Photoinduced Magnetism in Heterostructures of a Hofmann-like Framework and a Prussian Blue Analogue

Heterostructured films of the Prussian blue analogue (PBA), K${}_{k}$Ni[Cr(CN)${}_{6}$]${}_{l}$$\cdot$nH${}_{2}$O, and the 3D Hofmann-like Fe(azpy)[Pt(CN)${}_{4}$]$\cdot$mH${}_{2}$O (azpy = 4,4$^\prime$-azopyridine) spin crossover system have been studied by magnetometry and Raman spectroscopy. The magnetization of the ferromagnetic NiCr-PBA, $T_c$~$\approx$ 70~K, can be altered by white light irradiation when coupled with the photoactive Fe-Pt framework. The effect is attributed to interface strain that develops when cooling from room temperature. This lattice distortion is relaxed when irradiation causes the Fe(II) to experience a low spin $(S=0)$ to high spin $(S=2)$ transition at $T\leq 50$~K. This work extends our recent photo-controlled magnetic heterostructures studies\footnote{D. M. Pajerowski \textit{et al.}, J. Am. Chem. Soc. \textbf{132} (2010) 4058; M. F. Dumont \textit{et al.}, Inorg. Chem. \textbf{50} (2011) 4295.} to include Fe(II) spin crossover complexes.