Pseudo cyclic ionophores: ‘Binary-effect’ of quinolinyloxy groups at both ends of oligoethylene glycols on the conformational stabilization of their complexes with alkali metal salts

A series of noncyclic neutral ionophores has been synthesized by the reaction of oligoethylene glycol dihalides with 8-quinolinol. Complexation properties for alkali metal picrates were evaluated from solvent extraction and bulk liquid membrane transport experiments. Complexation profiles of the newly synthesized ionophores with a hexyl chain were similar to those of their homologues without the hexyl chain in the extraction experiments. Among them, the pentaethylene glycol derivatives showed the highest extraction efficiency and selectivity towards potassium ion. From the¹H NMR spectra (400 MHz), the change in chemical shifts of the aromatic protons upon the addition of alkali metal thiocyanates suggested the existence of a stabilization effect which is caused by intramolecular stacking conformations between the quinoline rings during complexation. Aryl stacking interactions depend on the size of the cations and on the chain length of the oligoethylene glycol. The relationship between transport ability towards alkali metal cations and lipophilicity of these ionophores is also discussed.     

HeII(304Å) photoelectron spectrum of N2O4

The 304 Å HeII photoelectron (PE) spectrum of a mixture of NO₂ and N₂O₄ in the gaseous phase has been measured in the region up to 29 eV. By subtracting the HeII spectrum of NO₂ from the mixed spectrum, the HeII spectrum due to N₂O₄ has been deduced, indicating that there are three new PE bands in the region 20—29 eV. Relative band intensities have also been obtained from the HeII of N₂O₄ below 16 eV, corrected for electron collecting efficiency.     

Towards the selective formation of specific isomers of fullerenes: T - and p-dependence in the yield of various isomers of fullerenes C60–C84

Systematic fractional change in the yield of various isomers of fullerenes was revealed to strongly depend on temperature of a buffer gas. A new kinetic consideration is proposed for understanding the observed temperature- and pressure-dependence of yield of fullerenes. The model consists of three competitive reactions in consideration of plausible behaviors of a precursor, (1) decomposition into smaller fragments, (2) isomerization leading to formation of a stable fullerene cage, and (3) growth into a larger carbon cluster. Arrhenius activation energy of formation of stable fullerenes was determined to be 0.8 eV for both C₆₀ and C₇₀, while a higher energy of 2.0?3.3 eV for seven different isomers of higher fullerenes ranging from C₇₆ to C₈₄. Correlation in the activation energy is noted for a series of higher fullerenes with different sizes, suggesting the existence of a specific precursor in their formation processes.     

Fluorometric sensing of alkaline Earth metal cations by new lariat ethers having plural pyrenylmethyl groups on the electron-donating sidearms

[structure: see text] New fluorescent compounds (1), lariat ethers having plural pyrenylmethyl groups on the sidearms, were prepared, and their complexation behavior with alkaline earth metal cations was examined by fluorescence spectrometry. The pyrene excimer emission decreased accompanied with an increase in the monomer emission upon complexation with the metal ion. This finding is ascribed to the cooperative participation of one of the two sidearms in the complexation of the crown ring with the metal ion.     

Collisional electron emission at solid surfaces induced by mass selected negative cluster ions

Electron emission efficiency induced by the collision of clusters with a solid surface was measured as a function of cluster size. Emitted electron energy distribution for the impact of mass selected negative ion clusters or mass selected neutral clusters was also measured in the energy region of 0–5 eV. The difference in the shape of the electron spectra was observed depending on the size and charge of the clusters.     

Photoelectron spectra and angular distribution in reson three-photon ionization of atomic iron: J dependence

Kenetic energies and angular distributions of photoelectrons emitted by three-photon ionization fo atomic iron through two-photon resonant state e⁷D_J and e⁵ D_J, were measured, by using visible lasers. J-resolved photoelectron bands attributab to the a⁶D_J and a⁴F_j ionic states are reported.     

Threshold electron spectra of semiconductor cluster ions

A simple threshold electron analyzer was constructed and laser photodetachment threshold electron spectra of Si^– and Si ₄ ^– were measured.