Bis(pyrazolato)-Based Metal-Organic Frameworks Fabricated with 4,4′-Bis((3,5-dimethyl-1H-pyrazol-4-yl)methyl)biphenyl and Late Transition Metals

The reaction between the flexible, bis(pyrazolato)-based ligand 4,4'-bis((3,5-dimethyl-1H-pyrazol-4-yl)methyl)biphenyl (H2DMPMB) and late transition metal ions allowed the isolation of the two series of thermally stable metal-organic frameworks [M(DMPMB)] (M = Co, Zn, Cd) and [M-2(DMPMB)] (M = Cu, Ag). X-ray powder diffraction (XRPD) structure determinations demonstrated that the anti conformation adopted by the ligand, juxtaposed to its exo-tetradentate coordination mode, induces the formation of a 3-D architecture with nonpervious 1-D channels in the three isomorphous species [M(DMPMB)] and of corrugated 2-D layers in [Cu-2(DMPMB)]. Coupling thermogravimetric analyses and variable temperature XRPD highlighted that the five materials are thermally stable at least up to 300 degrees C, both under nitrogen and in air, the Cd(II) derivative decomposing only at the remarkably high temperature of 500 degrees C. No thermal event could be detected; all the materials preserve their structural motifs up to decomposition. The adsorption properties of the five compounds were assayed toward N-2 at 77 K: while no adsorption was observed for [Cd(DMPMB)], the other species possess estimated BET and Langmuir specific surface areas in the ranges 64(1)-526(3) m(2)/g and 142(4)-713(27) m(2)/g, respectively, thus being an example of the interesting phenomenon known as porosity without pores. Finally, the luminescence properties of the Zn(II), Cd(II), and Cu(I) derivatives were investigated.