Homochiral Metal-Organic Frameworks for Enantioselective Separations in Liquid Chromatography

Selective separation of enantiomers is a substantial challenge for the pharmaceutical industry. Chromatography on chiral stationary phases is the standard method, but at a very high cost for industrial-scale purification owing to the high cost of the chiral stationary phases. Typically, these materials are poorly robust, expensive to manufacture and often too specific for a single desired substrate, lacking desirable versatility across different chiral analytes. Here we disclose a porous, robust homochiral metal-organic framework (MOF), TAMOF-1, built from copper(II) and an affordable linker prepared from natural L-histidine. TAMOF-1 has shown to be able to separate a variety of model racemic mixtures, including drugs, in a wide range of solvents of different polarity, outperforming several commercial chiral columns for HPLC separations. Although not exploited in the present article, it is worthy to mention that the preparation of this new material is scalable to the multikilogram scale, opening unprecedented possibilities for low-energy chiral separation at the industrial scale

A two-dimensional magnetic architecture with bridging polynitrile and 2,2′\prime -bipyrimidine ligands

A new polymeric, two-dimensional compound [ Co$_{2}$(bpym)(dcne)$_{4}$(H$_{2}$O)$_{2}$] (1) (dcne$^{- }$= [ (CN)$_{2}$CC(O)OEt)] $^{-}$ = 2,2-dicyano-1-ethoxyethenolate anion and bpym = 2,2' bipyrimidine) has been synthesized and characterized by X-ray crystallography. The structure is monoclinic space group $P$2$_{1}$/$a$ and consists of two-dimensional networks of octahedrally co-ordinated Co(II) ions, bridged by bis-bidentate 2,2'-bipyrimidine and $\mu _{2}$-dcne anions. Magnetic measurements revealed a broad maximum in the $\chi$$_{m }$vs T plot at 20 K which is characteristic of antiferromagnetic exchange between the high spin cobalt(II) centres. Key words. Cobalt complexes, magnetic measurements, 2.2'-bipyrimidine

New compounds with bridging dicyanamide and bis-chelating 2,2′-bipyrimidine ligands: Syntheses, structural characterisation and magnetic properties of the two-dimensional materials [Fe2(dca)4(bpym)]·H2O and [Fe2(dca)4(bpym)(H2O)2]

cited By 68International audienceThe new polymeric, two-dimensional compounds [Fe2(dca)4(bpym)]·H2O (1) and [Fe2(dca)4(bpym)(H2O)2] (2) (dca- = dicyanamide anion and bpym = 2,2′-bipyrimidine) have been synthesised and characterised by infrared spectroscopy and X-ray crystallography. Both compounds consist of two-dimensional networks of octahedrally co-ordinated iron(II) cations, bridged by bis-bidentate 2,2′-bipyrimidine and bridging dicyanamide anions. The metals are in a distorted octahedral environment due to the small bite angle of the bpym ligands [75.3(1)° in 1 and 73.7(1)° in 2]. The main difference between the two structures is the co-ordination mode of the dca ligands. In compound 1, the iron(II) cation is linked by four dca bridging ligands and by one bis-chelating bpym. In compound 2, each iron cation is linked by two trans-bridging dicyanamide ligands, one bis-chelating bpym and two unidentate ligands in a cis arrangement (one terminal dicyanamide and one water molecule). The main consequence of the different dca co-ordination modes is that each metal cation is connected to four neighbouring metals in 1 but to only three in 2. Magnetic measurements reveal a broad maximum in the χm vs. T plots at ca. 11 K for both compounds, which is characteristic of antiferromagnetic exchange interactions between the high-spin iron(II) centres (J = -1.6 cm-1, g = 2.20 for 1 and J = -1.8 cm-1, g = 2.15 for 2)

Two hybrid organometallic-inorganic layered magnets from the series [ ZIII{^{\rm III}}Cp2∗{^{*}_{2}}] [ MII{^{\rm II}}MIII{^{\rm III}}(ox)3{_{3}}] studied with μ+\mu^{+}SR

We present zero-field muon spin relaxation (ZF-$\mu^{+}$SR) measurements on two examples of a new series of hybrid organometallic-inorganic layered magnets, namely ferromagnetic [ FeCp$^{*}_{2}$] [ MnCr(ox)$_{3}$] and ferrimagnetic [ CoCp$^{*}_{2}$] [ FeFe(ox)$_{3}$] (where ox = oxalate and Cp$^{*}$ = pentame- thylcyclopentadienyl). Both materials show multi-component muon spin precession signals characteristic of quasistatic magnetic fields at several distinct muon sites. The temperature dependence of the precession frequencies allow critical exponents to be extracted. Possible muon sites are discussed on the basis of dipole field calculations. Key words. Muon-spin relaxation, layered magnets, oxalate complexes

Discrete dinuclear complexes and two-dimensional architectures from bridging polynitrile and bipyrimidine (bpym) ligands: Syntheses, structures and magnetic properties of [M2(bpym)(dcne)4(H2O)2 (M=MnII, CoII) and [M 2(bpym)(dcne)4(H2O)4]· 2H2O (M = FeII, CuII) (dcne-=[(CN)2CC(O)OEt)]-)

cited By 35International audienceOne-pot reactions in aqueous solutions of the polynitrile anion dcne - (2,2-dicyano-1-ethoxyethenolate = [(CN)2-CC(O)OEt)] -] with the MII ions (M = Mn, Fe, Co, Cu) in the presence of bpym (2,2′-bipyrimidine) afford the first mixed dcne/bpym compounds [M2(bpym)(dcne)4(H2O)2] (1: M = Mn; 2: M = Co) and [M2(bpym)(dcne)4(H2O) 4]·2H2O (3: M = Fe; 4: M = Cu). The new compounds have been characterized by IR spectroscopy and X-ray crystallography. Compounds 1 and 2 are isostructural, with each metal ion being located in an MN 5O pseudo-octahedral environment with three N atoms coming from three dcne- ligands, two nitrogen atoms from bpym and one oxygen atom from a water molecule. The extended structures of 1 and 2 are best described as dcne-bridged zigzag chains of MII ions running along the [100] direction; connections of these chains in the [010] direction, by the bis(chelating) bpym ligand, afford 2D structures. Compounds 3 and 4 are isostructural, and consist of discrete dinuclear units involving MN 4O2 octahedrally coordinated MII ions bridged by bis(bidentate) 2,2′-bipyrimidine and terminal dene ligands. Magnetic measurements for the 2D compounds 1 and 2 exhibit maxima in the χm vs. T plots (at about 4.5 K for 1 and about 20 K for 2) which are characteristic of weak antiferromagnetic exchange interactions between the high-spin metal centres. While the dinuclear iron complex 3 presents a similar behaviour (maximum in χm vs. T plot at 12 K), the antiferromagnetic exchange interactions are stronger in the copper complex 4. Fits of magnetic data for compounds 1, 3 and 4 with appropriate models led to J values of -0.6, -1.5 and -99.0 cm-1 respectively. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004