Stereochemical influence on tuning the transition temperature in Spin-Crossover molecules

Abstract

Spin-crossover molecules have been a subject of interest for chemists and physicists ever since they were first reported. The intrinsic technological applications of these systems have made them the focus of intense research. The change in the spin state of the metal center, which can be induced by different stimuli, comes with a notable change in the physical properties of the molecule, such as changes in the magnetic moment, the absorption spectra, and the coordination geometry, thus making these systems ideal candidates for molecular level-based switches. A key parameter in the characterization of such systems is the transition temperature, T1/2, which is the temperature with an equal population of both spin states. It has been shown experimentally that different isomers of Iron (II) systems with bidentate ligands exhibit differences in their spin-crossover properties, also affecting the T1/2. This fact reveals the possibility of having an interplay between geometry and magnetic properties. This work focuses on the modeling of [Fe(1-methyl-2-(pyrimidin-2-yl)-1H-benzo[d]imidazole)3]2+ and [Fe(phenanthroline)2(NCS)2] complexes, studying the differences the fac vs. mer, and cis vs. trans isomers show on the transition temperature and other thermochemical parameters associated with the spin transition, aiming to compare the results with the experimental data.