Determination of electron affinity of electron accepting molecules

The unoccupied π ^* states of the solid film of electron accepting organic molecules, 7,7,8,8-tetracyanoquinodimethane (TCNQ), fluorinated TCNQ derivatives, 11,11,12,12-tetracyanonaphtho-2,6-quinodimethane (TNAP), C₆₀, and 6,6-phenyl-C₆₁-butyric acid methyl ester (PCBM) have been studied by inverse photoemission spectroscopy. The assignment of the π ^* affinity levels of these typical electron accepting molecules provides the basic information for the organic electronics and the new electronic functional molecular design. The comparison with density functional theory calculations enables understanding how the electron affinity evolves in terms of molecular orbitals. The correlation between the film morphology and the irradiation damage on the TCNQ derivative samples by electron impact during the inverse photoemission measurements is also discussed.     

Isotope shift measurements of 11, 9, 7Be+

We have performed precision atomic spectroscopy of trapped radioactive Be isotopes aiming at studies of the charge and magnetization radii of these nuclei especially for a single-neutron halo nucleus ¹¹Be . Some experimental results and the status of the analysis are discussed.     

High-average-power light source below 200 nm from a KBe(2)BO(3)F(2) prism-coupled device

Using a 2.3 mm thick KBe(2)BO(3)F(2) crystal optically contacted with CaF(2) in a prism-coupled device, we have obtained an average output power of as much as 360 mW at 200 nm. Long-term stability was verified above a 150 mW level at 200 nm. An output power of 50 mW was also obtained with a narrow spectral width of 0.007 pm at 193.5 nm.     

X-ray evidence for a deformation of CDW during the sliding motion in K0.30MoO3

The wave vector and the correlation length of the CDW ordering in K_0.30MoO₃ are studied by x-ray diffraction as functions of electric fields applied along the one-dimensional axis. Several samples change their CDW-ordering above a threshold field. The change of the wave vector occurs mainly in the (2a¹-c¹) - direction, which is perpendicular to the one-dimensional b¹ - axis. It depends also on the field direction and magnitude. Time resolved x-ray experiments show that characteristic time of this change is of the order of 1 ms. The correlation length becomes longer along the (2a¹-c¹)-direction in the transient period.     

Catalytic asymmetric synthesis of (S)-oxybutynin and a versatile intermediate for antimuscarinic agents

A practical synthesis of (S)-oxybutynin, a muscarinic receptor antagonist, using catalytic enantioselective cyanosilylation of cyclohexyl phenyl ketone (9a) as a key step is described. The key reaction proceeded with 94% ee using 1 mol% of Gd-1 catalyst, and was performed on a 100 g-scale. In addition, a short catalytic enantioselective synthesis of the versatile intermediate for Scios Nova analogues of antimuscarinic agents (7) is described. Application of the catalytic enantioselective cyanosilylation to ketones containing two sterically similar substituents on the carbonyl group is also discussed.     

Catalytic enantioselective conjugate addition of cyanide to alpha,beta-unsaturated N-acylpyrroles

A catalytic enantioselective conjugate addition of cyanide to alpha,beta-unsaturated N-acylpyrroles was developed using the chiral gadolinium catalyst generated from Gd(OiPr)3 and d-glucose-derived ligand 2. Generally high enantioselectivity was obtained from a wide range of substrates; substrates with beta-aryl and beta-vinyl substituents and alpha,beta-disubstituted substrates can now be used. Using this reaction as a key step, short-step syntheses of several pharmaceuticals and their lead compounds were achieved, including the beta-phenyl-substituted GABA analogue and pregabalin.     

Catalytic enantioselective desymmetrization of meso-N-acylaziridines with TMSCN

A catalytic enantioselective desymmetrization of meso-N-p-nitrobenzoylaziridines with TMSCN was developed using a chiral gadolinium catalyst generated from Gd(OiPr)3 and d-glucose-derived ligand 1. In this reaction, the addition of a catalytic amount of trifluoroacetic acid (TFA) improved enantioselectivity. High enantioselectivity was obtained from a range of meso-aziridines at 0-60 degrees C. The product could be easily transformed into beta-amino acids. Thus, the developed catalytic enantioselective desymmetrization reaction allowed for efficient catalytic synthesis of chiral cyclic beta-amino acids. The incorporation of TFA into the catalyst complex was observed using ESI-MS. Generation of this new complex might be the origin of the improved enantioselectivity.     

Stereoregularity of poly(2-vinylpyridine) determined by 1H-NMR and 13C-NMR spectroscopy

In order to determine the stereoregularity of poly(2-vinylpyridine), 2-vinylpyridine-β,β-d₂ was synthesized. The ¹H-NMR spectra of the deuterated polymer in D₂SO₄ and o-dichlorobenzene solutions showed three peaks, which were assigned to triad tacticities. Since the absorptions of heterotactic and syndiotactic triads of methine protons overlap those of methylene protons in nondeuterated polymers, only isotactic triad intensities can be obtained from the ¹H-NMR spectra of nondeuterated poly(2-vinylpyridine). The ¹³C-NMR spectra of poly(2-vinylpyridine) were obtained in methanol and sulfuric acid solutions. In methanol solution the absorption was split into three groups, which cannot be explained by triads, and in sulfuric acid solution several peaks were observed. These splittings may be due to pentad tacticity. The results show that poly(2-vinylpyridine) obtained by radical polymerization is an atactic polymer.