Abstract
The influence of the spin state of the metal centre in spin crossover compounds on the aromaticity of the ligands has been investigated for iron(ii)tris-bipyridine (Fe(bpy)32+), and Fe(ii)(formazanate)2 (as a truncated model and the full phenyl substituted compound). It was found that the aromaticity of the bipyridine ligands is unaffected by changing the spin state of the central iron atom, but that of the formazanate ligands is reduced upon transition to the high-spin state. This change in aromaticity is rationalized using the symmetry selection rules for aromaticity in terms of virtual excitations from occupied to empty orbitals. A further consequence of this loss in aromaticity is a shift to higher energy in the ring vibrations of the formazanate compounds that can be observed in either its IR or Raman spectrum; this prediction has been confirmed here. This change in aromaticity as a consequence of change in spin state can be regarded as an indication for non-innocent ligands.
| Original language | English |
|---|---|
| Pages (from-to) | 2789-2796 |
| Number of pages | 8 |
| Journal | Dalton Transactions |
| Volume | 53 |
| Issue number | 6 |
| DOIs | |
| State | Published - Jan 10 2024 |
| Externally published | Yes |
Funding
This work was sponsored by NWO Exact and Natural Sciences for the use of supercomputer facilities (contract no. 17197 7095) and we thank S. Dolas (SURF, NL) for allowing us to perform calculations on the experimental AMD platform kleurplaat maintained and operated by SURF Open Innovation Lab. We acknowledge Prof. Dr W. R. Browne (University of Groningen) for fruitful discussions. We thank K. M. van der Geest (University of Groningen) for designing the Graphical abstract.