Cyanido-Bridged Heterobimetallic Molecular Squares: Low- Dimensional Models of Prussian Blue Analogues and Beyond

The cyanido-bridged square-like molecules with d/f metal ions occupying the corners of the square are considered molecular models of the Prussian Blue Analogues (PBAs) because they reproduce one face of their 3D face-centered cubic structure, being called low-dimensional PBAs. Such highly regular complexes provide unique insights into the short-range magnetic exchange interaction between the metal ions of PBAs and exhibit magnetic properties which are not found for PBAs. This review focuses on the preparative routes and magneto-structural characterization of d- d(d ')/d-f tetranuclears with a square-like topology generating rich families of molecular switches and nanomagnets. Relevant examples that provided a better comprehension of the magnetic behavior of PBAs, including subtle chemical factors that interfere in the photo-and thermally induced electron transfer are reviewed herein. A special attention is paid to the design of d-f cyanido-bridged squares, less numerous compared to the d-d/d ' ones, that proved to be suitable model compounds for the theoretical treatment of the magnetic exchange interaction between d and f spin carriers across the cyanide ligand. The square-shaped PBAs represent a very active area of research that is enriched yearly with new examples with potential for the development of molecular-scaled electronic devices.