Towards control of the intrinsic characteristics of Spin-crossover in ferrous materials

• Applicant: Professor Dr. Alfred X. Trautwein (†)
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2002 to 2008
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5383473

Spin-crossover complexes can be switched between low-spin and high-spin states by changing temperature, applied pressure, or by irradiation with light. These complexes are therefore not only of high interest for basic research, they are also promising materials for holographic optical information storage devices and for display devices. The aim of this joint project between the research teams in Toulouse and in Lübeck is to quantify the factors that determine important parameters of the spin crossover like the transition temperature, the thermal hysteresis or the character of the transition (gradual or abrupt). Quantifying these factors will be an important prerequisite for future technical applications of these materials. This project will start with the investigation of a large set of complexes that are already available in the Toulouse laboratory. These samples consist in a given iron(II) complex cation and many different counteranions, which have a considerable influence on the spin-crossover behaviour of the material. The project will continue with the synthesis of new complexes, which will be guided by the results of spectroscopic experiments and theoretical calculations for the existing samples. The experimental characterization of the complexes will be carried out using several complementary techniques including IR, Raman and Mössbauer spectroscopy, susceptibility measurements, nuclear forward scattering and nuclear inelastic scattering experiments. The theoretical characterization will be performed with the help of density functional calculations and simulations with Ising-like models. Both research teams have long-standing experience in the field of spin-crossover research. The experimental and theoretical tools used in the two laboratories are complementary to a large extent. A combined investigation of these complexes by both research teams will not only lead to a more complete description of the subject under study, but is essential for a continuous feedback between synthesis, experimental characterization and theoretical calculations.

• DFG Programme: Research Grants
• International Connection: France
• Participating Person: Professor Dr. Jean-Pierre Tuchagues