Chiral π-Conjugated Double Helical Aminyl Diradical with the Triplet Ground State DOI
Haoxin Guo, Joshua Bennett Lovell,

Chan Shu

и другие.

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(13), С. 9422 - 9433

Опубликована: Март 19, 2024

We report a neutral high-spin diradical of chiral C2-symmetric bis[5]diazahelicene with ΔEST ≈ 0.4 kcal mol–1, as determined by EPR spectroscopy/SQUID magnetometry. The is the most persistent among all aminyl radicals reported to date factor 20, half-life up 6 days in 2-MeTHF at room temperature. Its triplet ground state and excellent persistence may be associated unique spin density distribution within dihydrophenazine moiety, which characterizes two effective 3-electron C–N bonds analogous N–O bond nitroxide radical. enantiomerically enriched (ee ≥ 94%) (MM)- (PP)-enantiomers precursors diradicals are obtained either preparative supercritical fluid chromatography or resolution via functionalization auxiliary racemic tetraamine. barrier for racemization solid tetraamine ΔG‡ = 43 ± 0.01 mol–1 483–523 K range. experimentally estimated lower limit diradical, 26 293 K, comparable DFT-determined 31 gas phase 298 K. While pure displays strong chiroptical properties, anisotropy |g| |Δε|/ε 0.036 376 nm, 0.005 548 nm that recently ground-state dication. Notably, radical anion intermediate generation exhibits large SOMO-HOMO inversion, SHI 35 mol–1.

Язык: Английский

Stereospecific Synthesis of Enantiopure [6]Helicene Containing a Seven‐Membered Ring and [7]Helicene by Acid‐Promoted Stepwise Alkyne Annulations of Doubly Axial‐Chiral Precursors** DOI Creative Commons
Tomoyuki Ikai, Kosuke Oki,

Shoya Yamakawa

и другие.

Angewandte Chemie International Edition, Год журнала: 2023, Номер 62(18)

Опубликована: Март 3, 2023

Enantiopure [6]helicene containing an embedded seven-membered ring and carbo[7]helicene (>99 % ee) with opposite helicity were simultaneously quantitatively %) synthesized a perfect stereospecificity through stepwise acid-promoted intramolecular alkyne annulations of doubly axial-chiral cyclization precursors. The helical handedness the [6]- [7]helicenes was fully stereocontrolled by axial chirality precursors as result complete axial-to-helical transfer. cyclizations proceeded in manner; first six-membered formation followed kinetically controlled seven- or without helix-inversion [4]helicene intermediate generated during step, thus producing enantiopure circularly polarized luminescent helicity.

Язык: Английский

Процитировано

21
Spin polarization through axially chiral linkers: Length dependence and correlation with the dissymmetry factor DOI Creative Commons

Dana Amsallem,

Anil Kumar, Ron Naaman

и другие.

Chirality, Год журнала: 2023, Номер 35(9), С. 562 - 568

Опубликована: Март 9, 2023

The chiral-induced spin selectivity (CISS) effect relates to the spin-selective electron transport through chiral molecules; therefore, molecules act as filters. In past studies, correlation was found between magnitude of filtering and intensity circular dichroism (CD) spectrum (the first Compton peak) molecules. Since CD peak both electric magnetic dipole transitions, it not clear which these properties correlate with CISS effect. This work aims at addressing this question. By studying spin-dependent conduction spectra thiol-functionalized enantiopure binaphthalene (BINAP) ternaphthalene (TERNAP), we that BINAP TERNAP exhibit a similar polarization 50%, despite in being almost twice intense BINAP. These results can be explained by values their anisotropy (or dissymmetry) factor, gabs , is proportional transition moment. Hence, concluded moment molecules, namely, dissymmetry factor.

Язык: Английский

Процитировано

21
Induced Red Circularly Polarized Luminescence Emission Promoted by Intermolecular Förster Resonance Energy Transfer through a Cholesteric Liquid Crystal Medium DOI
Dan Xu,

Xinran Hua,

Chao Liu

и другие.

ACS Applied Materials & Interfaces, Год журнала: 2023, Номер 15(21), С. 25783 - 25790

Опубликована: Май 18, 2023

In this paper, planar chiral helicenes based on [2.2]paracyclophane PCPH5 acted as both inducers and energy donors to construct the circularly polarized luminescence (CPL)-active ternary cholesteric liquid crystals (T-N*-LCs) in a commercial nematic crystal (SLC1717, N-LCs) medium. Induced red CPL emission acceptor of achiral polymer DTBTF8 could be successfully promoted by intermolecular Förster resonance transfer mechanism. The resulting T-N*-LCs can generate intensive signals with glum up +0.70/–0.67. Interestingly, kind "on–off" switching manipulated applied direct current electric field.

Язык: Английский

Процитировано

19
Efficient Spin-Selective Electron Transport at Low Voltages of Thia-Bridged Triarylamine Hetero[4]helicenes Chemisorbed Monolayer DOI Creative Commons
Niccolò Giaconi, Lorenzo Poggini, Michela Lupi

и другие.

ACS Nano, Год журнала: 2023, Номер 17(15), С. 15189 - 15198

Опубликована: Июль 26, 2023

The Chirality Induced Spin Selectivity (CISS) effect describes the capability of chiral molecules to act as spin filters discriminating flowing electrons according their state. Within molecular spintronics, efforts are focused on developing chiral-molecule-based technologies control injection and coherence spin-polarized currents. Herein, for this purpose, we study selectivity properties a monolayer thioalkyl derivative thia-bridged triarylamine hetero[4]helicene chemisorbed gold surface. A stacked device assembled by embedding these between ferromagnetic diamagnetic electrodes exhibits asymmetric magnetoresistance with inversion signal handedness molecules, in line presence CISS effect. In addition, magnetically conductive atomic force microscopy reveals efficient electron filtering even at unusually low potentials. Our results demonstrate that thia[4]heterohelicenes represent key candidates development spintronic devices.

Язык: Английский

Процитировано

19
Chiral π-Conjugated Double Helical Aminyl Diradical with the Triplet Ground State DOI
Haoxin Guo, Joshua Bennett Lovell,

Chan Shu

и другие.

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(13), С. 9422 - 9433

Опубликована: Март 19, 2024

We report a neutral high-spin diradical of chiral C2-symmetric bis[5]diazahelicene with ΔEST ≈ 0.4 kcal mol–1, as determined by EPR spectroscopy/SQUID magnetometry. The is the most persistent among all aminyl radicals reported to date factor 20, half-life up 6 days in 2-MeTHF at room temperature. Its triplet ground state and excellent persistence may be associated unique spin density distribution within dihydrophenazine moiety, which characterizes two effective 3-electron C–N bonds analogous N–O bond nitroxide radical. enantiomerically enriched (ee ≥ 94%) (MM)- (PP)-enantiomers precursors diradicals are obtained either preparative supercritical fluid chromatography or resolution via functionalization auxiliary racemic tetraamine. barrier for racemization solid tetraamine ΔG‡ = 43 ± 0.01 mol–1 483–523 K range. experimentally estimated lower limit diradical, 26 293 K, comparable DFT-determined 31 gas phase 298 K. While pure displays strong chiroptical properties, anisotropy |g| |Δε|/ε 0.036 376 nm, 0.005 548 nm that recently ground-state dication. Notably, radical anion intermediate generation exhibits large SOMO-HOMO inversion, SHI 35 mol–1.

Язык: Английский

Процитировано

7