A New Systematic Construction of Novel Three-Dimensional Spin Crossover Coordination Polymers Based on the [Ag(I) (2)(CN)(3)] Building Unit.

New three-dimensional spin crossover (SCO) coordination polymers systematically constructed by the novel building unit [Ag(I) (2)(CN)(3)], Fe(II)(3-Br-5-CH(3)pyridine)(2)[Ag(I) (2)(CN)(3)][Ag(I)(CN)(2)] (1), Fe(II)(3-Br-5-Clpyridine)(2)[Ag(I) (2)(CN)(3)][Ag(I)(CN)(2)] (2), and Fe(II)(3,5-Brpyridine)(2)[Ag(I) (2)(CN)(3)][Ag(I)(CN)(2)] (3), have been synthesized and characterized. The bismonodentate binuclear [Ag(2)(CN)(3)](-) and mononuclear [Ag(I)(CN)(2)](-) units and Fe(II) atoms assemble to form a 3D network structure. The structures of 1-3 are crystallographically identical, which made up the triply interpenetration combined with complicated intermolecular interactions including Ag···Ag, Ag···X (pyridine substituents) and π-stacking interactions. Magnetic and differential scanning calorimetry studies were performed for 1-3. These compounds display a similar SCO behavior, while the critical temperatures (T (c)) are shifted by the substituent effect. Due to the identical structures of 1-3, the order of T (c) clearly corresponds with the Hammett constant.