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

New three-dimensional spin crossover (SCO) coordination polymers systematically constructed by the novel building unit [Ag (CN)], Fe(3-Br-5-CHpyridine)[Ag (CN)][Ag(CN)] (), Fe(3-Br-5-Clpyridine)[Ag (CN)][Ag(CN)] (), and Fe(3,5-Brpyridine)[Ag (CN)][Ag(CN)] (), have been synthesized and characterized. The bismonodentate binuclear [Ag(CN)] and mononuclear [Ag(CN)] units and Fe atoms assemble to form a 3D network structure. The structures of - 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 -. These compounds display a similar SCO behavior, while the critical temperatures ( ) are shifted by the substituent effect. Due to the identical structures of -, the order of clearly corresponds with the Hammett constant.