Efficient Chirality-Induced Spin Selectivity in Self-Assembled Monolayers of Ru ₂ ⁵ ⁺ Paddlewheel Complexes

High Resolution Image Download MS PowerPoint Slide The use of coordination compounds provides a promising strategy to unravel the factors governing chirality-induced spin selectivity (CISS), particularly the contribution of spin–orbit coupling (SOC) to its magnitude. Here, we report the formation of self-assembled monolayers on gold substrates of a chiral paramagnetic Ru 2 5+ paddlewheel complex, [Ru 2 (NCS){μ-( S )- or ( R )-pycsa} 2 (μ-OAc) 2 ] (pycsa = N -(pyridin-2-yl)-10-camphorsulfonamidate), denoted as ( S )- or ( R )- RuNCS . The incorporation of camphor groups confers point chirality to the molecule and causes a slight twisting around the Ru 2 unit, introducing also a helical chirality, as evidenced by single-crystal X-ray diffraction and dichroic electronic absorption. The complex features an axial ligand bearing a terminal sulfur atom that serves as a robust anchoring site to the metallic surface. The resulting SAMs are homogeneous, stable, and exhibit very reproducible electrical characteristics. Magnetic-conductive atomic force microscopy measurements on enantiopure Ni/Au– RuNCS junctions reveal remarkable spin polarizations reaching values from 60 to 80%, which is particularly noteworthy considering the monolayer nature of the film and the modest helicity of the paddlewheel motif.