Dimorphic Modifications of the Thiocyanato‐Bridged Coordination Polymer [Ni(NCS)2(pyridazine)(H2O)0.5]n with Different Magnetic Properties

Abstract

AbstractReaction of nickel(II) thiocyanate with pyridazine under hydrothermal conditions leads to the formation of the hemihydrate [Ni(NCS)2(pyridazine)(H2O)0.5]n (1I). The crystal structure was determined by X‐ray single‐crystal structure analysis. In the crystal structure two types of NiII cations are found. Both are coordinated by one μ‐1,1‐NCS‐ and two μ‐1,3‐NCS‐bridging thiocyanato anions as well as two μ‐1,2‐bridging pyridazine ligands. The octahedral coordination sphere of Ni1 is completed by one coordinating water molecule and that of Ni2 by one terminal N‐bonded thiocyanato anion. These building blocks are connected into chains, which are further connected into a 2D polymeric network by strong interchain hydrogen bonding. By thermal decomposition of the precursor compound 1I, a new anhydrate [Ni(NCS)2(pyridazine)]n (2) is obtained. On rehydration, this compound transforms into a new polymorphic hemihydrate modification 1II. Magnetic measurements of both forms show completely different behavior: Whereas modification 1I shows a long‐range antiferromagnetic ordering state at TN = 5.4 K, modification 1II only shows Curie–Weiss paramagnetism with weak ferromagnetic interactions.