Two cobalt(II) compounds, namely, {[Co(HL)(bpy)(H2O)2]·DMF}n (1), and {[Co(HL)(bpe)]·0.5bpe}n (2) (H3L = 1,3-bis(2-carboxylphenoxy)benzoic acid, bpy = 4,4′-bipyridine, bpe = 4,4′-vinylenedipyridine), have been synthesized using cobalt(II) transition metal salt with phenolic carboxylic acid and different N-donor ligands. The compounds were fully characterized by elemental analysis, infrared spectroscopy (IR), single crystal X-ray diffraction analysis, and thermogravimetric analysis (TGA). Both compounds exhibit 2-D (4,4)-sql networks but with a wavelike and a double layered arrangement, respectively. Remarkably, these two compounds not only exhibit field-induced single-ion relaxation magnetization but also exceptional catalytic activities of benzylic C–H oxidation (conv. 90.3–99%; sele. 98.1–99%).

•Two helical Eu(III) metal-organic frameworks were solventhermally synthesized in different solvents.•Both complexes can sensitively and selectively detect nitrobenzene and Cu2+ ions.•The mechanism of sensing properties were discussed in details.Two helical Eu(III) metal-organic frameworks, namely, {[Eu(L)(DMF)(H2O)]·0.5DMF}n (1) and [Eu(L)(DEF)(H2O)]n (2) (H3L=3,5-bis(2-carboxylphenoxy)benzoic acid, DMF=N,N-dimethylformamide, DEF=N,N-diethylformamide), have been solvothermally synthesized in different solvents, respectively. Both complexes possess helical structures through the connectivity of Eu atoms and phenolic-oxygen containing branches of the flexible multicarboxylate ligand. Based on different helices, these two complexes exhibited hexagonal and tetragonal channels, respectively. Both complexes possess (3,6)-connected (4.62)2(42.610.83) topology but with different long Schlafli symbol. The solvent plays an important role in the formation of the final frameworks. Both complexes can sensitively and selectively detect nitrobenzene and Cu2+ ions.Two helical Eu(III) compounds were synthesized from a phenolic multicarboxylate ligand, showing fluorescence sensing towards nitrobenzene and Cu2+ ions.Download high-res image (333KB)Download full-size image

•Two Zn(II) compounds were synthesized from two flexible phenolic carboxylic acid ligands.•These compounds were stable in the water and exhibit pH sensing properties.•The analytical efficiency in practical applications was performed on the real lake water.Two 2-D Zn(II) compounds, namely, [Zn(HL1)(bpy)]n (1) and {[Zn(HL2)(bpe)]·0.5bpe}n (2) (H3L1 = 5-(2′-carboxyl phenoxy)isophtalic acid, H3L2 = 1,3-bis(2-carboxylphenoxy)benzoic acid, bpy = 4,4′-bipyridine, bpe = 4,4′-vinylenedipyridine), have been solvothermally synthesized from two flexible phenolic carboxylic acid ligands. Both compounds exhibit 2-D layered structures with 4-conneted 44 and 3- connected 63 topology, respectively. PXRD indicated that these compounds were stable in the basic conditions with pH range of 7–11 and their fluorescence intensities are strongly correlated with the pH value. The protonated carboxylic groups may have influences on the resulting fluorescence intensities. The possible proton transfer mechanism was discussed for such pH sensors in details through FTIR and ICP measurements. In addition, the analytical efficiency and accuracy in practical applications of these sensors were performed on the real lake water.Two water-stable 2-D Zinc(II) compounds were reported with pH-dependent fluorescence sensing activities.Download high-res image (89KB)Download full-size image

From a methyl-substituted thieno[2,3-b]thiophene dicarboxylate, three types of three-dimensional (3-D) microporous lanthanide-based metal–organic frameworks, {[Ln(DMTDC)1.5(H2O)2]·DEF}n (type I, Ln = Eu 1, Tb 2), {[Ln(DMTDC)1.5(H2O)2]·0.5DMF·0.5H2O}n (type II, Ln = Gd 3, Dy 4, Er 5), and {[Ln4(DMTDC)6(DMF)2]·0.5DMF·1.5H2O}n (type III, Ln = Er 6) (H2DMTDC = 3,4-dimethylthieno[2,3-b]thiophene-2,5-dicarboxylic acid, DEF = N,N′-diethylformamide, DMF = N,N′-dimethylformamide), have been solventhermally synthesized. Types I and II are isostructural, which exhibit 1-D triangular channels constructed by double-stranded rod-shaped {Ln(CO2)2}n chains. Type III demonstrates an intriguing framework with triple-stranded rod-shaped {Ln(CO2)3}n chains arranged along the (1,1,0) and (1,–1,0) axes and possesses two kinds of triangular channels along two axes, respectively. Immobilization of the Lewis basic sites of thiophene groups induced gas adsorption and sensing properties into these microporous frameworks. Complexes 5(Er) and 6(Er) display moderate adsorption properties toward N2 and CO2, and the Qst of CO2 are as high as 36.3 and 34.8 kJ mol–1, respectively. Complexes 1(Eu) and 2(Tb) exhibit sensing properties toward nitrobenzene, acetone, and the Cu2+ ion in both DMF and aqueous solution. Complex 3(Gd) shows a significant magnetocaloric effect with ΔSm = 24.3 J·kg–1·K–1 at 3.0 K and 7 T. Complex 4(Dy) exhibits slow magnetic relaxation with the energy barrier Δ/kB of 48.29 K.

Two types of lanthanide coordination polymers, namely, [Ln(PA)(NO3)(DMA)3]n (Ln=Gd (1), Dy (2), Eu (3), Tb (4)) (type I), and {[Ln2(PA)3(DMF)4]·2DMF} (Ln=Eu (5), Tb (6)) (type II) (PA=Pamoic acid, DMA=dimethylacetamide, DMF=N,N-dimethylformamide), have been synthesized by the reaction of Ln(NO3)3·6H2O with pamoic acid through layer diffusion method. These complexes were characterized by single crystal X-ray diffraction, infrared spectroscopy (IR), thermogravimetric analysis (TGA), fluorescence and magnetic measurements. Solvents and lanthanide atoms in the reaction play an important role in controlling different structures. Type I demonstrated 1-D linear chain structure connected by Ln atoms and PA ligands. Type II exhibited non-interpenetrating 3-D 6-connected 43612 nets based on binuclear [Ln2(CO2)6(DMF)4] cores. Magnetic properties of complexes 1–4 were investigated in details. Complex 1 shows significant magnetocaloric effect with–ΔSm=20.37 J kg–1 K–1 at 3.0 K and 7 T. Complex 2 exhibits slow relaxation of the magnetization. Complexes 3–6 exhibit both ligand- and metal-centered fluorescent properties. Complex 6 demonstrates fluorescent sensing of DMF and Cu2+ ion.

Four coordination complexes based on two amino-alcohol derived Schiff base ligands, namely, [Cu(H2L1)(Cl)]·CH3OH (1), [Cu4(HL2)2(H2L2)2(H2O)(C2H5OH)]·2(ClO4)·2(C2H5OH) (2), [Ni2(H2L1)2(OAc)2(C2H5OH)2]2 (3) and [Ni4(HL2)3(μ3-O)(H2O)3]·9H2O (4) (H3L1 = {2-ethyl-2-((2-hydroxybenzylideneamino)propane-1,3-diol), and H3L2 = 2-ethyl-2-((2-hydroxy-3-methoxybenzylideneamino)propane-1,3-diol)}), were synthesized and characterized. Alkoxo and phenoxo groups of the Schiff base ligands bridge the metal atoms in diverse modes, leading to interesting mononuclear (1), dinuclear (3), and tetranuclear (2 and 4) complexes, respectively. The in vitro cytotoxic effect of these complexes on cancerous cell lines, including the human lung carcinoma cell line (A549), human colon carcinoma cell lines (HCT-116), human promyelocytic leukemia cells (HL-60) and the chronic myelogenous leukemia cell line (K-562) showed that all these complexes exhibited substantial cytotoxic activity. Their interactions with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) were also investigated using UV-visible, fluorescence and synchronous fluorescence spectroscopic methods. All complexes could quench the intrinsic fluorescence of BSA in a static quenching process. Variable temperature magnetic properties of these complexes were investigated in details. The nuclearity and metal centers play an important role in the properties of the complexes.

Eight mixed-ligand coordination compounds, [Zn(PA)(bpp)]n (1), {[Cd(PA)2(Hbpp)2(H2O)2]·2H2O}n (2), [Zn(PA)(bbi)]n (3), [Cd(PA)(bbi)(H2O)]n (4), {[Cd3(PA)2(bbi)3(Cl)2]}n (5), {[Zn6(PA)5(datrz)2(Hdatrz)2(H2O)2]·16DMF}n (6), [Cd2(PA)(datrz)2(DMF)2]n (7), and {[Cd2(PA)2(bix)2(DMF)2]·4DMF}n (8) (bpp = 1,3-bi(4-pyridyl)propane, bbi = 1,4-bis(imidazol-1-yl)butane, H2datrz = 3,5-diamino-1,2,4-triazole, bix = 1,4-bis(imidazol-1-ylmethyl)benzene), have been synthesized through the reaction of zinc and cadmium salts with pamoic acid (H2PA) and different N-donor ligands. The assembly of the ligands in different coordination modes and conformations leads to fascinating structures. 1 and 3 afford an interpenetrating polythreaded 2D → 3D motif composed of 44 sql undulated sheets, while right- and left-helices are alternatively arranged in 3. 2 possesses an interesting 3-D supramolecular network with 1-D hydrogen-bonded chains spanning different directions. 4 and 5 display both polyrotaxane and polycatenane characteristics. In 4, two 2,4-connected (4·85) nets interlocked with each other, forming a 2D → 2D polycatenating network. 5 exhibits a twofold interpenetrated (3,5,6)-connected (3·5·6)(3·52·67)(32·54·66·72·9) topology. 6 and 7 represent rare pentanodal (3,4)-connected and binodal (3,4)-connected frameworks with topologies of (4·5·6)(4·8·10)(52·6·8·9·11)(4·5·6·8·92)(4·5·7) and (4·6·8)(4·62·83), respectively. 8 displays 3-fold interpenetrated 4-connected SrAl2 topology with flexible bix ligands bridging Cd centers to form right- and left-helices. The mixed-ligand effect of the conformations of the PA ligand and N-heterocyclic coligands as well as the metal centers on the assembly of frameworks is unravelled in detail. Solid-state luminescence properties of all compounds were reported as well. Moreover, fluorescence properties of compounds 6 and 8 in various solvent suspensions at room temperature have also been investigated.

Five new complexes, [Co3(HL1)2(Py)8]·4CH3OH (1), [Ni3(HL1)2(Py)4]2·2DMF (2), [Co3(H2L2)2(Py)8]·2NO3 (3), [Ni2(HL2)(Py)6] (4) and [Cu4(HL2)2(Py)4]·4DMF (5) (H4L1 = N-propionyl-4-hydroxysalicylhydrazide, H44-hopshz; H5L2 = N-(3-carboxy-cis-2-propenoyl)-4-hydroxysalicylhydrazide, H54-hocpshz) have been obtained from two N,N′-diacylhydrazide ligands and characterized by elemental analysis, FT-IR, X-ray diffraction and antimicrobial activities. These di-, tri-, and tetrameric complexes are connected into three-dimensional supramolecular architectures with interesting topologies through O–H⋯O, C–H⋯O and C–H⋯π interactions. 1–3 are linear trimeric complexes with the ligands triply-deprotonated. Topological analysis indicates that they exhibit 2D (4,4), 3D (6,8)-connected (3349526)(3441257647) and 8-connected (42563) net, respectively. 4 and 5 possess dimeric and tetrameric structures, which are extended into 7-connected (33413536) and 4-connected (4,4) net, respectively.Based on two different N,N′-diacylhydrazides by changing the terminal groups from propionyl to 3-carboxy-cis-2-propenoyl, we have obtained five transition metal complexes with polynuclear structures. Two ligands exhibit diverse coordination modes due to the deprotonation and flexibility as well as different coordination geometry of metal centers. Through different O–H⋯O, C–H⋯O and C–H⋯π weak interactions, novel supramolecular nets are obtained.

Six complexes based on a flexible tripodal ligand H3TTTA (2,2′,2″-[1,3,5-triazine-2,4,6-triyltris(thio)]tris-acetic acid) have been hydrothermally synthesized and structurally characterized. X-ray single-crystal diffractions reveal that they have rich structural chemistry: mononuclear, [Zn(HTTTA)(2,2′-bpy)(H2O)3]n (1); dimeric metallamacrocycle, [Zn(HTTTA)(2,2′-bipy)(H2O)]n (2) and [Cd(HTTTA)(2,2′-bipy)(H2O)·H2O]n (3); two-dimensional networks with binodal (3,6)-connected CdI2 topology based on linear trinuclear M3(μ2–CO2)4(μ2–CO2)2 SBUs (Secondary Building Units), [M3(TTTA)2(2,2′-bipy)2(H2O)m·nH2O]n (M=Zn·4, m=0, n=4; Cd·5 and Mn·6, m=2; n=2). The value of pH and the metal ions has large influences on the resulting structures. The flexible tricarboxylic acid exhibits four coordination modes from monodentate to μ6-bridge. Fluorescence and magnetic properties of the complexes have also been investigated in details.Graphical abstractSix complexes based on a flexible tricarboxylate ligand exhibit rich structural chemistry from mononuclear to 2D (3,6)-connected networks. PH and metal ions have large influences on the resulting structures.Highlights► Six complexes based on a flexible multicarboxylate ligand have been reported. ► They exhibit diverse structures from mono- and binuclear molecules to 2-D layers. ► pH and metal ions have large influences on the final products.

Five novel Cu(II) metal–organic coordination polymers, [(CuL1)n] (1), [Cu2L22(Py)4] (2), [Cu(HL3)(DMF)2] (3), [Cu6L43(Py)6·H2O]n (4), [Cu6L43(Py)8(C10H8N2)2·8CH3OH]n (5) (H2L1 = N-2-hydroxy-naphthaldehyde-1-alkenyl-o-amino acid, H2L2 = N-2-hydroxy-naphthaldehyde-1-alkenyl-m-amino acid, H2L3 = N-2-hydroxy-naphthaldehyde-1-alkenyl-o-amino-terephthalic acid), have been synthesized and characterized by IR, elemental analysis, UV spectroscopy and single-crystal X-ray diffraction analyses. Complex 1 possesses helical chain structure, which are further assembled to form three-dimensional frameworks by π⋯π stacking interactions. Complex 2 and 3 exhibit dimeric and monomeric structure. Complex 4 is a novel two-dimensional layer structure based on two kinds of binuclear Secondary Building Units (SBUs), Cu2O2 and Cu2(CO2)4. Complex 5 exhibits a distorted zigzag chain by the alternate connectivity of L and bpy molecules. This result shows that the position of carboxylate groups play an important role in the formation of supramolecular networks.Highlights► Five Cu(II) coordination compounds based on three novel Schiff bases were reported. ► They exhibit interesting structural diversity. ► The positions of carboxylate groups play an important role.

Two cobalt(II) compounds, namely, {[Co(HL)(bpy)(H2O)2]·DMF}n (1), and {[Co(HL)(bpe)]·0.5bpe}n (2) (H3L = 1,3-bis(2-carboxylphenoxy)benzoic acid, bpy = 4,4′-bipyridine, bpe = 4,4′-vinylenedipyridine), have been synthesized using cobalt(II) transition metal salt with phenolic carboxylic acid and different N-donor ligands. The compounds were fully characterized by elemental analysis, infrared spectroscopy (IR), single crystal X-ray diffraction analysis, and thermogravimetric analysis (TGA). Both compounds exhibit 2-D (4,4)-sql networks but with a wavelike and a double layered arrangement, respectively. Remarkably, these two compounds not only exhibit field-induced single-ion relaxation magnetization but also exceptional catalytic activities of benzylic C–H oxidation (conv. 90.3–99%; sele. 98.1–99%).