Magneto-Chiral Dichroism in a Chiral Twistacene Ytterbium(III) One-dimensional Assembly of Single-Molecule Magnets

Here we report on one-dimensional nano objects of formula [Yb(hfac)3(M-or P-Ant-C8)]n where the Ant-C8 moiety refers to enantiopure M- and P-twistacenes decorated at positions 2,6 with 4-pyridyl-ethynyl units and helically locked into an end-to-end twist by an octyl tether. The crystal structure analysis reveals intertwined 1D nano-chains featuring two crystallographically independent Yb(III) ions. Under applied magnetic fields these systems show slow relaxation of the magnetization. The optical properties show the expected contributions of the 2F7/2 ← 2F5/2 electronic transition of the Yb(III) ions split by the crystal field. Magnetic field and temperature dependent Magneto-Chiral Dichroism (MChD) studies reveal contributions of opposite sign and similar intensity for the two crystallographically independent ions that cancel out for the 0-0’ and 0-2’ absorptions but not for the 0-1’. These findings, supported by ab intio theoretical calculations, demonstrate the important role of the structural arrangement of MChD-active ions when designing chiral magneto-optical materials responsive to light and magnetic fields.