Monodentate Carboxylate Groups Research Articles

Hydrothermal syntheses, structures and properties of two zinc complexes based on an azobenzene carboxylate ligand

Abstract Two zinc complexes [Zn(LH)2(phen)] (1) and [Zn(L)(H2O)] n (2) (LH− = 2-hydroxy-5-((3-nitrophenyl)azo)-benzoate, phen = 1,10-phenanthroline) were synthesized by hydrothermal methods and characterized by elemental analysis and IR spectroscopy. Complexes 1 and 2 crystallize in mononuclear and polymeric structures, respectively, where ligands L 2− are coordinated to the zinc ions via their carboxylate and phenolate groups in η 2,μ 2,κ 2 and η 2,μ 2,κ 1 mode, respectively. Introduction of the auxiliary chelating phen ligand results in the chelation of the zinc ions in 1 through both the phen ligand and the carboxylate group of the first LH− anion assisted further by the monodentate carboxylate group of the second LH− anion. In complex 2 the L 2− anions act as tridentate ligands utilizing their carboxylate and phenolate groups to coordinate to three zinc ions. The phenolate oxygen atom bridges two zinc ions resulting in the generation of a layer structure. Fluorescence measurements have indicated that complexes 1 and 2 exhibit similar luminescence emissions around 393 and 387 nm, respectively, which originate from intra-ligand π-π* transitions. The emission intensities were strengthened relative to the sodium complex NaLH owing to the enhancement of the rigidity of the aromatic system through the coordination interactions of the ligands with the more tightly bound zinc ions. Furthermore, the suspension of complex 2 can be used to selectively detect Fe3+ cations via the luminescence quenching process.

Optimized Coordination of Uranyl in Engineered Calmodulin Site 1 Provides a Subnanomolar Affinity for Uranyl and a Strong Uranyl versus Calcium Selectivity.

As an alpha emitter and chemical toxicant, uranium toxicity in living organisms is driven by its molecular interactions. It is therefore essential to identify main determinants of uranium affinity for proteins. Others and we showed that introducing a phosphoryl group in the coordination sphere of uranyl confers a strong affinity of proteins for uranyl. In this work, using calmodulin site 1 as a template, we modulate the structural organization of a metal-binding loop comprising carboxylate and/or carbonyl ligands and reach affinities for uranyl comparable to that provided by introducing a strong phosphoryl ligand. Shortening the metal binding loop of calmodulin site 1 from 12 to 10 amino acids in CaMΔ increases the uranyl-binding affinity by about 2 orders of magnitude to log KpH7 = 9.55 ± 0.11 (KdpH7 = 280 ± 60 pM). Structural analysis by FTIR, XAS, and molecular dynamics simulations suggests an optimized coordination of the CaMΔ-uranyl complex involving bidentate and monodentate carboxylate groups in the uranyl equatorial plane. The main role of this coordination sphere in reaching subnanomolar dissociation constants for uranyl is supported by similar uranyl affinities obtained in a cyclic peptide reproducing CaMΔ binding loop. In addition, CaMΔ presents a uranyl/calcium selectivity of 107 that is even higher in the cyclic peptide.

Alkali- and alkaline-earth metal–organic networks based on a tetra(4-carboxyphenyl)bimesitylene-linker

Four new 3D-metal–organic and supramolecular frameworks based on the 3,3′,5,5′-tetrakis(4-carboxyphenyl)-2,2′,4,4′,6,6′-hexamethyl-1,1′-biphenyl ligand (H4L) namely: [Na2(H4L)(H2L)(DMF)2(H2O)2]n (1), 2[Mg(H2O)6]·2H3L·H2L (2), [Mg2L(DMF)2(H2O)]·2.5DMF (3), and 2[Ca(H2L)(H2O)4.5(DMF)0.5]·[Ca(H2L)(H2O)5]n·2H2O (4) were obtained and fully characterized. The sodium ion in compound 1 is coordinated by six oxygen atoms in a distorted octahedral geometry, with the oxygen atoms provided by four monodentate carboxylate groups, one water and one DMF molecule. The polycarboxylate ligand acts as a bridge between four Na ions to form an extended 3D coordination network with (4,4) topology. In compound 2 two crystallographically independent [Mg(H2O)6]2+ complex cations and three non-coordinated mono- and doubly deprotonated tetracarboxylic acid molecules form a 3D supramolecular network consolidated by a multiple system of OH⋯O hydrogen bonds. Compound 3 consists of two Mg2+ cations, one L4− tetra-anion, two coordinated DMF molecules and one aqua ligand to form a 3D coordination polymer. The crystal structure of compound 4 includes three crystallographically independent and chemically non-equivalent molecular entities: two molecular complexes [Ca(H2L)(H2O)4.5(DMF)0.5] and a coordination-polymeric helical strand of repeating formula unit [Ca(H2L)(H2O)5]n. The crystal structure of compound 4 is described as a supramolecular architecture where 1D coordination polymers [Ca(H2L)(H2O)5]n and two molecular units [Ca(H2L)(H2O)4.5(DMF)0.5] are linked through numerous intermolecular H-bonds.

Peroxo–tungstate(VI) complexes: syntheses, characterization, reactivity, and DFT studies

Three new oxodiperoxo–tungsten(VI) complexes containing benzene core carboxylic acids, viz., benzoic acid, 2-chlorobenzoic acid, and 3-aminobenzoic acid as co-ligands have been synthesized from reaction of Na2WO6H4, 30% H2O2 and the corresponding co-ligands in aqueous medium. The compounds have been comprehensively characterized by elemental analyses, FT-IR, 1H NMR, UV–Vis spectral studies as well as by mass spectrometric and TGA analyses. The infrared spectra suggest occurrence of terminally bonded W=O as well as triangular bidentate peroxo groups (C2v) and monodentate carboxylate group bound to the WO4+ center. The mass spectra of the compounds are in good agreement with proposed molecular formulations. Thermogravimetric analyses indicate the existence of both lattice and coordinated water molecules in the complexes. Density functional theory (DFT) calculations were used to compute the frequencies of relevant vibrational modes, electronic properties and also to investigate structure of the compounds. Compound potassium(aquo)(2-chlorobenzoato)oxodiperoxo–tungstate(VI)dihydrate acts as an oxidant for bromide ion in aqueous phase bromination of chosen organic substrates to their corresponding bromo-organics.

Synthesis, structural characterization and cytotoxic activity of triorganotin 5‐(salicylideneamino)salicylates

Six new triorganotin complexes (1a–1c and 2a–2c) of 5‐(salicylideneamino)salicylic acid, [5‐(3‐X‐2‐HOC6H3CH═N)‐2‐HOC6H3COO]SnR3 (X = H, 1; CH3O, 2; R = Ph, a; Cy, b; CH2C(CH3)2Ph, c), have been synthesized by one‐pot reaction of 5‐aminosalicylic acid, salicylaldehyde and triorganotin hydroxide and characterized using elemental analysis and infrared and NMR (1H, 13C and 119Sn) spectra. The crystal structures of 1a, 1b, 2a·CH3OH, 2b·CH3OH and 2c·CHCl3 have been determined using single‐crystal X‐ray diffraction. In non‐coordinated solvent CDCl3, the tin atoms in the complexes are all four‐coordinated. In the crystalline state, these compounds adopt a four‐ or five‐coordination mode. Complex 1a exhibits a 44‐membered macrocyclic tetrameric structure with trigonal bipyramidal geometry around the tin atoms in which the axial positions are occupied by the oxygen atom of carboxylate group of the ligand and the phenolic oxygen atom from the adjacent ligand. The coordination geometry of tin atom in 1b and 2c·CHCl3 is a distorted tetrahedron shaped by three carbon atoms of alkyl groups and a carboxylate oxygen atom of the ligand. In 2a·CH3OH and 2b·CH3OH, the tin atom has a distorted trans‐C3SnO2 trigonal bipyramidal geometry formed by three alkyl groups, a monodentate carboxylate group and a coordinated methanol molecule. The molecules of 2a·CH3OH and 2b·CH3OH are linked via O─H···O hydrogen bonds into a one‐dimensional supramolecular chain and a centrosymmetric R44(22) macrocycle, respectively. Bioassay results against two human tumor cell types (A549 and HeLa) show the complexes are efficient cytostatic agents and may be explored as potential antitumor drugs.

Synthesis of non-toxic As and Cr nanoparticles through redox activity of highly flexible layered coordination polymer of Ni(II)

A simple method for the sequestration of As(III) and Cr(VI) from water has been demonstrated by utilizing a highly flexible porous coordination polymer (PCP) of Ni(II) in its as synthesized form or without solvent removal. This PCP reduces the high toxicity of As(III) and Cr(VI) ions into non-toxic As(0) and Cr/Cr2O3/CrO2 (zero, tri and tetravalent) nanoparticles (NPs) within its pores, and this is characterized by powder x-ray diffraction, x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy analysis. The high functionality of this polymer is due to the presence of monodentate carboxylate groups of a benzenetricarboxylate linker, which provide anchoring sites to the metal ions of the metal precursors. Due to the highly oxidising nature of these toxic ions, a redox reaction takes place between the framework metal ions and toxic metal ions, which is explained by an electron paramagnetic resonance study. This is the first report to synthesize non-toxic, as well as useful, NPs of As and Cr from their highly toxic ions within the cavities of a PCP for remediation of the toxic waste stream and contaminated waste water.

One Dimensional Coordination Polymer of Zn(II) for Developing Multifunctional Nanoparticles

A variety of nanoparticles (NPs) including Ag, Au, Pd, Cr and mixed Cu/Fe have been synthesized in a non-activated (without solvent removal) one dimensional coordination polymer (CP) of Zn(II) via two different mechanisms, acid formation and redox activity of the framework. Main driving force to grow these NPs within the cavities of CP is the presence of free oxygens of one of the monodentate carboxylate groups of BDC ligand. These free oxygens act as anchoring sites for the metal ions of the metal precursors. Chemical and physical characteristics of the NPs within the framework have been evaluated by the high resolution transmission electron microscopic (HRTEM) images. Excluding Ag(0) and Pd(0) other NPs are present as combinations of their elemental as well as oxide forms (Au/Au2O3, Cr/Cr2O3/CrO2 and Cu/Cu2O, Fe/FeO). Synthesized Ag NPs within the framework show remarkable antibacterial efficacy at extremely low concentrations. Ag, Au and Cu/Fe NPs show ferromagnetic properties within the framework at room temperature. This polymer has potential to sequester highly toxic Cr(VI) to non toxic Cr(0), Cr(III) and Cr(IV) species.

Enhancement of photocatalytic decarboxylation on TiO2 by water-induced change in adsorption-mode

Decarboxylation is an important process in the photocatalytic degradation of organic pollutants. In this study, the adsorption and photocatalytic decarboxylation of acetic acid and trichloroacetic acid were investigated by in-situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), which can distinguish carboxylate groups with different adsorption modes. We found that water molecules promote photocatalytic decarboxylation reaction and the promotional effect of water is attributed to the changed adsorption mode of the carboxylate group by the co-adsorbed water molecules. The IR study shows that degradation of the monodentate-coordinated acetic acids is much faster than that of the bidentate-coordinated one. The kinetic isotope effect studies and analysis of the intermediate products indicates that the degradation of acetic acids originates from the direct oxidation by holes even in the presence of water, rather than from the reaction of OH radicals as generally believed. DFT-based molecular dynamics calculations revealed that the formation of the monodentate-coordinated carboxylate group in the presence of water is attributed to competition between the O atom of the carboxylate group and water for the surface Ti sites. Because of its higher electron density, the monodentate carboxylate group is easier to be directly oxidized by holes than the bidentate group.

Flexible porous coordination polymer of Ni(II) for developing nanoparticles through acid formation and redox activity of the framework

Immobilization of the nanoparticles (NPs) in a two dimensional porous coordination polymer (PCP) is currently an emerging field for a number of applications. But still it is a great challenge to fabricate any specified metal NPs in a single network. Herein the synthesis of Au, Pd, Mn, Fe, Cu, Zn, Mg, Li, Fe/Cu, Zn/Mg etc, NPs in a highly flexible PCP of Ni(II); {[Ni3(TBIB)2(BTC)2(H2O)6]·5C2H5OH·9H2O}n [TBIB = 1,3,5-tri(1H-benzo[d]imidazol-1-yl)benzene, H3BTC = 1,3,5-benzenetricarboxylic acid] have been reported. This universal host is able to grow mixed metal NPs from mixed metal precursors. Monodentate carboxylate groups of BTC linker act as anchoring sites for the metal ions of the metal precursors. This is the main driving force to grow NPs within the cavities along with the high flexibility of this polymer at room temperature. Mechanism involves acid formation followed by redox reaction to synthesize metal NPs explained by EPR and FTIR. Paramagnetic properties have been shown by as-synthesized Fe NPs integrated framework at room temperature under applied magnetic field up to 17,500Oe.

Synthesis, Crystal Structure, and Properties of a New Coordination Polymer From 4-(4-Hydroxypyridinium-1-yl) Phthalic Acid

A copper supramolecular coordination polymer, {[CuL(H2O)2]2}n (1), has been hydrothermally synthesized and structurally characterized by IR, UV spectroscopy, and elemental analyses, and also by single-crystal X-ray diffraction (H2L = 4-(4-hydroxypyridinium-1-yl) phthalic acid). The coordination around Cu center is distorted octahedron coordination geometry involving six O atoms, and each L2– ligand links three center atoms in the μ3-η1: η1: η1 mode; Adjacent Cu(II) atoms are united by the monodentate carboxylate group and hydroxy group to form infinite 1D chains (···Cu1LCu2L···)n, which are further linked by coordinated bonds between Cu1 and chelating carboxylate groups to produce 2D layers. These 2D layers are extended by interlayer hydrogen-bonded interactions to form 3D supramolecular framework.

Synthesis and characterizations of Zn(II) and Co(II) coordination polymers based on 5-acetamidoisophthalate

Seven Zn(II) and Co(II) coordination polymers based on 5-acetamidoisophthalate (AcAIP) and flexible bis(imidazolyl) ligands, [Zn(H2O)0.5(AcAIP)]n (1), [Zn(AcAIP)(o-BIMB)]n·3nH2O (2), [Co(AcAIP)(o-BIMB)]n·3nH2O (3), [Zn(AcAIP)(m-BIMB)]n·3nH2O (4), [Co(AcAIP)(m-BIMB)]n·3nH2O (5), [Zn(AcAIP)(p-BIMB)]n (6) and [Co(AcAIP)(p-BIMB)]n (7) (o-BIMB=1,2-bis(imidazol-1-yl-methyl)benzene, m-BIMB=1,3-bis(imidazol-1-yl-methyl)benzene and p-BIMB=1,4-bis(imidazol-1-yl-methyl)benzene), were synthesized and well characterized. In complex 1, AcAIP serves as a μ4-bridge through μ2,η2-carboxylate, monodentate carboxylate and acetamido, and connects Zn(II) ions into a 3-D network, while acetamido group of AcAIP in 2–7 is not involved in coordination with metal ions owing to the presence of bis(imidazolyl) ligands. Notably, AcAIP in 2–6 bridges two metal ions through two monodentate carboxylate groups. AcAIP in 2–5 connects Zn(II) and Co(II) ions into 1-D chain, subsequent bridge by o-BIMB generates a 2-D corrugated layer, while m-BIMB connects two intra-chained metal ions to form [Zn2(AcAIP)(m-BIMB)] macrocycles. Interestingly, AcAIP in 6 links two Zn(II) ions into a 16-membered [Zn2(AcAIP)2] macrocycle, and subsequent bridge by anti-conformationed p-BIMB forms a 2-D layer. However, two carboxylate groups of AcAIP in 7 function in μ2,η2-bridging and chelating modes, AcAIP and gauche-conformationed p-BIMB bridge Co(II) ions to form a twofold interpenetrating framework consisting of dinuclear Co(II)-carboxylate units. Magnetic analysis of complex 7 shows that the existence of antiferromagnetic interactions. Fluorescent properties of Zn(II) coordination polymers in solid state were also investigated.

A two-dimensional cadmium(II) coordination polymer based on 5-(pyridin-4-yl)isophthalic acid: poly[[tetraaquabis[μ₃-5-(pyridin-4-yl)isophthalato]dicadmium(II)] pentahydrate

The title Cd(II) compound, {[Cd2(C13H7NO4)2(H2O)4]·5H2O}n, was synthesized by the hydrothermal reaction of Cd(NO3)2·4H2O and 5-(pyridin-4-yl)isophthalic acid (H2L). The asymmetric unit contains two crystallographically independent Cd(II) cations, two deprotonated L(2-) ligands, four coordinated water molecules and five isolated water molecules. One of the Cd(II) cations adopts a six-coordinate octahedral coordination geometry involving three O atoms from one bidentate chelating and one monodentate carboxylate group of two different L(2-) ligands, one N atom of another L(2-) ligand and two coordinated water molecules. The second Cd(II) cation adopts a seven-coordinate pentagonal-bipyramidal coordination geometry involving four O atoms from two bidentate chelating carboxylate groups of two different L(2-) ligands, one N atom of another L(2-) ligand and two coordinated water molecules. Each L(2-) ligand bridges three Cd(II) cations and, likewise, each Cd(II) cation connects to three L(2-) ligands, giving rise to a two-dimensional graphite-like 6(3) layer structure. These two-dimensional layers are further linked by O-H···O hydrogen-bonding interactions to form a three-dimensional supramolecular architecture. The photoluminescence properties of the title compound were also investigated.

A new one-dimensional coordination polymer of 5-(1,3-dioxo-4,5,6,7-tetraphenylisoindolin-2-yl)isophthalic acid with manganese.

The coordination polymer catena-poly[[(dimethylformamide-κO)[μ3-5-(1,3-dioxo-4,5,6,7-tetraphenylisoindolin-2-yl)isophthalato-κ(4)O(1),O(1'):O(3):O(3')](methanol-κO)manganese(III)] dimethylformamide monosolvate], {[Mn(C40H23NO6)(CH3OH)(C3H7NO)]·C3H7NO}n, has been synthesized from the reaction of 5-(1,3-dioxo-4,5,6,7-tetraphenylisoindolin-2-yl)isophthalic acid and manganese(II) acetate tetrahydrate in a glass tube at room temperature by solvent diffusion. The Mn(II) centre is hexacoordinated by two O atoms from one chelating carboxylate group, by two O atoms from two monodentate carboxylate groups and by one O atom each from a methanol and a dimethylformamide (DMF) ligand. The single-crystal structure crystallizes in the triclinic space group P\overline{1}. Moreover, the coordination polymer shows one-dimensional 2-connected {0} uninodal chain networks, and free DMF molecules are connected to the chains by O-H···O hydrogen bonds. The thermogravimetric and photoluminescent properties of the compound have also been investigated.

The molecular structure of three types of long-chain zinc(II) alkanoates for the study of oil paint degradation

The molecular structures of three types of zinc(II) alkanoates (Zn(Cn)2, ZnNa2(Cn)4 and ZnK2(Cn)4, Cn=CH3(CH2)n−2COO−, n=8–18) were investigated by Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD) to aid the study of degradation phenomena in oil paint. Each type of complex forms a homologous series in the studied chain length range. For (Zn(Cn)2 and ZnNa2(Cn)4, these homologous series indicate that the long-chain complexes have structures highly similar to those published for short-chain single-crystal analogs. Moreover, we introduce a chain tilt factor Ftilt to derive information about alkanoate chain angles from highly accurate PXRD long spacing values. The complex ZnK2(Cn)4 has not been reported before. It consists of metal sheets containing tetrahedrally coordinated Zn atoms and octahedrally coordinated K atoms bridged by effectively monodentate carboxylate groups, and alkanoate chains that are tilted relative to the long axis.

A novel three-dimensional ZnIIcoordination polymer with 1,3,5-tris(imidazol-1-ylmethyl)benzene and cyclohexane-1,3,5-tricarboxylate ligands

In the Zn(II) compound poly[[bis(μ3-cyclohexane-1,3,5-tricarboxylato)bis[μ3-1,3,5-tris(imidazol-1-ylmethyl)benzene]trizinc(II)] hexahydrate], {[Zn3(C18H18N6)2(C9H9O6)2]·6H2O}n, based on mixed 1,3,5-tris(imidazol-1-ylmethyl)benzene and cyclohexane-1,3,5-tricarboxylate ligands, there are two types of crystallographically independent Zn(II) centres, one in a general position and one on a crystallographic twofold axis. They have similar fourfold distorted tetrahedral coordination geometries, ligated by two monodentate carboxylate groups from two cyclohexane-1,3,5-tricarboxylate ligands and by two N atoms from two 1,3,5-tris(imidazol-1-ylmethyl)benzene ligands. The cyclohexane-1,3,5-tricarboxylate anions link the Zn(II) cations to generate a two-dimensional layered metal-organic structure running parallel to the (201) plane. Adjacent layers are further connected by tripodal 1,3,5-tris(imidazol-1-ylmethyl)benzene ligands, resulting in a three-dimensional network. The solvent water molecules are linked to the cyclohexane-1,3,5-tricarboxylate ligands via water-carboxylate O-H···O hydrogen bonds.

A fivefold interpenetrating diamondoid three-dimensional metal–organic framework constructed from benzene-1,4-diacetic acid and flexible triazole derivatives: poly[[(μ2-benzene-1,4-diacetato-κ2O:O){μ2-1,4-bis[(1H-1,2,4-triazol-1-yl)methyl]benzene-κ2N4:N4′}zinc(II)] monohydrate

In the title mixed-ligand metal-organic polymeric compound, {[Zn(C10H8O4)(C12H14N6)]·H2O}n, the asymmetric unit contains a divalent Zn(II) cation lying on a twofold axis, one half of a fully deprotonated benzene-1,4-diacetate (PBEA) ligand, one half of a 1,4-bis[(1H-1,2,4-triazol-1-yl)methyl]benzene (BTX) ligand and a water molecule, also lying on a twofold axis. Each Zn(II) centre is surrounded by two O-donor atoms from monodentate carboxylate groups belonging to two different PBEA(2-) ligands and by two triazole N-donor atoms from two different BTX ligands. Single-crystal X-ray diffraction analysis revealed that the compound has a fivefold interpenetrating diamondoid three-dimensional metal-organic framework.

A Chiral Decorated Metal–Isonicotinate Coordination Polymer

The isostructural coordination polymers, M(isonicotinate)(tyrosinate)(H2O)2 [M = Co or Ni] have been synthesized by microwave-assisted hydrothermal methods. These compounds crystallize in the non-centric space group P21. At 290 K, for the cobalt analogue the unit cell parameters are a = 6.0658(6), b = 15.540(2), c = 9.1328(9) A, β = 107.052(7)°, V = 823.05(16) A3; for the nickel compound a = 6.0946(8), b = 15.443(2), c = 9.1202(11) A, β = 107.803(10)°, V = 817.28(19) A3. The structure contains linear chains with composition [M(isonicotinate)]∞ in which the isonicotinate is arranged head-to-tail and binds to octahedral cations through both pyridine and monodentate carboxylate functions. At each metal centre the coordination is completed by two cis water molecules and tyrosinate that chelates to the metal centre through monodentate carboxylate and amine groups. The chains run parallel to the crystallographic [101] direction. Between the chains there is extensive hydrogen bonding between bound water and carboxylate groups. The cobalt compound loses water upon heating above room temperature and continues to lose mass in ill-defined steps upon further heating; in contrast the nickel compound loses mass in well-defined steps. An achiral one dimensional chain can be decorated with the chiral auxiliary tyrosine to produce a homochiral coordination polymer.

Supramolecular Signatures of Adenine-Containing Organostannoxane Assemblies

The reactions of 3-(N9-adeninyl) propanoic acid (LH) with various di- and triorganotin oxides have been investigated. Thus, the reaction of di-tert-butyltin oxide (t-Bu2SnO)3 in a 3:1 ratio afforded the dinuclear derivative [t-Bu2Sn(μ-OH)L]2·7H2O (1). A similar reaction involving bis(tri-n-butyltin)oxide, (n-Bu3Sn)2O, in a 2:1 ratio afforded the one-dimensional (1D) coordination polymer [n-Bu3SnL·0.33H2O]n (2). Similarly the reaction with (n-Bu2SnO)n in a 2:1 ratio afforded the tetranuclear [{n-Bu2Sn}2(μ3-O)(μ-OH)L]2 (3). On the other hand, a similar reaction in a 1:1 ratio also gave the tetranuclear product [{n-Bu2Sn}2(μ3-O)L2]2 (4). The molecular structure of 1reveals a central dinuclear Sn2O2 motif where the two tin centers are bridged by two μ-OH groups. Each tin is bound with a monodentate carboxylate group; the C═O unit of these carboxylates is involved in an intramolecular hydrogen bonding with the bridging OH unit. The supramolecular structure of 1 reveals the formation of a 1D zigzag chain mediated by intermolecular hydrogen bonding interaction through the Watson-Crick or the Hoogsteen faces. 2 is a 1D coordination polymer formed by the successive bridging of triorganotin units by the carboxylate ligand L. The supramolecular structure of 2 reveals that two 1D coordination polymers interact to generate novel adenine homotrimers formed as a result of alternating Watson-Crick–Watson-Crick and Hoogsteen–Watson-Crick interactions. The molecular structures of 3 and 4 reveal them to be tetranuclear possessing a ladder-like structure. The essential difference between their molecular structures is that in 4 there are four carboxylate ligands, while in 3 there are only two. Both of these complexes reveal intramolecular and intermolecular hydrogen bonding and π···π stacking interactions. The nematicidal activity of 1–3 was examined against Caenorhabditis elegans. Compound 2 was found to be highly active, effecting a high mortality even at very low concentrations such as 25 or 10 ppm.

A one-dimensional coordination polymer based on Cd2O2clusters: poly[aqua(μ3-4,4′-sulfonyldibenzoato)(3,4,7,8-tetramethyl-1,10-phenanthroline-κ2N,N′)cadmium(II)

In the title mixed-ligand metal-organic polymeric complex [Cd(C14H8O6S)(C16H16N2)(H2O)]n, the asymmetric unit contains a crystallographically unique Cd(II) atom, one doubly deprotonated 4,4'-sulfonyldibenzoic acid ligand (H2SDBA), one 3,4,7,8-tetramethyl-1,10-phenanthroline (TMPHEN) molecule and one water molecule. Each Cd(II) centre is coordinated by two N atoms from the chelating TMPHEN ligand, three O atoms from monodentate carboxylate groups of three different SDBA(2-) ligands and one O atom from a coordinated water molecule, giving a distorted CdN2O4 octahedral geometry. Single-crystal X-ray diffraction analysis reveals that the compound is a one-dimensional double-chain polymer containing 28-membered rings based on Cd2O2 clusters, with a Cd...Cd separation of 3.6889 (4) Å. These chains are linked by O-H...O and C-H...O hydrogen bonds to form a three-dimensional supramolecular framework. The framework is reinforced by π-π and C-O...π interactions.

A one-dimensional coordination polymer with a three-dimensional supramolecular framework:catena-poly[[[(3,4,7,8-tetramethyl-1,10-phenanthroline)cadmium(II)]-μ3-4,4′-sulfonyldibenzoato] trihydrate

In the title mixed-ligand metal-organic polymeric compound, {[Cd(C14H8O6S)(C16H16N2)]·3H2O}n, the asymmetric unit contains a crystallographically unique Cd(II) atom, one doubly deprotonated 4,4'-sulfonyldibenzoic acid (H2SDBA) ligand, one 3,4,7,8-tetramethyl-1,10-phenanthroline (TMPHEN) molecule and three solvent water molecules. Each Cd(II) centre is six-coordinated by two O atoms from a chelating carboxylate group of a SDBA(2-) ligand, two O atoms from monodentate carboxylate groups of two different SDBA(2-) ligands and two N atoms from a chelating TMPHEN ligand. There are two coordination patterns for the carboxylate groups of the SDBA(2-) ligand, with one in a μ1-η(1):η(1) chelating mode and the other in a μ2-η(1):η(1) bis-monodentate mode. Single-crystal X-ray diffraction analysis revealed that the title compound is a one-dimensional double-chain polymer containing 28-membered rings based on the [Cd2(CO2)2] rhomboid subunit. More interestingly, a chair-shaped water hexamer cluster is observed in the compound.