Studies on rotational barriers of N-C axially chiral compounds: increase in the rotational barrier by aromatization

The rotational barriers in axially chiral quinolin-2-one and quinazolin-2-one possessing N-(ortho-tert-butyl)phenyl group were found to significantly increase in comparison with those of corresponding dihydroquinolin-2-one and dihydroquinazolin-2-one. Analysis of transition state structure during N-Ar bond rotation based on DFT calculation indicates that the increase in the rotational barrier is due to considerable distortion of the nitrogen-containing heterocyclic part.     

Complex wavefront reconstruction of digital in-line holography with a spatial radial carrier

We propose a method for reconstructing a complex wavefront from a single-shot in-line digital hologram with a spatial radial carrier. In the proposed method, the spatial radial carrier is generated by a point source that is located in front of an image sensor, as close as possible to the sensor with the condition that the Nyquist limit is not exceeded. A signal processing method employed for elimination of the zeroth-order and conjugate wave components is presented. Computer simulations and optical experiments are performed to verify the proposed method.     

Theoretical study on the absorption spectra of fac-Ir(ppy)3 in the amorphous phase of organic electro-luminescent devices

Absorption spectra in the amorphous phase consisting of Ir(ppy)₃ and 4,4-bis(carbazol-9-yl)-2,2-biphenyl (CBP) molecules were theoretically investigated. The equilibrium structures in amorphous phase were simulated by QM/MM MD calculations. The results of calculation suggest that eleven CBP molecules exist as the closest neighbors of Ir(ppy)₃. Time-dependent density functional theory (TD-DFT) calculations successfully reproduced the experimental absorption spectra. For Ir(ppy)₃ in the gas phase, the most important spectral peak at the wavelength of 400 nm can be assigned principally to the one-electron excitation from HOMO-1 to LUMO+2, where the main component of HOMO-1 is the d orbital of the Ir atom and that of LUMO+2 is the π* orbital of the ligands. When Ir(ppy)₃ strongly interacts with a CBP molecule, the π* orbital of the ligand is delocalized into the CBP molecule. This is the reason why the spectral peak at the wavelength of 400 nm almost disappears in the amorphous phase.     

Strong Nuclear Ring Currents and Magnetic Fields in Pseudorotating OsH4 Molecules Induced by Circularly Polarized Laser Pulses

We design a circularly polarized laser pulse in the infrared frequency and femtosecond time domains, for excitation of the OsH₄ molecule in its first excited pseudorotational state of the triply‐degenerate bend. The OsH₄ molecule need not be pre‐oriented. After excitation, the central nucleus Os carries out pseudorotation about the axis parallel to the direction of propagation of the laser pulse. This pseudorotation causes a strong electric ring current with a value I=1.53 e fs^?1. The mean value of the radius of the ring current is very small, R=0.0031 a₀, where a₀ is the Bohr radius. According to the Biot–Savart law (| ( R = 0 )|～I/R), this nuclear ring current induces the strongest magnetic field predicted so far in molecules, with a central peak absolute value | ( R = 0 )|=623 T. To monitor the effect, we propose an IR‐pump–X‐ray‐probe versus an X‐ray‐probe‐only experiment, at the K‐ and L ‐edges of X‐ray ionization. The results are based on the general quantum theory of excitations of pseudorotations in tetrahedral molecules AB₄, driven by a circularly polarized laser pulse.     

1,1'-Binaphthyl-2,2'-diyl phosphoroselenoyl chloride as a chiral molecular tool for the preparation of enantiomerically pure alcohols and amines

Enantiomerically pure phosphoroselenoyl chloride bearing a binaphthyl group was synthesized. This phosphoroselenoyl chloride was used to discriminate and resolve simple secondary alcohols. Stereospecific conversions of diastereomerically pure phosphoroselenoic acid esters, obtained by reaction of the chloride with simple secondary alcohols, to enantiomerically pure alcohols and amines were also achieved.     

Dissociation potential curves of low-lying states in transition metal hydrides. 3. Hydrides of groups 6 and 7

The dissociation curves of low-lying spin-mixed states in monohydrides of groups 6 and 7 were calculated by using an effective core potential (ECP) approach. This approach is based on the multiconfiguration self-consistent field (MCSCF) method, followed by first-order configuration interaction (FOCI) calculations, in which the method employs an ECP basis set proposed by Stevens and co-workers (SBKJC) augmented by a set of polarization functions. Spin-orbit coupling (SOC) effects are estimated within the one-electron approximation by using effective nuclear charges, since SOC splittings obtained with the full Breit-Pauli Hamitonian are underestimated when ECP basis sets are used. The ground states of group 6 hydrides have Omega = (1)/(2)(X(6)Sigma(+)(1/2)), where Omega is the z component of the total angular momentum quantum number. Although the ground states of group 7 hydrides have Omega = 0(+), their main adiabatic components are different; the ground state in MnH originates from the lowest (7)Sigma(+), while in TcH and ReH the main component of the ground state is the lowest (5)Sigma(+). The present paper reports a comprehensive set of theoretical results including the dissociation energies, equilibrium distances, electronic transition energies, harmonic frequencies, anharmonicities, and rotational constants for several low-lying spin-mixed states in these hydrides. Transition dipole moments were also computed among the spin-mixed states and large peak positions of electronic transitions are suggested theoretically for these hydrides. The periodic trends of physical properties of metal hydrides are discussed, based on the results reported in this and other recent studies.     

Relativistic study on emission mechanism in palladium and platinum complexes

The present study investigates the spin-orbit coupling (SOC) effects in the radiative processes from the electronically excited states of bis[-2-(2-thienyl)-pyridine] platinum (Pt(thpy)2) and palladium (Pd(thpy)2). The transition probabilities among the low-lying spin-mixed states in these complexes are estimated using the discrete variable representation (DVR) method based on the assumption that the system obeys Fermi's golden rule. It is revealed that the low-lying excited singlets and triplets are strongly mixed with each other by SOC in Pt(thpy)2 and, as a result, a fast nonradiative transition occurs to the low-lying excited spin-mixed states. This is followed by the radiative transition from these low-lying spin-mixed states to the lowest spin-mixed state (the ground state); that is to say, a phosphorescence should be observed from these low-lying excited spin-mixed states in Pt(thpy)2. On the contrary, weak SOCs are obtained in Pd(thpy)2 and no phosphorescence at room temperature is expected to be observed in Pd(thpy)2. These results are in good agreement with the experimental reports.     

Thermodynamic Phase Transition Through Crystal‐to‐Crystal Process of Photochromic 1,2‐Bis(5‐phenyl‐2‐propyl‐3‐thienyl)perfluorocyclopentene

A photochromic diarylethene, 1,2‐bis(5‐phenyl‐2‐propyl‐3‐thienyl)perfluorocyclopentene ( 1a ), was found to have two polymorphic crystal forms, α‐ and β‐crystals. From X‐ray crystallographic analysis, the space groups of α‐ and β‐crystals were determined to be P2₁/c and C2/c, respectively. The difference between two crystal forms is ascribed to the orientation of two of four molecules in the unit cell. The thermodynamic phase transition from α‐ to β‐forms occurred via a crystal‐to‐crystal process, as confirmed by differential scanning calorimetry measurements, optical microscopic observations in the reflection mode and under crossed Nicols, and powder X‐ray diffraction measurements. The movement of the molecules in the crystal was evaluated by analyzing the change of face indices before and after the phase transition.     

Effect of gamma-irradiation on the levels of total and cis/trans isomers of beta-carotene in dehydrated parsley

Ionizing radiation is a method for preservation of foods that use the high energy of gamma rays or accelerated electrons, thereby ionizing molecules. The most important precursor of vitamin A is β-carotene, a carotenoid with pro-vitamin A activity. The highly unsaturated chain confers the instability of β-carotene, and some reactions, as isomerisation, can reduce the characteristics of pro-vitamin A. The present study investigated whether increasing doses of 0, 10 and 20 kGy lower the total β-carotene level and if an enhancement of cis-isomers occurred on samples of dehydrated parsley. No differences were observed of either fractions analyzed at doses applied in this study, nor did it contribute to the decrease of vitamin A.