2D coordination polymers of Nd(III) and Gd(III) with the phenoxyacetate ligand

The self-assembly of anionic phenoxyacetate ligands and Nd(III) cations in a 3:1 ratio leads to a 2D {Nd₂(PhOCH₂COO)₆(H₂O)₃ · H₂O}_n coordination polymer 1, which was structurally characterized. The metal centers are bridged by carboxylic groups to form infinite parallel chains separated (19.4 Å) by the π-π and C-H?π-stacked phenoxy groups of the ligands. The thermal dependence of the molar magnetic susceptibility for the isostructural gadolinium polymer 2 has been measured and analyzed according to the analytical expression of an infinite chain of classical spins derived by Fisher. The Gd?Gd interaction is ferromagnetic with a magnitude of 0.015(3) cm⁻¹. Modelling of the field-dependent magnetization at 2 K corroborates this result.     

Hydrothermal synthesis and characterization of a new 1-D polymeric lanthanum ethylenediaminetetraacetate with less metal-aqua coordination: {[La(EDTA)(H2O)]2}n

A new lanthanum ethylenediaminetetraacetate (EDTA) coordination polymer, {[La(EDTA)(H₂O)]₂}_n (EDTA³⁻ = [(CH₂N)₂(CH₂COOH)(CH₂COO⁻)₃]), was hydrothermally prepared from LaCl₃ solution and ethylenediaminetetracetic acid at 448 K. The compound was characterized by elemental analysis, FTIR, TG-DTA, and X-ray crystallography. The structure consists of ladder-like chains of [La(EDTA)(H₂O)]₂ dimers bridged by O-C-O groups. Hydrothermal method successfully reduced the high number of La-aqua coordinations in known lanthanum EDTA to one giving rise to relatively compact structure. It has high thermal stability up to 550 K. Every EDTA ligand with COOH group is involved in eight La-O(N) bonds to three nine-coordinated La centers.     

Hydrothermal synthesis and characterizations of a novel 2-D double-layers metal-organic coordination polymer involving in situ ligand synthesis

A novel 2-D metal-organic coordination polymer [Ni_0.5(apddica)(H₂O)] · H₂O 1 (Hapddica=2-(4-Amino-phenyl)-1,3-dioxo-2,3-dihydro-1H-isoindole-5-carboxylic acid) has been hydrothermally synthesized and structurally characterized by element analyses, IR and XPS spectra, TG analyses and single crystal X-ray diffraction. Crystal data: C₁₅H₁₃N₂Ni_0.5O₆, monoclinic, P2(1)/c, a=12.181(2) Å, b=7.9392(6) Å, c=14.835(3) Å, β=94.25(3) °, V=1430(75) ų, Z=4. Compound 1 exhibits a novel 2-D double-layers network based on apddica and Ni center. It is noteworthy that new ligand Hapddica was first prepared with hydrothermal technique involving in situ ligand synthesis and used for constructing coordination polymers. There are unusual parallelogram tunnels along a-axis in which the dissociative water molecules filled in. The magnetic property of compound has been studied.     

Water dimers connect [Cu(cda)(py)3] (cda = pyridine-4-hydroxy-2,6-dicarboxylate, py = pyridine) complex units to left- and right-handed helices that form a tubular coordination polymer through supramolecular bonding

The reaction between pyridine-4-hydroxy-2,6-dicarboxylic acid (cdaH₂) and Cu(NO₃)₂ · 3H₂O afford products that depend on the reaction conditions applied. In presence of excess of aqueous pyridine (1:2 v/v), equimolar amounts of the reactants form {[Cu(cda)(py)₃]₂ · 5H₂O}_n (1). In this complex, dimeric water clusters are H-bonded to carboxylate O atoms forming both left- and right-handed helices. These helices are further H-bonded to form a tubular coordination polymer. It crystallizes in the monoclinic space group P2₁/a with a = 14.235(5), b = 23.097(4), c = 15.542(6) Å, β = 114.392(5)°, V = 4654(2) Å³, Z = 4, R₁ = 0.0422, wR₂ = 0.0992, S = 0.899. When pyridine is used in place of aqueous pyridine, a new coordination polymer, {Cu(cda)(py)}_n(2) is formed that crystallizes in the monoclinic space group P2₁/c with a = 12.391(5), b = 12.770(5), c = 7.135(5) Å, β = 95.155(5)°, V = 1124(1) Å³, Z = 4, R₁ = 0.0415, wR₂ = 0.0882, S = 1.190. The structure of 2 consists of carboxylate-bridged [Cu(cda)(py)] units extending as a zigzag infinite chain where each metal ion shows square-pyramidal geometry. Variable temperature magnetic susceptibility measurements in the temperature range, 2-300 K for 2 is also reported.     

A copper(II) coordination polymer with alternating double EO-azido bridges and mixed EO-azido/alkoxo double bridges

A new one-dimensional (1D) copper(II) complex, [Cu₂(dpk · CH₂O)(N₃)₃]_n (dpk · CH₂OH = unimethylated diol of di-2-pyridyl ketone) (1), has been synthesized and characterized. X-ray crystal structure study reveals that 1 is composed of 1D copper(II) chain with alternating double EO-azido bridges and mixed EO-azido/alkoxo double bridges. The magnetic determination indicates that ferromagnetic interaction dominates in this new 1D S = 1/2 system.     

Synthesis and characterization of one lead(II) photoluminescent coordination polymer with the fumarate ligand

One lead(II) coordination polymer, {[Pb(fum)(phen)]·2H₂O}_n (fum = fumarate, phen = 1,10-phenanthroline), was synthesized through the self-assembly of the lead(II) ion with the mixed fum and phen ligands and characterized by FT-IR spectroscopy, elemental analysis, thermogravimetric analysis, X-ray analysis and solid state photoluminescence spectrum. The compound shows a center-symmetrical dinuclear-based 2D architecture and further assembles into porous 3D supramolecular framework with 1D channel via interlayer π-π stacking interactions. The six-coordinated lead atoms in the complex show hemidirected geometry. The compound exhibits photoluminescence with the maximum emission located in UV region.     

Synthesis, crystal structures and magnetic behavior of two 3D coordination polymers using N-(4/3-carboxyphenyl)iminodiacetic acids as bridging ligands

Research on structure and magnetic properties of polynuclear metal complexes to understand the structural and chemical factors governing the electronic exchange coupling mediated by multi-atom bridging ligands is of growing interest. Hydrothermal treatment of Ni(NO₃)₂·6H₂O with N-(4-carboxyphenyl)iminodiacetic acid [N-4(H₃CPIDA)] at 150 °C yielded a 3D coordination polymer of general formula [Ni₃{N-4(CPIDA)}₂(H₂O)₃]·6H₂O (1). An analogous network of general formula [Co₃{N-3(CPIDA)}₂(H₂O)₃]·3H₂O (2) was synthesized using N-(3-carboxyphenyl)iminodiacetic acid [N-3(H₃CPIDA)] in combination with Co(NO₃)₂·6H₂O under identical reaction condition. Both the complexes contain trinuclear secondary building unit, and crystallized in monoclinic system with space groups C2/c (1) and P2₁/c (2), respectively. Variable temperature magnetic characterization of these complexes in the temperature range of 2-300 K indicated the presence of overall ferromagnetic and antiferromagnetic behavior for 1 and 2, respectively. Density functional theory calculations (B3LYP functional) were performed for further insight on the trinuclear units to provide a qualitative theoretical interpretation on the overall magnetic behavior of the complexes 1 and 2.     

Syntheses, structures and photoluminescence properties of cadmium(II) and zinc(II) complexes with pyridinylcarboxamide-containing ligand

Four new coordination complexes [Cd(DPBA-3)₂(H₂O)₂](ClO₄)₂·2H₂O (1), [Cd(DPBA-3)(DMF)(NO₃)₂]·DMF (2), [Cd₃(DPBA-3)₂(SCN)₆]·2DMF·4H₂O (3) and [Zn(DPBA-3)(SCN)₂] (4) [DPBA-3 = N,N′-di(pyridin-3-yl)pyridine-3,5-dicarboxamide] have been synthesized and characterized by elemental analysis, IR and single crystal X-ray diffraction. Complexes 1, 3 and 4 exhibit three different types of one-dimensional (1D) chain structures constructed by the metal ions and DPBA-3 ligands, and the Cd(II)-DPBA-3 1D chains in 3 are further linked by bridging SCN⁻ ligands to afford a three-dimensional (3D) framework. Complex 2 possesses a (6,3) two-dimensional (2D) layer structure. In 1-4, the hydrogen bonds involving the amide groups play important role to stabilize the resultant frameworks. The photoluminescence properties of the DPBA-3 and the complexes were studied in the solid state at room temperature.     

Sonochemical syntheses of strawberry-like nano-structure mixed-ligand lead(II) coordination polymer: Thermal, structural and X-ray powder diffraction studies

Nano-structure of a new Pb(II) two-dimensional coordination polymer, {[Pb(2-pyc)(N₃)(H₂O)]_n (1), 2-Hpyc = 2-pyridinecarboxylic acid} was synthesized by a sonochemical method. The new nano-structure was characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analyses. Compound 1 was structurally characterized by single crystal X-ray diffraction and consists of two-dimensional polymeric units. The thermal stability of compound 1 was studied by thermal gravimetric and differential thermal analyses and compared. PbO nano-powder was obtained by calcination of the nano-structure of compound 1 at 400 °C. This study demonstrates the coordination polymers may be suitable precursors for the preparation of nano-scale materials and dependent on their packing they may produce different and interesting morphologies.     

Self-assembled synthesis, characterization and antimicrobial activity of zinc(II) salicylaldimine complexes

One-pot metal promoted reactions between salicylaldehyde and 4-methyl-1,3-phenylenediamine in the presence of metal salts acting as template agents yield zinc(II) salicylaldimine complexes containing N,N′-bis(salicylidene)-4-methyl-1,3-phenylenediamine (H₂L) as a result of the [2 + 1] Schiff base condensation. The complexes of formula [Zn(HL)Cl(H₂O)₂] · C₂H₅OH and [Zn(H₂L)₂Cl(NO₃)(H₂O)] · CH₃OH were characterized as powder solids and in solution by spectroscopic methods (IR, ¹H and ¹³C NMR, FAB-MS, ESI-MS, UV-Vis), thermogravimetric and elemental analysis, potentiometry, and tested for antimicrobial activity against Staphylococcusaureus in a minimum inhibitory concentration (MIC) experiment. In these two powder solid species, the salicylaldimine, formed in a self-assembly process, acts in two different coordination modes: as monodeprotonated bidentate chelator with an N,O donor set or as a neutral monodentate using exclusively oxygen as the donor atom without involving the nitrogen atoms in the coordination. However, crystals of these two complexes are isomorphous, with 1:2 metal:ligand stoichiometry, and display the latter, relatively rare coordination pattern. In solution, the presence of a 1:1 complex of monodeprotonated state is only detected. The complexes exhibit antimicrobial activity against S.aureus.     

Structure and luminescence of sodium and lanthanide(III) coordination polymers with pyridine-2,6-dicarboxylic acid

A series of coordination polymers constructed by sodium, lanthanide(III), and pyridine-2,6-dicarboxylate (dipic),NaLn(dipic)₂ · 7H₂O (Ln = Eu, Gd, Tb), have been prepared under a hydrothermal condition. The crystal structures of the three compounds which are isostructual were determined by single-crystal X-ray diffraction. The two-dimensional layers found in the compounds are built up from six-folded {NaO₆} polyhedra and nine-folded {LnN₂O₇} polyhedra, these being edge-shared each other along the c axis and bridged by carboxylate groups of dipic along the b axis, respectively. This two-dimensional framework provides cavities inside the layer and interlayer spaces outside the layer for accommodation of the two dipic molecules coordinated to a lanthanide(III) ions. The dehydrated materials obtained by heating the as-synthesized crystals at 200 °C held their crystal structure, and absorbed the same amounts of water molecules as those of the as-synthesized crystals upon the exposure of 100% relative humidity at room temperature. The Eu and Tb compounds showed strong red and green emissions, respectively, due to an energy transfer from dipic molecules to trivalent emission ions.     

A dicarboxylate with asymmetric coordination ability: Characterization of a two dimensional coordination polymer of copper(II) exhibiting spin canting

A copper(II) coordination polymer {[Cu₂(cpa)₂]}_n (1) (cpaH₂ = 4-carboxyphenoxyacetic acid) has been synthesized by hydrothermal technique. The X-ray structure of the compound shows that it is a 2D coordination polymer where Cu(II) ions are pentacoordinated in a square pyramidal fashion. The magnetic measurement of 1 in different magnetic fields suggest a weak ferromagnetic ordering taking place below 20 K, arising from spin canting phenomenon due to the non-coplanar basal planes of copper ions.     

First examples of ternary lanthanide 2,2′-bipyridine-3,3′-dicarboxylate coordination polymers with zigzag chains structures assembled from lanthanide ions, 2,2′-bipyridine-3,3′-dicarboxylate and 1,10-phenanthroline

Four lanthanide coordination polymers, [{Ln₂(bpdc)₃(phen)₂(H₂O)₂} · (H₂O)₆]_n (Ln = Sm (1); Eu (2); Gd (3), Tb (4)), were self-assembled from 2,2′-bipyridine-3,3′-dicarboxylic acid (H₂bpdc),1,10-phenanthroline(phen) and corresponding lanthanide oxides by hydrothermal synthesis. Compounds 1-4 are found to be isomorphous and isostructural. Single-crystal X-ray diffraction studies show that compounds 1-4 are all of one-dimensional zigzag chain structures and extend to two-dimensional networks through π-π interactions and hydrogen bonds. The pyridyl nitrogen atoms of the 2,2′-bipyridyl unit in the bpdc ligand are uncoordinated in an anti-conformation along the central C-C bond of the ligand. Thermogravimetric analysis of 1-4 showed an obvious thermal stability indicating that the coordination habit of the metal ions with bpdc and phen has an effect on the overall framework. Photoluminescence measurement indicates that compound 2 and compound 4 are strong red and green emitters, respectively.     

New Ag(I) coordination polymers of 2,6-pyridine-dicarboxamide: In situ ligand formation and a unique secondary building unit

The hydrothermal reactions of 2,6-dicyanopyridine with AgX (X = NO₃, ClO₄, BF₄) yielded intriguing network structures. The syntheses involve in situ generation of 2,6-pyridine-dicarboxamide (pcam), forming [Ag(pcam)₂X]_n·mH₂O [X = NO₃ (1), m = 0; BF₄ (2), m = 1; ClO₄ (3), m = 1]. These solids contain an unprecedented SBU, involving simultaneous AgO bonds/interactions and NH···O hydrogen bonding. The SBUs combine to form 2D square grids, which are stacked orderly by weak Ag···O contacts and π-π stacking interactions, forming 3D networks with infinite 1D channels, in which anions are residing. Weak Ag···O interactions play a key role in these solids and they display dynamic behaviors in solution as demonstrated by NMR spectroscopy and ESI-MS. The importance of the supramolecular synthons in the SBU was demonstrated by varying the structure of the organic tecton. Attempts to prepare similar network structures based on stronger OH···O interactions from pyridine-2,6-dicarboxylic acid (H₂dipic) afforded a topologically different 2D coordination polymer.     

Influence of coanions on construction of copper(II)/4,4′-dipyridyl sulfide(dps) coordination polymers

The influence of coanion on self-assembly of CuSO₄ and 4,4′-dipyridyl sulfide (dps) was studied in this paper. During the formation of Cu(II)/dps coordination polymers, coanions Cl⁻, SCN⁻ and were added in the solution respectively. Three novel coordination polymers were obtained, {[Cu(dps)₂ · (SO₄)₂][Cu(dps) · Cl · (H₂O)₂]₂ · 12H₂O}_n (1 · 12H₂O, a 3D network), {[Cu(SCN)₂(dps)(CH₃OH)₂][Cu(dps)₂ · SO₄][Cu(dps)(CH₃CH₂OH)₂ · SO₄] · 5H₂O}_n (2 · 5H₂O, a 3D network), and {[Cu(dps)₂(H₂O)₂] · (PF₆)₂ · 3H₂O}_n (3 · 3H₂O, a 2D lattice network). Different coanion shows different influence on framework construction. In 1 and 2, Cl⁻ and SCN⁻ act as terminal ligands and similar 3D frameworks were composed of [Cu(dps)] layer with larger cavity (ca. 400 Å) and sulfate bridge; in 3, replaces entirely and the 3D framework was broken due to the removal of bridging anions. However, a 2D [Cu(dps)]₄ undulating grid was preserved in 3.     

Synthesis, crystal structure and DNA cleavage activity of a novel Ni(II)-Cd(II) coordination polymer

A novel one-dimensional heterometallic complex, {Cd₂[NiL]₂(SCN)₄(H₂O)}_n (1), has been synthesized and characterized by single-crystal X-ray analysis, where L is dianion of 2,3-dioxo-5,6,13,14-dibenzo-9,10-cyclohexyl-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene. The most striking feature of 1 is that in the structure there is one type of S-S bond (1.823(13) Å) formed by two thiocyanate groups which has not been reported to our knowledge. The DNA cleavage activity of 1 in the presence of H₂O₂ was compared with those of nickel(II) ion, cadmium(II) ion and corresponding mononuclear precursor NiL (2). The DNA cleavage kinetics was studied and the corresponding activation parameters of 1 were obtained.     

Silver(I) coordination networks constructed with di-2-pyrazinylmethanediol

The new ligand di-2-pyrazinylmethanone (di-2-pyrazinyl ketone), (2-C₄H₃N₂)₂CO, has been synthesized, and two silver(I) coordination polymers of its hydrated gem-diol (2-C₄H₃N₂)₂C(OH)₂, namely {Ag[(2-C₄H₃N₂)₂C(OH)₂](CF₃SO₃)}_∞ (1) and {Ag[(2-C₄H₃N₂)₂C(OH)₂](CF₃CO₂)}_∞ (2), have been characterized by X-ray crystallography. A (4,4) net was found in compound 1. In the case of 2, the silver(I) atom functions as a rare five-connected node to conjunct the (2-C₄H₃N₂)₂C(OH)₂ ligands into an extended coordination network which can be viewed as an α-Po topology of the NaCl-type.     

Hydrothermal synthesis, crystal structures and photoluminescent properties of four cadmium(II) coordination polymers derived from diphenic acid and auxiliary ligands

Four novel metal coordination polymers, [Cd(dpa)(H₂O)]_n (1), [Cd(dpa)(2,2′-bipy)]_n (2), {[Cd₂(dpa)₂(4,4′-bipy)₃](4,4′-bipy)(H₂O)₂}_n (3) and [Cd(dpa)(bim)₂(H₂O)]}_n (4) (H₂dpa = 2,4′-biphenyl-dicarboxylic acid, 2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine, bim = benzimidazole), have been synthesized and structurally characterized by elemental analysis, IR and X-ray diffraction. Single-crystal X-ray analyses reveal that the 2,4′-diphenic acids acts as bridging ligands, exhibiting rich coordination modes to link metal ions: bis-monodentate, bidentate chelating, chelating/bridging, monoatomic bridging and monodentate modes. In addition, the luminescent properties for compound 1-4 are also investigated in this work.     

Thermolysis preparation of zinc(II) oxide nanoparticles from a new micro-rods one-dimensional zinc(II) coordination polymer synthesized by ultrasonic method

The reaction of the zinc(II) acetate and 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene (3-bpdb) in presence of perchlorate anions produces a new one-dimensional coordination polymer, {[Zn(μ-3-bpdb)(3-bpdb)₂(H₂O)₂](ClO₄)₂·3-bpdb}_n (1). The compound 1 has been characterized by IR, ¹HNMR and ¹³CNMR spectroscopies. The single crystal X-ray data shows an infinite one-dimensional structure that grows in two- and three-dimensions by hydrogen bonding and π-π stacking. The compound 1 also has been synthesized at micro-size by sonochemical processes and characterized by IR and X-ray powder diffraction (XRD). The scanning electron microscopy (SEM) shows compound 1 has been grown as micro-rod morphology. The thermal stabilities at bulk and micro-size scale were studied by thermal gravimetric (TG) and differential thermal analysis (DTA). The ZnO nanoparticles were obtained by direct calcination at 400 °C under air atmosphere and by thermolysis in oleic acid at 200 °C. The obtained zinc(II) oxide nanoparticles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).     

High-coordinated lanthanum(III) complexes with new mono- and bidentate phosphoryl donors; spectroscopic and structural aspects

Monodentate and bidentate ligands PhNHP(O)(NC₄H₈O)₂ (1) and PhC(O)NHP(O)(NH(tert-C₄H₉))₂ (2) were used to prepare new 7, 9 and 10-coordinated lanthanum(III) complexes; La(1)₂Cl₃(H₂O)₂ (3), La(1)₂(NO₃)₃H₂O.La(1)₂(NO₃)₃CH₃CN (4) and La(2)₂(NO₃)₃ (5), respectively. Crystallization of compound 2 in CH₃OH:CH₃CN leads to one conformer in contrast to the crystallization result from CHCl₃:n-C₇H₁₆ (two conformers). Compound 4 contains two independent nine-coordinated La(III) complexes that are different in the solvated molecules (H₂O and CH₃CN). Some structural and electronic perturbations in coordinated ligand were occurred upon complexation, that are confirmed by increase of ²J_PH, ³J_PH and ⁶J_PH coupling constants from the free ligand 1 to complexes 3 and 4. The steric repulsions in the first coordination sphere of La³⁺ ion, metal-ligand (M-L) binding strength and PO stretching frequency are very influenced by changing the counter ion from Cl⁻ to . Comparing the X-ray crystallography data of free ligand 2 with bis-chelated complex 5, it is found that the phosphoryl group is more reactive than carbonyl counterpart. A blue shift of the ν(N-H) vibration is observed in line with the weakening of the hydrogen bond from N-H···O_Phosphoryl in 1 to N-H···Cl in 3. Three dimensional butterfly-shape structures are seen in the unit cell of complex 3, which are produced by O_Water-H···O_Morpholine hydrogen bonds.