Single-molecule magnets (SMMs) and single-chain magnets (SCMs), also known as molecular nanomagnets, are molecular species of nanoscale proportions with the potential for high information storage density and spintronics applications. Metal-organic frameworks (MOFs) are three-dimensional ordered assemblies of inorganic nodes and organic linkers, featuring structural diversity and multiple chemical and physical properties. The concept of using these frameworks as scaffolds in the study of molecular nanomagnets provides an opportunity to constrain the local coordination geometries of lanthanide centers and organize the individual magnetic building blocks (MBBs, including both transition-metal and lanthanide MBBs) into topologically well-defined arrays that represent two key factors governing the magnetic properties of molecular nanomagnets. In this tutorial review, we summarize recent progress in this newly emerging field.

Lanthanide permanent magnets are widely used in applications ranging from nanotechnology to industrial engineering. However, limited access to the rare earths and rising costs associated with their extraction are spurring interest in the development of lanthanide‐free hard magnets. Zero‐ and one‐dimensional magnetic materials are intriguing alternatives due to their low densities, structural and chemical versatility, and the typically mild, bottom‐up nature of their synthesis. Here, we present two one‐dimensional cobalt(II) systems Co(hfac)2(R‐NapNIT) (R‐NapNIT=2‐(2′‐(R‐)naphthyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide, R=MeO or EtO) supported by air‐stable nitronyl nitroxide radicals. These compounds are single‐chain magnets and exhibit wide, square magnetic hysteresis below 14 K, with giant coercive fields up to 65 or 102 kOe measured using static or pulsed high magnetic fields, respectively. Magnetic, spectroscopic, and computational studies suggest that the record coercivities derive not from three‐dimensional ordering but from the interaction of adjacent chains that compose alternating magnetic sublattices generated by crystallographic symmetry.

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Switchable "on/off" single-molecule magnet (SMM) behavior can be realized in lanthanide metal-organic frameworks (Ln-MOFs) tuned by the temperature-induced change of the coordination geometry of the lanthanide centers.

Two mononuclear DyIII single-molecule magnets (SMMs) with C2v coordination symmetry were synthesized. Both of them have strong uniaxial magnetic anisotropy with high effective energy barriers for magnetization reversal over 600...