The impact of halogen ions on the guest dependent spin crossover behaviour and porosity of Co(II) one-dimensional coordination polymers [CoX₂(4′-(4-pyridyl)-2,2′:6′,2′′-terpyridine)] (X = Cl and Br)

Discrete Co(II) spin crossover (SCO) compounds have attracted much attention for constructing highly sensitive molecular devices; however, the use of Co(II) SCO-coordination polymers (CPs) in such applications is extremely limited. The syntheses of the one-dimensional Co(II) SCO-CPs, [CoX₂(pyterpy)] (pyterpy = 4′-(4-pyridyl)-2,2′:6′,2′′-terpyridine; X = Cl (1), Br (2)), are presented. The structure of 1 shows a ‘closed’ packing arrangement that exhibits gate-type water adsorption at room temperature while 2 has an ‘open’ packing arrangement that shows type I water adsorption behaviour at room temperature. In addition, both 1 and 2 adsorb CO₂ at 201 K. Following water adsorption, 1·H₂O and 2·H₂O showed cooperative SCO at 226 K and 299 K, respectively.