2D Coordination Polymer Built from Lithium Dimethylmalonate and Co II Ions: The Influence of Dehydration on Spectral and Magnetic Properties

2D coordination polymer [Li 2 Co(H 2 O) 4 (Me 2 Mal) 2 ] n ( 1 ) was synthesized by interaction of lithium dimethylmalonate (Li 2 Me 2 mal) and cobalt(II) acetate. The structure of 1 can be described as {Li(H 2 O) 2 (Me 2 Mal‐κ‐ O , O′ )} anions linked by Co II cations through bridging water molecules and Me 2 Mal 2– dianions. Upon heating to 130–190 °C, compound 1 loses water molecules and transforms into [Li 2 Co(Me 2 Mal) 2 ] n ( 2 ). Compound 2 is non‐porous and amorphous, its rehydration by water leads to formation of 1 , as shown by powder XRD. Dehydration of 1 is associated with a drastic color change from pink to violet. The temperature dependency of magnetic susceptibility χ M for 1 in the range 2–300 K was analyzed by using a model, which takes into account spin–orbit coupling in Co II and exchange interactions as a molecular field. Transformation 1 → 2 leads to less than 6 % change of χ M T in the temperature range 2–300 K; this small change of magnetic susceptibility is consistent with conclusions that most of the Co II ions in 2 are in pseudo‐octahedral donor sets. Analysis of the χ M T versus T curve for 2 was performed by using three models, which consider magnetism of uniform Co II ions or the co‐existence of Co II species in different donor sets.