Reversible Photo- and Thermo-Induced Spin-State Switching in a Heterometallic {5d-3d} W2Fe2 Molecular Square Complex

Following the complex-as-a-ligand strategy, self-assembly of [W(CN)(8)](3-) and iron(II) with bidentate nitrogen donor ligand bik (bik = bis(1-methyl-1H-imidazol-2-yl)ketone) ligand affords a cyanide-bridged [W2Fe2] molecular square complex [HNBu3](2){[W(CN)(8)](2)[Fe(bik)(2)](2)}center dot(H2O)-H-6 center dot CH3OH (1). The complex was characterized by single-crystal X-ray diffraction analyses, (photo)magnetic studies, optical reflectivity, electrochemical studies, and spectroscopic studies. Structural analyses revealed that in the [W2Fe2] square motif tungsten(V) and iron(II) centers reside in an alternate corner of the square and are bridged by the cyanide ligands. Complex 1 exhibits thermo-induced spin crossover (SCO) between {W-V (S = 1/2) - Fe-LS(II) (S = 0)} and {W-V (S = 1/2) - Fe-HS(II) (S = 2)} pairs near room temperature and photoinduced spin-state switching with T-LIESST = 70 K under light irradiation at low temperature. To the best of our knowledge, 1 represents the first complex containing iron(II) and [W-V(CN)(8)](3-) units exhibiting both SCO and photomagnetic effect.

Automated summary

By utilizing the complex-as-a-ligand strategy, a cyanide-bridged [W2Fe2] molecular square complex has been successfully self-assembled, demonstrating thermo-induced spin crossover and photoinduced spin-state switching effects.