A First and Homoleptic Rare Earth 3D-Bipyrazolate MOF: (3)(infinity)[Eu(Me(4)BpzH)(3)(Me(4)BpzH(2))]

The homoleptic framework (3)(infinity)[Eu(Me(4)BpzH)(3)(Me(4)BpzH(2))], Me(4)BpzH(-) = 3,3',5,5'-tetramethyl-4,4'-bipyrazolate anion, C10H13N4-, Me(4)BpzH(2) = 3,3',5,5'-tetramethyl-4,4'-bipyrazole, C10H14N4, is obtained by a high-temperature oxidation of the metal curopium with a self consuming melt of 3,3',5,5'-tetramethyl-4,4'-bipyrazole above 300 degrees C. The framework structure initiates from a three-dimensional linkage of curopium atoms and bridging ligands that coordinate with one nitrogen atom of each aromatic ring linking eta(1):eta(1) through front and backside of the bicyclic ring system. The framework has a (4,8) topology and is the first example of a rare earth bipyrazolate. Thus, for the trivalent eightfold by nitrogen atoms coordinated europium, a sterically rather crowded ligand with four methyl groups is able to yield a 3D-framework. The crystal structure was refined from systematically eightfold twinned crystals as meroedric fourfold twins with a subsequent racemic twinning of the fourfold twin individuals.