Magneto-chiral dichroism in a chiral twistacene ytterbium(iii) one-dimensional assembly of single-molecule magnets

Abstract

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 ²F_7/2 ← ²F_5/2 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.