Single component conductors for chirality induced effects – SECRETS_Ukraine

Chirality generally refers to molecules, objects, or materials which can coexist in two non-superimposable forms, called enantiomers, showing mirror image relationship, and is therefore present in many scientific areas related to chemistry, biology, astronomy and physics. Although chiral materials in the broadest sense have been known for a while, the direct influence of chirality on physical properties such as magnetism, conductivity or spin transmission selectivity constitutes relatively recent directions. Therefore, the controlled preparation of chiral functional structures is an important challenge for materials science because of the interesting properties that can arise from the resulting assemblies.
The SECRETS project consists of the synthesis and characterization of two families of chiral single component organic conductors (SCC) for investigating chirality induced physical phenomena such as the electrical magneto-chiral anisotropy (eMChA) effect, the inverse eMChA and chirality induced spin selectivity (CISS). The CISS effect is of paramount importance as it allows the generation of spin polarized currents without the need of a permanent magnetic layer, with potentially important applications in enantioselective electrochemistry. The present proposal will explore these new emerging areas, with the clear objective to identify and understand those effects and materials that have a potential in molecular electronics and spintronics, or in data storage.
SCC form a particularly interesting class of organic conducting materials, as the absence of counter ions generally favors higher dimensionality of the electron transport properties, e.g. quasi-2D or 3D. The two families of chiral SCC envisaged herein are: 1) gold bis(dithiolene) and bis(diselenolene) complexes; 2) helicene dithiadiazolyl (DTDA) stable radicals.
Thus, the primary objectives of the project SECRETS are:
(i) to prepare crystalline chiral SCC based on gold bis(dithiolene) and bis(diselenolene) complexes and to investigate their direct and inverse eMChA and CISS effects;
(ii) to prepare the first helical DTDA derivatives and investigate eMChA and CISS effects.

The expected results are:
- The preparation of complete series, that is to say the production of both enantiomers and the racemate, of chiral neutral gold bis(dithiolene) and bis(diselenolene) complexes as bulk single component conductors.
- Measurements of the MChA effect in gold bis(dithiolene) and bis(diselenolene) based SCC in the semiconducting/metallic/superconducting regimes. In particular, understanding the role of spin-orbit coupling.
- First experimental observations of inverse eMChA by 77Se NMR in chiral neutral gold bis(diselenolene) complexes.
- First observation of the CISS effect in bulk SCC gold bis(dithiolene)/bis(diselenolene) complexes; evidence for the CISS effect in the linear conducting regime.
- The preparation of helicene-dithiadiazolyl (Hel-DTDA) stable radicals as single component (semi)conductors.
- Measurements of the CISS effect in Hel-DTDA either deposited on surfaces or as bulk materials.
- Measurements of the eMChA effect in crystalline neutral or doped Hel-DTDA based materials.

The project SECRETS will greatly contribute to the understanding of magnetochiral effects in conductivity and spin polarization of chiral organic media, and to the evaluation of their applications in molecular electronics and spintronics.