Spin-crossover and LIESST Effect for Iron(III) Complex Based on π–π Stacking by Coordination Programming

Abstract

Abstract Spin-crossover (SCO) iron(III) compounds, [Fe(qnal-OMe)2]PF6·acetone (1) and [Fe(qnal-OMe)2]BPh4·2MeOH (2) (qnal-OMe: 7-methoxy-1-[(8-quinolinylimino)methyl]-2-naphthalenol), were prepared and characterized by X-ray single-crystal structure analysis, temperature-dependent magnetic susceptibility, and Mössbauer spectroscopy measurements. The compounds exhibited SCO behavior with thermal hysteresis loop (T1/2↑ = 202 K, T1/2↓ = 194 K for 1 and T1/2↑ = 304 K, T1/2↓ = 194 K for 2). Moreover, the light-induced excited spin-state trapping (LIESST) effect was observed for the compounds when the samples were illuminated (1000 nm) at 5 K. We suggest that the introduction of a strong intermolecular interaction, such as π–π stacking, can play an important role in the observed dynamic phase transition.