Spin-crossover in iron(ii)-Schiff base complexes

The spin-crossover (SCO) phenomenon is one of the most prominent examples of bi-stability in molecular chemistry, and the SCO complexes are proposed for nanotechnological applications such as memory units, sensors, and displays. Since the discovery of the SCO phenomenon in tris(N,N-dialkyldithiocarbamato)iron(iii) complexes, numerous investigations have been made to obtain bi-stable SCO complexes undergoing spin-state switching at or around room temperature (RT). Valiant efforts have also been made to elucidate the structure-property relationship in SCO complexes to understand the factors-such as ligand-field strength, molecular geometry, and intermolecular interactions-governing the SCO. Schiff base ligands are an important class of nitrogen-rich chelating ligands used to prepare SCO complexes, because the Schiff base ligands are easy to synthesize and tailor with additional functionalities. Iron(ii)-Schiff base SCO complexes are a well-studied class of SCO active complexes due to the propensity of the complexes to undergo bi-stable SCO. In this context, this perspective attempts to elucidate the structure-SCO property relationships governing SCO in selected mono-, bi-, and multi-nuclear iron(ii)-Schiff base complexes.