A series of three mono-dimensional polymers [Dy(hfac)₃((S/R)-L²)]_n ((S/R)-2), [Dy(hfac)₃((S/R)-L³)]_n ((S/R)-3) and [Dy(hfac)₃((S/R)-L⁴)]_n ((S/R)-4) involving different binaphthyl-2,2′-diyl phosphate ligands ((S/R)-L^2–4) were designed from our pioneer reported system of formula [Dy(hfac)₃((S/R)-L¹)]_n ((S/R)-1). The single-crystal X-ray diffraction structures revealed that the final compounds are in their enantiopure form with the ligands bearing the same chirality in the free and coordinated mode. All the polymers can be described as assemblies of mononuclear single-molecule magnets (SMM) in both zero and applied magnetic field. The fitting of the thermal dependence of the relaxation times shows that magnetic relaxation takes place through a combination of thermally activated mechanism (Raman) and quantum tunneling of the magnetization (QTM in zero applied magnetic field). The effect of the nature of the antenna and the number of chiral centres of the BINOL-derived bisphosphate ligands on both chiroptical and magnetic properties were studied. Photophysical and magnetic properties were rationalized by TD-DFT and ab initio calculations. Finally magneto-structural correlations between Dy(III) luminescence, calculations and magnetism were performed.

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 investigated both in solution and solid-state.

Complexes of lanthanide(III) ions (Ln) with tetraazacyclododecane-N,N′,N′′,N′′′-tetraacetate (DOTA) are a benchmark in the field of magnetism due to their well-investigated and sometimes surprising features. Ab initio calculations suggest that the ninth ligand, an axial water molecule, is key in defining the magnetic properties because it breaks the potential C₄ symmetry of the resulting complexes. In this paper, we experimentally isolate the role of the water molecule by excluding it from the metal coordination sphere without altering the chemical structure of the ligand. Our complexes are therefore designed to be geometrically tetragonal and strict crystallographic symmetry is achieved by exploiting a combination of solution ionic strength and solid state packing effects. A thorough multitechnique approach has been used to unravel the electronic structure and magnetic anisotropy of the complexes. Moreover, the geometry enhancement allows us to predict, using only one angle obtained from the crystal structure, the ground state composition of all the studied derivatives (Ln = Tb to Yb). Therefore, these systems also provide an excellent platform to test the validity and limitations of the ab initio methods. Our combined experimental and theoretical investigation proves that the water molecule is indeed key in defining the magnetic anisotropy and the slow relaxation of these complexes.

Field-induced single-molecule magnet behavior and circularly polarized luminescence were observed in a series of ytterbium one-dimensional coordination polymers involving chiral BINOL-derived bisphosphate ligands.

Heterotopic divergent ligand N-oxide-4,4′-bipyridine (bipyMO) has been herein exploited for the preparation of hetero-bimetallic coordination polymers where Ln(hfac)₃ and M(hfac)₂ nodes regularly alternate (Hhfac = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione), bipyMO being able to selectively use its two potential coordination sites to discriminate the metal ions. The synthesis of three coordination polymers, [Ln(hfac)₃M(hfac)₂(bipyMO)₂]_n (Ln = Eu, M = Zn, 1; Ln = Eu, M = Cu, 2, Ln = Dy, M = Co, 3), was carried out by reacting the appropriate [M(hfac)₂(bipyMO)]_n and [Ln(hfac)₃] precursors in toluene in the presence of a given stoichiometric amount of bipyMO. The products were characterized by elemental analysis, X-ray powder diffraction, and FTIR spectroscopy. Single crystal X-ray diffraction studies carried out on 2 showed that it was formed by chains containing the hexa-coordinated 3d metal (Cu(hfac)₂[N]₂) and the octa-coordinated lanthanide (Eu(hfac)₃[O]₂) nodes, where [N] and [O] stand for the donor atom of the bridging divergent ligand. The X-ray powder diffraction patterns of the three compounds and the comparison of their cell constant values allowed establishing that the derivatives were isotypic. Photoluminescence (PL) studies on microcrystalline sample powders evidenced a bright red emission for 1 with an absolute PL quantum yield of 0.24. The sensitized emission of Eu³⁺ can be excited in a wide wavelength range, from UV to visible, up to ≈450 nm. Conversely, europium emissions are not detectable in 2 due to the presence of Cu(hfac)₂(bipyMO) moieties whose strong absorption overlaps Eu³⁺ transitions. Magnetic measurements conducted on 3 revealed the presence of a weak ferromagnetic interaction below 2.1 K. An ac susceptibility study highlighted a slow relaxation of the magnetization of 3 with an applied static magnetic field of 0.1 T, which could be equally fitted with a Orbach-direct or a Raman-direct mechanism. No relaxation dynamics was detected without the application of a static magnetic field.