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Metal–organic frameworks (MOFs) as proton-conductive materials have attracted increasing attention due to their applications in proton-exchange membrane fuel cells. While the majority of the MOFs are based on transition metals, group II metals with unusual configurations have received relatively less attention. In this work, we selected three tetrazole-based acetic acids, N,N-di(2-carboxymethyltetrazol-5-yl)amine (H2L1), 1,3,5-tri(2-carboxymethyltetrazol-5-yl)benzene (H3L2), and 4,5-di(tetrazol-5-yl)imidazolylacetic acid (H3L3), as ligands and prepared three MOFs with barium(II) ions: [Ba2(L1)2(H2O)5]·2H2O (1), (Me2NH2)[Ba(L2)(H2O)]·3H2O (2), and [Ba3(μ2-H2O)(L3)2(H2O)3]·2H2O (3). Ba-MOFs have been unambiguously characterized by elemental, FT-IR spectroscopy and single-crystal X-ray diffraction analyses. In the solid state, 2D MOF 1 with two nine-coordinated Ba(II) centers shows a rare hula hoop-like geometry at the Ba1 atom and a distorted tricapped trigonal prismatic geometry around the Ba2 one. Unusual sphenocorona geometry is also found in MOF 2 with a ten-coordinated Ba(II) ion. In MOF 3, three different Ba(II) ions coexist with two nine-coordinated Ba1 and Ba2 displaying a muffin-like configuration and a distorted tricapped trigonal prism geometry, respectively, and an eight-coordinated Ba3 having a distorted biaugmented trigonal prism geometry. In addition, MOF 2 exhibits an unprecedented trinodal 3,7,7-connected 3D network with the Schläfli symbol (37·46·52·62·74)(37·46·52·63·73)2(63) and MOF 3 displays a novel trinodal 4,5,9-connected 3D framework with the Schläfli symbol (421·615)(45·6)(48·62). Due to the presence of extensive hydrogen bonded networks consisting of dimethyl ammonium and water molecules in the 1D channels, MOF 2 shows a high proton conductivity of 4.47 × 10−3 S cm−1 at 85 °C and 98% relative humidity (RH). [ABSTRACT FROM AUTHOR]

The catalytic activities of eight copper(i) halide clusters assembled from copper(i) halide and ferrocenyltelluroethers, 1–8, were investigated in C–N formation under various conditions. A catalytic procedure using poly(ethylene glycol) (PEG-400) as a greener alternative organic solvent has been developed. The PEG-400/5 system can achieve 99% targeted yield with a mild reaction temperature and short reaction time. After the isolation of the products by extraction with diethyl ether, this PEG-400/cluster system could be easily recycled. Spectroscopic studies elucidate a stepwise mechanism: firstly, proton-coupled electron transfer (PCET) involving the transfer of an electron from Cu+ and a proton from imidazole results in the formation of a labile penta-coordinated Cu2+ and aryl radical; the following effective electron transfer from the ferrocene unit reduces Cu2+ and forms the target product; finally, the ferrocenium unit is reduced by the I− anion. The merits of this eco-friendly synthesis are the efficient utilization of reagents and easy recyclability. [ABSTRACT FROM AUTHOR]

Three 3D lanthanide–organic frameworks (LOFs), [LnL(HCO2)(DMF)]n (Ln = Eu (1), Gd (2), Dy (3); H2L = 2,2′-dimethoxy-4,4′-biphenyldicarboxylic acid), have been prepared by the solvothermal reaction of Ln(NO3)3·6H2O and H2L in DMF–H2O mixed solvent. Crystallographic data show that LOFs 1–3 are isomorphous and crystallize in the orthorhombic space group Pna21. Each Ln(iii) is eight-coordinated to four O atoms from four L2− ligands, one O atom from the DMF molecule and three O atoms from HCO2−. The adjacent Ln(iii) ions are linked by the carboxylate groups of the L2− ligands and HCO2− to form a 1D inorganic rod-shaped [Ln(CO2)2(HCO2)]n chain as a secondary building unit (SBU). The infinite 1D chains are interconnected by the biphenyl groups, giving rise to a 3D framework along the c axis. LOFs 1–3 are the first neutral Ln-carboxylate/HCO2− chain-based sra-nets. 1 exhibits characteristic luminescence of Eu3+ upon 343 nm excitation. The investigation of magnetic properties shows very weak ferromagnetic interactions (J = 0.0092(3) cm−1) between Gd(iii) ions in 2 with a Gd–O–Gd bridging angle of 125.6(1)°, and ϑ = −1.9(2) K in 3 due to thermal depopulation of the Stark levels of Dy(iii) ions and/or the possible antiferromagnetic interactions between Dy(iii) ions in contrast to the single-ion behavior observed in 1. [ABSTRACT FROM AUTHOR]