Selected Examples of Iron and Cobalt Complexes Exhibiting Spin-Crossover Behavior

The study of spin crossover phenomenon (SCO) has remained a very fascinating and dynamic field for inorganic chemists. The design of such molecules in which metal exists in two stable spin states and can be switched reversibly under the influence of external stimulus like temperature, pressure, light etc. is of huge interest in the domain of molecular magnetism. A brief survey of the known chemistry of mononuclear Fe(II) and Co(II) octahedral systems with suitable N-donor ligands exhibiting SCO behavior has been highlighted in this chapter. In this regard, conjugated pyridine and Schiff’s base derived Fe(II) complexes and terpryidine based Co(II) complexes have been selected as a topic of discussion (Scheme 1). To achieve the spin transition phenomenon at ambient conditions still remains a challenge. The characteristics of SCO (spin-crossover) in complexes containing Fe(II) and Co(II) have been examined, taking into account the various factors that influence them. Emphasis has been placed on the potential uses of SCO in the advancement of memory devices, display devices, optical storage devices, sensors, and other related applications. In this chapter, various characterization methods which are commonly employed to establish spin crossover behavior in transition metal complexes have also been discussed.