On the role of the imide axial ligand in the spin and oxidation state of Mn corrole and corrolazine complexes

Identifier:  PC:1524

Handle: https://hdl.handle.net/20.500.11797/PC1524

Authors:  Rosa Caballol; Gerard Alcover; Kristin Pierloot; Coen de Graaf

Abstract:
Electronic structure calculations have been performed on four different Mn corrole and corrolazine complexes to clarify the role of the imide axial ligand on the relative stability of the different spin states and the stabilization of the high valent Mn ion in these complexes. Multiconfigurational perturbation theory energy calculations on the DFT optimized geometries shows that all complexes have a singlet ground state except the complex with the strongest electron withdrawing substituent on the imide axial ligand, which is found to have a triplet ground state. The analysis of the sigma and pi interaction between metal and imide ligand shows that this spin crossover is caused by a subtle interplay of geometrical factors (Mn-N distance and coordination angle) and the electron withdrawing character of the substituent on the imide, which reduces the electron donation to the metal centre. The analysis of the multiconfigurational wave functions reveals that the formally MnV ion is stabilized by an important electron transfer from both the equatorial corrole/corrolazine ligand and the axial imide. The macrocycle donates roughly half an electron, being somewhere between the closed-shell trianionic and the dianionic radical form. The imide ligand transfers 2.5 electrons to the metal center, resulting in an effective d-electron count close to five in all complexes.