Through-Bond and Long-Range Ferromagnetic Spin Alignment in a .pi.-Conjugated Polyradical with a Poly(phenylenevinylene) Skeleton

1995 ◽  
Vol 117 (1) ◽  
pp. 548-549 ◽  
Author(s):  
Hiroyuki Nishide ◽  
Takashi Kaneko ◽  
Takeshi Nii ◽  
Kohya Katoh ◽  
Eishun Tsuchida ◽  
...  
Keyword(s):  
Long Range ◽  
Spin Alignment ◽  
Pi Conjugated

scholarly journals Liquid crystal phase of counter-rotating staircases – A case of antiferrochirality

2021 ◽  
Author(s):  
Ya-xin Li ◽  
Hong-fei Gao ◽  
Rui-bin Zhang ◽  
Kutlwano Gabana ◽  
Qing Chang ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Long Range ◽  
Short Range ◽  
Liquid Crystal Phase ◽  
Helical Structures ◽  
New Approach ◽  
Chiroptical Properties ◽  
Pi Conjugated ◽  
Left Handed ◽  
Straight Rod

Abstract Helical structures continue to inspire, and there is considerable temptation to attribute helicity to columnar liquid crystals (LC). While short isohelical sequences are undoubtedly present, and longer ones in chiral or chiral-doped compounds, the order is only short-range, equivalent to a paramagnet without or with field. However, here we report a confirmed example of a true LC phase of achiral compounds consisting of columns, each being a long-range homochiral helix. Long-range periodicity and isochirality are maintained by intercolumnar interaction. This orthorhombic LC, spacegroup Fddd, is discovered in compounds with either bent or straight rod-like pi-conjugated cores. There are 4 right and 4 left-handed ribbons or star-profiled columns per unit cell. The structure is equivalent to an antiferromagnet with twist replacing spins. A theory based on interacting quadrupoles confirms this structure as energetically favoured over alternatives. The findings open a new approach to homochirality in achiral compounds, with promising optical/chiroptical properties.

scholarly journals Controlled Surface Reconstruction on Ferromagnetic Oxides: Spin Pinning Effect to the Oxyhydroxide Layer and Its Enhanced Oxygen Evolution Activity

2021 ◽  
Author(s):  
Tianze Wu ◽  
Xiao Ren ◽  
Yuanmiao Sun ◽  
Shengnan Sun ◽  
Guoyu Xian ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Long Range ◽  
Spin Polarization ◽  
Water Electrolysis ◽  
Intrinsic Activity ◽  
Spin Alignment ◽  
Pinning Effect ◽  
Production Of Hydrogen ◽  
Ferromagnetic Oxides ◽  
Kinetic Barriers

The production of hydrogen by water electrolysis suffers from the kinetic barriers in the oxygen evolution reaction (OER) that limits the overall efficiency. As spin-dependent kinetics exist in OER, the spin alignment in active OER catalysts is critical for reducing the kinetic barriers in OER. It is effective to facilitate the spin polarization in ferromagnetic catalysts by applying external magnetic field, which increases the OER efficiency. However, more active OER catalysts tend to have dynamic open-shell orbital configurations with disordered magnetic moments, without showing an apparent long-range interatomic ferromagnetism; thus controlling the spin alignment of these active catalysts is challenging. In this work, we report a strategy with spin pinning effect to make the spins in active oxyhydroxides more aligned for higher intrinsic OER activity. Such strategy bases on a controllable reconstruction: ferromagnetic oxides with controlled sulfurization can evolve into stable oxide<sub>FM</sub>/oxyhydroxide configurations with a thin oxyhydroxide layer under operando condition. The spin pinning effect is found at the interface of oxide<sub>FM</sub>/oxyhydroxide. The spin pinning effect can promote spin selective electron transfer on OER intermediates to generate oxygens with parallel spin alignment, which facilitates the production of triplet oxygen and increases the intrinsic activity of oxyhydroxide by ~ 1 order of magnitude. Under spin pinning, the spins in oxyhydroxide can become more aligned after magnetization as long-range ferromagnetic ordering is established on the magnetic domains in oxide<sub>FM</sub>. The OER kinetics are facilitated accordingly after magnetization, implying that the spin pinning effect is involved in the rate-determining step and this step is spin dependent. The spin polarization process in OER under spin pinning is also believed to be sensitive to the existence of active oxygen ligand (O(-)) in oxyhydroxide. When the O(-) is created in 1<sup>st</sup> deprotonation step under high pH, the spin polarization of ligand oxygens will be facilitated, which reduces the barrier for subsequent O-O coupling and promotes the O<sub>2</sub> turnover.

scholarly journals Controlled Surface Reconstruction on Ferromagnetic Oxides: Spin Pinning Effect to the Oxyhydroxide Layer and Its Enhanced Oxygen Evolution Activity

2021 ◽  
Author(s):  
Tianze Wu ◽  
Xiao Ren ◽  
Yuanmiao Sun ◽  
Shengnan Sun ◽  
Guoyu Xian ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Long Range ◽  
Spin Polarization ◽  
Water Electrolysis ◽  
Intrinsic Activity ◽  
Spin Alignment ◽  
Pinning Effect ◽  
Production Of Hydrogen ◽  
Ferromagnetic Oxides ◽  
Kinetic Barriers

The production of hydrogen by water electrolysis suffers from the kinetic barriers in the oxygen evolution reaction (OER) that limits the overall efficiency. As spin-dependent kinetics exist in OER, the spin alignment in active OER catalysts is critical for reducing the kinetic barriers in OER. It is effective to facilitate the spin polarization in ferromagnetic catalysts by applying external magnetic field, which increases the OER efficiency. However, more active OER catalysts tend to have dynamic open-shell orbital configurations with disordered magnetic moments, without showing an apparent long-range interatomic ferromagnetism; thus controlling the spin alignment of these active catalysts is challenging. In this work, we report a strategy with spin pinning effect to make the spins in active oxyhydroxides more aligned for higher intrinsic OER activity. Such strategy bases on a controllable reconstruction: ferromagnetic oxides with controlled sulfurization can evolve into stable oxide<sub>FM</sub>/oxyhydroxide configurations with a thin oxyhydroxide layer under operando condition. The spin pinning effect is found at the interface of oxide<sub>FM</sub>/oxyhydroxide. The spin pinning effect can promote spin selective electron transfer on OER intermediates to generate oxygens with parallel spin alignment, which facilitates the production of triplet oxygen and increases the intrinsic activity of oxyhydroxide by ~ 1 order of magnitude. Under spin pinning, the spins in oxyhydroxide can become more aligned after magnetization as long-range ferromagnetic ordering is established on the magnetic domains in oxide<sub>FM</sub>. The OER kinetics are facilitated accordingly after magnetization, implying that the spin pinning effect is involved in the rate-determining step and this step is spin dependent. The spin polarization process in OER under spin pinning is also believed to be sensitive to the existence of active oxygen ligand (O(-)) in oxyhydroxide. When the O(-) is created in 1<sup>st</sup> deprotonation step under high pH, the spin polarization of ligand oxygens will be facilitated, which reduces the barrier for subsequent O-O coupling and promotes the O<sub>2</sub> turnover.

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