Metalorganic frameworks based on the 1,4-bis(5-tetrazolyl) benzene ligand: The Ag and Cu derivatives

The recently proposed high-yield synthesis of the 1,4-bis(5-tetrazolyl)benzene ligand (H2btb) allowed the preparation of three new metal organic frameworks, namely Ag2(btb), 1, Cu2(btb), 2, and Cu2(OH)2(btb), 3. These polycrystalline materials were fully characterised by spectroscopic, gas adsorption, thermal and diffraction methods, the latter revealing rather dense frameworks for 1 and 3. Despite many different synthetic approaches, 2 invariably gave a poorly resolved, but highly reproducible, powder diffraction trace, hampering a complete structural characterisation. Magnetic measurements performed on 3 showed that it behaves as an antiferromagnetic material, the r.t. magnetic moment per Cu atom being only 1.24 BM. The reactivity of 1 was proved in excess of triphenylphosphine (PPh3), allowing the isolation of the dinuclear species 4, [(PPh3)3Ag]2(btb). An additional species 5, formulated as [(PPh3)Ag]2(btb), could be selectively isolated on varying the reaction conditions; at variance, pyrazine, in solution or in molten form, did not react with 1.