response (n = 6). The repeatability and day‐to‐day reproducibility were calculated to be less than 10% (residual standard deviation) for all eight species. The method was validated by analyzing a certified reference material (DORM‐2, dogfish muscle) and then successfully applied to several marine samples, e.g. oyster, fish muscle, shrimp and marine algae. The low power microwave digestion was employed for the extraction of arsenic from seafood products. Copyright © 2004 John Wiley & Sons, Ltd.     

Solvent and Structural Effects on the Photoreduction of Cobalt(III)-Aryl Amine Complexes in Water–Organic Solvent Media*

Photoreduction of [Co(En)₂Cl(RC₆H₄NH₂)]²⁺ ions (where R = p-OMe, p-OEt, p-Me, m-Me, H, p-F, and m-OMe) in varying compositions of water–methanol and water–1,4-dioxane mixtures containing 15–40% (vol.) of organic co-solvent is carried out. Ultraviolet excitation of the above complexes in air-equilibrated solutions causes bleaching of its intense LMCT excited states with concurrent production of Co²⁺ion. As seen from the quantum yield data, _Co(II) increases smoothly with increasing content of organic co-solvent in the binary mixtures. The observed values indicate that the metal center is reduced by both ligands and solvent. The quantum yield _Co(II) is considerably affected by the substituent R of the amine, RC₆H₄NH₂ ligand. The effects of solvent and substituted ligands on the _Co(II) are estimated quantitatively using linear regression and multiple correlation methods. The former analysis was carried out using Grunwald–Winstein (Y) Gutmann donor number (DN ^N) and Krygowski–Fawcett E ^N _T (solvent empirical parameters). In addition, Kamlet–Taft's , , and * solvatochromic parameters were also used to study the effect of solute–solvent interaction. The effect of substitution on the aromatic amine ligand affects the quantum yield values, which was established using Hammett's substituent constant . Extensive tabulations of percentage contributions of these parameters, calculated using methods reported earlier, provide suitable values which are presumed to explain the quantitative effects of solvent and structural changes in the aromatic ligand on photoreduction of the cobalt(III) complexes.     

Calculating intensities using effective Hamiltonians in terms of Coriolis-adapted normal modes

The calculation of rovibrational transition energies and intensities is often hampered by the fact that vibrational states are strongly coupled by Coriolis terms. Because it invalidates the use of perturbation theory for the purpose of decoupling these states, the coupling makes it difficult to analyze spectra and to extract information from them. One either ignores the problem and hopes that the effect of the coupling is minimal or one is forced to diagonalize effective rovibrational matrices (rather than diagonalizing effective rotational matrices). In this paper we apply a procedure, based on a quantum mechanical canonical transformation for deriving decoupled effective rotational Hamiltonians. In previous papers we have used this technique to compute energy levels. In this paper we show that it can also be applied to determine intensities. The ideas are applied to the ethylene molecule.     

A simple TiCl4 promoted arylation of orthoformate and benzyl ethers by N,N-dialkylarylamines

N,N-Dialkylarylamines react with trimethyl orthoformate and TiCl₄ under ambient conditions to give the corresponding formyl derivatives in 75-89% yields, whereas the corresponding arylated products are obtained from benzyl ethers and acetals in 42-78% yields.     

Self-assembled coordination cage as a reaction vessel: triplet sensitized [2+2] photodimerization of acenaphthylene, and [4+4] photodimerization of 9-anthraldehyde

Inner cavity of Pd-nanocage has been used as a reaction vessel for performing triplet sensitized [2+2] photodimerization of acenaphthylene using water soluble xanthene dyes (Eosin Y and Rose Bengal) as sensitizers, and [4+4] photodimerization of 9-anthraldehyde. Although the [4+4] photodimerization of 9-anthraldehyde gave similar results to solution reaction, the xanthene dye sensitized [2+2] triplet state photodimerization of acenaphthylene encapsulated within Pd-nanocage yielded the syn dimer in quantitative yield. The results obtained from the triplet state [2+2] photodimerization of acenaphthylene within Pd-nanocage is remarkable given the fact that the photodimerization reaction when performed in methanol in the presence of Eosin Y and Rose Bengal gave the syn and anti dimers in the ratio 0.5 and 0.6, respectively. Preaggregation of molecules encapsulated inside Pd-nanocage in a syn fashion seems to be the governing factor for such a behavior.     

A novel arylation of arylacetic acid esters using tertiary arylamines and TiCl4

The reactions of arylacetic acid esters with tertiary arylamines in the presence of TiCl₄ give α-arylated products in 65-90% yields, as well as 10-20% yields of the corresponding benzidines.