CW and TR EPR study of photomagnetic properties of heptanuclear Fe(II)–Fe(III) complex

The photomagnetic behavior of a mixed-valence heptanuclear complex [Fe(II)(CN)6{Fe(III)L}6](SCN)2, where L = dianion N,N'-bis(1-hydroxy-2-benzyliden)-1,7-diamino-4-azaheptane, has been investigated. The structure of the complex was optimized using density functional theory with the def2-SVP basis set and the Tao-Perdew-Staroverov-Scuseria functional. Continuous wave (CW) and time-resolved electron paramagnetic resonance (TR EPR) spectroscopy measurements at low temperatures (20-65 K) reveal a reversible, light-induced change in EPR signal intensity, indicating photoswitching between high-spin and low-spin states. The analysis of the CW and TR EPR spectroscopy results identified two types of effects related to sample magnetization: local sample heating by light and magnetization changes associated with photoinduced high-spin to low-spin transitions. These results demonstrate the potential of this complex as a photoswitchable magnetic material.