Issue 6, 2024

Changes in aromaticity of spin-crossover complexes: a signature for non-innocent ligands

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.

Graphical abstract: Changes in aromaticity of spin-crossover complexes: a signature for non-innocent ligands

Supplementary files

Article information

Article type
Paper
Submitted
13 Oct 2023
Accepted
10 Jan 2024
First published
10 Jan 2024
This article is Open Access
Creative Commons BY license

Dalton Trans., 2024,53, 2789-2796

Changes in aromaticity of spin-crossover complexes: a signature for non-innocent ligands

A. V. Cunha, F. Milocco, E. Otten and R. W. A. Havenith, Dalton Trans., 2024, 53, 2789 DOI: 10.1039/D3DT03404F

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