Chiral Induced Spin Selectivity

Abstract

Since the initial landmark study on the chiral induced spin selectivity (CISS) effect in 1999, considerable experimental and theoretical efforts have been made to understand the physical underpinnings and mechanistic features of this interesting phenomenon. As first formulated, the CISS effect refers to the innate ability of chiral materials to act as spin filters for electron transport; however, more recent experiments demonstrate that displacement currents arising from charge polarization of chiral molecules lead to spin polarization without the need for net charge flow. With its identification of a fundamental connection between chiral symmetry and electron spin in molecules and materials, CISS promises profound and ubiquitous implications for existing technologies and new approaches to answering age old questions, such as the homochiral nature of life. This review begins with a discussion of the different methods for measuring CISS and then provides a comprehensive overview of molecules and materials known to exhibit CISS-based phenomena before proceeding to identify structure−property relations and to delineate the leading theoretical models for the CISS effect. Next, it identifies some implications of CISS in physics, chemistry, and biology. The discussion ends with a critical assessment of the CISS field and some comments on its future outlook.

Chiral π-Conjugated Double Helical Aminyl Diradical with the Triplet Ground State

“…It is conceivable that the coexistence of strong molecular chirality and a high-spin ground state could benefit the development of novel spin filters. , Notably, the diamagnetic [5]-, [6]-, and [7]­helicene derivatives with spin polarizations of ≤80% were studied. − High-spin diradicals were theoretically predicted to provide up to 100% spin polarizations, , and recently, large magnetoresistance in an open-shell diradical polymer was discovered …”

No More Conductance Decay: Toward Efficient Long-Range Transport in Molecular Wires

“…Molecular wires, as the fundamental units in molecular electronics, hold promise for overcoming the existing challenges associated with conventional silicon-based electronics in terms of device miniaturization and tuning the charge transport quantum mechanically. The vast diversity and structural freedom of organic-based molecules have spurred increasing interest in probing and manipulating charge transport through single molecules. , Molecular analogs have been developed to mimic the behavior of conventional electronic devices, such as diodes, , transistors, , sensors, , photoswitches, − and thermoelectric units. − More importantly, owing to quantum mechanically dominated charge transport in single molecules, new transport phenomena that are absent in macroscopic semiconductor devices have been unfolded, including but not limited to quantum interference − and chirality induced spin selectivity. − Nonetheless, one of the major roadblocks toward developing applicable molecular electronics is the inherent low conductivity of organic molecules. , The commonly investigated molecules acting as conducting elements in a circuit are molecules with highly conjugated π-building blocks. Charge transport through a single molecule has been extensively explored using the single-molecule junction platforms that are capable of covalently connecting a molecule to two electrodes. − To date, most of the studied conjugated molecules have been shown to conduct electrons in an off-resonant, coherent regime.…”