High-resolution mass spectra of anti- and syn-isomers of acylferrocene oximes

High-resolution mass spectra of anti- and syn-acylferrocene oximes were examined at various ionizing voltages and fragmentation patterns of the oximes are presented. Significant differences between the anti- and syn-isomers were found in the fragmentation behaviour of the low voltage (15 to 20 eV) spectrum of formylferrocene oxime.     

Molecular dynamics and rheological properties of concentrated solutions of rodlike polymers in isotropic and liquid crystalline phases

A molecular theory is presented for the dynamics of rodlike polymers in concentrated solutions. The theory describes the rotational motion of rods in both the isotropic phase and the liquid crystalline phase. Combined with the molecular expression of the stress tensor, it also gives a unified rheological constitutive equation which predicts the nonlinear viscoelasticity in both phases. As an illustrative example, the steady-state viscosity η at zero-shear-rate is calculated. The predicted dependence of η on molecular weight and concentration agrees fairly well with experiments.     

Laser-induced fluorescence study of fast desorption of ground-state K atoms from potassium halides excited by synchrotron radiation

The nanosecond desorption of ground-state K atoms from potassium halides was investigated for the first time using a laser-induced fluorescence method with synchrotron radiation and laser pulses. It was found that the desorption consists of a nanosecond component and a slow one of > 180 ns response time. The fast desorption is several orders of magnitude faster than existing results for the time response of ground-state alkali desorption. Therefore, the fast desorption of ground-state alkali atoms cannot be interpreted in terms of the existing mechanisms based on thermal processes and requires a new desorption model. We suggest that the lattice instability due to electronic excitation in the surface layer may play an important role in the fast desorption of ground-state alkali atoms.     

Permeation of complexed metal ions through a hydrophobic membrane

Selective concentration of a heavy metal complex with acetylacetone (acac) through a hydrophobic polystyrene membrane was carried out under a pressure gradient. A chelate forming heavy metal was selectively concentrated about 2 fold by this method. When using a coating membrane with a high water flux, the permeabilities increased with increasing complex fraction in the aqueous solution, while using a membrane with a low water flux, a bulky complex was not highly concentrated because of steric hindrance. The complex partitioned on the membrane surface was transported and concentrated under a pressure gradient and a linear relationship was found to exist between permeabilities and partition coefficients. It will be possible to concentrate hydrophobic organic solutes by this method, for acac was concentrated when the Cu—acac complex was formed. As the permeabilities increased with decreasing pressure and membrane compaction was strong for a coating membrane, it seems effective to permeate at a low pressure.     

Thermo-driven chiroptical switching polysilane featuring 2-cyclopentylethyl side group

A new rod-like helical polysilane, poly{(S)-3,7-dimethyloctyl-(2-cyclopentylethyl)silane}, was found to undergo a thermo-driven, helix-helix transition at –33 ° C in isooctane associated with the discontinuous changes in the Si -Si *transition energy and intensity in the transition temperature region. This is the first example of a helix-helix transition polysilane with a cycloalkyl group. A similar rod-like polysilane derivative, poly{(S)-3,7-dimethyloctyl-(1-cyclopentylmethyl)silane}, however, did not undergo any helix-helix transition between –61 and 80 ° C.     

Synthesis of (22S, 23S)-homobrassinolide and brassinolide from stigmasterol

(22S, 23S)-Homobrassinolide (2α, 3α, 22S, 23S-tetrahydroxy-24S-etyl-B-homo-7-oxa-5α-cholestan-6-one) and brassinolide (2α, 3α 22R, 23R-tetrahydroxy-24S-methyl-B-homo-7-oxa-5α-cholestan-6-one) were synthesized from stigmasterol and shown to promote plant growth.