Jin-Li Qi

New Ce(III) sulfate–tartrate-based MOFs: an insight into the controllable self-assembly of acentric metal–organic complexes

Hydrothermal reactions yielded five new Ce(III) sulfate–tartrate-based MOFs, namely, α-[Ce2(H2O)2(L-tar)2(SO4)]·4H2O 1, α-[Ce2(H2O)2(D-tar)2(SO4)]·4H2O 2, β-[Ce2(H2O)2(L-tar)2(SO4)]·4H2O 3, β-[Ce2(H2O)2(D-tar)2(SO4)]·4H2O 4 and Ce2(H2O)3(L/D-tar)(SO4)25. The two α-enantiomorphs (1, 2) crystallize in the polar monoclinic C2 space group, and the two β-enantiomorphs (3, 4) crystallize in the non-polar orthorhombic space group P21212, while 5 crystallizes in the monoclinic space group P21/c. The acentric MOFs 1–4 belong to the 3∞{2∞[M2(H2O)x(tar)b2]Ap}·nH2O family (hereby A = SO42−), and the [Ce2(tar)2] dimeric motifs rig up the 2D positively charged 2∞[Ce2(H2O)2(tar)2]2+ networks of a four-connected uninodal (42·64) topology, which are further pillared by sulfate anions into the 3∞{2∞[Ce2(H2O)2(tar)2](SO4)} framework of the (4,5)-connected dinodal (42·64)(42·67·8) topology with the lattice water molecules in the tunnels. Within 5, the [Ce(tar)] motifs rig up the 2D 2∞[Ce2(H2O)3(tar)]4+ patterns, which were stabilized by sulfate anions to form a 2D 2∞[Ce2(H2O)3(tar)(SO4)]2+ layer of a (3,4)-connected bi-nodal (63)(66) topology, and the 2D layers are pillared by additional sulfate anions into the 3D 3∞{2∞[Ce2(H2O)3(L/D-tar)(SO4)]SO4} framework of an unprecedented (3,4,5,6)-connected penta-nodal (4·62)(4·65)(4·67·82)(44·62)(45·68·82) topology. The results suggest that the acentricity of the 3∞{2∞[M2(H2O)x(tar)b2]Ap}·nH2O MOF is crucially determined by the tartrate forms incorporated in the 2D 2∞[M2(H2O)x(tar)b2] sheet, and the distances between the 2D sheets are tunable by the judicious selection of the pillaring auxiliary ligands. The polar α-MOFs (1, 2) display a promising ferroelectricity with a remnant polarization (Pr) of ca. 0.158 μC cm−2 for 1 (ca. 0.323 μC cm−2 for 2), a coercive field (Ec) of ca. 27.05 kV cm−1 for 1 (ca. 42.00 kV cm−1 for 2), and saturation of the spontaneous polarization (Ps) occurs at ca. 0.335 μC cm−2 for 1 (ca. 0.400 μC cm−2 for 2). The magnetic behaviors of the title compounds obey a modified Curie–Weiss law χ = χTIP + C/(T − θ) with χTIP = 200–230 × 10−6 cm3 mol−1, C = 0.228–0.329 cm3 K mol−1, θ = −0.03– −0.06 K, and the decrease of χMT with the lowering temperature and the negative value of θ may be due to the populations of the Stark levels and/or the possible antiferromagnetic interactions between the Ce3+ ions. Furthermore, the title complexes were subjected to microelemental analyses, IR spectroscopic measurements and thermal analyses, and the results are also discussed.

Three Cu(II) (R)-2-chloromandelato complexes generated from dipyridyl-type ligands with different spacer lengths: syntheses, crystal structures, and ferroelectric properties

Three Cu(II) complexes, Cu2(bpy)(H2O)(Clma)2 (1), Cu2(bpe)(H2O)2(Clma)2 (2), and Cu(bpp)(Clma) (3), were synthesized (HClma = (R)-2-Chloromandelic acid, bpy = 4,4′-dipyridine, bpe = 1,2-di(4-pyridyl)ethylene, bpp = 1,3-di(4-pyridyl)propane). Complexes 1, 2, and 3 are constructed from 1-D coordination arrays generated from Cu2(H2O)(Clma)2, Cu2(H2O)2(Clma)2, and Cu2(Clma)2 moieties and linked through bpy, bpe, and bpp co-ligands, respectively. 1 and 2 are assembled into 3-D supramolecular networks via O–H⋯O hydrogen bonds with topology of (63)(69·8) and (412·63), respectively, and 3 is assembled into a 3-D architecture through C–H⋯O hydrogen bonds with topology of (43·63)(43)(44·65·8)(46·66·83). Compounds 1, 2, and 3 crystallized in acentric space groups P21, P1, and P21, which exhibit significant ferroelectricity (remnant polarization Pr = 0.008 μC cm−2, coercive field Ec = 21.4 kV cm−1, the spontaneous saturation polarization Ps = 0.167 μC cm−2 for 1, Pr = 0.183 μC cm−2, Ec = 1.69 kV cm−1, and Ps = 0.021 μC cm−2 for 3). Results from infrared and thermal analyses are also discussed. Graphical Abstract

Synthesis, Crystal Structure and Magnetic Properties of a Copper(II) p-Formylbenzoate Complex

A new Cu(II) complex was prepared at room temperature from the reaction of p-formylbenzoic acid, phenanthroline, CuCl2⋅2H2O, and NaOH under ethanolic aqueous conditions. The complex has been characterized by X-ray diffraction, IR spectroscopy, TG-DTA analyses, and magnetic measurements. Single-crystal X-ray diffraction analysis indicated that the complex crystallizes in the triclinic space group P1̄ with the cell dimensions a=7.875(2), b=10.724(2), c=15.317(3) Å , α =102.65(3), β =93.71(3), γ =107:64(3)°. The Cu atoms are in the environment of distorted CuN2O3 tetragonal pyramids. These discrete complex molecules are packed through intermolecular π...π-stacking interactions and C-H...O hydrogen bonds forming a supramolecular structure. The title complex obeys the Curie-Weiss law with a Curie constant C=0:53 cm3 K mol-1 and a Weiss constant θ = -0:27 K. The shape of the xmT curve is characteristic of weak ferromagnetic interactions between the Cu(II) centers from 300 to 7 K, while there are weak antiferromagnetic interactions below 7 K. Graphical Abstract Synthesis, Crystal Structure and Magnetic Properties of a Copper(II) p-Formylbenzoate Complex

Three Acentric Cu(II) D-(–)-quinate Complexes: Solvent-Dependent Assemblies, Magnetic and Ferroelectric Properties

Reaction of copper salts and D-(–)-quinic acid (H5L) yielded three complexes, [Cu(H2O)(H3L)]2·2H2O 1, [Cu(H2O)(H4L)(NO3)]n·(H2O)n 2, and [Cu(H2O)(H4L)(ClO4)]n·(2H2O)n 3. An interesting law was observed that solvent selection influenced the structural assemblies, namely, in an aqueous solution utilizing CuCl2·2H2O/Cu(NO3)2·6H2O/Cu(ClO4)2·6H2O and D-(–)-quinic acid only obtained [Cu(H2O)(H3L)]2·2H2O 1, while the environment was replaced by an alcoholic system, afforded three polymers: [Cu(H2O)(H4L)Cl]n·(H2O)n 4, [Cu(H2O)(H4L)(NO3)]n·(H2O)n 2, and [Cu(H2O)(H4L)(ClO4)]n·(2H2O)n 3, respectively. Complex 1 crystallizes in the polar monoclinic C2 space group, while complexes 2 and 3 in the nonpolar orthorhombic space group P212121. In compound 1, the binuclear Cu(II) units are assembled into 3D network through hydrogen bonds and the overall topology can be described as a 7-connected dinodal net topology of (36·48·57) with the Schläfli symbol of (3.3.3.3.3.3.4.4.4.4.4.4.4.4.5.5.5.5.52.52.52). In 2 and 3, the D-(–)-quinic acid anions are function as tetradentate ligands bridging Cu(II) ions to build up 3D metal-organic frameworks (MOFs) with {103} topological representation. The polar complex 1 displays a promising ferroelectricity with a remnant polarization (Pr) of ca. 0.07 μC/cm2, coercive field (Ec) of ca. 2.43 kV/cm, and saturation of the spontaneous polarization (Ps) of ca. 0.128 μC/cm2. The magnetic behavior of 1 suggests significant antiferromagnetic coupling interactions between Cu(II) ions bridged by carboxylic groups, while considerable ferromagnetic coupling interactions in complexes 2 and 3. Furthermore, the title complexes 1–3 were subjected to microelement analyses, IR spectroscopic measurements, and thermal analyses.

(2,2′-Bipyridine-κ2N,N′)bis­(4-formyl­benzoato-κO1)copper(II)

The title mononuclear CuII complex, [Cu(C8H5O3)2(C10H8N2)], is comprised of a CuII cation, two 4-formylbenzoate (L −) ligands and a 2,2′-bipyridine (bipy) ligand. The CuII ion and bipy ligand lie on a crystallographic twofold rotation axis; the CuII ion is coordinated by two N atoms from one bipy ligand and two O atoms from two different carboxylate groups of two L − ligands, exhibiting effectively a distorted square-planar geometry. The complex molecules are interlinked to generate two-dimensional supramolecular layers in the ab plane, formed by C—H⋯O hydrogen bonds, where the O acceptor is the O atom from the carboxylate group not involved in coordination to the CuII ion. The two-dimensional layers are stacked in a sequence via C—H⋯O hydrogen-bonding interactions where the formyl O atom acts as acceptor.

Bis(2,2′-bipyridine-κ2N,N′)(3-methyl­benzoato-κ2O,O′)zinc 3-methyl­benzo­ate–3-methyl­benzoic acid–water (1/1/2)

The title compound, [Zn(C8H7O2)(C10H8N2)2](C8H7O2)·C8H8O2·2H2O, is comprised of a Zn2+ cation, two 2,2′-bipydine (bipy) ligands and one 3-methylbenzoate anion (L −) together with one uncoordinating L − anion, one uncoordinating HL molecule and two lattice water molecules. The ZnII atom is coordinated by four N atoms of two bipy ligands and two O atoms from one L − ligand in a distorted octahedral geometry. Pairs of centrosymmetrically related complex molecules form dimers via slipped π-stacking interactions between bipy ligands with an interplanar distance of 3.470 (4) Å. The dimers are linked into supramolecular chains along [111], via C—H⋯O hydrogen bonds. The uncoordinated L − anions, HL molecules and water molecules are connected with each other via O—H⋯O hydrogen bonds, forming chains between the metal complex chains and binding them together via C—H⋯O contacts. The resulting layers parallel to (010) are further assembled into a three-dimensional supramolecular architecture through additional C—H⋯O interactions.

Bis(2,2′-bipyridine-κ2N,N′)(3-methylbenzoato-κ2O,O′)zinc 3-methylbenzoate–3-methylbenzoic acid–water (1/1/2)

The title compound, [Zn(C8H7O2)(C10H8N2)2](C8H7O2)·C8H8O2·2H2O, is comprised of a Zn2+ cation, two 2,2′-bipydine (bipy) ligands and one 3-methylbenzoate anion (L −) together with one uncoordinating L − anion, one uncoordinating HL molecule and two lattice water molecules. The ZnII atom is coordinated by four N atoms of two bipy ligands and two O atoms from one L − ligand in a distorted octahedral geometry. Pairs of centrosymmetrically related complex molecules form dimers via slipped π-stacking interactions between bipy ligands with an interplanar distance of 3.470 (4) Å. The dimers are linked into supramolecular chains along [111], via C—H⋯O hydrogen bonds. The uncoordinated L − anions, HL molecules and water molecules are connected with each other via O—H⋯O hydrogen bonds, forming chains between the metal complex chains and binding them together via C—H⋯O contacts. The resulting layers parallel to (010) are further assembled into a three-dimensional supramolecular architecture through additional C—H⋯O interactions.

Bis(2,2'-bipyridine-κ(2)N,N')(3-methyl-benzoato-κ(2)O,O')zinc 3-methyl-benzo-ate-3-methyl-benzoic acid-water (1/1/2).

The title compound, [Zn(C8H7O2)(C10H8N2)2](C8H7O2)·C8H8O2·2H2O, is comprised of a Zn2+ cation, two 2,2′-bipydine (bipy) ligands and one 3-methylbenzoate anion (L −) together with one uncoordinating L − anion, one uncoordinating HL molecule and two lattice water molecules. The ZnII atom is coordinated by four N atoms of two bipy ligands and two O atoms from one L − ligand in a distorted octahedral geometry. Pairs of centrosymmetrically related complex molecules form dimers via slipped π-stacking interactions between bipy ligands with an interplanar distance of 3.470 (4) Å. The dimers are linked into supramolecular chains along [111], via C—H⋯O hydrogen bonds. The uncoordinated L − anions, HL molecules and water molecules are connected with each other via O—H⋯O hydrogen bonds, forming chains between the metal complex chains and binding them together via C—H⋯O contacts. The resulting layers parallel to (010) are further assembled into a three-dimensional supramolecular architecture through additional C—H⋯O interactions.

4-[3-(Pyridin-4-yl)prop-yl]pyridinium 2-carb-oxy-benzoate.

In the title molecular salt, C13H15N2 +·C8H5O4 −, the 2-carboxybenzoate anions are joined into a chain along [010] by strong O—H⋯O hydrogen bonds, with the H atoms disordered about the intervening centres of inversion. The presence of N—H⋯O hydrogen bonds between cations generates an additional chain along [010] and parallel to that of the anions. The chains are assembled into a three-dimensional framework via weak C—H⋯O interchain interactions. In the cation, thee dihedral angle between the pyridine rings is 48.91 (4)°.