Tridentate Bridging Research Articles

Crystal structures and spectroscopic properties of copper(II)–dipicolinate complexes with benzimidazole ligands

The syntheses, crystal structures and spectroscopic properties of three Cu(II)–dipicolinate complexes with benzimidazole ligands, namely [Cu(bzim)(dipic)(MeOH)] (1), [Cu2(2-Etbzim)2(dipic)2]n·0.5nH2O (2) and [Cu2(2-iPrbzim)2(dipic)2]n (3), where dipic = dipicolinate, bzim = 1-H-benzimidazole, 2-Etbzim = 2-ethyl-1-H-benzimidazole and 2-iPrbzim = 2-isopropyl-1-H-benzimidazole, are reported. Crystal structure studies revealed different coordination modes of the dipicolinate ligands; tridentate chelating for monomeric complex 1, and both tridentate chelating and bridging for similar polymeric complexes 2 and 3. Polymers 2 and 3 both contain two units, in which the Cu(II) central atoms Cu1 and Cu2 have different coordination polyhedra. The first unit {Cu(dipic)2} with Cu1 is connected to the second via two bidentate carboxylate groups of an μ3-bridging dipicolinate. In the second unit, Cu2 is coordinated by two imidazole nitrogen atoms from 2-ethyl-1-H-benzimidazole (2) or 2-isopropyl-1-H-benzimidazole (3) ligands. Complex 2 is of higher symmetry and has a localized Cu(II) atom Cu2 in a special position on the twofold axis. EPR spectra of all three Cu(II) complexes, which were measured at both room temperature and 98 K, indicate distorted tetragonal coordination spheres for all the Cu(II) atoms. The g-factor relation (g//> g┴ > 2.0023) is consistent with a $$d_{{x^{2} - y^{2} }}$$ ground electronic state in each case.

A new polymorphic modification and chemisorption activity of mercury(II) N,N-di-iso-propyldithiocarbamate: Synthesis and characterisation of the heteronuclear double complex of ([Au{S2CN(iso-C3H7)2}2]2[Hg2Cl6]·OC(CH3)2)n

A new crystalline modification (γ-form, 1) of the mercury(II) N,N-di-iso-propyldithiocarbamate (Hg-iso-PDtc) has been identified and structurally characterised using single-crystal X-ray diffraction analysis. The crystal structure of 1 is presented by centrosymmetric binuclear molecules of [Hg2{S2CN(iso-C3H7)2}4], in which the mercury atoms are interconnected by two tridentate bridging iso-PDtc ligands. The chemisorption activity of the freshly precipitated Hg-iso-PDtc was tested with respect to gold(III) in a 2M HCl solution. The novel heteronuclear gold(III)–mercury(II) double complex was found to be the sole gold-containing product of the chemisorption. The isolated compound was crystallised as a solvated form, ([Au{S2CN(iso-C3H7)2}2]2[Hg2Cl6]·OC(CH3)2)n (2). It was revealed that compound 2 adopts a polymeric structure comprising two types (‘A’ and ‘B’) of isomeric gold(III) cations [Au{S2CN(iso-C3H7)2}2]+ and centrosymmetric binuclear mercury(II) anions [Hg2Cl6]2–. The supramolecular self-organisation of 2 occurs due to the relatively weak Au···S secondary interactions between neighbouring isomeric [Au{S2CN(iso-C3H7)2}2]+ cations resulting in the formation of linear cation-cationic chains of (⋯‘A’⋯‘B’⋯‘A’⋯‘B’⋯)n. The thermal behaviour of polycrystalline samples of Hg-iso-PDtc and 2 was studied by simultaneous thermal analysis (STA). It was shown that thermal decomposition is accompanied by the formation of HgS (for the original mercury(II) complex) or quantitative reduction of gold(III) to elemental gold and formation of HgCl2 along with its partial transformation to HgS (for 2).

Two 3D Zinc(II) coordination frameworks constructed from pyrazine-2,3-dicarboxylate and 1,2-bis(4-pyridyl)ethylene

Two 3D coordination polymers, {[Zn(μ3-pzdc)(μ-dpeten)0.5]∙3H2O}n (1) and [Zn(μ3-pzdc)(μ-dpeten)0.5]n (2) (H2pzdc = pyrazine-2,3-dicarboxylic acid and dpeten = 1,2-bis(4-pyridyl)ethylene) have been synthesized by hydrothermal methods and structurally characterized by elemental analysis, IR spectroscopy, single-crystal and powder X-ray diffraction. In complex 1, each pzdc ligand bridges three Zn(II) ions through forming two-dimensional layers. The adjacent 2D layers are further connected by dpeten ligand to generate a novel 3D framework containing one-dimensional large porous channel. It displays a 5-connected bnn hexagonal topology with point symbol {46.64}. Although the complex 2 was obtained under the same reaction conditions together with complex 1, it exhibits 3D→3D a 2-fold interpenetration network with 6-connected pcu α-Po primitive cubic topology with point symbol {412.63}. The adjacent three Zn(II) ions are linked by tridentate bridging pzdc ligands to form a 2D layer structure. The 2D layers are further bridged by dpeten ligand to form a 3D pillar-layered network. Moreover, thermal and photoluminescent properties of complexes 1 and 2 have also been studied.

Maleate ions as ligands in crystal structures of coordination compounds, including two uranyl complexes

Synthetic techniques, FTIR spectra and the crystal structures of two new uranyl complexes with maleate ions are reported. The crystal structure of (NH4)2[UO2(C4H2O4)2] (I) is constructed of chains with the [UO2(C4H2O4)2]2− composition. Maleate ions in I have the tridentate bridging and chelating T11-4 coordination mode with the formation of 4-membered U-containing rings. The crystal structure of Cs2[(UO2)3(C4H2O4)4]·2H2O (II) is constructed of layers with the [(UO2)3(C4H2O4)4]2− composition. Half of the maleate ions in II have the bridging and chelating Q21-4 coordination mode, with the formation of 4-membered rings, while the other half have the Q21-7 coordination mode with the formation of 7-membered rings. The coordination modes of the maleate ions in all the crystal structures of coordination compounds from the CSD were analyzed. The non-planarity of the maleate ions is confirmed by calculation of different geometric parameters. Though in all crystal structures most of the maleate ions tend to realize coordination modes with the formation of 7-membered rings, geometrical difficulties of 7-membered ring formation are shown. The presented data on the coordination modes of the maleate ions in crystal structures are of particular interest for crystal engineering and crystal structure prediction.

Crystal and molecular structure of novel binuclear ten coordinated praseodymium(III) with octadentateethylenediaminetetraacetate – Synthesis, characterization and antioxidant, antiviral and anticancer activities

A novel ten coordinated binuclear hydrated praseodymium(III) ethylenediaminetetraacetate with phenyl hydrazine has been synthesized and characterized by analytical, spectral and thermal techniques. The structure of the compound determined by X-ray crystallography reveals the binuclear nature of the complex with ten coordination around Pr(III) ions. Neutral phenyl hydrazine molecules present outside the coordination sphere and four inner sphere water molecules found to occupy the coordination sites (each Pr(III) ions possessing two coordinated water molecules). Among five more water molecules, four are involved in hydrogen bonding with phenyl hydrazine and EDTA4− and hence present in the second sphere. The remaining water molecule is present as bulk water. Interestingly, in the present case EDTA4− ions act as heptadentate ligand with one acetate group from each EDTA4− ion showing novel tridentate bridging behavior. The biological studies such as antioxidantal, antiviral and cytotoxicity studies reveal that this complex indeed shows promising activity.

Four- and five-coordinate metal atoms in a supramolecular polymeric assembly of silver(I) with (4-methyl-2-quinolylthio)acetate

The coordination compound [Ag2L2(H2O)2] · 2H2O (I), L = C12H10NO2S has been synthesized by the reaction of AgNO3 with 4-methyl-2-quinolylthioacetic acid (HL) preliminarily neutralized with an equimolar amount of NBu4OH. Its crystal structure has been determined, and luminescence properties have been studied. Crystals of I are monoclinic, space group C2/c, a = 31.239(6) A, b = 12.056(2) A, c = 16.846(3) A, β = 122.17(3)°, V = 5370.4(2) A3, ρcalc = 1.861 g/cm3, Z = 16. The structure is formed by two crystallographically nonequivalent silver atoms Ag(1) and Ag(2) and two tridentate bridging ligands L coordinated through the S, N, and O atoms. These atoms, together with water molecules, form the coordination environments of the metal atoms with CN = 5 and 4, respectively. The Ag+ ions and the tridentate ligands form infinite [Ag4L4] n bands extended in the [001] direction. The presence of outer-sphere water molecules involved in O–H···O hydrogen bonding is responsible for the formation of a supramolecular framework structure. The photoluminescence spectrum of compound I shows two bands at ~450 and ~485 nm corresponding to the blue spectral range.

Two mixed-ligand cadmium(ii) compounds bearing 5-nitrosopyrimidine and N-donor aromatic blocks: self-assembly generation, structural and topological features, DFT studies, and Hirshfeld surface analysis

Using the mixed-ligand strategy, two novel cadmium(II) coordination compounds, namely, the discrete 0D dimer [Cd2(μ2-H2Vi)4(benzim)2]·2MeOH (1) and the 1D coordination polymer [Cd(μ2-DMV)(DMV)(2-apy)]n (2), were self-assembled in aqueous methanol medium under ambient conditions from the cadmium(II) nitrate–H3Vi/HDMV–benzim/2-apy system {where H3Vi = violuric acid [5-(hydroxyimino)pyrimidine-2,4,6(1H,3H,5H)-trione], benzim = benzimidazole, HDMV = N,N′-dimethylvioluric acid [5-(hydroxyimino)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione], and 2-apy = 2-aminopyridine}. Both products were isolated as crystalline solids and were structurally characterized. The violurate ligands adopt a tridentate bridging mode in 1, whereas in 2 simultaneous coordination modes [bis(bidentate) bridging + bidentate] are displayed by dimethylviolurate ligands. The nature of the substituent on the violurate ring and the presence of different N-donor ligands play a role in the generation of distinct products. The crystal structures of 1 and 2 reveal a number of strong intermolecular hydrogen bonds that are responsible for the 0D → 3D (1) or 1D → 2D (2) structure extension, resulting in rather complex H-bonded networks. These networks were topologically classified as underlying nets with the sqc2 and 3,4L18 topologies in 1 and 2, respectively. By means of DFT calculations (BP86-D3/def2-TZVPD), the computation of the energetic features of the different noncovalent interactions, such as lone pair (lp)–π, π–π, and C–H/π, was performed aiming at rationalizing their roles in the crystal packing of 1 and 2. Notably, the lp–π interactions observed in 2 present one of the shortest lp–π distances (2.74 A) reported to date. Hirshfeld surface analysis was also carried out to provide qualitative and quantitative insights into the intermolecular interactions in 1 and 2. Furthermore, luminescence properties of the compounds were investigated.

PH dependent synthesis of structurally diverse praseodymium(III) coordination polymers based on isomeric ligands

Reactions of two isomeric ligands, 5-(n-pyridyl)tetrazole-2-acetato potassium salt (Kn-pytza, n=2,4) and PrCl3·6H2O under solvothermal conditions, afforded three new complexes, [Pr(2-pytza)(SO4)(H2O)3]·H2O(1), [Pr(4-pytza)3(H2O)2]·2H2O (2) and [Pr4(4-pytza)5(OH)4(H2O)7Cl]Cl2·4H2O (3), whose structures are controlled by not only the different positions of the nitrogen atom of the pyridine ring but also the pH value of the solvent system. These compounds have been characterized by elemental analysis, IR and single crystal X-ray diffraction. The X-ray analysis reveals that compound 1 is a two dimensional layer structure made up of a Pr2O6 binuclear unit and the tridentate bridging SO42− ligand; compound 2 is an unusual one dimensional ladder like chain structure consisting of a Pr2O10 binuclear unit and 4-pytza which acts as a tetradentate ligand via the pyridine-N and the carboxylate group in a μ1,1,3-COO bridging mode while compound 3 is an unprecedented two dimensional network composed of a tetranuclear cubane-shaped Pr4(OH)48+ cluster (SBU) and tridentate 4-pytza via the pyridine-N and the carboxylate group in a μ1,3-COO bridging mode. Various hydrogen bonds exist to assemble the 1D chains or 2D layers into 3D supramolecular network structures. Furthermore, the luminescence properties investigated at room temperature in the solid state show only intraligand emission for 1 and both intraligand and characteristic peaks of Pr3+ for either compound 2 or 3.

A novel 3D energetic coordination polymer containing Co(II) atoms in a pentanuclear cluster

A novel coordination polymer [Co5(OH)2(dnbpdc)4(H2O)6]·16H2O (1) (dnbpdc = 6,6′-dinitro-4,4′-biphenyldicarboxylic acid) is obtained from a hydrothermal reaction. The structure of complex 1 is characterized by elemental analysis, IR spectroscopy, and single crystal X-ray diffraction analysis. The title compound (C56H70Co5N8O56, Mr = 2045.85) crystallizes in the triclinic space group P-1 with a = 11.9349(2) A, b = 12.1895(2) A, c = 15.420(2) A, α = 109.390(7)°, β = 94.786(1)°, γ = 108.027(9)°, V = 1968.4(4) A3, Z = 1, Dc = 1.726 g/cm3, F(000) = 1045, μ(MoKα) = 1.154 mm–1, T = 133(2) K, the final R = 0.0316 and wR = 0.0692 for 7032 observed reflections with I > 2σ(I). The coordination polymer is built of a pentanuclear Co(II) cluster, four dnbpdc ligands, two hydroxyl groups, six coordination water and sixteen crystal water molecules. Ligand oxygen atoms exhibit three types of coordination modes (monodentate, syn-syn bridging bidentate and bridging tridentate). Moreover, the infinite three-dimensional supramolecular network is generated by coordination and hydrogen bonds. The thermal stability of complex 1 is evaluated by differential scanning calorimetry and thermogravimetric analysis.

Reactions of Cd(OAc)2·2H2O with variously substituted pyridines. Efforts to unravel the factors that determine structure/nuclearity of the products

The reactions of Cd(OAc)2·2H2O with variously substituted pyridines in methanol afforded unique one-dimensional coordination polymers (1D CPs), [Cd2(μ2-κ2:κ1-OAc)2(μ2-κ1:κ1-OAc)2L2] (L=NC5H5 (1), NC5H4Me-3 (2), and NC5H3Me2-3,5 (3)) and [Cd3(μ3-κ1:κ2-OAc)3(μ2-κ2-OAc)(μ2-κ2:κ1-OAc)2(NC5H3Me2-3,4)2] (4), and discrete and bimolecular complexes, [(Cd(OAc)2(NC5H3Me2-3,4)2(H2O)2] (5), [Cd(κ2-OAc)2(NC5H4Me-4)2(H2O)]·[Cd(κ2-OAc)2(H2O)2)] (6), [Cd(κ2-OAc)2L2L′]·xH2O (x=0, L′=H2O, L=NC5H4(OMe)-4 (7); NC5H4tBu-4 (8); x=2, L=L′=NC5H4(NMe2)-4 (9·2H2O)). The products were characterised by elemental analysis, IR, solution NMR (1H and 13C), solid-state CP-MAS 13C{1H} and 113Cd NMR, TGA/DTA analyses, and single crystal X-ray diffraction. Phase purity of 1–4 was verified by powder X-ray diffraction (PXRD). Plausible mechanisms of formation of the products are proposed based on a point zero charge model. 4 represents the first cadmium containing 1D CP that possesses a tridentate bridging (μ3-κ1:κ2) acetate coordination mode and 6 represents the first structurally characterised bimolecular cadmium(II) complex containing two different neutral cadmium(II) coordination species per formula unit. 9·2H2O was calcined at 500°C to afford CdO as confirmed by PXRD and the morphology of CdO was studied by scanning electron microscopy.

Synthesis, crystal structure, and luminescence properties of the complex of silver(I) perrhenate with N-(2-aminoethyl)piperazine

The reaction of AgReO4 with N-(2-aminoethyl)piperazine, C6H15N3 (L), gave a new compound Ag(L)(ReO4)(I). The crystals of I are monoclinic, space group P21/c, a = 15.067(1) A, b = 11.616(1) A, c = 14.259(1) A, β= 108.40(1)°, V = 2368.0(3) A3, ρ(calcd.) = 2.734 g/cm3, Z = 8. The structure of I consists of cationic polymeric chains [Ag(L)]∞+ connected to the [ReO4]− anions by the N-H⋯O hydrogen bonds to form a 3D supramolecular assembly. The Ag+ ions have a T-shaped coordination with the ligand N atom functioning as a tridentate bridge between the silver atoms (CIF file CCDC no. 1034044). Compound I possesses fluorescence.

Cd(II) complexes with different nuclearity and dimensionality based on 3-hydrazino-4-amino-1,2,4-triazole

A series of zero- to two-dimensional Cd(II) coordination compounds have been synthesized by the reaction of Cd(II) salts and 3-hydrazino-4-amino-1,2,4-triazole di-hydrochloride (HATr·2HCl). [CdCl2(HATr)2] (1) and [Cd2Cl4(HATr)2(H2O)2] (2) have discrete mononuclear and binuclear structures, respectively. [Cd(HATr)2(ClO4)2]n (3) presents polymeric 1-D chain and [Cd2(NO3)2Cl2(HATr)2]n (4) shows 2-D frameworks. All Cd(II) ions exhibit distorted octahedral configurations in 1–3, whilst both hexa and heptacoordinated Cd(II) are formed in 4. The HATr ligands adopt chelating coordinated mode in 1, while tri-dentate bridging–chelating mode in 2–4. The chloride ion is a mono-coordinated ligand in 1 and 2, but it bridges two adjacent metal ions in 4. Furthermore, thermal behaviors have been investigated and the results reveal that all complexes have good thermal stability. The impact sensitivity test indicates that complex 3 is sensitive to impact stimuli.

Syntheses, crystal structures and properties of complexes with two anthracene-based bulky backbone ligands

Three metal–organic complexes with two anthracene-based bulky backbone ligands 9,10-dioxo-9,10-dihydroanthracene-1,5-dicarboxylic acid (H2 L 1) and 2-phenylquinoline-4-carboxylic acid (HL 2), namely {[Mn(L 1)0.5(L 1)0.5(phen)(H2O)2](H2O)1.5}∞ (1), [Mn2(L 2)4(phen)2(H2O)2](H2O)2 (2) and [Cd3(L 2)2(pp)2Cl4]∞ (3) (phen = 1,10-phenanthroline, pp = 3-(2-pyridyl)pyrazole), have been synthesized and characterized. X-ray single-crystal diffraction indicates that H2 L 1 adopts a bis-monodentate bridging mode in complex 1, whereas HL 2 adopts monodentate and bidentate bridging modes in 2 and a tridentate bridging mode in 3. The chelating ligands phen and pp give rise to a 1D zigzag chain in complexes 1 and 3, and a binuclear structure in 2, by preventing the formation of higher-dimensional structures. Notably, the anions play an important role in the structure of complex 3. In addition, the magnetic and luminescent properties of these complexes were investigated. Three metal–organic compounds, showing a 1D zigzag chain, a binuclear structure and a 1D zigzag chain, have been successfully constructed by using 9,10-dioxo-9,10-dihydroanthracene-1,5-dicarboxylic acid and 2-phenylquinoline-4-carboxylic acid, together with incorporating auxiliary bridging ligands 1,10-phenanthroline or 3-(2-pyridyl)pyrazole. The present results reveal that chelated ligands phen and pp play an important role in the formation of frameworks of 1–3, which prevent the formation of higher-dimensional structures. Moreover, intense luminescent emissions of 1–3 were attributed to the LLCT of corresponding ligand. And antiferromagnetic coupling interaction exists between the binuclear MnII ions in 2.

Specific features of the reaction between tris(5-bromo-2-methoxyphenyl)antimony and 2-oxybenzaldoxime: Structure of bis(μ3-2-oxybenzaldoximato-O,O′,N)-(μ2-oxo)-bis(5-bromo-2-methoxyphenyl)antimony

Bis(μ3-2-oxybenzaldoximato-O,O′,N)-(μ2-oxo)-bis(5-bromo-2-methoxyphenyl)antimony, which crystallizes from toluene in the form of a solvate, has been synthesized by the reaction between tris(5-bromo-2-methoxyphenyl)antimony and 2-oxybenzaldoxime in the presence of hydrogen peroxide. According to X-ray diffraction data, the structurally equivalent antimony atoms in a binuclear complex molecule are linked via two tridentate bridging ligands and an oxygen atom and have a distorted octahedral coordination to the C2O3N surrounding The trans-angles of the octahedron are CSbO (168.7(1)°), CSbN (164.1(1)°), and OSbO (159.3(1)°), and the bond lengths are Sb-C (2.127(4), 2.159(3) A) and Sb-N (2.238(3) A). A molecule contains the three types of Sb-O distances with a bridging oxygen atom (1.950(1) A), the oxygen atoms of oxy groups (2.002(2) A), and the oxygen atoms of oxime groups (2.091(2) A). Sb⋯OCH3 intramolecular contacts (3.097, 3.290 A) also exist.

Investigation of the structure variation of metal diphosphonates with the changing of N-donor auxiliary ligands and their properties

Nine metal diphosphonates, [Co(H2L)(pyz)(H2O)][(H2O)0.3] (1), [Ni(H2L)(pyz)(H2O)2] (2), [Ni(H2L)(2,2′-bipy)2][(H2O)2] (3), [Ni(H2L)(4,4′-bipy)(H2O)][(H2O)2] (4), [Ni(H2L)(dpe)(H2O)2][(H2O)2] (5), [Cu(H2L)(pyz)(H2O)2] (6), [Cu(H2L)(4,4′-bipy)][(H2O)2] (7), [Zn(H2L)(2,2′-bipy)(H2O)2] (8) and [Cd(H2L)(pyz)(H2O)2] (9), have been synthesized from a diphosphonate ligand 2,5-dimethyl-1,4-phenylenediphosphonic acid (H4L) and four N-donor auxiliary ligands (pyz = pyrazine, 2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine, dpe = 1,2-di(4-pyridyl)ethylene). In compound 1, pyrazine molecules behave as pillars which connect the Co(H2L) layers into a 3D network structure. Compounds 2, 6 and 9 are isostructural and also show 3D framework structures, in which metal centers are linked by the bidentate diphosphonate ligands into 1D infinite chains and are connected by the pyrazine linkers. In compounds 3 and 8, the diphosphonate ligands, showing bidentate or tetradentate coordination modes, bridge the respective metal ions (Ni2+ and Zn2+) into a 1D infinite chain or 2D layer structure, respectively, in which the 2,2′-bipy ligands chelate to the central metal ions and complete the coordination spheres. In compound 4, the 4,4′-bipy molecules also behave as pillars between the 2D layers, which are constructed from tridentate bridging diphosphonate ligands and six-coordinated Ni2+ ions. Compounds 5 and 7 have similar square grid layered structures which are constructed from bridging bidentate diphosphonate ligands and 4,4′-bipy or dpe linkers. Photophysical measurements indicate that compounds 8 and 9 display ligand centered emissions. Magnetic studies reveal that dominant antiferromagnetic interactions are propagated in compounds 1–3 between the magnetic centers.

Lanthanide Complexes Assembled from 3‐Fluorophthalate and 1,10‐Phenanthroline: Syntheses, Crystal Structure, Photoluminescence, and White‐Light Emission

AbstractTwo different crystal forms, [Ln4(Fpht)6(phen)6(H2O)4]·nH2O (Ln = Eu 1, n = 14; Tb 2, n = 12) and [Ln(Fpht)(HFpht)(phen)(H2O)] (Ln = La 3, Eu 4, Tb 5) were obtained from the one‐pot reaction of LnIII ions with 3‐fluorophthalic acid (H2Fpht) and 1,10‐phenanthroline (phen). Complexes 1 and 2 are centrosymmetric tetranuclear molecules with two crystallographically different LnIII ion environments, [Ln(1)O6N2] and [Ln(2)O4N4]. The complexes have a tridentate bridging Fpht ligand and a bidentate terminal Fpht ligand. Complexes 3–5 show 2D networks with [LnO7N2] polyhedra. There are two kinds of ligands, Fpht and HFpht, which adopt chelating‐bridging/monodentate and bidentate‐bridging coordination modes, respectively. The LaIII complex shows ligand‐centered fluorescence. EuIII and TbIII complexes display red 5D0 → 7F0–4 and green 5D4 → 7F6–2 characteristic luminescence, respectively. Intriguingly, white‐light emission was produced when EuIII and TbIII were codoped into the 2D LaIII complex.

Tuning of Metal–Metal Interactions in Mixed-Valence States of Cyclometalated Dinuclear Ruthenium and Osmium Complexes Bearing Tetrapyridylpyrazine or -benzene

New dinuclear ruthenium or osmium complexes with cyclometalated bonds in either tridentate bridging (BL) or ancillary ligands (L), [(L)M(BL)M(L)] (where M = Ru, Os; L = bis(N-methylbenzimidazolyl)pyridine, -benzene; BL= tetrapyridylpyrazine (tppz), -benzene (tpb)), were synthesized, and their mixed-valence-state characteristics were investigated. All of the complexes showed successive one-electron redox processes, each of which correspond to M(II/III) (M = Ru, Os) or ligand reduction waves. In addition, an M(III/IV) couple was observed in cyclometalated [M2(bis(benzimidazolyl)benzene)2(BL)] complexes (M = Ru, Os). Effects of the cyclometalated bonds on the redox behaviors and the accessibility to the mixed-valence M(II)–M(III) dinuclear complexes are discussed. Introduction of a cyclometalated bond induced a large negative potential shift in the redox potentials of dinuclear ruthenium and osmium complexes, depending on either bridging or ancillary sites of the cyclometalated bonds: the change falls within...

Syntheses, characterization and crystal structures of eight Cd(II) carboxylates containing 3,5-dimethylpyrazole

Eight new complexes, namely [Cd(Hdmpz)2(L1)20.5H2O]2 (1) (Hdmpz=3,5-dimethylpyrazole, L1=trichloroacetate), [Cd(Hdmpz)2(L2)2]·H2O (2) (L2=indole-3-acetate), Cd(Hdmpz)2(L3)2 (3) (L3=4-methylbenzoate), Cd(Hdmpz)4(L4)2 (4) (L4=3-methylbenzoate), Cd(Hdmpz)4(L5)2 (5) (L5=4-methoxybenzoate), Cd(Hdmpz)2(L6)2 (6) (L6=2-chloronicotinate), Cd(Hdmpz)(HL7)2 (7) (HL7=2-hydroxy-5-(phenyldiazenyl)benzoate) and [Cd2(Hdmpz)6(L8)2]·(Hdmpz)2 (8) (L8=o-phthalate) have been prepared by the self-assembly of Cd ions, 3,5-dimethylpyrazole and carboxylic acids at room temperature. All the complexes were characterized by elemental analysis, IR spectra, TG and single crystal X-ray diffraction analysis. The X-ray studies revealed that these complexes display mononuclear to dinuclear structures, with an octahedral geometry around each cadmium ion. The 3,5-dimethylpyrazole ligand in all the compounds is coordinated only in a monodentate fashion by its neutral N group. In 2, 3 and 6, the carboxylate groups behave as chelating bidentate ligands. In 4 and 5, the carboxylate groups act as monodentate ligands. The COO− group in 1 is coordinated to the Cd centre in both monodentate and bridging bidentate modes. The carboxylates in 7 coordinate to the Cd centre in tridentate chelating bridging and bidentate bridging fashions, simultaneously, while in 8 there exists a tridentate bridging carboxylate ligand. Based on the X-ray crystallographic study, extensive intra- and intermolecular non-covalent interactions, such as classical hydrogen bonds, CH–Cl, CH3–Cl, Cl⋯Cl, Cl⋯O, CH–N, CH3–N, C–H⋯O, CH3⋯O, C–H⋯π, CH2⋯π, CH3–π and π–π interactions, are analyzed. These compounds display different structures, such as a 0D discrete mononuclear arrangement, sheet, 3D network, and 3D layer network. The thermal stabilities for 1–8 were examined and the results show that the complexes display good thermal stability.

Dinuclear and polynuclear copper(II) complexes with 3,3′-thiodipropionate and unprecedented coordination mode

Three new coordination compounds, {[Cu(μ3-tdp)(phen)]·2H2O}n (1), {[Cu(μ3-tdp)(bipy)]·H2O}n (2), [Cu2(μ2-tdp)(phen)4](NO3)2·2H2O (3) [tdpH2=3,3′-thiodipropionic acid, phen=1,10-phenanthroline, bipy=2,2′-bipyridine] were synthesized and characterized by the IR spectroscopy, elemental analysis, magnetic measurements and single crystal X-ray diffraction. Thermal behaviors and thermochromic properties of the complexes were investigated in detail. Complexes 1 and 2 are 1D coordination polymers while complex 3 is dinuclear structure. In complexes 1 and 2, the tdp acts as a tridentate bridging ligand to coordinate the two different Cu(II) centers to form 1D chain, which are extended into a 3D networks by hydrogen bonding and π⋯π interactions. The 3,3′-thiodipropionate ligand adopts a new coordination mode in 3. Furthermore, complex 3 changed the color from blue to green at 140°C at solid state.

基于柔性配体5-[N-乙酸根(4-吡啶基)]四唑(a4-pytz)与Fe(II)和Sm(III)两个配合物的合成与表征

5-[N-乙酸根(4-吡啶基)]四唑钾盐(简写为Ka4-pytz)与(NH4)2Fe(SO4)2和SmCl3·6H2O在水-甲醇体系中反应，得到两个新的配合物，[Fe(a4-pytz)2·2H2O]·2H2O (1)和[Sm4(a4-pytz)8(H2O)18]Cl3·10H2O (2)。通过元素分析，红外光谱分析及X-射线单晶衍射对两个配合物进行结构表征。单晶衍射结果显示了配合物1和2都具有一维链状结构。但不同的是，配合物1的一维链是通过a4-pytz作为双齿配体，经四唑环上的氮原子和羧基的一个氧原子与Fe(II)相连而成的；而配合物2的结构形成源于羧基的桥联作用，氮原子未配位。通过氢键作用，配合物1和2形成了三维结构。室温下研究了配合物1和2的荧光性质。 Two new coordination compounds, namely, [Fe(a4-pytz)2·2H2O]·2H2O (1) and [Sm4(a4-pytz)8 (H2O)18]Cl3·10H2O (2) were prepared by reactions of K4-pytz[Ka4-pytz=5-(N-acetato(4-pyridyl)) tetrazole potassium salt] with (NH4)2Fe(SO4)2 or SmCl3·6H2O in a mixture of distilled water and methanol solution. These compounds were characterized by elemental analysis, IR and single crystal X-ray diffraction. The diffraction reveals that both 1 and 2 show 1D chains. In compound 1, a4-pytz acts as a bidentate ligand via its tetrazole-N atom and one of the carboxylate-O atoms while a4-pytz acts as tridentate bridging ligand via the two carboxylate atoms in 2. Compounds 1 and 2 show the 3D networks through hydrogen bonding interactions. Furthermore, the luminescent properties were also investigated at room temperature in the solid state.