The resonant secondary emission of the F center in alkali halides

The secondary radiation after resonant excitation of F center and its linear polarization P correlated to the polarization of resonant light have been measured for five alkali halides at low temperatures. In KC1, the spectrum of P over the whole Stokes region is divided into three successive regions, the depolarization range at the one-phonon Raman scattering, the near plateau range, and the depolarization range down to vanishing. The former two have common relevance to resonant energy and symmetries of coupled phonons. These relevances are interpreted adopting a configuration coordinate model for 2s- and 2p-like excited states.     

Expansion of Photostable Luminescent Radicals by Meta-Substitution

Polychlorinated pyridyldiphenylmethyl radicals having substituents meta to the position bearing the carbon-centered radical (α-carbon) are synthesized. All of them are stable in ambient conditions in solutions and fluorescent in cyclohexane. The fluorescence of the radicals with bromo, phenyl, 4-chlorophenyl, or 2-pyridyl substituents are enhanced in chloroform, while the emission of the radicals with 2-thienyl or 2-furyl substituents are quenched in chloroform. DFT and TD-DFT calculations indicate that the first doublet excited states of the former are locally excited, while the first doublet excited states of the latter are charge transfer states from the π-electron-donating substituent to the accepting radical. The latter also show much higher photostability under 370-nm light irradiation compared with the first reported photostable fluorescent radical, (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical (PyBTM), with pronounced bathochromic shifts of the fluorescence.     

Holographic window for solar power generation

A new photovoltaic generation unit based on the application of holographic technologies called a Holo-Window is proposed in this work. The basic principle and the optical configuration used for the basic experimental unit are described. Suitable fabrication technology for a hologram with the broadband spectrum required to provide the appropriate sunlight capture capability is then discussed. Finally, a laboratory-prototype Holo-Window unit was developed and its performance was evaluated.     

Multipod structures of lamellae‐forming diblock copolymers in three‐dimensional confinement spaces: Experimental observation and computer simulation

The three‐dimensional (3D) confinement effect on the microphase‐separated structure of a diblock copolymer was investigated both experimentally and computationally. Block copolymer nanoparticles were prepared by adding a poor solvent into a block copolymer solution and subsequently evaporating the good solvent. The 3D structures of the nanoparticles were quantitatively determined with transmission electron microtomography (TEMT). TEMT observations revealed that various complex structures, including tennis‐ball, mushroom‐like, and multipod structures, were formed in the 3D confinement. Detailed structural analysis, showed that one block of the diblock copolymer slightly prefers to segregate into the particle surface compared with the other block. The observed structures were further elaborated using cell dynamics computer simulation. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1702–1709     

Transition‐Metal‐Mediated Cleavage of Fluoro‐Silanes under Mild Conditions

Si?F bond cleavage of fluoro‐silanes was achieved by transition‐metal complexes under mild and neutral conditions. The Iridium‐hydride complex [Ir(H)(CO)(PPh₃)₃] was found to readily break the Si?F bond of the diphosphine‐ difluorosilane {(o‐Ph₂P)C₆H₄}₂Si(F)₂ to afford a silyl complex [{[o‐(iPh₂P)C₆H₄]₂(F)Si}Ir(CO)(PPh₃)] and HF. Density functional theory calculations disclose a reaction mechanism in which a hypervalent silicon species with a dative Ir→Si interaction plays a crucial role. The Ir→Si interaction changes the character of the H on the Ir from hydridic to protic, and makes the F on Si more anionic, leading to the formation of H^δ+???F^δ? interaction. Then the Si?F and Ir?H bonds are readily broken to afford the silyl complex and HF through σ‐bond metathesis. Furthermore, the analogous rhodium complex [Rh(H)(CO)(PPh₃)₃] was found to promote the cleavage of the Si?F bond of the triphosphine‐monofluorosilane {(o‐Ph₂P)C₆H₄}₃Si(F) even at ambient temperature.     

Rational Design for Rotaxane Synthesis through Intramolecular Slippage: Control of Activation Energy by Rigid Axle Length

We describe a new concept for rotaxane synthesis through intramolecular slippage using π‐conjugated molecules as rigid axles linked with organic soluble and flexible permethylated α‐cyclodextrins (PM α‐CDs) as macrocycles. Through hydrophilic–hydrophobic interactions and flipping of PM α‐CDs, successful quantitative conversion into rotaxanes was achieved without covalent bond formation. The rotaxanes had high activation barrier for their de‐threading, so that they were kinetically isolated and derivatized even under conditions unfavorable for maintaining the rotaxane structures. ¹H NMR spectroscopy experiments clearly revealed that the restricted motion of the linked macrocycle with the rigid axle made it possible to control the kinetic stability by adjusting the length of the rigid axle in the precursor structure rather than the steric bulkiness of the stopper unit.