Modulation of the Interlayer Structures and Magnetic Behavior of 2D Spin-Crossover Coordination Polymers [FeII(L)2PtII(CN)4]



Two 2D Hofmann-type spin-crossover coordination polymers, [Fe(stpy)2Pt(CN)4]·0.5MeOH (stpy = 4-styrylpyridine; 1) and [Fe(pep)2Pt(CN)4] {pep = 4-(2-phenylethyl)pyridine; 2}, have been prepared by using long co-ligands with different flexibilities. These compounds form 3D interdigitate structures based on 2D layers extended by Pt–CN–Fe linkages with different interlayer structures depending on the nature of the axial co-ligand. The stpy co-ligand forms one-directional π–π networks between the layers, whereas pep forms two-directional π–π networks as a result of its perpendicularly twisted structure. Coordination polymer 1 exhibits a half-spin transition with Tc = 106 K and Tc = 110 K. In contrast, coordination polymer 2 shows a sharp, two-step spin transition in the temperature range 184–236 K. The difference in spin-transition behavior is discussed in terms of the interlayer packing structure.