Spin-crossover (SCO) in transition metal complexes allows switching between the low-spin (LS) and high-spin (HS) states under various external stimuli. The photo-induced SCO, arguably, is the most attractive option from the application viewpoint, as light is an inexpensive and convenient trigger for wavelength-specific spin-state switching with short response time and rapid power dissipation. We report a study of light-induced excited spin state trapping (LIESST) in heteroleptic iron(II) complexes [Fe(tpma)(L)](ClO4)2, where L represents a bidentate 2,2’-biimidazole ligand functionalized with xylene or naphthalene pendants. While both materials exhibit the LIESST effect, we find that the stability of the LIESST state is increased upon going from the xylene- to naphthalene-substituted ligand. We discuss the influence of crystal packing on the kinetics of the HS-to-LS relaxation and possible pathways to further influence the LIESST behavior.

Photomagnetic behavior of SCO complex [Fe(tpma)(xnap-bim)](ClO4)2

ACS Spring 2022

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