Two-dimensional molecular pattern in the structure of a calcium(II) complex with pyrazine-2,3-dicarboxylate and water ligands

The structure of di(aquo-O)(pyrazine-2,3-dicarboxylato-N,O; -O′,O′′) calcium(II) hydrate [Ca(2,3-PZDC)(H₂O)₂·;H₂O] contains molecular sheets in which Ca(II) ions are bridged by the carboxylate groups of the ligand molecules. Two bridging paths are evident. In the first, an N,O-bonding moiety formed by a hetero-ring nitrogen atom and the carboxylate oxygen atom nearest to it and both oxygen atoms of the second carboxylic group are active. The second path is formed by the other oxygen atom from the carboxylic group involved in the N,O-bonding moiety and an oxygen atom from the second carboxylic group. The latter atom is bidentate. A two-dimensional molecular pattern is formed. Each Ca(II) ion is also coordinated by two water oxygen atoms, making the number of coordinated atoms eight. The coordination polyhedron is a distorted pentagonal bipyramid with an oxygen atom at the apex on one side of the equatorial plane and two oxygen atoms forming the apices on the other side.     

Catenated polymeric molecular patterns in structures of two calcium(II) complexes with pyridine-2,3-dicarboxylate (quinolinic) and water ligands

The structure of triclinic catena-tetraquo(μ-pyridine-2,3-dicarboxylato-N,O; O′)calcium(II) is composed of two symmetry independent Ca(II) ions and two independent ligand molecules. Each Ca(II) is coordinated by a N,O-bonding moiety of a ligand, four water oxygens, and a carboxylate oxygen donated by an adjacent bridging ligand. The resulting molecular ribbons are propagating in the [010] crystal direction. Both Ca(II) ions are eight coordinate forming a capped pentagonal bipyramidal with strongly distorted pentagonal equatorial planes. Hydrogen bonds between carboxylate oxygens and coordinated waters are responsible for the stability of the structure. The orthorhombic structure of catena-trisaquo[(μ-2, 3-dicarboxypyridin-1-ium-O,O′; O′′) (H pyridine-2,3-dicarboxylato-N,O)]calcium(II) is composed of molecular ribbons in which the bridging of Ca(II) ions occurs through a ligand using one bidentate carboxylate. The other carboxylate of this ligand donates only one O atom to Ca(II), the second remaining inactive. A proton is attached to the hetero-nitrogen. Each Ca(II) is also chelated by a N,O-bonding moiety of a second ligand, which does not bridge and its second carboxylate remains protonated. Three water oxygen atoms complete the coordination around the Ca(II) ion to eight. The resulting coordination polyhedron is a capped pentagonal bipyramid with a strongly distorted equatorial plane. Hydrogen bonds in which coordinated waters act as donors are responsible for the stability of the structure.     

Synthesis and characterization of Co(II), Ni(II), Zn(II) and Cu(II) complexes with a new tetraazamacrocyclic Schiff base ligand containing a piperazine moiety: X-ray crystal structure determination of the Co(II) complex

Two macrocyclic Schiff base ligands, L¹ [1+1] and L² [2+2], have been obtained in a one-pot cyclocondensation of 1,4-bis(2-formylphenyl)piperazine and 1,3-diaminopropane. Unfortunately, because of the low solubility of both ligands, their separation was unsuccessful. In the direct reaction of these mixed ligands (L¹ and L²) and the appropriate metal ions only [CoL¹(NO₃)]ClO₄, [NiL¹](ClO₄)₂, [CuL¹](ClO₄)₂ and [ZnL¹(NO₃)]ClO₄ complexes have been isolated. All the complexes were characterized by elemental analyses, IR, FAB-MS, conductivity measurements and in the case of the [ZnL¹(NO₃)]ClO₄ complex with NMR spectroscopy.     

A novel dimeric zinc(II) complex with a tripodal peptide ligand: a structure stabilized by ligand sharing

The crystal structure of a novel dimeric zinc(II) complex, [ZnL(H₂O)]₂(ClO₄)₂·4H₂O (L?=?N-(bis(2-pyridyl)methyl)-2-pyridinecarboxamide), has been determined by X-ray diffraction. In this complex each planar N_py–N_amido–N_py moiety of the ligand coordinates to one zinc ion and the pendant pyridine of one [ZnL] unit completes the coordination sphere of a [ZnL] neighbor. Units of the complex are connected in a two-dimensional network by intermolecular hydrogen bonds. The thermodynamic properties of the ligand with bivalent metal ions Co(II), Ni(II), Cu(II) and Zn(II) were studied by potentiometric titration and the order of the stability constants is in agreement with the Irving–Williams series. The dimeric complex is stabilized through ligand sharing, as confirmed by the crystal structure and thermodynamic properties.     

Synthesis and structure of highly substituted pyrazole ligands and their complexes with platinum(II) and palladium(II) metal ions

Reaction of 3-methoxycarbonyl-2-methyl- or 3-dimethoxyphosphoryl-2-methyl-substituted 4-oxo-4H-chromones 1 with N-methylhydrazine resulted in the formation of isomeric, highly substituted pyrazoles 4 (major products) and 5 (minor products). Intramolecular transesterification of 4 and 5 under basic conditions led, respectively, to tricyclic derivatives 7 and 8. The structures of pyrazoles 4a (dimethyl 2-methyl-4-oxo-4H-chromen-3-yl-phosphonate) and 4b (methyl 4-oxo-2-methyl-4H-chromene-3-carboxylate) were confirmed by X-ray crystallography. Pyrazoles 4a and 4b were used as ligands (L) in the formation of ML₂Cl₂ complexes with platinum(II) or palladium(II) metal ions (M). Potassium tetrachloroplatinate(II), used as the metal ion reagent, gave both trans-[Pt(4a)₂Cl₂] and cis-[Pt(4a)₂Cl₂], complexes with ligand 4a, and only cis-[Pt(4b)₂Cl₂] isomer with ligand 4b. Palladium complexes were obtained by the reaction of bis(benzonitrile)dichloropalladium(II) with the test ligands. trans-[Pd(4a)₂Cl₂] and trans-[Pd(4b)₂Cl₂] were the exclusive products of these reactions. The structures of all the complexes were confirmed by IR, ¹H NMR and FAB MS spectral analysis, elemental analysis and Kurnakov tests.     

Molecular sheets in the crystal structure of a Ba(II) complex with imidazole-4,5-dicarboxylate and water ligands

The structure of poly-tetraaquabis(μ-Himidazole-4,5-dicarboxylato-N,O;-O′)barium(II) dihydrate, Ba(C₅H₃N₂O₄)₂(H₂O)₄·2H₂O is built of molecular sheets in which singly-deprotonated imidazole-4,5-dicarboxylate [H(4,5-IDA)] bridges metal ions using its N, O bonding moiety and one oxygen atom of its second carboxylate group. Each barium(II) is coordinated by N, O bonding moieties of two ligands, two carboxylate oxygen atoms of two other ligands and four waters. The coordination number of Ba(II) is ten, and the coordination polyhedron contains fourteen faces. A network of hydrogen bonds is responsible for the stability of the crystal.     

Synthesis,spectra, crystal structure and thermal properties of a polymeric 1-D cobalt(II) cyanato complex with hexamethylenetetramine

A new cobalt(II) cyanato complex, [Co(NCO)₂(H₂O)₂(hmt)] (I) where hmt is hexamethylenetetramine, has been synthesized and structurally characterized. The electronic spectra of the solid compound suggest octahedral cobalt and IR spectra revealed monodentate N-cyanato groups and aqua ligands, while hmt is a bridging N, N′-bidentate leading to a 1-D infinite polymeric chain. The structure has been confirmed from single crystal X-ray diffraction. Crystal data for I : Fw 319.20, a = 9.234(2), b = 11.252(2), c = 12.576(3) Å, β = 107.75(3)°, V = 1244.5(4) ų, Z = 4, T = 100 K. Crystal system : monoclinic, space group : C2/c. Hydrogen bonds of the type O–H ··· O and O–H ··· N between aqua molecules and O atom of the terminal N-cyanato groups or an N atom of hmt ligands consolidate and extend the structure to a 3-D network. The thermal properties of I are reported.     

Synthesis,crystal structures and fluorescence of cadmium(II) coordination polymers with derivatives of pyrazine-1,4-dioxide and thiocyanate as mixed-bridging ligands

Two Cd(II) coordination polymers have been synthesized with derivatives of pyrazine-1,4-dioxide and thiocyanate anion as bridging ligands and structurally determined by X-ray crystallography. Complex 1, [Cd(μ_1,3-SCN^?)₂(μ_1,6-L1)] _n (L1?=?2,5-dimethylpyrazine-1,4-dioxide), belongs to the triclinic, space group P 1 with a?=?5.7627(18)?Å, b?=?7.182(2)?Å, c?=?7.509(2)?Å, α?=?74.042(3)°, β?=?84.766(4)°, γ?=?88.162(4)°; complex 2, [Cd₂(μ_1,3-SCN^?)₄(μ₄-L2)] _n (L2?=?2,3,5,6-tetramethylpyrazine-1,4-dioxide), crystallizes in a monoclinic system with space group C2/m with a?=?10.194(4)?Å, b?=?13.491(6)?Å, c?=?8.140(3)?Å, β?=?120.372(4)°. Complex 1 shows a two-dimensional sheet structure, and in a direction the Cd(II) ions were coordinated by μ_1,3-SCN^? forming the one-dimensional chain and the L1 bridging ligand made the chains connect in the c direction leading to formation of a two-dimensional sheet on the ac plane. For 2 the one-dimensional chains in the a axis were constructed by coordination of μ_1,3-SCN^? bridging ligands with the Cd(II) ions, and in b and c directions the chains were joined by L2 bridging ligands leading to a three-dimensional structure. In 2 L2 displays a μ₄-bridging coordination mode. Both complexes exhibit strong fluorescence emission.     

Synthesis,crystal structure,spectroscopy and magnetism of a trinuclear nickel(II) complex with 3,5-pyrazoledicarboxylic acid as bridge ligands

A new complex of [Ni₃(dcp)₂(H₂O)₁₀] (1) (H₃dcp = 3,5-pyrazoledicarboxylic acid) has been synthesized from H₃dcp and Ni(NO₃)₂·6H₂O by hydrothermal reaction. Complex 1 has the discrete trinuclear structure. Three Ni(II) ions are bridged by two dcp³⁻ ligands, with 10 coordinated water molecules as terminal ligands. The molecules of [Ni₃(dcp)₂(H₂O)₁₀] extend into three-dimensional supramolecular architectures by intermolecular O–H···O hydrogen bonds as well as π-π stacking interactions. Magnetic susceptibility measurement shows that a weak antiferromagnetic interaction is operative between nickel(II) ions and an excellent simulation of the experimental data gives D = 5.27 cm⁻¹, J = −2.19 cm⁻¹ and g = 2.05.     

Synthesis,crystal structure,and magnetic properties of a new Fe(II) complex with reduced radical ligands

A new Fe(II) complex, [Fe(HIM2Py)₂(N(CN)₂)₂]?·?2H₂O (HIM2py?=?1-hydroxyl-2(2′-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1?H-imidazole), has been synthesized and characterized. The X-ray analysis reveals that HIM2py ligands are coordinated to iron as an unusual six-membered bidentate chelate with κ²N(py), O(HIM) mode. The variable-temperature magnetic susceptibility suggests that weak antiferromagnetic interactions exist in the complex.     

Preparation and characterization of Mg(II)-, Ca(II) and Cd(II) complexes of 1,2-ethanediol and water

Mixed ligand complexes of different compositions were prepared with water, sulfate ion and 1,2-ethanediol as ligand. IR spectra and the thermoanalytical curves of the complexes were recorded. Oxygen atoms bound by one or two coordinate bonds to the metal ion, or by hydrogen-bonds in the crystal, were observed. As for the water molecule, 1,2-ethanediol molecules of crystal and monohydrate type were found, depending on the type of binding of the oxygen atoms.This revised version was published online in November 2005 with corrections to the Cover Date.     

Chloro-bridged complexes of copper(II) and manganese(II) derived from unsymmetric bidentate ligands: synthesis,crystal structure and characterization

Two new usymmetric bidentate Schiff-base ligands (2-pyridyl-2-furylmethyl)imine (L1) and (2-pyridyl-phenylmethyl)imine (L2) were prepared. The crystal structures of two chloro-bridged complexes [Cu₂(μ-Cl)₂(L1)₂Cl₂] (1) and [Mn (μ-Cl)₂(L2)] (2) derived from the each ligand have been confirmed by single-crystal X-ray diffraction analysis. The complexes were characterized by IR, elemental analysis and spectroscopic methods. In complex 1, the two copper atoms are five-coordinate involving a square-pyramidal geometry having a N₂Cl₃ donor set with the two chlorine atoms bridging the two copper atoms. In complex 2, the manganese atoms are both six-coordinate. In contrast to 1, all chlorine atoms in 2 are bridging chlorides and link adjacent manganese atoms together forming 1-D infinite chains.     

Crystal structure of a calcium(II) complex with pyrazine-2,3-dicarboxylate,nitrate and water ligands

The structure of catena-[tris(aquo-O)(nitrato-O,O′)(µ-hydrogen pyrazine-2,3-dicarboxylato-O,N–O′,N′)calcium(II)][tetra(aquo-O)(μ-hydrogen pyrazine-2,3-dicarboxylato-O,N–O′,N′) calcium(I)] nitrate, {Ca[H(2,3-PZDC)](H₃O)₃(NO₃)}{Ca[H(2,3-PZDC)](H₂O)₄}⁺ (NO₃)^?, is composed of molecular ribbons in which calcium atoms are bridged by both N,O-bonding moieties of singly deprotonated ligand molecules. The hydrogen atom donated by one carboxylic group is linked by a short intramolecular hydrogen bond of 2.37 Å to an oxygen atom of the second carboxylic group of the same ligand. Two crystallographically independent Ca(II) ions exhibit different coordination modes. One is coordinated by two bonding moieties of the bridging ligand molecules, three water oxygen atoms and two oxygen atoms of a nitrate ligand. The other calcium ion is chelated by two bonding moieties donated by the bridging ligand molecules and four water oxygen atoms, forming a positively charged assembly with a nitrate anion located nearby. The coordination polyhedron of the first calcium ion is a strongly deformed bicapped pentagonal bipyramid with nine-coordinated atoms; the second calcium ion is also in a strongly deformed pentagonal bipyramid with one apex on one side of the equatorial plane and two apices on the other. Coordinated water oxygen atoms act as donors in a hydrogen-bond network.     

双大环配体与铜双核配合物的合成、晶体结构和磁偶合性质

由新型双功能配体2,6-双(1,5,9-三氮杂环十二烷)-2,6-二甲基苯甲酸(L)与溴化铜在甲醇中反应得到新型铜双核配合物[Cu~2LBr~2]Br.3H~2O单晶。晶体结构分析表明:2个Cu(II)中心离子由配体L中的羧酸基团桥联;2个等价的Cu(II)中心离子均由双功能配体L的1,5,9-三氮杂环十二烷([12aneN~3)的3个氮原子和羧酸的1个氧原子及1个Br^-离子配位,并都处在三角双锥的配位环境中;分子内Cu...Cu双核间的距离为0.5884(6)nm。变温磁化率数据表明:在同一分子中的2个铜核之间存在反铁磁偶合作用(J=-22.49cm^-^1)。     

Syntheses and crystal structures of nickel(II), copper(II), and zinc(II) complexes with a biphenyl-bridged bis(pyrrole-2-yl-methyleneamine) ligand

The reactions of nickel(II), copper(II), and zinc(II) acetate salts with a potentially tetradentate biphenyl-bridged bis(pyrrole-2-yl-methyleneamine) ligand yielded three complexes with different coordination geometries. X-ray crystal structural analysis reveals that in the nickel(II) complex each nickel is five-coordinate, distorted trigonal bipyramid. In the copper(II) complex, each copper is four-coordinate, between square planar and tetrahedral. In the zinc(II) complex, each zinc is four-coordinate with a distorted tetrahedral geometry and the molar ratio of the zinc and ligand is 1 : 2.     

Self-assembled vesicles from amphiphilic platinum(II) terpyridyl complex in water

A new cationic amphiphile (1) functionalised with platinum(II) terpyridyl unit was designed and synthesised to realize self-assembly in water. Using UV–vis and emission spectroscopy, scanning electron microscopy, cryogenic transmission electron microscopy, dynamic light scattering and time-correlated single-photon counting technique, we have demonstrated that amphiphile 1 can self-assemble into stable vesicular aggregates upon direct dissolution in water, which is rarely observed in the literature.     

A study of complex equilibria of phenylglycine with nickel(II), copper(II) and zinc(II) in water and in water - methanol solution

The complex equilibria of the systems phenylglycine — nickel(II), copper(II) and zinc(II) in water and in water — methanol solution have been studied by computer analysis of potentiometric data. The mode of coordination has been established by¹³C-NMR and IR studies.

---

Gleichgewichtsuntersuchungen der Komplexbildung von Phenylglycin mit Nickel(II), Kupfer(II) und Zink(II) in Wasser und Wasser - Methanol-Lösung

Zusammenfassung Anhand einer Computer-Analyse von potentiometrischen Daten wurden die Bildungsgleichgewichte in den Systemen Phenylglycin — Nickel(II), Kupfer(II) und Zink(II) untersucht. Der Koordinationstyp wurde mittels¹³C-NMR und IR festgestellt. Die Lösungsmittel waren Wasser und Wasser — Methanol.

     

Theoretical investigation on molecular structure of a new mononuclear copper(II) thiocyanato complex with tridentate Schiff base ligand

An asymmetrical Schiff base ligand, 4-bromo-2-(2-pyridylmethyliminomethyl)phenol (HL), and its copper(II) complex, [Cu(L)SCN] (1), have been synthesized. Complex 1 is experimentally characterized by elemental analysis, FT-IR and UV–vis spectroscopic techniques, and cyclic voltammetry. The structure of the complex has been established by single-crystal X-ray diffraction studies, which reveal a square planar geometry of the central copper(II) ion in 1. The neighboring molecules of the complex connect each other by π–π stacking interactions with centroid-to-centroid ring distance 3.653 Å. The ligand can display two possible tautomeric forms; therefore, 1 can have an alternate molecular structure. DFT calculations have been employed to investigate the structure and relative stabilities of the suggested tautomeric forms of the ligand and its corresponding copper(II) complex.     

Structures and fluorescent properties of picolinato zinc(II) and cadmium(II) complexes based on tridentate and tetradentate benzimidazole ligands

Five picolinato zinc(II) and cadmium(II) complexes, [Zn(ntb)(pic)]ClO₄·CH₃OH·2H₂O (1), [Zn(bbma)(pic)]NO₃·2CH₃OH (2), [Cd(ntb)(pic)]ClO₄·0.75CH₃OH·H₂O (3), [Cd₂(bbma)₂(pic)₂](ClO₄)₂ (4), and [Cd₂(bbp)(bbp_-H)(pic)₂(C₂H₅OH)]ClO₄ (5), have been synthesized, where pic is the anion of picolinic acid, ntb is tris(2-benzimidazolylmethyl)amine, bbma is bis(benzimidazol-2-yl-methyl)amine, and bbp is 2,6-bis(benzimidazol-2-yl)pyridine. All the complexes were characterized by X-ray single-crystal diffraction, elemental analysis, IR, fluorescence spectroscopy, and thermal gravimetric analysis. 1–3 are mononuclear complexes in which picolinate adopts a N,O-chelating mode. 4 is a symmetrical dinuclear complex bridged by two anti-parallel picolinates in a N,O,O-coordination mode. 5 is also a dinuclear complex in which only one picolinate is a bridge. A 1-D double chain is formed by extensive H-bonds and π–π stacking in 1, while single zigzag chains are formed in 5. Complexes 2–4 all exhibit 6³-hcb 2-D frameworks. They extend to form four-connected 6⁶-dia 3-D topological nets for 2 and 4 and five-connected 4⁶·6⁴-bnn 3-D topological nets for 3. The five complexes show emission maxima in the blue region in the solid state.