Acta Pharm. 50 (2000) 75-81

Metal complexes with short memory effect

SMILJKO ASPERGER^1* and BISERKA CIZMEK ²

¹Research Units of the Croatian, Academy of Sciences and Arts, Zagreb, Croatia
²Department of Analytics and Control of Medicines, Faculty of Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia

With lower temperatures, a certain class of transition metal complexes changes from high-spin to low-spin state. This is accompanied by changes in magnetic and optical properties. The phenomenon is usually called the spin crossover phenomenon, as well as spin transition and molecular bistability. It might occur in the solid state and in solution, rather often in complexes of iron(II), iron(III), cobalt(II), less often in complexes of nickel(II), cobalt(III) and manganese(III).
The spin crossover phenomenon is a spectacular example of molecular bistability that can be used as an active element in memory devices, as recently demonstrated by Kahn and his coworkers in a series of papers. Some other research groups are active in the field in different world centres. Applications are expected in medicine (e.g. treatment of tumours by hyperthermy). It appears that bistable molecular states are on the way to introduce memory as a new dimension in the molecular chemistry.

Keywords: spin crossover, metal complexes, metal complexes with memory, metal complexes thermal hysteresis