Structural, electronic and magnetic properties of neutral and anionic Fe2(BO2)n (n=1–3n=1–3) clusters

• Charge states have significant effect on the geometry of Fe2(BO2)n clusters.
• Electronic properties change with increasing BO2 in neutral and anionic Fe2(BO2)n.
• The magnetic coupling between Fe atoms in Fe2 can be effectively tuned by BO2.
• Fe2 coupling changes from direct exchange to super exchange with increasing BO2.

Using Fe2 dimer as a prototype of transition-metal cluster calculations based on density functional theory have been carried out to study the effect of ligand and charge states on the geometry, bonding feature and magnetic coupling of neutral and anionic Fe2(BO2)n (n=1–3n=1–3) clusters. For neutral Fe2(BO2)n clusters the spin multiplicity of the complex changes from 7 to 8 when n goes from 0 to 1, 2, and 3. With increasing number of ligands the Fe–Fe distance increases, the magnetic coupling between Fe–Fe changes from direct exchange to super exchange, and 3d–2p hybridization between Fe and O atoms becomes predominant. For anionic Fe2(BO2)n (n=1–3n=1–3) clusters, the corresponding total magnetic moment is 0, 7 and 6μB6μB, respectively. Compared with neutral clusters the HOMO–LUMO gaps of anionic species increase rapidly as more BO2 units are introduced. This study sheds light on the potential of superhalogens to tune electronic and magnetic properties of Fe clusters.