Helicenes—A New Class of Organic Spin Filter

Abstract

Chiral helicene, a fully conjugated system without stereogenic carbon, can filter spins effectively at room temperature, a consequence of the chiral-induced spin-selectivity effect. The chirality dictates the spin of the electrons transferred through helicene, and magnetoresistance devices based on these molecules show antisymmetric magnetoresistance versus H plots.

Spin Selective Charge Transport through Cysteine Capped CdSe Quantum Dots

“…Although some variation in the MR response with temperature exists, the differences are relatively minor (typical variations are only 0.1 to 0.2%). The mostly temperature independent MR is consistent with former works, 17,43 suggesting that a high degree of spatial confinement in the QD inhibits electron motion in the lattice and therefore minimizes the D'yakonov-Perel' (DP) scattering. 46 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 13…”

“…The present work explores whether chiral induced spin selectivity (CISS), 8,9 which has been demonstrated for helical DNA, 10,11,12,13 α-helical peptides, 14,15,16 helicenes, 17 and other biomolecules, 18,19 can be used as an alternative approach to affect charge transport through quantum dot films. The present work demonstrates that quantum dot thin films composed of chiral semiconductors preferentially transmit electrons with a particular spin orientation.…”

Structure dependent spin selectivity in electron transport through oligopeptides

“…The CISS effect relates to the ability of chiral molecules to transmit electrons in a spin-selective manner, hence the molecules act as spin filters. 6,7 Several chiral molecular species including DNA, [8][9][10][11][12] oligopeptides, [13][14][15] bacteriorhodopsin (bR), 16,17 a chiral conductive polymer, 18 1, 2-diphenyl-1,2-ethanediol (DPED), 19 helicenes, 20 and recently chiral CdSe quantum dots 21 have demonstrated efficient spin filtering. The spin filtering ability can be tuned by various means, for example, by varying the length of the chiral molecule, 8,9,13 by exposure to light, 22 or by varying the temperature.…”

A Triskelion‐Shaped Saddle–Helix Hybrid Nanographene

“…[1] Aside from bowls,h oops, and twisted acenes, [2] saddle-shaped [3] and helical aromatics [4] constitute two important classes of non-planar carbon-based p-conjugated systems.B oth fields have been developing rapidly because of the unique properties,s uch as low molecular aggregation, high solubility,and dynamic behavior, of the final compounds.F urthermore,n egatively curved saddle aromatics,g enerally obtained by the inclusion of ah eptagon or octagon, have been proposed to show interesting mechanical, electronic, and magnetic properties [5] while non-racemizable enantiopure carbo[n]helicene systems are characterized by their intrinsic chiroptical properties,such as optical rotation, circular dichroism, [6] or chiral-induced spin selectivity (CISS) effects, [7] finding applications as switches or sensors. [1] Aside from bowls,h oops, and twisted acenes, [2] saddle-shaped [3] and helical aromatics [4] constitute two important classes of non-planar carbon-based p-conjugated systems.B oth fields have been developing rapidly because of the unique properties,s uch as low molecular aggregation, high solubility,and dynamic behavior, of the final compounds.F urthermore,n egatively curved saddle aromatics,g enerally obtained by the inclusion of ah eptagon or octagon, have been proposed to show interesting mechanical, electronic, and magnetic properties [5] while non-racemizable enantiopure carbo[n]helicene systems are characterized by their intrinsic chiroptical properties,such as optical rotation, circular dichroism, [6] or chiral-induced spin selectivity (CISS) effects, [7] finding applications as switches or sensors.…”

“…[4a] Combining both curved motifs,n amely as even-membered carbocycle and ac arbo[n]helicene,i nas ingle conjugated structure would lead to exotic distorted geometries and, more importantly,novel synergies of interesting properties.D espite their potential, saddle-helix hybrid compounds are very scarce. [10] Simultaneously,u nique structural motifs,s uch as laterally p-extended pentabenzo [5]helicene [9a] or heptabenzo [7]helicene [9b] units, were created in such distorted PA Hs.Those enantiopure helix led to the first CPL-active nanographenes,o pening the door to new optoelectronic applications for carbon nanomaterials. [10] Simultaneously,u nique structural motifs,s uch as laterally p-extended pentabenzo [5]helicene [9a] or heptabenzo [7]helicene [9b] units, were created in such distorted PA Hs.Those enantiopure helix led to the first CPL-active nanographenes,o pening the door to new optoelectronic applications for carbon nanomaterials.…”