Effect of the Transition Metal Ions on the Single-Molecule Magnet Properties in a Family of Air-Stable 3d-4f Ion-Pair Compounds with Pentagonal Bipyramidal Ln(III) Ions.

Single-molecule magnets (SMMs) are expected to be promising candidates for the applications of high-density information storage materials and quantum information processing. Lanthanide SMMs have attracted considerable interest in recent years due to their excellent performance. It has always been interesting but not straightforward to study the relaxation and blocking mechanisms by embedding 3d ions into 4f SMMs. Here we report a family of air-stable 3d-4f ion-pair compounds, YFe (), DyCr (), DyFe (), DyCo (), and DyYFe (), composed of pentagonal bipyramidal () Ln cations and transition metallocyanate anions. The ion-pair nature makes the dipole-dipole interactions almost the only component of the magnetic interactions that can be clarified and analytically resolved under proper approximation. Therefore, this family provides an intuitive opportunity to investigate the effects of 3d-4f and 4f-4f magnetic interactions on the behavior of site-resolved 4f SMMs. Dynamic magnetic measurements of under a 4 kOe external field reveal slow magnetic relaxation originating from the isolated [Fe] ( = /) ions. Under zero dc field, compounds show similar magnetic relaxation processes coming from the separated pentagonal bipyramidal () Dy ions with high Orbach barriers of 592(5), 596(4), 595(3), and 606(4) K, respectively. Comparatively, both compounds and exhibit two distinct relaxation processes, respectively from the [Fe] and Dy [ = 596(4) K for and 610(7) K for ] ions, under a 4 kOe dc field. The dipolar interactions between the neighboring TM (TM = transition metal, Cr or [Fe]) and Dy ions were revealed to have little effect on the thermal relaxation in compounds , , and , or the coexistence of the two separate relaxation processes in compounds and under a 4 kOe dc field, but they significantly affect the quantum tunneling of magnetization and the magnetic hysteresis behavior of and at low temperatures compared to those of .