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Metal-Metalloligand Coordination Polymer Embedding Triangular Cobalt-Oxo Clusters: Solvent- and Temperature-Induced
Kun Fan1, Feng Xu2,3, Mohamedally Kurmoo4
1State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210023, People's Republic of China.
Abstract:
Reaction of the metalloligand IrIII(ppy-COOH)3 and the anisotropic paramagnetic CoII ion under solvothermal conditions resulted in a metal-metalloligand coordination polymer, [CoII3(μ3-O)(μ-OH2){IrIII(ppy-COO)2(ppy-COOH)}2(H2O)4]·2DMF·xH2O (I). It consists of trimeric Co3O secondary building units (SBUs) bridged by pairs of Ir to form chains of alternate orthogonal squares. The compound undergoes two single-crystal to single-crystal transformations while retaining its general structural features. A chemical transformation occurs to give [CoII3(μ3-O){IrIII(ppy-COO)2(ppy-COOH)}2(H2O)4(DMF)]·DMF·H2O (II) by soaking in acetone, where a bridging water molecule departs and the solvent DMF bonds to the vacant site of the Co center. Both I and II undergo a temperature-induced transformation to [CoII3(μ3-O){IrIII(ppy-COO)2(ppy-COOH)}2(H2O)3(DMF)]·DMF (III), where one more coordinated water molecule is lost. The major difference in the three phases is in the Co coordination spheres, which have considerable consequences on the magnetism. Compound I displays paramagnetism down to 2 K, whereas II and III show weak ferromagnetism with TC values of 14 and 17 K, respectively.
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