Search results for "Length"

The diels-alder intermediate as a chain-transfer agent in spontaneous styrene polymerization. II. Evidence from the comparison of the chain-length di…

1977

Ejection of molecules from WO3 under ion bombardment: the role of the crystal structure

1992

Abstract Emission of molecular ions from WO 3 and Na x WO 3 was studied by SIMS. It was found that the phenomenon of ejection of molecules had not arisen from specific WO bond lengths and strengths in tungsten trioxide.

Polymer support synthesis

1989

Non-porous silica gel microbeads of diameter 1.5 microns have been investigated as supports for oligonucleotide synthesis. In the preparation of oligothymidylates of chain length up to 150 bases, with 5'-di-p-anisylphenylmethyl-3'-phosphoramidite as an intermediate, the average yields per chain elongation were up to 99%. Lower overall yields were observed in the case of a support which developed a strong tendency towards aggregation after the build up of an oligonucleotide coating.

Spectrally selective holographic optical elements based on a thick polymer medium with diffusional amplification

2000

A thick rigid polymer recording medium with self-amplification of holograms owing to diffusion of phenanthrenequinone molecules was used to find efficient holographic optical elements with high-spectral-selectivity interference filters and multiple demultiplexers. Several examples of practical applications are briefly described in this paper, showing the benefits of such optical elements for the fields of astronomy, spectroscopy and communication technologies.

Experimental and theoretical investigations of the contact ion pairs formed by reactions of the anions [(EPR2)2N]- (R = (i)Pr, (t)Bu; E = S, Se) with…

2010

Reactions of the sodium salts [(EPR(2))(2)N]Na(TMEDA) (R = (i)Pr, (t)Bu; E = S, Se) with the iodide salts [(TePR(2))(2)N]I (R = (i)Pr, (t)Bu) in toluene produce the mixed-chalcogen systems [(EPR(2))(2)N][(TePR(2))(2)N] (6b, E = Se, R = (t)Bu; 6c, E = S, R = (t)Bu; 7b, E = Se, R = (i)Pr; 7c, E = S, R = (i)Pr). Compounds 6b, 6c, 7b, and 7c have been characterized in solution by variable-temperature multinuclear ((31)P, (77)Se, and (125)Te) NMR spectroscopy and in the solid state by single-crystal X-ray crystallography. The structures are comprised of contact ion pairs linked by bonds between Te and S or Se atoms. For the tert-butyl derivatives 6b and 6c, the anionic half of the molecule is co…

Bonding in the heavy analogue of hydrogen cyanide: the curious case of bridged HPSi.

2010

The bonding of firstand second-row elements differ dramatically. The simplest unsaturated silicon hydrides Si2H2 and Si2H4 exhibit quite unusual geometries [1] compared to the analogous hydrocarbon molecules. For example, the most stable form of Si2H2 is nonplanar with C2v symmetry and two bridging H atoms, in sharp contrast to linear acetylene, HC! CH. Phosphorus and nitrogen share many of the same bonding characteristics, but P prefers single over multiple bonds. For these reasons, it may be difficult to predict the most stable isomeric arrangement, even for a small molecule with a single Por Si atom and especially when it contains both. Silicon–phosphorus bonds are important in materials…

Structure and properties of N-methyl-N-(4-pyridyl)-nitramine and 1,4-dihydro-1-methyl-4-nitriminopyridine

2002

Abstract The molecular structure and spectral properties of N -methyl- N -(4-pyridyl)-nitramine ( 1 ) and 1,4-dihydro-1-methyl-4-nitriminopyridine ( 3 ) were investigated by the X-ray diffraction, FTIR, nuclear magnetic resonance (NMR) methods and DFT theoretical calculations. N -methyl- N -(4-pyridyl)-nitramine ( 1 ) crystallises in the orthorhombic Pbca space group. It is composed of two planar fragments; nitramino (N 2 O 2 ) group and the pirydyl ring. These two groups are twisted at about 70° with respect to each other, along the Ar–N bond. On the contrary, in compound 3 , they are coplanar to each other. Twist of the nitramino group in 1 with respect to the pirydyl ring leads to a sign…

Bacterial communities in Arctic fjelds of Finnish Lapland are stable but highly pH-dependent

2007

The seasonal and spatial variations of microbial communities in Arctic fjelds of Finnish Lapland were studied. Phospholipid fatty acid analysis (PLFA) and terminal restriction fragment analysis (T-RFLP) of amplified 16S rRNA genes were used to assess the effect of soil conditions and vegetation on microbial community structures along different altitudes of two fjelds, Saana and Jehkas. Terminal restriction fragments were additionally analysed from c . 160 cloned sequences and isolated bacterial strains and matched with those of soil DNA samples. T-RFLP and PLFA analyses indicated relatively similar microbial communities at various altitudes and under different vegetation of the two fjelds. …

A theoretical study of neutral and reduced tetracyano-p-quinodimethane (TCNQ)

2004

Abstract The molecular structure of neutral, anionic, and dianionic tetracyano- p -quinodimethane (TCNQ), as well as the electron affinity of TCNQ, have been studied with HF, MP2, and different density functional theory (DFT) procedures. The optimized geometries compare well with the available experimental data, although the C N bond distance is not correctly described at the MP2 level. The calculated parameters are rather insensitive to the basis set employed, and the addition of diffuse functions does not yield significant changes. When the extra electrons are added, the central ring of TCNQ progressively becomes more aromatic. Compared with the CCSD(T) estimate, the value of the adiabati…

2-Chloro/phenyl-7-arylimino-6,6-dimethylcyclopenta[b]pyridylnickel chlorides: Synthesis, characterization and ethylene oligomerization

2017

Abstract 2-Chloro/phenyl-7-arylimino-6,6-dimethylcyclopenta[b]pyridylnickel chlorides (Ni1–Ni8) were synthesized from the respective ligands L1–L8 and characterized. Upon activation with either methylaluminoxane (MAO) or ethylaluminium sesquichloride (EASC), they show high catalytic activity of up to 10.84 × 106 g(oligomer) mol− 1(Ni) h− 1 in ethylene oligomerization. The products range from butenes to dodecenes for Ni1–Ni4, but are limited to butenes and hexenes in the case of Ni5–Ni8. DFT calculations indicate that the Ni C bond length in the model alkyl complexes depends both on the nature of the substituents at the heterocycles and the kind of the alkyl group, shedding some light on the…