Synthesis and crystal structures of two new lead(II) complexes with the pincer-type ligand 4′-(4-chlorophenyl)-2,2′:6′,2″-terpyridine (Cl-Ph-tpy): subtle interplay of weak intermolecular interactions

A dinuclear and a tetranuclear complex of lead(II) with the pincer-type ligand 4′-(4-chlorophenyl)-2,2′:6′,2″-terpyridine (Cl-Ph-tpy), [Pb2(Cl-Ph-tpy)2(μ-I)2I2] (1) and [Pb4(Cl-Ph-tpy)4(μ-Br)4(μ-OH2)Br4]·2CH3OH (2), have been synthesized and characterized by elemental analysis, FT-IR and 1H NMR spectroscopy, and by single-crystal X-ray diffraction. In the binuclear structure of 1, the Pb atom has a hemidirected PbN3I3 environment with a Pb(μ-I)2Pb central unit. In the tetranuclear structure of 2, two crystallographically independent Pb(II) centres having hemidirected PbN3Br3 and PbN3OBr2 environments are connected to Pb(μ-Br)Pb(μ-Br)2(μ-OH2)Pb(μ-Br)Pb chains. The supramolecular features in 1 and 2 are supported through weak but directional C–H···Cl, C–H···I and C–H···Br, C–H···O, O–H···Br, and O···Br interactions and aromatic π-π stacking.

Nitronyl Nitroxide Biradical-Based Binuclear Lanthanide Complexes: Structure and Magnetic Properties

Employing a new nitronyl nitroxide biradical NITPhPzbis(NITPhPzbis = 5-(1-pyrazolyl)-1,3-bis(1’-oxyl-3’-oxido-4’,4’,5’,5’-tetramethyl-4,5-hydro-1H-imidazol-2-yl)benzene), a series of 2p-4f complexes [Ln2(hfac)6(H2O)(NITPhPzbis)] (LnIII = Gd1, Tb2, Dy3; hfac = hexafluoroacetylacetonate) were successfully synthesized. In complexes 1–3, the designed biradical NITPhPzbis coordinates with two LnIII ions in chelating and bridging modes to form a four-spin binuclear structure. Direct-current magnetic study of Gd analogue indicates that ferromagnetic exchange exists between the Gd ion and the radical while antiferromagnetic coupling dominates between two mono-radicals. Dynamic magnetic data show that the χ” signals of complex 3 exhibit frequency dependence under zero field, demonstrating slow magnetic relaxation behavior in complex 3. And the estimated values of Ueff and τ0 are about 8.4 K and 9.1 × 10−8 s, respectively.

Biomimetic Water Oxidation Catalyzed by a Binuclear Ruthenium (IV) Nitrido-Chloride Complex with Lithium Counter-Cations

The lithium salt of the binuclear nitrido complex of ruthenium (IV) Li3(Ru2NCl8·2H2O) was synthesized. Using UV spectroscopy and voltammetry, we studied complex behavior in aqueous solutions. It was found that in dilute solutions of this compound, Cl− ions are replaced by H2O molecules, and the intra-sphere redox reaction between Ru (IV) and H2O, as well as the oxidation of water with the formation of oxygen and the acidic dissociation of coordinated water molecules also have been taking place. It was established by IR spectroscopy and ESI mass spectrometric analysis that not only the binuclear structure of the complex is preserved in acidic solutions, but also its dimerization product into the tetra-ruthenium dinitrido cluster Ru4N2O5+, which is a catalyst for the water oxidation reaction. The activity of the catalyst was TOF = 0.33 s−1, TON = 304.

Coordination of a triazine ligand with CuII and AgI investigated by spectral, structural, theoretical and docking studies

Two complexes of 5-phenyl-3-(pyridin-2-yl)-1,2,4-triazine (PPTA), namely (ethanol-κO)bis(nitrato-κO)[5-phenyl-3-(pyridin-2-yl-κN)-1,2,4-triazine-κN 2]copper(II), [Cu(NO3)2(C14H10N4)(C2H6O)] or [Cu(NO3)2(PPTA)(EtOH)] (1), and bis[μ-5-phenyl-3-(pyridin-2-yl)-1,2,4-triazine]-κ3 N 1:N 2,N 3;κ3 N 2,N 3:N 1-bis[(nitrato-κO)silver(I)], [Ag2(NO3)2(C14H10N4)2] or [Ag2(NO3)2(μ-PPTA)2] (2), were prepared and characterized by elemental analysis, FT–IR spectroscopy and single-crystal X-ray diffraction. The X-ray structure analysis of 1 revealed a copper complex with square-pyramdial geometry containing two O-donor nitrate ligands along with an N,N′-donor PPTA ligand and one O-donor ethanol ligand. In the binuclear structure of 2, formed by the bridging of two PPTA ligands, each Ag atom has an AgN3O environment and square-planar geometry. In addition to the four dative interactions, each Ag atom interacts with two O atoms of two nitrate ligands on adjacent complexes to complete a pseudo-octahedral geometry. Density functional theory (DFT) calculations revealed that the geometry around the Cu and Ag atoms in 1 opt and 2 opt (opt is optimized) for an isolated molecule is the same as the experimental results. In 1, O—H...O hydrogen bonds form R 1 2(4) motifs. In the crystal network of the complexes, in addition to the hydrogen bonds, there are π–π stacking interactions between the aromatic rings (phenyl, pyridine and triazine) of the ligands on adjacent complexes. The ability of the ligand and complexes 1 and 2 to interact with ten selected biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS, Top II and B-DNA) was investigated by docking studies. The results show that the studied compounds can interact with proteins better than doxorubicin (except for TrxR and Top II).

Spectral, structural and theoretical study of the effects of thiocyanato and dicyanamido ligands on the geometry of PbIIcomplexes containing a triazinic ligand

Two lead(II) complexes of 5,6-bis(furan-2-yl)-3-(pyridin-2-yl)-1,2,4-triazine (DFPT), namely one-dimensional (1D)catena-poly[[bis[5,6-bis(furan-2-yl)-3-(pyridin-2-yl-κN)-1,2,4-triazine-κN2]lead(II)]-di-μ-thiocyanato-κ2N:S;κ2S:N], [Pb(NCS)2(C16H10N4O2)2]n,1, and binuclear di-μ-dicyanamido-κ2N1:N5;κ2N5:N1-bis{[5,6-bis(furan-2-yl)-3-(pyridin-2-yl-κN)-1,2,4-triazine-κN2](nitrato-κ2O,O′)lead(II)}, [Pb2(C2N3)2(NO3)2(C16H10N4O2)4],2, as well as DFPT itself, were prepared and identified by elemental analysis, FT–IR,1H NMR spectroscopy and single-crystal X-ray structural analyses. In the double-chain 1D coordination polymer of1and the binuclear structure of2, the Pb atom has ahemidirected-PbN6S2and a rareholodirected-PbN6O2environment, respectively, with a distorted cubic geometry. All the coordination modes of dicyanamide ligands within lead complexes were studied using the Cambridge Structural Database (CSD) to compare them with the structures of1and2. In addition to hydrogen bonds, the crystal networks are stabilized by π–π stacking interactions between the triazine, furyl and pyridine aromatic rings. The most stable theoretical structures of the title compounds predicted by density functional theory (DFT) calculations were compared with the solid-state results.

Cd and Hg coordination complexes based on a heterocyclic multidentate ligand: Synthesis, structures and photoluminescence properties

The complexes [Cd(cpbi)Cl2]·(H2O), [Hg2(cpbi)2Cl4] and [Hg(cpbi)Br2] (cpbi = [5-chloro-2-(pyrazin-2-yl)-1H-benzoimidazole]) have been synthesised using solvent evaporation reactions and structurally characterised by single-crystal X-ray diffraction. The first complex displays a one-dimensional (1-D) chain structure, the second has a binuclear structure, while the third is mononuclear. The complexes show different luminescence properties.

Structural study of the coordination behavior of a tetradentate NO3-donor amino alcohol ligand toward a CdII:HgII mixture

In this work, the reaction of 2,2′,2″-nitrilotriethanol (NTE) with a 1:1 mixture of CdI2and HgI2is investigated. The complex [Cd(NTE)2][Hg2(μ-I)2I4] was synthesized and identified by elemental analysis, FT-IR,1H NMR spectroscopy and single-crystal X-ray diffraction. The structure of the [HNTE]Cl salt is also presented. In the crystal structure of the complex, the cadmium atom has a CdN2O6environment in a slightly distorted cube geometry. This geometry is one of the rare cube geometries with a minimum distortion among the Cambridge Structural Database structures for cadmium complexes. The anionic moiety has a binuclear structure with the mercury atoms being in tetrahedral environments. In the network of the complex, in addition to O−H · · · I hydrogen bonds, there are I · · · I interactions which lead to ten-membered rings.

Mono- and binuclear tris(3-tert-butyl-2-sulfanylidene-1H-imidazol-1-yl)hydroborate bismuth(III) dichloride complexes: a soft scorpionate ligand can coordinate top-block elements

Tris(pyrazolyl)hydroborate ligands have been utilized in the fields of inorganic and coordination chemistry due to the ease of introduction of steric and electronic substitutions at the pyrazole rings. The development and use of the tris(pyrazolyl)hydroborate ligand, called a `scorpionate', were pioneered by the late Professor Swiatoslaw Trofimenko. He developed a second generation for his ligand system by the introduction of 3-tert-butyl and 3-phenyl substituents and this new ligand system accounted for many remarkable developments in inorganic and coordination chemistry in stabilizing monomeric species while maintaining an open coordination site. Bismuth is remarkably harmless among the toxic heavy metalp-block elements and is now becoming popular as a replacement for highly toxic metal elements, such as lead. Two bismuth(III) complexes of the anionic sulfur-containing tripod tris(3-tert-butyl-2-sulfanylidene-1H-imidazol-1-yl)hydroborate ligand were prepared. By recrystallization from MeOH/CH2Cl2, orange crystals of dichlorido(methanol-κO)[tris(3-tert-butyl-2-sulfanylidene-1H-imidazol-1-yl-κS)hydroborato]bismuth(III), [Bi(C21H34BN6S3)Cl2(CH4O)], (I), were obtained, manifesting a mononuclear structure. By using a noncoordinating solvent, red crystals of the binuclear structure with bridging Cl atoms were obtained, namely di-μ-chlorido-bis{chlorido[tris(3-tert-butyl-2-sulfanylidene-1H-imidazol-1-yl-κS)hydroborato]bismuth(III)}, [Bi2(C21H34BN6S3)2Cl4], (II). These complexes show {BiIIIS3Cl2O} and {BiIIIS3Cl3} coordination geometries with average BiIII—S bond lengths of 2.73 and 2.78 Å in (I) and (II), respectively. The overall BiIIIcoordination geometry is distorted octahedral due to stereochemically active lone pairs. The three BiIII—S bond lengths are almost equal in (I) but show considerable differences in (II), with one long and two shorter distances that also correlate with changes in the UV–Vis and1H NMR spectra. For direct measurements of the Bi—S/Cl coordination, ligand K-edge X-ray absorption measurements were carried out in combination with ground and excited-state electronic structure analyses. Forp-block elements, these sulfur-containing ligands are useful for preparing the appropriate complexes due to their flexible coordination geometry.

Synthesis, structure and magnetic properties of a binuclear copper(II) complex constructed by a new coordination mode of the tetrachlorophthalate ligand

A binuclear complex [Cu2(tcpa)2(bipy)2(H2O)3] (1) (H4tcpa = tetrachlorophthalic acid, bipy = 2,2′-bipyridine) has been synthesized and structurally characterized. Two independent CuII centers Cu1 and Cu2 are both five-coordinated in distorted square pyramids. The tetrachlorophthalate (tcpa2–) anions show a new coordination mode: one is monodentate at Cu1, and the other displays a bridging μ2-O,O″ fashion linking Cu1 and Cu2, thus forming the binuclear structure of 1. Variable-temperature magnetic susceptibility data show weak antiferromagnetic coupling between the two CuII ions.

Crystal structure, magnetic, fluorescent, electrochemical properties and thermal stability of a new copper(II) coordination polymer [Cu2(C5H4NCOO)2(C7H5N4)2]n

A new copper(II) coordination polymer [Cu2(C5H4NCOO)2(C7H5N4)2]n (1) has been synthesized with 4-pyridinecarboxylate and 3-(pyridin-2-yl)-1,2,4-triazolyl ligands. The crystal structure shows that two neighboring copper(II) ions are coordinated with two deprotonated (anionic) 3-(pyridin-2-yl)-1,2,4-triazole ligands to form a binuclear structure. Adjacent binuclear units are linked by 4-pyridinecarboxylate anions to form a three-dimensional network structure. The magnetic, fluorescent, and electrochemical properties and thermal stability of 1 were studied. The results show that 1 exhibits antiferromagnetic interaction, and upon excitation at 318 nm, it has an intense fluorescent emission at approximately 430 nm. The electron transfer of 1 is irreversible in electrode reactions. The thermogravimetric analysis shows that 1 is stable below 240 °C.