Abstract
<jats:p>In this study, we present the first experimental determination of the spin-states of spin-crossover-active transition metal complexes by using X-ray wavefunction refinement. Two complexes–(NH4)2Fe(SO4)2 · 6H2O 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.</jats:p>