Nitro-functionalized Bis(pyrazolate) Metal-Organic Frameworks as Carbon Dioxide Capture Materials under Ambient Conditions.

The metal-organic frameworks (MOFs) M(BPZNO2 ) (M=Co, Cu, Zn; H2 BPZNO2 =3-nitro-4,4'-bipyrazole) were prepared through solvothermal routes and were fully investigated in the solid state. They showed good thermal stability both under a N2 atmosphere and in air, with decomposition temperatures peaking up to 663 K for Zn(BPZNO2 ). Their crystal structure is characterized by 3D networks with square (M=Co, Zn) or rhombic (M=Cu) channels decorated by polar NO2 groups. As revealed by N2 adsorption at 77 K, they are micro-mesoporous materials with BET specific surface areas ranging from 400 to 900 m2 g-1 . Remarkably, under the mild conditions of 298 K and 1.2 bar, Zn(BPZNO2 ) adsorbs 21.8 wt % CO2 (4.95 mmol g-1 ). It shows a Henry CO2 /N2 selectivity of 15 and an ideal adsorbed solution theory (IAST) selectivity of 12 at p=1 bar. As a CO2 adsorbent, this compound is the best-performing MOF to date among those bearing a nitro group as a unique chemical tag. High-resolution powder X-ray diffraction at 298 K and different CO2 loadings revealed, for the first time in a NO2 -functionalized MOF, the insurgence of primary host-guest interactions involving the C(3)-NO2 moiety of the framework and the oxygen atoms of carbon dioxide, as confirmed by Grand Canonical Monte Carlo simulations. This interaction mode is markedly different from that observed in NH2 -functionalized MOFs, for which the carbon atom of CO2 is involved.

Syntheses and biological studies of nitroimidazole conjugated heteroscorpionate ligands and related Cu(I) and Cu(II) complexes.

Copper(I) and copper(II) complexes of 5-nitroimidazole conjugated heteroscorpionate ligands have been synthesized. In particular, the new 2,2-bis(pyrazol-1-yl)-N-(2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)acetamide ligand (LHMN) was synthesized by direct coupling of preformed side chain acid with 5-nitroimidazole and its coordination chemistry was investigated towards Cu(I) and Cu(II) acceptors and compared with that of the related 2,2-bis(3,5-dimethyl-1-H-pyrazol-1-yl)-N-(2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)acetamide ligand (LMeMN). The copper(II) complexes {[(LMeMN)2Cu]Cl2} and {[(LHMN)2Cu]Cl2} were prepared by the reaction of CuCl2·2H2O with LHMN or LMeMN ligands in methanol solution. The water soluble copper(I) complexes {[(LMeMN)Cu(PTA)2]}(PF6) and {[(LHMN)Cu(PTA)2]}(PF6) were prepared by the reaction of Cu(CH3CN)4PF6 and 1,3,5-triaza-7-phosphaadamantane (PTA) with LHMN or LMeMN ligands in acetonitrile solution. The new Cu(I) and Cu(II) complexes as well as the corresponding uncoordinated ligands were evaluated for their cytotoxic activity against 2D monolayer cultures of multiple human cancer cell lines and 3D-cultured HCT-15 colon cancer spheroids. Morphological analysis by Transmission Electron Microscopy (TEM) revealed the induction of a massive cytoplasmic vacuolization consistent with a paraptotic-like cancer cell death.