Determination and Recovery of Spin-States for a High-Spin and a Spin-Crossover Complex by Means of X-Ray Wavefunction Refinement.

In this study, we present the first experimental determination of the spin-states of a spin-crossover-active transition metal complex by using x-ray wavefunction refinement. Two complexes- ( NH 4 ) 2 Fe ( SO 4 ) 2 · 6 H 2 O and Fe ( phen ) 2 ( SCN ) 2 -were investigated using the method with wavefunctions in different spin-states. The correct spin-states can be identified by comparing different refinement indicators and resulting residual electron densities. The application of this method to spin-crossover complexes revealed that the spin-state can be partially recovered by the refinement method even when initially assumed incorrectly. This work demonstrates the potential for x-ray wavefunction refinement to be used in order to gain insight not only into the geometric but also into the electronic structure of transition metal complexes.