Synthesis and structures of three d metal coordination polymers constructed from flexible polycarboxylate and 1,10-phenanthroline ligands

Three novel d¹⁰ metal coordination polymers, {[Cd(H₂odpa)(phen)₂]·H₂O}_n (1), [Cd₂(odpa)(phen)(H₂O)₂]_n (2), {[Zn₄(odpa)₂(phen)₂(H₂O)₂]·H₂O}_n (3), (H₄odpa = 4,4′-oxydiphthalic acid, phen = 1,10-phenanthroline) were obtained with different metal/ligand ratios through hydrothermal method and characterized. Compound 1 forms a one dimensional zigzag chain, in which two phen ligands chelate to one cadmium atom. Compound 2 shows a three dimensional network structure comprised of new tetranuclear cadmium clusters as the nodes and (odpa)⁴⁻ anions as the linkers, exhibits an unusual topological structure. Compound 3 is an unprecedented three dimensional polymer based on octanuclear zinc clusters cross-linked by (odpa)⁴⁻ anions. In 1-3, central Cd^II/Zn^II ions and (odpa)⁴⁻ ligand display completely different coordination modes and conformations. In addition, the thermal stabilities and photoluminescence properties of 1-3 were also studied.     

Seven organic-inorganic hybrid compounds constructed from 2,4,6-tris-(pyridyl)-1,3,5-triazine and polyoxometalates

Seven new organic-inorganic hybrid compounds containing inorganic polyoxometalates and trigonal organic ligand 2,4,6-tris-(3/4-pyridyl)-1,3,5-triazine (3/4-tpt), namely [Mo₈O₂₆M(Htpt)₂(H₂O)₂]_n (M = Zn (1), Co (2), Ni (3)), [Mo₈O₂₆Cu(Htpt)₂(H₂O)₂]_n·2nH₂O (4), [Mo₈O₂₆(H₂tpt)₂]·6H₂O (5), [Mn(Mo₄O₁₃)(4-tpt)₂]_n (6) and [Fe₃(Mo₄O₁₅)(3-tpt)]_n·nH₂O (7), were synthesized hydrothermally and characterized by EA, IR, TG, and PXRD techniques. Single crystal X-ray structural analysis revealed that compounds 1-4 are 1-D coordination polymers constructed from [Mo₈O₂₆]⁴⁻ cluster and [M(Htpt)₂(H₂O)₂]⁴⁺ fragments. Compound 5 is an isolated cluster composed of [Mo₈O₂₆]⁴⁻ anion and monodentate H₂tpt²⁺ cation. 3-Tpt ligands in 1-5 are partially protonated and act as monodentate ligands. Octamolybdates adopt β- and γ-[Mo₈O₂₆]⁴⁻ structural mode in compounds 1-4 and 5, respectively. In compound 6, each [Mo₄O₁₃]²⁻ tetramer links four Mn(II) ions to form a 2-D wave-like polymeric layer. The 2-D [MnMo₄O₁₃] bimetallic layers are pillared by neutral 4-tpt bidentately to generate a 3-D metal-organic framework. Compound 7 is a 3-D coordination polymer constructed from 2-D [Fe₃(Mo₄O₁₅)] bimetallic polymeric layer and pillared by neutral tridentate 3-tpt. These compounds are thermal stable under 250 °C. The compounds 1 and 5 display luminescence with emission maximum at 481 and 442 nm, respectively.     

Mononuclear and polynuclear halide and nitrate Cu(II) compounds with 1,4,5-triazanaphthalene as a ligand: Characterization, magnetism and X-ray structures

Using the ligand 1,4,5-triazanaphthalene (abbreviated as tan) in combination with Cu(II) salts, three mononuclear compounds, Cu(tan)₂Cl₂ (1), Cu(tan)₂Br₂ (3), Cu(tan)₂(NO₃)₂ (5) and three polynuclear compounds, [Cu(tan)Cl₂]_n (2), [Cu(tan)Br₂]_n (4), [Cu(tan)(NO₃)₂]_n (6) have been synthesized and characterized by UV-Vis, EPR, FTIR and Far-FTIR spectroscopies. The crystal structures of compounds 1, 3, 5 and 6 are reported, as well as that of the dioxane adduct of compound 4, [Cu(tan)Br₂(C₄H₈O₂)](C₄H₈O₂) (4A).The structure of (2) was solved by X-ray powder diffraction. The coordination geometry around the Cu(II) atoms is tetrahedral for (1) and (3), square-pyramidal for (4A) and distorted octahedral for (5) and (6). Magnetic susceptibility measurements on the polynuclear compounds revealed weak antiferromagnetic interactions between the Cu(II) atoms with interaction constants (J) of J = −9.1 and −10.5 cm⁻¹, for 4 and 6, respectively. For compound 2 two options for possible interactions were considered, with interaction constants which vary for J_rung −22.0 to −13.5 cm⁻¹ and J_rail −19.6 to −17.0 cm⁻¹. These figures are discussed in the light of relevant structural parameters and literature.     

Structural and thermal properties of three novel alkaline earth metal coordination polymers based on 5-hydroxyisophthalate ligand

Three novel coordination polymers [Ca(5-OH-BDC)(H₂O)₃] · H₂O (1), [Sr(5-OH-BDC)(H₂O)₄] · H₂O (2) and [Ba(5-OH-BDC)(H₂O)₃] (3) were obtained by self-assembly of the corresponding alkaline earth metal chlorate with a ligand, 5-hydroxyisophthalic acid (5-OH-H₂BDC), and their structures were determined by X-ray crystallography. The results revealed that complexes 1, 2 and 3 have two-dimensional network with (6, 3) topology observed in the bc plane. Moreover, the two-dimensional layers can be assembled into three-dimensional supramolecular architectures via intermolecular hydrogen bonds. The two carboxylate groups of 5-OH-BDC²⁻ ligand adopt the same coordination mode in complex 1 as that in 2: a μ3-η2:η1 mode and a chelated mode while in complex 3 they coordinate to Ba(II) ions in a μ3-η2:η1 mode and a monodentate mode, which is not observed in previous reports. The constant-volume combustion energies, Δ_cU, of these complexes were determined by a precise rotating-bomb calorimeter at 298.15 K, then their standard enthalpies of combustion, , and the standard enthalpies of formation, , have been calculated.     

Cobalt and cadmium complexes with N-heterocyclic dicarboxylic acid ligands: Syntheses, structures, magnetic and fluorescent properties

Two new complexes, [Co(Himdc)₂(H₂O)₂] (1) and {[Cd(pzdc)(H₂O)]·H₂O}_n (2) (H₂imdc = imidazole-4, 5-dicarboxylic acid, H₂pzdc = pyrazine-2, 3-dicarboxylic acid), have been synthesized and structurally characterized. Compound 1 is a new triclinic mononuclear complex formed by two Himdc⁻ ligands trans coordinated to the Co^II center in bidentate chelate mode and two water ligands. Compound 2 shows a two dimensional layer structure in which pzdc²⁻ dianion ligand adopts unique doubly bridging bis-bidentate μ₄ coordination mode. Temperature-dependent magnetic susceptibilities and thermal stability for 1 and solid-state fluorescent properties for 2 have been discussed in detail.     

Structural analysis and magnetic properties of the copper(II) dicyanamide complexes [Cu2(dmphen)2(dca)4], [Cu(dmphen)(dca)(NO3)]n and [Cu(4,4-dmbpy)(H2O)(dca)2] (dca=dicyanamide; dmphen=2,9-dimethyl-1,10-phenanthroline; 4,4-dmbpy=4,4-dimethyl-2,2-bipyridine)

The preparation, crystal structures and magnetic properties of three copper(II) compounds of formulae [Cu₂(dmphen)₂(dca)₄] (1), [Cu(dmphen)(dca)(NO₃)]_n (2) and [Cu(4,4^′-dmbpy)(H₂O)(dca)₂] (3) (dmphen=2,9-dimethyl-1,10-phenanthroline, dca=dicyanamide and 4,4^′-dmbpy=4,4^′-dimethyl-2,2^′-bipyridine) are reported. The structure of 1 consists of discrete copper(II) dinuclear units with double end-to-end dca bridges whereas that of 2 is made up of neutral uniform copper(II) chains with a single symmetrical end-to-end dca bridge. Each copper atom in 1 and 2 is in a distorted square pyramidal environment: two (1) or one (2) nitrile-nitrogen atoms from bridging dca groups, one of the nitrogen atoms of the dmphen molecule (1 and 2) and either one nitrile-nitrogen from a terminal dca ligand (1) or a nitrate-oxygen atom (2) build the equatorial plane whereas the second nitrogen atom of the heterocyclic dmphen fills the axial position (1 and 2). The copper-copper separations through double (1) and single (2) end-to-end dca bridges are 7.1337(7) (1) and 7.6617(7) (2). Compound 3 is a mononuclear copper(II) complex whose structure contains two neutral and crystallographically independent [Cu(4,4^′-dmbpy)(H₂O)(dca)₂] molecules which are packed in two different layer arrangements running parallel to the bc-plane and alternating along the a-axis. The copper atoms in both molecules have slightly distorted square pyramidal surroundings with the two nitrogen atoms of the 4,4^′-dmbpy ligand and two dca nitrile-nitrogen atoms in the basal plane and a water oxygen in the apical position. A semi co-ordinated dca nitrile-nitrogen from a neighbour unit [2.952(6) Å for Cu(2)-N] is in trans position to the apical water molecule in one of the two molecules, this feature representing part of the difference in supramolecular connections in the alternating layers referred to above. Magnetic susceptibility measurements for 1-3 in the temperature range 1.9-290 K reveal the occurrence of weak antiferromagnetic interactions through double [J=−3.3 cm⁻¹ (1), ] and single [J=−0.57 cm⁻¹ (2), ] dca bridges and across intermolecular contacts [θ=−0.07 K (3)].     

UV-Vis and fluorimetric Al, Zn, Cd and Pb complexation studies of two 3-hydroxyflavones and a 3-hydroxythioflavone

The complexation of Al³⁺, Zn²⁺, Cd²⁺ and Pb²⁺ by the 3-hydroxyflavones: 3-hydroxy-2-(2-methoxyphenyl)-4H-1-benzopyran-4-one (H1) and 3-hydroxy-2-(4-methoxyphenyl)-4H-1-benzopyran-4-one (H2), and by the 3-methoxythioflavone: 3-hydroxy-2-(2-methoxyphenyl)-4H-1-benzopyran-4-thione (H3) have been studied spectrophotometrically and fluorimetrically to determine the corresponding complexation constants, K_sp and K_fl, in 5:95 water:ethanol (v/v) solution for which [HClO₄] was either 10⁻² or 10⁻⁵ mol dm⁻³ and I = 0.10 mol dm⁻³ (NaClO₄) at 298.2 K. Complexation occurs dominantly through the deprotonated ligand for [Al(1)]²⁺ and [Al(2)]²⁺ for which log K_sp = 4.51 and 4.73, respectively, in 10⁻² mol dm⁻³ HClO₄ and 4.21 and 4.61 in 10⁻⁵ mol dm⁻³ HClO₄. For Pb²⁺ complexation by H1, H2 and H3 is characterized by log K_sp = 2.20, 2.57 and 3.22, respectively, in 10⁻² mol dm⁻³ HClO₄ and 4.70, 5.38 and 5.74 in 10⁻⁵ mol dm⁻³ HClO₄. Equilibrium mixtures of [Pb(H1)]²⁺ and [Pb1]⁺, [Pb(H2)]²⁺ and [Pb2]⁺, and [Pb(H3)]²⁺ and [Pb3]⁺ appear to be formed. Complexation of Zn²⁺ and Cd²⁺ by all three ligands was only detected in 10⁻⁵ mol dm⁻³ HClO₄. For Zn²⁺ complexation by H1, H2 and H3 log K_sp = 3.22, 3.74 and 4.46 and for Cd²⁺ the corresponding values are 2.39, 2.40 and 3.72 for Cd²⁺. Only [Al1]²⁺ and [Al2]²⁺ show significant fluorescence and are characterized by log K_fl = 6.30 and 7.49 in 10⁻² mol dm⁻³ HClO₄.     

Two new supermolecular structures of organic-inorganic hybrid compounds: [Zn(phen)(SO4)(H2O)2]n and [Cu(phen)(H2O)2] · SO4 (phen = 1,10-phenanthroline)

Two new organic-inorganic hybrid compounds [Zn(phen)(SO₄)(H₂O)₂]_n (1) and [Cu(phen)(H₂O)₂] · SO₄ (2) have been prepared by conventional aqueous solution synthesis and characterized by single-crystal X-ray diffraction, IR spectroscopy, thermal gravimetric analysis (TGA) and fluorescent spectroscopy. In compound 1, the sulfate group adopts bidentate mode to coordinate with two Zn(II) ions to form one-dimensional polymer. The one-dimensional polymers are further linked together via the intermolecular hydrogen-bonding and π-π stacking interactions to form a 3D supramolecular framework. Compound 2 is build up of discrete [Cu(phen)(H₂O]²⁺ cations and SO₄²⁻ anions to form a three-dimensional framework via hydrogen-bonding and π-π stacking interactions. Furthermore, the luminescent properties of both 1 and 2 were studied. The complexes 1 and 2 excited at 280 nm wavelength produced characteristic luminescence features, arising maybe due to the π-π transitions.     

Organic-inorganic hybrid materials: Ligand influences on the structural chemistry of copper-vanadates

Hydrothermal reactions were used in the preparation of a series of bimetallic organic-inorganic hybrid materials of the M(II)/V_xO_y/organonitrogen ligand class. Compound 1, [{Cu₂(bpa)₂(C₂O₄)}₂V₄O₁₂]·H₂O, is molecular, while [{Cu(terpy)}₂V₆O₁₇] (2), [Cu₂(bpyrm)V₄O₁₂] (4) and [{Cu(phen)(H₂O)₂}VOF₄(H₂O)]·2H₂O (5) are two-dimensional, three-dimensional and one-dimensional, respectively (bpa = 2,2′-bipyridylamine; terpy = 2,2′:6,2″-terpyridine; bpyrm = 2,2′-bipyrimidine; phen = 1,10-phenanthroline). In contrast to the 2-D structure of 2, the Ni(II) analogue [{Ni(terpy)}₂V₄O₁₂]·2H₂O (3) is one-dimensional. The {V₄O₁₂}⁴⁻ cluster is a building block of structures 1, 3, and 4 while 2 is constructed from {V₆O₁₇}⁴⁻ rings.     

Syntheses and crystal structures of three Mn(II) complexes with 2-hydroxynicotinate

Three new Mn(II) complexes [Mn(HnicO)₂(H₂O)₂] (1), [Mn₂(HnicO)₂SO₄(H₂O)₂]_n (2), and [NaMn(HnicO)₃]_n (3) (H₂nicO = 2-hydroxynicotinic acid) have been synthesized and determined by X-ray diffraction. For complex 1, the mononuclear units with two bidentate HnicO⁻ ions and two water molecules are assembled into a 3D architecture via hydrogen bonding and π-π interactions. For 2, Mn(II) ions are connected by μ₃-HnicO⁻ and bridging ligands, producing a 2D (6,3) coordination network. For 3, binuclear Na(I)-Mn(II) units with three carbonyl oxygen bridges are interlinked by carboxylate groups, resulting in a 3D 6-connected coordination network with distorted α-Po topology. The magnetic properties of 2 are discussed.     

Crystal structure and properties of the copper(II) complex of sodium monensin A

The preparation and structural characterization of a new copper(II) complex of the polyether ionophorous antibiotic sodium monensin A (MonNa) are described. Sodium monensin A binds Cu(II) to produce a heterometallic complex of composition [Cu(MonNa)₂Cl₂]·H₂O, 1. The crystallographic data of 1 show that the complex crystallizes in monoclinic space group C2 with Cu(II) ion adopting a distorted square-planar geometry. Copper(II) coordinates two anionic sodium monensin ligands and two chloride anions producing a neutral compound. The sodium ion remains in the inner cavity of the ligand retaining its sixfold coordination with oxygen atoms. Replacement of crystallization water by acetonitrile is observed in the crystal structure of the complex 1. Copper(I) salt of the methyl ester of MonNa, 2, was identified by X-ray crystallography as a side product of the reaction of MonNa with Cu(II). Compound 2, [Me-MonNa][H-MonNa][CuCl₂]Cl, crystallizes in monoclinic space group C2 with the same coordination pattern of the sodium cation but contains a chlorocuprate(I) counter [CuCl₂]⁻, which is linear and not coordinated by sodium monensin A. The antibacterial and antioxidant properties as two independent activities of 1 were studied. Compound 1 is effective against aerobic Gram(+)-microorganisms Bacillus subtilis, Bacillus mycoides and Sarcina lutea. Complex 1 shows SOD-like activity comparable with that of the copper(II) ion.     

Speciation, stability constants and structures of complexes of copper(II), nickel(II), silver(I) and mercury(II) with PAMAM dendrimer and related tetraamide ligands

The acid-base properties and Cu(II), Ni(II), Ag(I) and Hg(II) binding abilities of PAMAM dendrimer, L, and of the simple model compounds, the tetraamides of EDTA and PDTA, L¹, were studied in solution by pH-metric methods and by ¹H NMR and UV-Vis spectroscopy. PAMAM is hexabasic and six pK_a values have been determined and assigned. PAMAM forms five identifiable complexes with copper(II), [CuLH₄]⁶⁺, [CuLH₂]⁴⁺, [CuLH]³⁺, [CuL]²⁺ and [CuLH_-1]⁺ in the pH range 2-11 and three with nickel(II), [NiLH]³⁺, [NiL]²⁺ and [NiLH_-1]⁺ in the pH range 7-11. The complex [CuLH₄]⁶⁺, which contains two tertiary nitrogen and three amide oxygen atoms coordinated to the metal ion, is less stable than the analogous EDTA and PDTA tetraamide complexes [CuL¹]²⁺, which contain two tertiary nitrogen and four amide oxygen atoms, due to ring size and charge effects. With increasing pH, [CuLH₄]⁶⁺ undergoes deprotonation of two coordinated amide groups to give [CuLH₂]⁴⁺ with a concomitant change from O-amide to N-amidate coordination. Surprisingly and in contrast to the tetraamide complexes [CuL¹]²⁺, these two deprotonation steps could not be separated. As expected the nickel(II) complexes are less stable than their copper(II) analogues. The tetra-N-methylamides of EDTA, L¹(b), and PDTA form mononuclear and binuclear complexes with Hg(II). In the case of L¹(b) these have stoichiometries HgL¹(b)Cl₂, [HgL¹(b)H₋₂Cl₂]²⁻, [Hg₂L¹(b)Cl₂]²⁺, Hg₂L¹(b)H₋₂Cl₂ and [Hg₂L¹(b)H₋₅Cl₂]³⁻. Based on ¹H NMR and pH-metric data the proposed structure for HgL¹(b)Cl₂, the main tetraamide ligand containing species in the pH range <3-6.5, contains L¹(b) coordinated to the metal ion through the two tertiary nitrogens and two amide oxygens while the structure of [HgL¹(b)H₋₂Cl₂]²⁻, the main tetraamide ligand species at pH 7.5-9.0, contains the ligand similarly coordinated but through two amidate nitrogen atoms instead of amide oxygens. The proposed structure of [Hg₂L¹(b)Cl₂]²⁺, a minor species at pH 3-6.5, also based on ¹H NMR and pH-metric data, contains each Hg(II) coordinated to a tertiary amino nitrogen, two amide oxygens and a chloride ligand while that of [Hg₂L¹(b)H₋₅Cl₂]³⁻, contains each Hg(II) coordinated to a tertiary amino nitrogen, two amidate nitrogens, a chloride and a hydroxo ligand in the case of one of the Hg(II) ions. The parent EDTA and PDTA amides only form mononuclear complexes. PAMAM also forms dinuclear as well as mononuclear complexes with mercury(II) and silver(I). In the pH range 3-11 six complexes with Hg(II) i.e. [HgLH₄Cl₂]⁴⁺, [HgLH₃Cl₂]³⁺, [Hg₂LCl₂]²⁺, [Hg₂LH₋₁Cl₂]⁺, [HgLH₋₁Cl₂]⁻ and [HgLH₋₂Cl₂]²⁻ were identified and only two with Ag(I), [AgLH₃]⁴⁺ and [Ag₂L]²⁺. Based on stoichiometries, stability constant comparisons and ¹H NMR data, structures are proposed for these species. Hence [HgLH₄Cl₂]⁴⁺ is proposed to have a similar structure to [CuLH₄]⁶⁺ while [Hg₂LCl₂]²⁺has a similar structure to [Hg₂L¹(b)H₋₅Cl₂]³⁻.     

A series of metal-organic frameworks constructed with 2,2′-bipyridine-3,3′-dicarboxylate: Syntheses, structures, and physical properties

To determine the influence of metal ion and the auxiliary ligand on the formation of metal-organic frameworks, six new coordination polymers, {[Mn₂(bpdc)(bpy)₃(H₂O)₂] · 2ClO₄ · H₂O}_n (1), {[Mn(bpdc)(dpe)] · CH₃OH · 2H₂O}_n (2), {[Cu(bpdc)(H₂O)₂]}_n (3), {[Zn(bpdc)(H₂O)₂]}_n (4), {[Cd(bpdc)(H₂O)₃] · 2H₂O}_n (5), and {[Co(bpdc)(H₂O)₃] · 0.5dpe · H₂O}_n (6) (H₂bpdc = 2,2′-bipyridine-3,3′-dicarboxylic acid, bpy = 2,2′-bipyridine, dpe = 1,2-di(4-pyridyl) ethylene), have been synthesized and characterized. Compound 1 forms 1D helical chain structure containing two unique Mn^II ions. In 2, the bridging ligand dpe links Mn-bpdc double zigzag chains to generate a layer possesses rectangular cavities. In 3, bpdc²⁻ ligand connects to three metal centers forming a 2D network. Different from the above compounds, 4 displays a 1D double-wavelike chain. Compound 5 features a helical chain. Compound 6 also displays a helical chain with guest molecule dpe existing in the structure. These diverse structures illustrate rational adjustment of metal ions and the second ligand is a good method for the further design of helical compounds with novel structures and properties. In addition, the magnetic properties of 2, 3 and 6, the thermal stabilities and photoluminescence properties of 4 and 5 were also studied.     

Group II metal-directed structural variation of coordination compounds derived from 5-[N-acetato(4-pyridyl)]tetrazolate ligand

Reactions of MCl₂ (M = Mg, Ca, Sr, Ba) and a4-ptz (a4-ptz = 5-[N-acetato (4-pyridyl)] tetrazolate) potassium salt in water, respectively, and produced four new complexes [Mg(H₂O)₆] · (a4-ptz)₂ · 2H₂O (1), [Ca(a4-ptz)₂(H₂O)₂]_n · 2nH₂O (2), [Sr(a4-ptz)₂(H₂O)₂]_n · 2nH₂O (3), [Ba₄(a4-ptz)₈(H₂O)₈]_n · 4nH₂O (4). These compounds were structurally characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Compound 1 has mononuclear structure bearing distinct intermolecular hydrogen-bond interactions to form a three-dimensional supramolecular network. While compounds 2-4 have one-dimensional polymeric chains that are bridged by two water molecules linker, respectively. The luminescence properties of 1-4 were investigated at room temperature in the solid state.     

Synthesis, structures and properties of alkaline earth metal benzene-1,4-dioxylacetates with three-dimensional hybrid networks

Three novel alkaline earth metal benzene-1,4-dioxylacetates M(L)H₂O (M = Ca, Sr or Ba, L = benzene-1,4-dioxylacetate) with three-dimensional (3D) hybrid frameworks were reported. Both Ca(L)H₂O (1) and Sr(L)H₂O (2) crystallize in the monoclinic space group P2₁/c while Ba(L)H₂O (3) in the monoclinic space group P2₁. As determined by X-ray single-crystal analysis, in these compounds each metal ion is coordinated by eight O atoms: four from different carboxylate groups, two from one carboxylate group, one from the ether oxygen and one from one water molecule. Each L²⁻ ligand coordinates to five alkaline earth metal centers through one of its ether oxygen atoms and two carboxylate groups adopting novel μ₃-η²:η²-bridging and μ₂-η¹:η¹-bridging coordination modes to give rise to a 3D network. The luminescence analysis shows that complexes 1 and 2 exhibit fluorescence in the solid state at room temperature.     

Hydrothermal syntheses, structures and properties of five rare earth coordination polymers with (1,3,4-thiadiazole-2,5-diyldithio)diacetic acid

Hydrothermal reactions of rare earth ions(III) with a flexible building unit (1,3,4-thiadiazole-2,5-diyldithio)diacetic acid (H₂tzda) lead to five novel coordination polymers with 1D chain and 3D network structures, namely, {[Y₂(tzda)₃(H₂O)₁₀] · 5H₂O}_n (1) and [Ln₂(tzda)₃(H₂O)₅]_n [Ln = Er (2), Pr (3), Nd (4), Eu (5)]. Compound 1 has one-dimensional ribbon-like chain structure constructed by [Y₂(tzda)₃] units through the syn-anti bidentate bridging mode of carboxylate groups. Compounds 2-5 possess compact three-dimensional network structures which are made up of [Ln₂(tzda)₃] (Ln = Er, Pr, Nd and Eu) units bridged by carboxylate groups. In these compounds, the flexible tzda²⁻ ligand is versatile and displays six different coordination fashions to meet the requirement of the coordination preference of the metal center. Furthermore, the magnetic behaviors for 2-5 in the temperature range of 5.0-300 K and photoluminescent property of 5 are significantly investigated in this paper.     

Synthesis, structures and thermal stabilities of five copper(II) coordination polymers based on 2,4,6-tris(pyridyl)-1,3,5-triazine and 1,2,4,5-benzenetetracarboxylate ligands

Hydrothermal reactions of Cu(II) salts with 2,4,6-tris(3/4-pyridyl)-1,3,5-triazine (3/4-tpt) and 1,2,4,5-benzenetetracarboxylic acid (H₄btec) afforded five novel coordination polymers, namely [Cu₄(3-tpt)₂(btec)₂(H₂O)₄]_n·6nH₂O (1), [Cu(3-tpt)₂(H₂btec)]_n (2), [Cu₃(3-Htpt)₂(H₂btec)₂(btec)]_n·4nH₂O (3), [Cu₂(4-tpt)₃(H₂btec)₂]_n·4nH₂O (4), and [Cu₃(4-tpt)₂(Hbtec)₂(H₂O)]_n·3nH₂O (5). These complexes exhibit various polymeric networks due to diverse coordination modes of tpt and H₄btec. Complex 1 displays a 3-D metal-organic framework in which 3-tpt is an exo-tridentate ligand and μ₄-btec⁴⁻ coordinates to two square-pyramidal Cu(II) and two square Cu(II) ions. Complex 2 is a 1-D chain coordination polymer which contains μ₂-H₂btec²⁻ bridge and monodentate 3-tpt. Complex 3 shows a 3-D metal-organic framework constructed from protonated bidentate 3-Htpt⁺, tridentate H₂btec²⁻ and tetradentate btec⁴⁻. Complex 4 is a 1-D ladder-like coordination polymer assembled by μ₂-H₂btec²⁻, mono- and bidentate 4-tpt. Complex 5 exhibits a porous 3-D metal-organic framework constructing from tridentate 4-tpt and μ₃-Hbtec³⁻. Their thermal stabilities were also investigated.     

Palladium(II) complexes of imidazolin-2-ylidene N-heterocyclic carbene ligands with redox-active dimethoxyphenyl or (hydro)quinonyl substituents

Four novel imidazolium salts, precursors to N-heterocyclic carbene (NHC) ligands, with 2,5-dimethoxybenzyl or 2,5-dihydroxybenzyl (i.e., p-hydroquinone) substituents have been prepared. The crystal structure of the hydroquinone-substituted imidazolium salt H₃L³Br reveals Br⁻?H-O bridged chiral chains of alternating [H₃L³]⁺ cations and Br⁻ counter-ions parallel to the x-axis. Palladium(II) complexes were accessible from reactions of the dimethoxyphenyl-substituted imidazolium precursors with palladium(II) acetate, but not from reactions of imidazolium cations with hydroquinonyl substituents. The crystal structure of the bis(dimethoxybenzyl)-substituted bis(NHC)Pd complex, cis-[PdBr₂(L²)] (2), is described. Puckering of the bis(NHC) ligand leads to a cleft in which an included molecule of dimethylformamide is situated. The cleft is closed by one of the dimethoxybenzyl groups which π-stacks with the dimethylformamide; the other dimethoxybenzyl group points away from the cleft and Pd(II) centre. Reaction of complex 2 with BBr₃ afforded the targeted bis(hydroquinone)-substituted bis(NHC)Pd(II) complex 3 (97% yield) which, in turn, was oxidised by 2,3-dichloro-5,6-dicyano-benzoquinone to the corresponding p-benzoquinone-substituted bis(NHC)Pd(II) complex 4 (98% yield). The cyclic voltammograms of the Pd(II) complexes 2-4 reveal waves that are attributed to an admix of the anticipated ligand-centred and [Pd(C-NHC)₂Br₂]-centred processes.     

A rare case of solution and solid state inter-conversion of two copper(II) dimers and a copper(II) chain

Three Cu(II)-azido complexes of formula [Cu₂L₂(N₃)₂] (1), [Cu₂L₂(N₃)₂]·H₂O (2) and [CuL(N₃)]_n (3) have been synthesized using the same tridentate Schiff base ligand HL (2-[(3-methylaminopropylimino)-methyl]-phenol), the condensation product of N-methyl-1,3-propanediamine and salicyldehyde). Compounds 1 and 2 are basal-apical μ-1,1 double azido bridged dimers. The dimeric structure of 1 is centrosymmetric but that of 2 is non-centrommetric. Compound 3 is a μ-1,1 single azido bridged 1D chain. The three complexes interconvert in solution and can be obtained in pure form by carefully controlling the synthetic conditions. Compound 2 undergoes an irreversible transformation to 1 upon dehydration in the solid state. The magnetic properties of compounds 1 and 2 show the presence of weak antiferromagnetic exchange interactions mediated by the double 1,1-N₃ azido bridges (J = −2.59(4) and −0.10(1) cm−¹, respectively). The single 1,1-N₃ bridge in compound 3 mediates a negligible exchange interaction.     

Ternary copper(II) complexes with hippurate derivatives and 1,10-phenanthroline: Synthesis and biological activity

Several new Cu-hippurate derivative-phenanthroline ternary complexes have been prepared. The X-ray structure of one of them, [Cu(hip)(phen)₂]⁺·(hip⁻) (2) (where hip is hippurate and phen is 1,10-phenanthroline) has been solved. The structure of this new compound shows important differences (3D-pattern) to other similar related complexes (2D-pattern). A study of the biological activity of [Cu(hip)(phen)₂]⁺·(hip⁻)·2H₂O (2), [Cu(BGG)(phen)₂]⁺·(BGG⁻)·6H₂O (3), [Cu(B^IGG)₂(phen)](H₂O) (4) and [Cu(I-hip)(bpy)₂]⁺·(I-hip⁻)·3.5H₂O (5) (where I-hip is ortho-iodohippurate, BGG corresponds to benzoylglycilglycine, and B^IGG is ortho-iodobenzoylglycilglycine) is included and compared with the anti-proliferative activity of [Cu(I-hip)(phen)₂]⁺·(I-hip⁻)·7H₂O (1) previously described, resulting in a greater cytotoxic activity of the compounds with 1,10-phenanthroline instead of those with 2,2′-bipyridyl, in the same way that removing iodine substitution or lengthening the peptidic chain diminishes the activity of compounds compared with 1. The presence of an ortho-iodine group and the direct bond between Ar-CO and glycine moieties yield to the best results.