One-electron reduction of the complex [(TPyA)2Fe II2(NPhL2-)]2+ (TPyA = tris(2-pyridylmethyl)amine, NPhLH2 = azophenine = N,N′,N″,Nâ€́-tetraphenyl-2,5-diamino-1, 4-diiminobenzoquinone) affords the complex [(TPyA)2Fe II2(NPhL3-•)]+. X-ray diffraction and Mössbauer spectroscopy confirm that the reduction occurs on NPhL2- to give an S = 1/2 radical bridging ligand. Dc magnetic susceptibility measurements demonstrate the presence of extremely strong direct antiferromagnetic exchange between S = 2 FeII centers and NPhL3-• in the reduced complex, giving an S = 7/2 ground state with an estimated coupling constant magnitude of |J| ≥ 900 cm-1. Mössbauer spectroscopy and ac magnetic susceptibility reveal that this complex behaves as a single-molecule magnet with a spin relaxation barrier of Ueff = 50(1) cm-1. To our knowledge, this complex exhibits by far the strongest magnetic exchange coupling ever to be observed in a single-molecule magnet.
ASJC Scopus subject areas
- Colloid and Surface Chemistry