From Simple Palladium(II) Monomers to 2D Heterometallic Sodium-Palladium(II) Coordination Networks with 2-Halonicotinates.

The 2D heterometallic sodium-palladium(II) coordination polymers with 2-halonicotinates [2-chloropyridine-3-carboxylate (2-chloronicotinate), 2-Clnic- and 2-bromopyridine-3-carboxylate (2-bromonicotinate), 2-Brnic-], {[Na2(H2O)2(µ-H2O)4PdCl2(µ-2-Clnic-N:O')2]}n (1), and {[Na2(H2O)2(µ-H2O)4PdBr2(µ-2-Brnic-N:O')2]·2H2O}n (2) were prepared in aqueous solutions under the presence of NaHCO3, while palladium(II) monomers with the neutral 2-chloronicotinic and 2-bromonicotinic acid ligands, [PdCl2(2-ClnicH-N)2]·2DMF (3) and [PdCl2(2-BrnicH-N)2]·2DMF (4), were prepared in DMF/water mixtures (DMF = N,N'-dimethylformamide). The zigzag chains of water-bridged sodium ions are in turn bridged by [PdCl2(2-Clnic)2]2- moieties in 1 or by [PdBr2(2-Brnic)2]2- moieties in 2, leading to the formation of the infinite 2D coordination networks of 1 or 2. The DFT calculations showed the halosubstituents type (Cl vs Br) does not have an influence on the formation of either trans or cis isomers. The trans isomers were found in all reported compounds; being more stable for about 10 to 15 kJ mol-1. The 2D coordination networks 1 and 2 are more stabilized by the formation of Na-Ocarboxylate bonds, comparing to the stabilization of palladium(II) monomers 3 and 4 by hydrogen-bonding with DMF molecules. The difference in DFT calculated energy stabilization for 1 and 2 is ascribed to the type of halosubstituents and to the presence/absence of lattice water molecules in 1 and 2. The compounds show no antibacterial activity toward reference strains of Escherichia coli and Staphylococcus aureus bacteria and no antiproliferative activity toward bladder (T24) and lung (A549) cancer cell lines.

Anion-assisted supramolecular assemblies of zinc(II) complexes with isonicotinamide.

Five zinc(II) coordination compounds, [ZnCl2(isn)2] (1), [ZnBr2(isn)2] (2), [Zn(NO3)2(H2O)(isn)2] (3), [Zn(CH3COO)2(isn)]2 (4) and [Zn(isn)4(H2O)2](ClO4)2 (5) (isn = isonicotinamide), were prepared by the reactions of the isonicotinamide (pyridine-4-carboxamide, isn) and corresponding zinc(II) salts. Their crystal structures were determined by the single-crystal X-ray diffraction method. The coordination environment of zinc(II) is tetrahedral in the compounds containing small halide anions (chloride, bromide), 1 and 2. An expansion of the zinc(II) coordination environment to the octahedral is observed in the presence of the monodentate and bridging nitrate ions in 3. The coordination environments of both zinc(II) ions in dimeric acetate complex 4 is also enlarged in the comparison with 1 and 2, one zinc(II) ion being octahedrally coordinated and the other being pentacoordinated. The zinc(II) ion in 5 also reaches higher coordination environment (octahedral), which is enabled by binding of additional water molecules, since the perchlorate ion is uncoordinated. The supramolecular amide-amide homosynthon R 2 2 ( 8 ) is preserved in the presence of halide, nitrate and acetate ions (1-4), but it is completely disrupted in the crystal packing of 5 due to the presence of the bulky perchlorate anion. Spectroscopic analysis of compounds 1-5 was performed by IR spectroscopy in the solid state and by 13C NMR spectroscopy in the DMSO solutions. The NMR data support a complete decomposition of 3 in the DMSO solution, but 1, 2, 4 and 5 remain unchanged in the solution. Thermal properties of the coordination compounds were also investigated by TGA and DSC methods.

The Solvent Effect on Composition and Dimensionality of Mercury(II) Complexes with Picolinic Acid.

Three new mercury(II) coordination compounds, {[HgCl(pic)]}n (1), [HgCl(pic)(picH)] (2), and [HgBr(pic)(picH)] (3) (picH = pyridine-2-carboxylic acid, picolinic acid) were prepared by reactions of the corresponding mercury(II) halides and picolinic acid in an aqueous (1) or alcohol-methanol or ethanol (2 and 3) solutions. Two different types of coordination compounds were obtained depending on the solvent used. The crystal structures were determined by the single-crystal X-ray structural analysis. Compound 1 is a one-dimensional (1-D) coordination polymer with mercury(II) ions bridged by chelating and bridging N,O,O'-picolinate ions. Each mercury(II) ion is four-coordinated with a bidentate picolinate ion, a carboxylate O atom from the symmetry-related picolinate ion and with a chloride ion; the resulting coordination environment can be described as a highly distorted tetrahedron. Compounds 2 and 3 are isostructural mononuclear coordination compounds, each mercury(II) ion being coordinated with the respective halide ion, N,O-bidentate picolinate ion, and N,O-bidentate picolinic acid in a highly distorted square-pyramidal coordination environment. Compounds 1-3 were characterized by IR spectroscopy, PXRD, and thermal methods (TGA/DSC) in the solid state and by 1H and 13C NMR spectroscopy in the DMSO solution.

Synthesis and crystal structure of a 6-chloro-nicotinate salt of a one-dimensional cationic nickel(II) coordination polymer with 4,4'-bi-pyridine.

A 6-chloro-nicotinate (6-Clnic) salt of a one-dimensional cationic nickel(II) coordination polymer with 4,4'-bi-pyridine (4,4'-bpy), namely, catena-poly[[[tetra-aqua-nickel(II)]-µ-4,4'-bi-pyridine-κ2 N:N'] bis-(6-chloro-nicotinate) tetra-hydrate], {[Ni(C10H8N2)(H2O)4](C6H3ClNO2)2·4H2O} n or {[Ni(4,4'-bpy)(H2O)4](6-Clnic)2·4H2O} n , (1), was prepared by the reaction of nickel(II) sulfate hepta-hydrate, 6-chloro-nicotinic acid and 4,4'-bi-pyridine in a mixture of water and ethanol. The mol-ecular structure of 1 comprises a one-dimensional polymeric {[Ni(4,4'-bpy)(H2O)4]2+} n cation, two 6-chloro-nicotinate anions and four water mol-ecules of crystallization per repeating polymeric unit. The nickel(II) ion in the polymeric cation is octa-hedrally coordinated by four water mol-ecule O atoms and by two 4,4'-bi-pyridine N atoms in the trans position. The 4,4'-bi-pyridine ligands act as bridges and, thus, connect the symmetry-related nickel(II) ions into an infinite one-dimensional polymeric chain extending along the b-axis direction. In the extended structure of 1, the polymeric chains of {[Ni(4,4'-bpy)(H2O)4]2+} n , the 6-chloro-nicotinate anions and the water mol-ecules of crystallization are assembled into an infinite three-dimensional hydrogen-bonded network via strong O-H⋯O and O-H⋯N hydrogen bonds, leading to the formation of the representative hydrogen-bonded ring motifs: tetra-meric R 2 4(8) and R 4 4(10) loops, a dimeric R 2 2(8) loop and a penta-meric R 4 5(16) loop.

The first coordination compound of 6-fluoro-nicotinate: the crystal structure of a one-dimensional nickel(II) coordination polymer containing the mixed ligands 6-fluoro-nicotinate and 4,4'-bi-pyridine.

A one-dimensional nickel(II) coordination polymer with the mixed ligands 6-fluoro-nicotinate (6-Fnic) and 4,4'-bi-pyridine (4,4'-bpy), namely, catena-poly[[di-aqua-bis-(6-fluoro-pyridine-3-carboxyl-ato-κO)nickel(II)]-µ-4,4'-bi-pyri-dine-κ2 N:N'] trihydrate], {[Ni(6-Fnic)2(4,4'-bpy)(H2O)2]·3H2O} n , (1), was prepared by the reaction of nickel(II) sulfate hepta-hydrate, 6-fluoro-nicotinic acid (C6H4FNO2) and 4,4'-bi-pyridine (C10H8N2) in a mixture of water and ethanol. The nickel(II) ion in 1 is octa-hedrally coordinated by the O atoms of two water mol-ecules, two O atoms from O-monodentate 6-fluoro-nicotinate ligands and two N atoms from bridging 4,4'-bi-pyridine ligands, forming a trans isomer. The bridging 4,4'-bi-pyridine ligands connect symmetry-related nickel(II) ions into infinite one-dimensional polymeric chains running in the [10] direction. In the extended structure of 1, the polymeric chains and lattice water mol-ecules are connected into a three-dimensional hydrogen-bonded network via strong O-H⋯O and O-H⋯N hydrogen bonds, leading to the formation of distinct hydrogen-bond ring motifs: octa-meric R 8 8(24) and hexa-meric R 8 6(16) loops.

The first coordination compound of deprotonated 2-bromo-nicotinic acid: crystal structure of a dinuclear paddle-wheel copper(II) complex.

A copper(II) dimer with the deprotonated anion of 2-bromo-nicotinic acid (2-BrnicH), namely, tetrakis(µ-2-bromonicotinato-κ2 O:O')bis[aquacopper(-II)](Cu-Cu), [Cu2(H2O)2(C6H3BrNO2)4] or [Cu2(H2O)2(2-Brnic)4], (1), was prepared by the reaction of copper(II) chloride dihydrate and 2-bromo-nicotinic acid in water. The copper(II) ion in 1 has a distorted square-pyramidal coordination environment, achieved by four carboxyl-ate O atoms in the basal plane and the water mol-ecule in the apical position. The pair of symmetry-related copper(II) ions are connected into a centrosymmetric paddle-wheel dinuclear cluster [Cu⋯Cu = 2.6470 (11) Å] via four O,O'-bridging 2-bromo-nicotinate ligands in the syn-syn coordination mode. In the extended structure of 1, the cluster mol-ecules are assembled into an infinite two-dimensional hydrogen-bonded network lying parallel to the (001) plane via strong O-H⋯O and O-H⋯N hydrogen bonds, leading to the formation of various hydrogen-bond ring motifs: dimeric R 2 2(8) and R 2 2(16) loops and a tetra-meric R 4 4(16) loop. The Hirshfeld surface analysis was also performed in order to better illustrate the nature and abundance of the inter-molecular contacts in the structure of 1.

Mechanically Responsive Crystalline Coordination Polymers with Controllable Elasticity.

Crystalline coordination polymers tend to be brittle and inelastic, however, we now describe a family of such compounds that are capable of displaying mechanical elasticity in response to external pressure. The design approach successfully targets structural features that are critical for producing the desired mechanical output. The elastic crystals all comprise 1D cadmium(II) halide polymeric chains with adjacent metal centres bridged by two halide ions resulting in the required stacking interactions and short "4 Å" crystallographic axes. These polymeric chains (structural "spines") are further organized via hydrogen bonds and halogen bonds perpendicular to the direction of the chains. By carefully altering the strength and the geometry of these non-covalent interactions, we have demonstrated that it is possible to control the extent of elastic bending in crystalline coordination compounds.

Building inorganic supramolecular architectures using principles adopted from the organic solid state.

In order to develop transferable and practical avenues for the assembly of coordination complexes into architectures with specific dimensionality, a strategy utilizing ligands capable of simultaneous metal coordination and self-complementary hydrogen bonding is presented. The three ligands used, 2(1H)-pyrazinone, 4(3H)-pyrimidinone and 4(3H)-quinazolinone, consistently deliver the required synthetic vectors in a series of CdII coordination polymers, allowing for reproducible supramolecular synthesis that is insensitive to the different steric and geometric demands from potentially disruptive counterions. In all nine crystallographically characterized compounds presented here, directional intermolecular N-H⋯O hydrogen bonds between ligands on adjacent complex building blocks drive the assembly and orientation of discrete building blocks into largely predictable topologies. Furthermore, whether the solids are prepared from solution or through liquid-assisted grinding, the structural outcome is the same, thus emphasizing the robustness of the synthetic protocol. The details of the molecular recognition events that take place in this series of compounds have been clearly delineated and rationalized in the context of calculated molecular electrostatic potential surfaces.

Vibrational spectroscopic and DFT calculation studies of cobalt(II) complexes with 3-hydroxypicolinic acid.

Two cobalt(II) complexes with 3-hydroxypicolinic acid (3-hydroxypyridine-2-carboxylic acid, 3-OHpicH), trans-[Co(3-OHpic)2(py)2] (2) and cis-[Co(3-OHpic)2(4-pic)2] (3) (py=pyridine; 4-pic=4-picoline or 4-methylpyridine), previously synthesized and characterized by X-ray diffraction, are here studied by Raman and mid-infrared spectroscopy with the help from the corresponding DFT vibrational calculations using B3LYP/6-311G(d,p) computational model. Intramolecular O-H⋯O hydrogen bond appears in both complexes 2 and 3, while weak C-H⋯O hydrogen bonds assemble molecules of 2 or 3 into 3D architecture. A complete presentation of all Raman, infrared and theoretical results is given for complex 3. The measured spectra are shown, relative intensities and bandwidths are discussed and the assignment of vibrational bands is given on the basis of the DFT calculations. The calculated spectra agree very well with the presented experimental findings, thanks to the suitable grouping of modes. The same vibrational calculations also reveal insignificant influence of H→CH3 substitution for the spectroscopic characterization of the complex. A careful study of differences between calculated and observed wavenumbers suggests that modified single-factor scaling is actually better than the classic multi-factor scaling approach.

A new coordination mode of 6-methylnicotinic acid in trans-tetraaquabis(6-methylpyridine-3-carboxylato-kappaO)cobalt(II) tetrahydrate.

The title compound, [Co(C7H6NO2)2(H2O)4] x 4 H2O, contains a Co(II) ion lying on a crystallographic inversion centre. The Co(II) ion is octahedrally coordinated by two 6-methylpyridine-3-carboxylate ligands in axial positions [Co-O = 2.0621 (9) A] and by four water molecules in the equatorial plane [Co-O = 2.1169 (9) and 2.1223 (11) A]. There are also four uncoordinated water molecules. The 6-methylpyridine-3-carboxylate ligands are bound to the Co(II) ion in a monodentate manner through a carboxylate O atom. There is one strong intramolecular O-H...O hydrogen bond, and six strong intermolecular hydrogen bonds of type O-H...O and one of type O-H...N in the packing, resulting in a complex three-dimensional supramolecular structure.

A one-dimensional CdII coordination polymer: catena-poly[cadmium(II)-bis(mu-6-methylpicolinato)].

In the title compound, [Cd(C(7)H(6)NO(2))2]n, the Cd(II) ion has a distorted octahedral geometry. The 6-methylpyridine-2-carboxylate anions are perpendicular to one another and act as bidentate and bridging ligands. Two carboxylate O atoms bridge the Cd(II) ions, forming centrosymmetric dinuclear units. These units are further connected via carboxylate O atoms into a one-dimensional polymeric chain which extends in the [100] direction.

trans-Bis(dimethyl sulfoxide-kappaO)bis(3-oxo-3,4-dihydroquinoxaline-2-carboxylato-kappa2N1,O2)copper(II).

The title compound, [Cu(C(9)H(5)N(2)O(3))(2)(C(2)H(6)OS)(2)], consists of octahedrally coordinated Cu(II) ions, with the 3-oxo-3,4-dihydroquinoxaline-2-carboxylate ligands acting in a bidentate manner [Cu-O = 1.9116 (14) A and Cu-N = 2.1191 (16) A] and a dimethyl sulfoxide (DMSO) molecule coordinated axially via the O atom [Cu-O = 2.336 (5) and 2.418 (7) A for the major and minor disorder components, respectively]. The whole DMSO molecule exhibits positional disorder [0.62 (1):0.38 (1)]. The octahedron around the Cu(II) atom, which lies on an inversion centre, is elongated in the axial direction, exhibiting a Jahn-Teller effect. The ligand exhibits tautomerization by H-atom transfer from the hydroxyl group at position 3 to the N atom at position 4 of the quinoxaline ring of the ligand. The complex molecules are linked through an intermolecular N-H...O hydrogen bond [N...O = 2.838 (2) A] formed between the quinoxaline NH group and a carboxylate O atom, and by a weak intermolecular C-H...O hydrogen bond [3.392 (11) A] formed between a carboxylate O atom and a methyl C atom of the DMSO ligand. There is a weak intramolecular C-H...O hydrogen bond [3.065 (3) A] formed between a benzene CH group and a carboxylate O atom.