Using a Combination of Experimental and Computational Methods To Explore the Impact of Metal Identity and Ligand Field Strength on the Electronic Structure of Metal Ions

Abstract

In this exercise, students apply a combination of techniques to investigate the impact of metal identity and ligand field strength on the spin states of three d5 transition-metal complexes: Fe(acac)3, K3[Fe(CN)6], and Ru(acac)3, where acac– is acetylacetonate. Students first use crystal field theory to predict the most likely spin state based on the metal identity (3d versus 4d metal) and the ligand field strength of the acac– and CN– ligands (weak-field versus strong-field ligands). Next, students use density functional theory (DFT) to determine the geometries and the energies of the high- and low-spin electronic configurations of each complex, allowing them to predict the most energetically favorable configuration and to compare their computed geometries with X-ray structural data. Finally, students experimentally determine the magnetic susceptibility and spin state of each complex and compare these results with their predictions. This combined application of basic chemical principles, computational chemistry, and experimental measurement provides students with practical insight into the application of complementary methods to better understand chemical properties.