Spin-Based Enantiorecognition at Chiral-Porphyrin-Functionalized Interfaces: A Physical Effect Due to the Chiral-Induced Spin Selectivity.

Enantiorecognition is a fundamental process in bioscience, ruling most life-related processes. This work focuses on the physics underlying chiral recognition, suggesting that the electron-spin/molecular-handedness interaction plays an important role here. Results obtained exploiting three complementary experimental techniques are compared, where metal surfaces are functionalized using a chiral porphyrin (cPorf): (1) cyclic voltammetry is used to probe the handedness of the electrode surface exploiting a chiral redox couple; (2) spin-dependent electrochemistry measurements were performed using a ferromagnetic electrode as spin injector; (3) magnetoconductive atomic force microscopy measurements proved that the charge transport through cPorf bundles adsorbed on a nickel surface is spin-polarized (spin polarization percentage, SP%, ranging between 20% and 50%). Mueller matrix polarimetry (MMP) spectra confirmed that the electronic circular dichroism of cPorf in solid-state thin films is not merely apparent but is true. The overall experimental results suggest that spin plays a fundamental role in the enantiorecognition process, as a possible manifestation of the Naaman-Waldeck chiral-induced spin selectivity effect.