Self-assembly of polymer and sheet structures in palladium(II) complexes containing carboxylic acid substituents

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.

Isostructural coordination polymers of the tethering naphthalene anchored bis(2-methylpyridinecarboxamide) ligand: single crystal, XPS, EDS and theoretical studies

Interesting correlation between various analytical techniques has been made in this work concerning new isostructural CPs.

Controlled Synthesis of Palladium Nanoparticles with Size-Dependent Catalytic Activities Enabled by Organic Molecular Cages

Particle size plays a key role in the performance of metal nanoparticles (MNPs). However, the size-controlled synthesis of MNPs still represents a challenging task. In this work, we revealed a strong solvent effect on the growth of palladium nanoparticles (PdNPs), which was directed by a porous [2 + 3] organic molecular cage (OMC, Phos-cage) containing triphenylphosphine moieties. PdNPs with different average diameters of 0.8, 1.2, and 3.3 nm supported by Phos-cage were obtained by simply varying the reaction media. The catalytic performance of such ultrafine PdNPs in the reduction of p-nitrophenol and a Suzuki-Miyaura coupling reaction has been studied, which clearly shows size-dependent catalytic activity and stability. The knowledge gained in this study, controlling the size of PdNPs supported by the OMC template in different solvents, will open new possibilities for size-controlled synthesis of ultrafine MNPs with high catalytic activity and stability.

Cyclometallated platinum(ii) and palladium(ii) complexes containing 1,5-diarylbiguanides: synthesis, characterisation and hydrogen bond-directed assembly

[M(ppy)(big)] (M = Pt(ii), Pd(ii), big = 1,5-diarylbiguanide) complexes are synthesised and their promise as tectons for hydrogen bond-directed assembly is explored.

Organometallic chemistry meets crystal engineering to give responsive crystalline materials

Dynamically porous crystalline materials have been obtained by engineering organometallic molecules. This feature article deals with organometallic wheel-and-axle compounds, molecules with two relatively bulky groups (wheels) connected by a linear spacer. The wheels are represented by half-sandwich Ru(ii) moieties, while the spacer can be covalent or supramolecular in character. Covalent spacers are obtained using divergent bidentate ligands connecting two [(arene)RuX2] groups. Supramolecular spacers are instead obtained by exploiting the dimerization of COOH or C(O)NH2 groups appended to N-based ligands. A careful choice of ligand functional groups and X ligands leads to the isolation of crystalline materials with remarkable host-guest properties, evidenced by the possibility of reversibly capturing/releasing volatile guests through heterogenous solid-gas reactions. Structural correlations between the crystalline arrangement of the apohost and the host-guest compounds allow us to envisage the structural path followed by the system during the exchange processes.

Guest induced head-to-tail columnar assembly of 5,17-difunctionalized calix[4]arene

Calix[4]arenes often form dimeric capsules or up-down bilayer arrangements in the solid state. The head-to-tail polymeric columnar structure found in the cocrystals composed of 5,17-difunctionalized calix[4]arene 1 and organic guests represents another structural motif for calix[4]arenes.

Hydrogen-bond networks in polymorphs and solvates of metallorganic complexes containing ruthenium and aminoamide ligands

The hydrogen-bond networks of half-sandwich Ru(ii) complexes containing primary and secondary amide groups are described together with their guest inclusion properties.

A three-dimensional supramolecular framework of silver(I), 2-phenylquinoline-4-carboxylate and 4,4′-bipyridine

A novel supramolecular framework,catena-poly[[[aqua(2-phenylquinoline-4-carboxylato-κO)silver(I)]-μ-4,4′-bipyridine-κ2N:N′] dihydrate], {[Ag(C16H10NO2)(C10H8N2)(H2O)]·2H2O}n, has been synthesized and structurally characterized. The AgIcentres are four-coordinated and bridged by 4,4′-bipyridine (4,4′-bipy) ligands to form a one-dimensional Ag–bipy chain. The Ag–bipy chains are further linked together by intermolecular O—H...O and O—H...N hydrogen-bonding interactions between adjacent chains, resulting in a three-dimensional framework.

A versatile diphosphine ligand: cis and trans chelation or bridging, with self association through hydrogen bonding

The diphosphine ligand, N,N'-bis(2-diphenylphosphinoethyl)isophthalamide, dpipa, contains two amide groups and can form cis or trans chelate complexes or cis,cis or trans,trans bridged complexes. The amide groups are likely to be involved in intramolecular or intermolecular hydrogen bonding. This combination of properties of the ligand dpipa leads to very unusual structural properties of its complexes, which often exist as mixtures of monomers and dimers in solution. In the complex [Au2(μ-dpipa)2]Cl2, the ligands adopt the trans,trans bridging mode, with linear gold(I) centers, and the amide groups hydrogen bond to the chloride anions. In [Pt2Cl4(μ-dpipa)2], the ligands adopt the cis,cis bridging mode, with square planar platinum(II) centers, and the amide groups form intermolecular hydrogen bonds to the chloride ligands to form a supramolecular one-dimensional polymer. Both the monomeric and dimeric complexes [PtMe2(dpipa)] and [Pt2Me4(μ-dpipa)2] have cis-PtMe2 units with cis chelating or cis,cis bridging dpipa ligands respectively; each forms a supramolecular dimer through hydrogen bonding between amide groups and each contains an unusual NH···Pt interaction. An attempted oxidative addition reaction with methyl iodide gave the complex [PtIMe(dpipa)], which contains trans chelating dpipa, while a reaction with bromine gave a disordered complex with approximate composition [Pt2Me3Br5(μ-dpipa)2], which contains trans,trans bridging dpipa ligands.

Tetra-kis(μ-2-phenyl-quinoline-4-carboxyl-ato-κ(2)O:O')bis-[(methanol-κO)copper(II)]

The title complex, [Cu₂(C₁₆H₁₀NO₂)₄(CH₃OH)₂], consists of centrosymmetric wheel-shaped dinuclear neutral mol­ecules in which each Cu^II atom is coordinated in a slightly distorted square-pyramidal geometry by four O atoms of carboxyl­ate groups from different ligands at the basal plane and an O atom of a methanol mol­ecule at the axial position. In the crystal, the dinuclear complex mol­ecules are linked into one-dimensional supra­molecular columns parallel to the b axis by O—H⋯N hydrogen bonds and π–π stacking inter­actions [centroid–centroid distance = 3.7259 (11) Å].

catena-Poly[[[aqua-(5-carb-oxy-pyridine-3-carboxyl-ato-κN)copper(I)]-μ-4,4'-bipyridine-κN:N'] monohydrate]

In the title compound, {[Cu(C₇H₄NO₄)(C₁₀H₈N₂)(H₂O)]·H₂O}_n, the Cu^I ion is coordinated by the N atom from a 5-carb­oxy­pyridine-3-carboxyl­ate anion, two N atoms from two 4,4′-bipyridine (4,4′-bipy) ligands and one water mol­ecule in a distorted tetra­hedral geometry. The 4,4′-bipy ligands bridge the Cu^I ions into polymeric chains propagating in [201]. The latticeand the coordinating water mol­ecules as well as the carboxy OH function are involved in the formation of inter­molecular O—H⋯O hydrogen bonds, which consolidate the crystal packing.

trans-Dichloridobis[(pyridin-4-yl)boronic acid-κN]palladium(II) dimethyl sulfoxide disolvate

In the title compound, [PdCl₂(C₅H₆BNO₂)₂]·2C₂H₆OS, the Pd^II ion is located on an inversion centre and is four-coordinated in a trans square-planar geometry by two chloride ions and two (pyridin-4-yl)boronic acid ligands. The Pd—N and Pd—Cl distances are 2.023 (2) and 2.2977 (7) Å, respectively, and the average N—Pd—Cl angle is 90°. The dimethyl sulfoxide solvent mol­ecules play a key role in the crystal structure by bridging the complex mol­ecules via O—H⋯O hydrogen bonds, forming tapes running along the b axis. C—H⋯O inter­actions also contribute to the cohesion of the crystal.

Bis(μ-2-phenyl-quinoline-4-carboxyl-ato)-κO,O':O;κO:O,O'-bis-[(2,2'-bipyridine-κN,N')(2-phenyl-quinoline-4-carboxyl-ato-κO,O')cadmium(II)]

The neutral binuclear title complex, [Cd(2)(C(16)H(10)NO(2))(4)(C(10)H(8)N(2))(2)], is centrosymmetric, with the inversion center generating the central (μ-O)(2)Cd(2) bridge. The Cd(II) ion is in a strongly distorted CdN(2)O(5) penta-gonal-bipyramidal geometry, defined by two N atoms from one 2,2'-bipyridine ligand and five O atoms from three 2-phenyl-quinoline-4-carboxyl-ate ligands, one monodentate, two bidentate. Weak inter-molecular π-π inter-actions [centroid-centroid distance = 3.712 (3) Å] help to establish the packing of the structure.

1H, 13C and 15N nuclear magnetic resonance coordination shifts in Au(III), Pd(II) and Pt(II) chloride complexes with phenylpyridines

1H, 13C and 15N nuclear magnetic resonance studies of gold(III), palladium(II) and platinum(II) chloride complexes with phenylpyridines (PPY: 4-phenylpyridine, 4ppy; 3-phenylpyridine, 3ppy; and 2-phenylpyridine, 2ppy) having the general formulae [Au(PPY)Cl3], trans-/cis-[Pd(PPY)2Cl2] and trans-/cis-[Pt(PPY)2Cl2] were performed and the respective chemical shifts (delta1H, delta13C and delta15N) reported. 1H, 13C and 15N coordination shifts (i.e. differences between chemical shifts of the same atom in the complex and ligand molecules: Delta(coord)(1H) = delta(complex)(1H)-delta(ligand)(1H), Delta(coord)(13C) = delta(complex)(13C)-delta(ligand)(13C), Delta(coord)(15N) = delta(complex)(15N)-delta(ligand)(15N)) were discussed in relation to the type of the central atom (Au(III), Pd(II) and Pt(II)), geometry (trans-/cis-) and the position of a phenyl group in the pyridine ring system.

4-Carb-oxy-2-methyl-1H-imidazol-3-ium-5-carboxyl-ate monohydrate

In the title compound, C₆H₆N₂O₄·H₂O, one carboxyl group is deprotonated and one imidazole N atom is protonated. The organic mol­ecule, excluding methyl H atoms, is essentially planar, with an r.m.s. deviation of 0.0156 (1) Å. In the crystal structure, inter­molecular N—H⋯O hydrogen bonds link mol­ecules into chains along the b axis; these chains are further linked via O—H⋯O hydrogen bonds involving the water O atoms and carboxyl O atoms, generating a two-dimensional supra­molecular framework.

Poly[bis(μ-2,6-dimethylpyridinium-3,5-dicarboxylato-κ2O3:O5)copper(II)]

In the title coordination polymer, [Cu(C₉H₈NO₄)₂]_n, the Cu atom, located on a twofold rotation axis, is four coordinate in a distorted square-planar environment. Each 2,6-dimethyl­pyridinium-3,5-dicarboxyl­ate anion bridges two Cu atoms, forming a two-dimensional coordination polymer. A three-dimensional supra­molecular network is built from N—H⋯O hydrogen bonds involving the pyridinium NH and the carboxyl COO groups.

Curcumin and cyclopalladated complexes: a recipe for bifunctional biomaterials

The first examples of binuclear and mononuclear ortho-palladated complexes based on a functionalized 2-phenylquinoline ligand have been synthesized and fully characterized. Conjugating cyclopalladated fragments to curcumin family biologically active beta-diketones gives in one single molecule two different functionalities. The structural variations based on the curcuminoid structure have been tested for their in vitro cytotoxic activity. The activity of complexes comprised of a cyclopalladated fragment conjugated to functionalized bioactive ligands, represents the potential of organometallic systems in generating new bifunctional biomaterials.

Structural variation in copper(I) complexes with pyridylmethylamide ligands: structural analysis with a new four-coordinate geometry index, tau4

Four Cu(I) complexes were synthesized with a family of pyridylmethylamide ligands, HL(R) [HL(R) = N-(2-pyridylmethyl)acetamide, R = null; 2,2-dimethyl-N-(2-pyridylmethyl)propionamide, R = Me(3); 2,2,2-triphenyl-N-(2-pyridylmethyl)acetamide, R = Ph(3))]. Complexes 1-3 were synthesized from the respective ligand and [Cu(CH(3)CN)(4)]PF(6) in a 2 : 1 molar ratio: [Cu(HL)(2)]PF(6) (1), [Cu(2)(HL(Me3))(4)](PF(6))(2) (2), [Cu(HL(Ph3))(2)]PF(6) (3). Complex 4, [Cu(HL)(CH(3)CN)(PPh(3))]PF(6), was synthesized from the reaction of HL with [Cu(CH(3)CN)(4)]PF(6) and PPh(3) in a 1 : 1 : 1 molar ratio. X-Ray crystal structures reveal that complexes 1, 3 and 4 are mononuclear Cu(I) species, while complex 2 is a Cu(I) dimer. The copper ions are four-coordinate with geometries ranging from distorted tetrahedral to seesaw in 1, 2, and 4. Complexes 1 and 2 are very air sensitive and they display similar electrochemical properties. The coordination geometry of complex 3 is nearly linear, two-coordinate. Complex 3 is exceptionally stable with respect to oxidation in the air, and its cyclic voltammetry shows no oxidation wave in the range of 0-1.5 V. The unusual inertness of complex 3 towards oxidation is attributed to the protection from bulky triphenyl substituent of the HL(Ph3) ligand. A new geometric parameter for four-coordinate compounds, tau(4), is proposed as an improved, simple metric for quantitatively evaluating the geometry of four-coordinate complexes and compounds.