Amine‐Templated Cobalt(II) Coordination Polymer Exhibiting Novel Magnetic Properties: Effect of Dehydration

An amine‐templated 2D coordination polymer of Co II with the formula {[EDAH 2 ][Co 2 F 2 (SO 4 ) 2 (H 2 O) 2 ]} n ( 1 ) (EDA = ethylenediamine), has been synthesised and structurally characterised. It consists of a 1D chain bridged by F – ions, which are interconnected by SO 4 2– tetrahedra forming a 2D [Co 2 F 2 (SO 4 ) 2 (H 2 O) 2 ] n 2– corrugated sheet. The diprotonated cation [EDAH 2 ] is intercalated between the sheets. Temperature‐dependent magnetic measurements reveal the presence of spin‐canted antiferromagnetism and hard‐magnet‐like behaviour with large a magnetic hysteresis with a coercive field ( H c ) of 16.2 kOe and a remnant magnetisation ( M R ) of 1.64 μ B . The coordinated water molecules in 1 can be removed by heating at 250 °C under vacuum to obtain the dehydrated phase {[EDAH 2 ][Co 2 F 2 (SO 4 ) 2 ]} n ( 1′ ), which – upon exposure to water vapour for 24 h – gave the monoaqua compound, {[EDAH 2 ][Co 2 F 2 (SO 4 ) 2 (H 2 O)]} n ( 1″ ). This dehydration/rehydration process is accompanied by a structural transformation and a magnetic phase transition between the spin‐canted antiferromagnetic state of the hydrated phase to the antiferromagnetic state of the dehydrated phase.