Modulation of the interlayer structures and magnetic behavior of 2D spin-crossover coordination polymers [Fe^II(L)₂Pt ^II(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 twodirectional 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 spintransition behavior is discussed in terms of the interlayer packing structure.