Hong-Lin Zhu

New pyridine-2,4,6-tricarboxylato coordination polymers: Synthesis, crystal structures and properties

Three new pyridine-2,4,6-tricarboxylic acid (H3ptc) complexes, [Mn3(ptc)2(H2O)9]n (1), [Co3(ptc)2(H2O)2]n (2), and [Co(bpy)(H2O)4]n[Co(ptc)(H2O)]2n (3) were hydrothermally synthesized and characterized by single-crystal X-ray diffraction methods, elemental analyses, IR spectroscopy, thermal analyses and magnetic measurements along with ferroelectric measurement for 1 were carried out. Compound 1 crystallizes in the acentric space groupCc and exhibits significant ferroelectricity (a remnant polarization Pr = 0.0188 μC cm−2, coercive field Ec = 9 kV cm−2, saturation of the spontaneous polarization Ps = 0.1326 μC cm−2). To the best of our knowledge, 1 represents the first example of a pyridine-2,4,6-tricarboxylato coordination polymer that exhibits possible ferroelectric behavior. Within 1, both seven- and six-coordinated Mn2+ ions are bridged by ptc3− anions to generate 1D bands, which are assembled into a 3D supramolecular architecture through extensive hydrogen bonds. The CoN2O4 and CoO6 octahedra in 2 are corner-shared to form 2D sigmoid layers, which are further interconnected by organic linkers into topologically 3D MOF of (32·46·56·6)2(32·48·512·66) type. The six-coordinated Co2+ ions in 3 are bridged by bpy and ptc ligands to give polymeric 1∞[Co(bpy)(H2O)4]2+ chains and 1∞[Co(ptc)(H2O)]1− chains, respectively, and the extensive hydrogen bonds are responsible for the construction of the 3D supramolecular architecture. Additionally, the ptc ligand exhibits two unprecedented coordination modes η5μ2 and η5μ3. The magnetic measurements of 1–3 show overall antiferromagnetic interactions between the metal ions.

A cyclic water octamer in a binuclear copper(II) complex: synthesis, crystal structure, and properties

A cyclic octameric water cluster is trapped in a 3-D supramolecular architecture [Cu2(H2O)2(bpca)2L] 8H2O, where bpca = bis(2-pyridylcarbonyl)amide and L = sebacic acid. The striking feature of the octameric cluster is that each water donates one hydrogen to adjacent waters to form a circular water ring in a (O–H O–H )4 connecting fashion, with the same orientations of OH bonds in the ring. Thermogravimetric and magnetic properties are also reported.

Syntheses, crystal structures, and magnetism of two phenylacetate imidazolate copper(II) complexes

The influence of pH for the reaction system involving CuCl2 · 2H2O, imidazole (Him) and phenylacetic acid (HL) at room temperature was investigated. Cu2(Him)4L4 · 2H2O (1) and Cu3(Him)2(im)2L4 (2) were synthesized at pH 6.5 and 7.5, respectively. In 1, the Cu is coordinated by two nitrogen atoms of two Him and three oxygen atoms from three phenylacetates to form a square pyramid CuN2O3. Adjacent square pyramids share edges to form Cu2N4O4 dimers, which are assembled by hydrogen bonds into a 2-D layer parallel to the (001) plane. In 2, copper atoms are interlinked by im− and L− to form a 2-D layer parallel to (100). The resulting layers have C–H···O hydrogen bonds leading to a 3-D supramolecular architecture. Variable temperature magnetism of 1 and 2 suggests a weak ferromagnetic or antiferromagnetic coupling exchange (J = 0.58 cm−1 for 1, J = −10.24 cm−1 for 2).

Mono-, di-, and trinuclear phosphonate oxygen-bridged copper(II) complexes: syntheses, structures, and properties

Abstract Reactions of copper salts, zoledronic acid, and 2,2′-bipyridine/1,10-phenanthroline in aqueous ethanolic solutions afforded four phosphonate oxygen-bridged copper complexes, Cu(bipy)(H4zdn)(HSO4) (1), [Cu2(bipy)2(H2zdn)(H2O)(Cl)]·4H2O (2), [Cu2(phen)2(H2zdn)(H2O)(Cl)]·2.5H2O (3), and [Cu3(bipy)3(H4zdn)(H2zdn)(SO4)]·5H2O (4) (H5zdn = zoledronic acid, bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline). The copper centers of 1–4 have square pyramidal coordination geometries. The Cu(II) ions are coordinated to bipy/phen, zoledronate, and HSO4−/Cl− forming mononuclear units for 1, dinuclear for 2 and 3, and trinuclear for 4. These building units are further extended into 3-D supramolecular networks via multiple hydrogen bond interactions. Temperature-dependent magnetic properties of 2 and 4 suggest weak antiferromagnetic coupling (J = −4.53(8) cm−1 for 2, J = −1.69(4) cm−1 for 4). The antitumor activity of 2 was evaluated against the human lung cancer cell line and indicates effective time- and dose-dependent cytotoxic effects.

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.

Self-assembly of new Zn(II) supramolecular complexes from 4,4′-dipyridyldisulfide

Three new supramolecular complexes, [Zn(dpds)(C6H5COO)2] n (1), [Zn(dpds)(C7H7COO)2] n (2), and [{Zn(dpds)[C6H4(COO)2]} · H2O] n (3) (dpds = 4,4′-dipyridyldisulfide, C6H5COOH = benzoic acid, C7H7COOH = m-methylbenzoic acid, C6H4(COOH)2 = phthalic acid), have been synthesized by using the flexible ligand 4,4′-dipyridyldisulfide (dpds) with benzoic acid, m-methylbenzoic acid, and phthalic acid. The [Zn(C6H5COO)2] moieties in 1 are connected by dpds to generate a 1-D helical chain. In 2, the [Zn(C7H7COO)2] moieties are bridged by two dpds ligands of different chiralities to form a discrete achiral macrocycle chair-like structure. The ZnN2O2 tetrahedra in 3 are alternately linked by a pair of dpds and phthalato ligands to form a 1-D double-stranded chain, which are assembled via S ··· S weak interactions into a 2-D layer. The resulting 2-D layers are inclined parallel into 3-D supramolecular architecture.

Structural diversity for three Zn(II) coordination polymers from 4-nitrobenzene-1,2-dicarboxylate and bispyridyl ligand

Abstract Three Zn(II) complexes, [Zn2(bpp)2(FNA)2]·H2O (1), [Zn(bpp)(FNA)]·H2O (2), and Zn2(bpp)2(FNA)2 (3) (bpp = 1,3-bi(4-pyridyl)propane, H2FNA = 4-nitrobenzene-1,2-dicarboxylic acid), were synthesized and characterized by single-crystal and powder X-ray diffraction methods, IR spectroscopy, TG analyses, elemental analyses, and fluorescent analysis. In 1, the Zn(II) ions are linked by FNA anions and bpp into 2-D layers. The Zn(II) ions in 2 are bridged by FNA anions into chiral chains, which are interlinked by bpp into 3-D metal–organic framework with (65·8) CdS topology. Complex 3 features 1-D zigzag chains, which are interconnected by bpp ligands to give a 3-D framework with (6·74·8)(64·7·8) topology. Complexes 2 and 3 exhibit significant ferroelectric behavior (for 2 remnant polarization Pr = 0.050 μC cm−2, coercive field Ec = 1.13 kV cm−1, saturation of the spontaneous polarization Ps = 0.239 μC cm−2; for 3 Pr = 0.192 μC cm−2, Ec = 4.64 kV cm−1, Ps = 0.298 μC cm−2).

Structural diversity controlled by alkali/alkaline earth metals for heterometallic AeI/AeII-ZnII coordination polymers based on 4-nitrobenzene-1,2-dicarboxylate

Abstract Six heterometallic Zn(II) coordination polymers, Zn(H2O)3(FNA) (1), [NH4]2[Zn(H2O)2(FNA)2] (2), [ZnNa2(FNA)2]·3H2O (3), [ZnK2(FNA)2]·H2O (4), [ZnRb2(FNA)2]·2H2O (5) and [ZnMg(FNA)2]·4H2O (6) (H2FNA = 4-nitrobenzene-1,2-dicarboxylic acid), were synthesised by introducing different alkali/alkaline earth (AeI/AeII) metals. These complexes exhibit diverse structures with the different AeI/AeII metals used and distinct ligand coordination modes the ions provide. For 1 and 2, the Zn(II) centres with distorted octahedra are connected by FNA to form 1-D chain structures. The Zn(II) centres in 3–6 with distorted tetrahedra are linked by FNA to form 2-D anionic grid layers. For 3–5, these 2-D anionic grid layers are connected by alkali metal (Na, K and Rb) with the O–AeI–O connectivity to exhibit 3-D framework structures, while 6 features a 2-D Zn–Mg network. Luminescence properties of 1–6 have been investigated. Graphical Abstract

Bis(μ-adamantane-1,3-dicarboxyl-ato-κO,O:O,O)bis-[aqua-(3-carboxy-adam-antane-1-carboxyl-ato-κO)(1,10-phen-an-throline-κN,N')erbium(III)] dihydrate.

The asymmetric unit of the binuclear centrosymmetric title compound, [Er2(C12H14O4)2(C12H15O4)2(C12H8N2)2(H2O)2]·2H2O, contains one ErIII atom, one coordinated water molecule, one 1,10-phenanthroline (phen) ligand, two differently coordinated adamantane-1,3-dicarboxylate (H2L) ligands and one lattice water molecule. The ErIII ion is eight-coordinated by four O atoms from bridging L 2−, one O atom from HL −, one O atom from the coordinated water and two N atoms from a phen ligand. Extensive O—H⋯O hydrogen-bonding interactions result in the formation of chains which are further linked into a layer-like network by π–π stacking interactions centroid–centroid distance = 3.611 (3) Å] between adjacent phen ligands belonging to neighbouring chains. The carboxy group of the HL − ligand is equally disordered over two positions.

catena-Poly[[[diaqua-copper(II)]-bis-(μ(2)-di-4-pyridyl disulfide-κN:N')] bis-(hydrogen phthalate) monohydrate].

The asymmetric unit of the title compound, {[Cu(C10H8N2S2)2(H2O)2](C8H5O4)2·H2O}n, contains one CuII ion, two bridging di-4-pyridyl disulfide (4-DPDS) ligands of the same chirality, two coordinating water molecules, two hydrogen phthalate anions and one uncoordinated water molecule. The polymeric structure consists of two types of polymeric chains, each composed from repeated chiral rhomboids. The CuII ions adopt a distorted octahedral coordination geometry and are coordinated by four pyridine N atoms and two water O atoms. The coordinated water molecules and hydrogen phthalate anions are located between the repeated rhomboidal chains, and form hydrogen bonds with the coordinated water molecules.