Chiral Crystals, Jack, Conductivity and Magnetism

Abstract

In Memory of Jack DunitzRecently, the application of magnetic fields to chiral chemical systems has been rewarding. In a forwardlooking 1986 paper, 'Chiral Metals?', Wallis, Karrer, and Jack D. Dunitz forecast 'that the limitation to proper symmetry elements in a chiral conductor could be associated with the emergence of new properties, those connected with interactions between applied electric and magnetic fields and their internal counterparts.' This was a prescient remark, but it has become manifest in ways that would not have been foreseen in its details by the authors. Here are reviewed the development of chiral conductors broadly imagined by Dunitz and coworkers, based on enantiopure tetrathiafulvalene derivatives that restrict space groups to those that have only symmetry operations of the first kind, as well as the new emergent properties associated with the transport of electrons when magnetic fields are applied to chiral crystals among other systems. These include electrical magnetochiral anisotropy (eMChA), inverse electrical magnetochiral anisotropy (ieMChA), helimagnetism and chirality induced spin selectivity (CISS). The conclusion discussing the circumstances under which achiral TTF crystals becomes chiral, only seems to introduce an oxymoron.

Impact of Chiral Symmetry Breaking on Spin-Texture and Lone Pair Expression in Chiral Crystals of Hybrid Antimony and Bismuth Halides

“…Because chiral molecules lack a center of inversion, hybrid semiconductors containing chiral organic cations can exhibit properties that are only found in noncentrosymmetric crystal structures, such as second-harmonic generation, , ferroelectricity, , circularly polarized photoluminescence (CP-PL), − and CP light detection. − Chiral molecules can also afford control of spin-based properties; the chiral hybrid Ruddlesden–Popper perovskites ( R / S -methylbenzylammonium) 2 PbI 4 and ( R / S -methylbenzylammonium) 2 SnI 4 exhibit spin-dependent charge transport due to the chirality-induced spin-selectivity (CISS) effect, , which has enabled a room-temperature spin-polarized light-emitting diode without the use of magnetic components . Furthermore, chiral crystals are a relatively unexplored chemical system with potential for new functionalities …”

“…33 Furthermore, chiral crystals are a relatively unexplored chemical system with potential for new functionalities. 34 The exciting properties of chiral hybrid perovskite systems motivate an understanding of the interplay of the chiral organic cations and the optoelectronic properties in chiral hybrids with alternative structural topologies. Bismuth and antimony have been exploited to expand the compositional and structural phase space of these hybrid semiconductors.…”

Leveling up Organic Semiconductors with Crystal Twisting

“…It has been previously demonstrated that a small internal magnetic field is generated when a voltage is applied parallel to the axis of a helicoidal conductive crystal, similar to a solenoid. The conductivity is maximized when an external magnetic field aligns with the internally generated field and minimized when the external field opposes the internal one, − following the equation Δ R R = 2 γ D / L B · I where γ D/L represents the magnetochiral anisotropy factor between right and left handed twists, B is the magnetic field, and I is the current. Electric magnetochiral anisotropy has been observed in twisted bismuth wires, crystals of a chiral TTF derivative, and carbon nanotubes, among other structures.…”

Achiral 2‐pyridone and 4‐aminopyridine act as chiral inducers of asymmetric autocatalysis with amplification of enantiomeric excess via the formation of chiral crystals

“…The origin and amplification of chirality as seen in L‐amino acids and D‐sugars are of great interest because they have been one of the prerequisites for the chemical origin of life. Among the credible theories, 1–28 chiral crystallization of achiral compounds 29,30 is one of the fundamental phenomena of the generation of chirality. Because stereospecific reactions utilizing the chirally oriented crystals as a substrate have been reported, 31–37 enantioenriched chiral compounds could be obtained based on the crystal chirality of achiral compounds.…”