Solid-state versus solution investigation of a luminescent chiral BINOL-derived bisphosphate single-molecule magnet

Abstract

The enantiopure coordination polymer [Dy(hfac)₃((S/R)-L)]_n ([(S/R)-1]_n) involving a BINOL-derived bisphosphate ligand (S/R)-L is reported. Paramagnetic NMR and computational investigations demonstrated the formation of mononuclear species [(S/R)-1] in CH₂Cl₂ solution and its optimized structure was determined. The experimental electronic circular dichroism signals of (S/R)-L were strongly enhanced after metal coordination [(S/R)-1]. Both polymeric and mononuclear structures displayed field-induced Single-Molecule Magnet (SMM) behaviour with similar multi-relaxation processes due to the retention of crystal-field splitting determined by CASSCF calculations, despite the strong structural transformation between the two media. The HOMO → LUMO transition of the (S)-L ligand induced the classical Dy(III) emission at 77 K that was correlated with the magnetic properties. [(S)-1]_n is described as one-dimensional assembly of chiral luminescent Single-Ion Magnets (SIMs).