Eight coordinated mononuclear dysprosium complexes of heptadentate aminophenol ligands: the influence of the phenol substituents and the ancillary donors on the magnetic relaxation

The mononuclear complexes [Dy(3Br,5Cl-H3L1,1,4)(D)]center dot solvate (D = H2O, solvate = 0.25MeOH, 1W center dot 0.25MeOH; D = Py without solvate, 1Py), and [Dy(3NO(2),5Br-H3L1,1,4)(H2O)] (2W) were isolated. The crystal structures of 1W center dot 0.25MeOH, 1Py and 2W center dot 2CH(3)C(6)H(5) show that the Dy-III ion is octacoordinated, in N4O4 or N5O3 environments, with distorted geometries, between square antiprism, biaugmented trigonal prism and triangular dodecahedral. A similar environment for the metal ion is shown in the chiral crystals of the diamagnetic yttrium analogue (Y(3Br,5Cl-H3L1,1,4)(MeOH)] (3M), which were spontaneously resolved. Magnetic analyses of the three dysprosium complexes, and their diluted analogous 1W@Y, 1Py@Y and 2W@Y, reveal that none of them seem to relax through an Orbach mechanism at H-dc = 0. However, the three complexes show Orbach relaxation under H-dc = 1000 Oe, and 1Py is the in-field SIM with the highest energy barrier among these complexes, with a U-eff value of 358 K. Analysis of ac magnetic data shows that the electron-withdrawing substituents on the phenol rings of the aminophenol ligands, as well as the auxiliary oxygen donors from water ligands, reduce the energy barriers of the complexes, which is attributed to a charge reduction in the coordinating atoms of the aminophenol donor. Ab initio calculations support the experimental results.

Automated summary

The study isolated three dysprosium complexes and their diluted yttrium analogues to investigate their magnetic behaviors. The complexes exhibit Orbach relaxation under a certain magnetic field, with 1Py showing the highest energy barrier. The experiment demonstrates that electron-withdrawing substituents on the ligands and water molecules affect the energy barriers of the complexes.