N-Borane-Substituted Cyclic Phosphine Imides (BCPIs)

Phosphine imides are ubiquitous nucleophiles/Lewis bases in modern organic chemistry. The introduction of unexplored substituents on the phosphine imidoyl nitrogen and/or phosphorus atoms should facilitate the discovery of unprecedented utility for phosphine imides. Herein, we have designed and prepared a novel class of phosphine imides known as N-borane-substituted cyclic phosphine imides (BCPIs). Experimental and theoretical analyses of the electronic structure of BCPIs demonstrate the existence of substantial negative hyperconjugation between the nitrogen and the phosphorus atoms. Given a characteristic nucleophilic/Lewis basic reactivity of BCPIs, we represent the first experimental demonstration that a 5-oxazaphosphetane species is a key intermediate in the transformation of CO2 using phosphine imides. Moreover, although it has been previously considered unlikely, the spontaneous heterolysis of a BCl bond in a BCPI-coordinated chloroborane has been directly observed, suggesting that such process is a plausible key step in the Lewis acid-promoted generation of borenium species from chloroboranes. These results thus provide evidence of two species that have been missing in contemporary organic chemistry

Circularly polarized luminescence from a common alkoxy pillar[5]arene and its co‐aggregates with π‐conjugated rods

Abstract Cylinder‐shaped macrocycles composed of π‐panels have attracted special attention as one of the best platforms for the development of organic molecule‐based chiroptical materials. Pillar[n]arenes are a class of macrocycles with the advantage of easy preparation but have not been extensively investigated from the perspective of luminescent molecules. However, common alkoxy pillar[n]arenes are fluorescent in non‐haloalkane solvents, showing potential to be used for molecule‐based chiroptical materials. In this work, circularly polarized luminescence (CPL) spectra are reported for a pillar[5]arene with stable planar chirality using tetrahydrofuran (THF) and cyclohexane as solvents, which has been missing for many years. The pillar[5]arene also forms co‐aggregates with 1,4‐bis(phenylethynyl)benzene and 1,4‐bis[(pentafluorophenyl)ethynyl]benzene in THF/H2O mixtures, owing to a hydrophobic effect. The co‐aggregates with the fluorinated π‐rod display a new low‐energy absorption peak and broad emission band as well as intense circular dichroism and CPL signals. Chiral information from the enantiopure pillar[5]arene core is efficiently transmitted to the co‐aggregates with the π‐conjugated rod, leading to the highest dissymmetry factor for CPL (2.9 × 10−2 at 472 nm) among pillar[n]arene‐based CPL materials

Spectroscopy of ¹⁷C via one-neutron knockout reaction

21st International Conference on Few-Body Problems in Physics, Chicago, IL, USA, May 18-22, 2015.A spectroscopic study of ¹⁷C was performed via the one-neutron knockout reaction of ¹⁸C on a carbon target at RIKEN-RIBF. Three unbound states at excitation energies of 2.66(2), 3.16(5), and 3.97(3) MeV (preliminary) were observed. The energies are compared with shell-model calculations and existing measurements to deduce their spin-parities. From the comparison, the states at 2.66(2) and 3.97(3) MeV are suggested to be 1/2⁻ and 3/2⁻, respectively. From its decay property, the state at 3.16(5) MeV is indicated to be 9/2⁺

Study of ¹⁹C by One-Neutron Knockout

21st International Conference on Few-Body Problems in Physics, Chicago, IL, USA, May 18-22, 2015.The spectroscopic structure of ¹⁹C, a prominent one-neutron halo nucleus, has been studied with a ²⁰C secondary beam at 290 MeV/nucleon and a carbon target. Neutron-unbound states populated by the one-neutron knockout reaction were investigated by means of the invariant mass method. The preliminary relative energy spectrum and parallel momentum distribution of the knockout residue, ¹⁹C∗, were reconstructed from the measured four momenta of the¹⁸C fragment, neutron, and beam. Three resonances were observed in the spectrum, which correspond to the states at Ex = 0.62(9), 1.42(10), and 2.89(10) MeV. The parallel momentum distributions for the 0.62-MeV and 2.89-MeV states suggest spin-parity assignments of 5/2⁺ and 1/2⁻, respectively. The 1.42-MeV state is in line with the reported 5/22⁺ state

Spectroscopy of 17C via one-neutron knockout reaction

A spectroscopic study of 17C was performed via the one-neutron knockout reaction of 18C on a carbon target at RIKEN-RIBF. Three unbound states at excitation energies of 2.66(2), 3.16(5), and 3.97(3) MeV (preliminary) were observed. The energies are compared with shell-model calculations and existing measurements to deduce their spin-parities. From the comparison, the states at 2.66(2) and 3.97(3) MeV are suggested to be 1/2− and 3/2−, respectively. From its decay property, the state at 3.16(5) MeV is indicated to be 9/2+

Spectroscopy of C-17 Above the Neutron Separation Energy

Spectroscopy of an unbound nucleus C-17 was performed using the SAMURAI spectrometer at RIBF of RIKEN. Six resonances were observed for the C-16+n system with relative energies of 0.52, 0.77, 1.36, 1.91, 2.22 and 3.20 MeV. The excitation energies (E-x) of the observed resonances were deduced, by taking into account the states of the C-16 fragments identified by coincident gamma rays, as E-x =(3.02), 1.51, (3.86), 2.65, (4.72) and 3.94MeV. The orbital angular momenta of the two observed states in C-17 at E-x =2.65 and 3.94 MeV were determined as 1 by comparing parallel momentum distributions with theoretical predictions.11Nsciescopu

Structure beyond the dripline in the Boron isotopes: 16;18;20;21^{16;18;20;21}B

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Study of 19C by One-Neutron Knockout

The spectroscopic structure of 19C, a prominent one-neutron halo nucleus, has been studied with a 20C secondary beam at 290 MeV/nucleon and a carbon target. Neutron-unbound states populated by the one-neutron knockout reaction were investigated by means of the invariant mass method. The preliminary relative energy spectrum and parallel momentum distribution of the knockout residue, 19C*, were reconstructed from the measured four momenta of the 18C fragment, neutron, and beam. Three resonances were observed in the spectrum, which correspond to the states at Ex = 0.62(9), 1.42(10), and 2.89(10) MeV. The parallel momentum distributions for the 0.62-MeV and 2.89-MeV states suggest spin-parity assignments of 5/2+ and 1/2−, respectively. The 1.42-MeV state is in line with the reported 5/22+ state

Study of 19^{19}C by One-Neutron Knockout

This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.International audienceThe spectroscopic structure of 19C, a prominent one-neutron halo nucleus, has been studied with a 20C secondary beam at 290 MeV/nucleon and a carbon target. Neutron-unbound states populated by the one-neutron knockout reaction were investigated by means of the invariant mass method. The preliminary relative energy spectrum and parallel momentum distribution of the knockout residue, 19C*, were reconstructed from the measured four momenta of the 18C fragment, neutron, and beam. Three resonances were observed in the spectrum, which correspond to the states at Ex = 0.62(9), 1.42(10), and 2.89(10) MeV. The parallel momentum distributions for the 0.62-MeV and 2.89-MeV states suggest spin-parity assignments of 5/2+ and 1/2−, respectively. The 1.42-MeV state is in line with the reported 5/22+ state

Invariant Mass Spectroscopy of 17^{17}C via One-neutron Knockout Reaction of 18^{18}C

International audienceUnbound states in 17C were investigated via one-neutron knockout of 18C. The experiment was performed using SAMURAI spectrometer in RIBF at RIKEN. By invariant mass spectroscopy, three resonances were measured at excitation energies of 3.03(12), 2.74(3), and 4.03(6) MeV as preliminary results. For the excited state at 2.74(3) MeV, the parallel momentum distribution was satisfactorily described by the distribution calculated for p-wave knockout from 18C