Magneto‐Chiral Dichroism of Tris‐Chelated Cr(III) Complexes for Magneto‐Chiral Photochemistry Studies

Here we report on the preparation and investigation of a pair of enantiopure chiral complexes of chromium(III) featuring the chiral (1 R ,2 R )‐diaminocyclohexane and (1 S ,2 S )‐diaminocyclohexane ligands. Single‐crystal X‐ray crystallography reveals an octahedral tris‐chelated propeller‐like coordination geometry. Natural circular dichroism spectroscopy in solution and in the solid state indicates that both spin‐allowed and spin‐forbidden d–d electronic transitions of the Cr(III) ion are optically active. Variable temperature and variable magnetic field magneto‐chiral dichroism spectroscopy reveals that the spin‐forbidden absorption bands are MChD active and provide low‐temperature g MChD dissymmetry factors comparable to those of tris(oxalato)chromate(III). On these bases, magneto‐chiral photochemistry experiments aimed at inducing a preferential enantiomeric excess of one enantiomer over the other by irradiating a racemic solution of the complexes with unpolarized light under an applied magnetic field have been conducted.