Dinuclear enantiopure Ln 3+ complexes with ( S -) and ( R -) 2-phenylbutyrate ligands. Luminescence, CPL and magnetic properties.

The reaction of Ln(NO 3 ) 2 ·6H 2 O (Ln = Nd, Sm, Eu, Tb, Dy, Tm and Yb) with the respective enantiopure ( R )-(-)-2-phenylbutyric or ( S )-(+)-2-phenylbutyric acid ( R / S -2-HPhBut) and 4,7-diphenyl-1,10-phenanthroline (Bphen) allows the isolation of chiral dinuclear compounds of the formula [Ln 2 (μ- R / S -2-PhBut) 4 ( R / S -2PhBut) 2 (Bphen) 2 ] where Ln = Nd 3+ (R/S-Nd-a), Sm 3+ (R/S-Sm-a), Eu 3+ (R/S-Eu-a), Tb 3+ (R/S-Tb-a and R/S-Tb-b), Dy 3+ (R/S-Dy-a and R/S-Dy-b), Tm 3+ (R/S-Tm-b) and Yb 3+ (R/S-Yb-b). Single crystal X-ray diffraction was performed for compounds S-Eu-a and S-Tm-b. Powder crystal X-ray diffraction was performed for all complexes. From the crystallographic data two different structural motifs were found which are referred to as structure type a and structure type b . In structure type a , the Ln 3+ atoms are bridged through four R or S -2-PhBut ligands with two different kinds of coordination modes whereas in structure type b the two Ln 3+ atoms are bridged through four R or S -2-PhBut ligands showing only one kind of coordination mode. For those lanthanide ions exhibiting both structure types, Tb 3+ and Dy 3+ , a difference in the luminescence and magnetism behavior is observed. All compounds (except R/S-Tm-b) exhibit sensitized luminescence, notably the Eu 3+ and Tb 3+ analogues. Circular Dichroism (CD) and Circular Polarized Luminescence (CPL) in the solid state and in 1 mM dichloromethane (DCM) solutions are reported, leading to improved chiroptical properties for the DCM solutions. The asymmetry factor ( g lum ) in 1 mM DCM is ±0.02 (+ for R-Eu-a) for the magnetically allowed transition 5 D 0 → 7 F 1 and ±0.03 (+ for R-Tb-a and R-Tb-b) for the 5 D 4 → 7 F 5 transition. Magnetic properties of all compounds were studied and the Dy 3+ compound with the structural motif b (R-Dy-b) shows Single Molecular Magnet (SMM) behavior under a 0 T magnetic field. However, R-Dy-a is a field-induced SMM.