Dinuclear Units Research Articles

Synthesis, crystal structure and thermal properties of the dinuclear complex bis-(μ-4-methylpyridine N-oxide-κ2O:O)bis-[(methanol-κO)(4-methylpyridine N-oxide-κO)bis-(thio-cyanato-κN)cobalt(II)

Reaction of Co(NCS)2 with 4-methyl-pyridine N-oxide in methanol leads to the formation of crystals of the title compound, [Co2(NCS)4(C6H7NO)4(CH4O)2] or Co2(NCS)4(4-methyl-pyridine N-oxide)4(methanol)2. The asymmetric unit consist of one CoII cation, two thio-cyanate anions, two 4-methyl-pyridine N-oxide coligands and one methanol mol-ecule in general positions. The H atoms of one of the methyl groups are disordered and were refined using a split model. The CoII cations octa-hedrally coordinate two terminal N-bonded thio-cyanate anions, three 4-methyl-pyridine N-oxide coligands and one methanol mol-ecule. Each two CoII cations are linked by pairs of μ-1,1(O,O)-bridging 4-methyl-pyridine N-oxide coligands into dinuclear units that are located on centers of inversion. Powder X-ray diffraction (PXRD) investigations prove that the title compound is contaminated with a small amount of Co(NCS)2(4-meth-yl-pyridine N-oxide)3. Thermogravimetric investigations reveal that the methanol mol-ecules are removed in the beginning, leading to a compound with the composition Co(NCS)2(4-methyl-pyridine N-oxide), which has been reported in the literature and which is of poor crystallinity.

Ibuprofen: A multi-purpose active pharmaceutical ingredient as versatile ligand for zinc(II) and copper(II). Solid state and solution studies

Two new, Zn(II) and Cu(II), complexes of the non-steroidal anti inflammatory drug (NSAID) ibuprofen (HIbu) are reported. Results from their solid state investigation are complemented by potentiometric and 1H NMR studies in view of the role that chelation of these biologically relevant metal ions might play in affecting the Active Pharmaceutical Ingredient (API) biological properties, but also of the use of metallo-ibuprofen drugs. In the solid state, the ibuprofenate anion (Ibu−) gives rise to 0- and 1-D species, [Zn(Ibu)2(H2O)2] and [Cu(Ibu)2]n, respectively. The [Zn(Ibu)2] species is also present in H2O/EtOH 50 % v/v solution (pKw = 14.41(1)) and starting from pH 4–4.5 coexists in solution with the [Zn(Ibu)]+ one. As for the copper structure, it represents, to the best of our knowledge, the first example of 1-D coordination polymer consisting of copper-ibuprofen dinuclear paddle-wheel units. Interestingly, this crystal phase is the only one obtained irrespective of the different synthetic and crystallization procedures adopted. Potentiometric titrations evidence that copper(II) gives the more stable complexes (also in this case [Cu(Ibu)2] and[Cu(Ibu)]+ coexist in solution) with respect to the zinc ones. Lastly, in light of the increasing interest around the antibacterial activities of NSAIDs and NSAIDs-containing compounds, the antimicrobial effects of ibuprofen, [Zn(Ibu)2(H2O)2] and [Cu(Ibu)2]n were preliminary evaluateted on Bacillus Subtilis, chosen as a model of Gram-positive bacteria.

Synthesis, crystal structure and thermal properties of poly[[μ-1,2-bis-(pyridin-4-yl)ethene-κ2N:N'-μ-bromido-copper(I)] 1,2-bis-(pyridin-4-yl)ethene 0.25-solvate

The reaction of copper(I) bromide with 1,2-bis-(pyridin-4-yl)ethene in aceto-nitrile leads to the formation of the title compound, {[CuBr(C12H10N2)]·0.25C12H10N2}n or CuBr(4-bpe)·0.25(4-bpe) [4-bpe = 1,2-bis-(pyridin-4-yl)ethene]. The asymmetric unit consists of one copper(I) cation and one bromide anion in general positions as well as two crystallographically independent half 4-bpe ligands and a quarter of a disordered 4-bpe solvate mol-ecule that are completed by centers of inversion. The copper(I) cations are tetra-hededrally coordinated as CuBr2N2 and linked by pairs of μ-1,1-bridging bromide anions into centrosymmetric dinuclear units that are further connected into layers by the 4-bpe coligands. Between the layers, inter-layer C-H⋯Br hydrogen bonding is observed. The layers are arranged in such a way that cavities are formed in which the disordered 4-bpe solvate mol-ecules are located. Powder X-ray (PXRD) investigations reveal that a pure sample has been obtained. Thermogravimetric (TG) and differential thermoanalysis (DTA) measurements show two mass losses that are accompanied by endothermic events in the DTA curve. The first mass loss correspond to the removal of 0.75 4-bpe mol-ecules, leading to the formation of (CuBr)2(4-bpe), already reported in the literature as proven by PXRD.

Structural determinations of homo and heterodi- or tetra-nuclear lanthanide complexes and their characterization by μ-Squid experiments

Two families of homo- and heterodinuclear complexes are prepared and structurally characterized, thus demonstrating that genuine complexes involving two lanthanide ions closely located in the lanthanide series can be obtained, taking into account a simple rule that necessitates introduction of the better Lewis acid Ln ion (the smallest Ln ion) into the inner coordination site of the main ligand used in this synthesis. In the first family, the presence of a deprotonated orthovanillin ligand (ovan) around the Ln ion positioned in the outer coordination site of the main ligand allows a good isolation of the dinuclear complexes. These complexes behave as SMSs when a Dy ion is coordinated in the outer site but a weak magnetic magnetic Ln-Dy interaction is needed to create a weak magnetic field able to suppress collapsing of the hysteresis loops in zero external applied field at very low temperature. In the second family, the ovan ligand is replaced by a chloride ligand, so that two dinuclear units are linked together by two Cl…HOMe hydrogen bonds to yield tetranuclear complexes that are not SMMs. Eventually these two preparation pathways are expected to give novel and genuine examples of homo or hetero-dinuclear and tetranuclear lanthanide complexes likely to furnish in future coordination complexes useful in quantum computing.

Synthesis, crystal structure and reactivity of bis-(μ-2-methyl-pyridine N-oxide-κ2O:O)bis-[di-bromido-(2-methyl-pyridine N-oxide-κO)cobalt(II)] butanol monosolvate.

Reaction of CoBr2 with 2-methyl-pyridine N-oxide in n-butanol leads to the formation of the title compound, [CoBr2]2(2-methyl-pyridine N-oxide)4·n-butanol or [Co2Br4(C6H7NO)4]·C4H10O. The asymmetric unit of the title compound consists of one CoII cation as well as two bromide anions and two 2-methyl-pyridine N-oxide coligands in general positions and one n-butanol mol-ecule that is disordered around a center of inversion. The CoII cations are fivefold coordinated by two bromide anions and one terminal as well as two bridging 2-methyl-pyridine N-oxide and linked by two symmetry-related μ-1,1(O,O) 2-methyl-pyridine N-oxide coligands into dinuclear units that are located on centers of inversion. In the crystal structure, the dinuclear units are also connected via pairs of C-H⋯Br hydrogen bonds into chains that elongate in the b-axis direction. The n-butanol mol-ecules are located between the chains and are linked via O-H⋯Br hydrogen bonds each to one chain. Powder X-ray diffraction (PXRD) measurements reveal that a pure phase has been obtained. Measurements using thermogravimetry and differential thermoanalysis shows one mass loss up to 523 K, in which the n-butanol mol-ecules are removed. PXRD measurements of the residue obtained after n-butanol removal shows that a completely different crystalline phase has been obtained and IR investigations indicate significant structural changes in the Co coordination.

Two different 4,5-dichlorophthalate-extended Cu(II) 1D coordination polymers. Crystal structures, solvatochromism, and magnetic studies

A new 1D Cu-coordination polymer with formula {[Cu2(tmeda)2(dcpa)2(H2O)]·H2O}∞, 1 (tmeda=N,N,N´,N´-tetramethylethylenediamine, dcpa=4,5-dichlorophthalate) has been synthesized by a self-assembly solution reaction between the aqua complex [Cu(tmeda)(H2O)x](ClO4)2 and the salt K2dcpa. The use of piperidinium (Pip) salt of dcpa under the same conditions induced the crystallization of a different 1D polymer {[Cu(tmeda)(dcpa)]·Pip(ClO4)}∞, 2. The 1D Cu-polymers-based 1–2 were structurally analyzed by single-crystal X-ray diffraction, Hirshfeld surfaces, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and multiple spectroscopic tools. X-ray analysis showed that the unusual inclusion of the ionic pair (PipClO4) into the single-crystal of 2 modified the Cu(II)…Cu(II) distances, Cu(II) geometries, supramolecular interactions, UV–Vis absorptions, and magnetic properties compared to 1.Polymer 1 consists of dinuclear Cu2 units bridged by deprotonated dcpa ligands with weak antiferromagnetic interactions (C = 0.74 emu K/mol, θ= −3.89 K). In contrast, polymer 2 is formed by mononuclear Cu units with antiferromagnetic interactions (C = 0.35 emu K/mol, θ= −4.49 K).Polymer 1 shows solvatochromism in the presence of non-protic solvents, and the solvent-dependent absorption maxima in the visible region (λmax = 637–685 nm) has a linear behavior as a function of the dielectric constant. The visible absorption bands of 1 originated from a combination of d-d transitions and ligand-to-metal charge transfers, as is evidenced by time-dependent density-functional theory calculations.

Investigation of Charge-Ordered Barium Iron Fluorides with One-Dimensional Structural Diversity and Complex Magnetic Interactions.

Three mixed-valence barium iron fluorides, Ba7Fe7F34, Ba2Fe2F9, and BaFe2F7, were prepared through hydrothermal redox reactions. The characteristic structures of these compounds feature diverse distributions of FeIIF6 octahedra and FeIIIF6 groups. Ba7Fe7F34 contained one-dimensional infinite ∞[FeIIFeIII6F34]14- double chains, comprising cis corner-sharing octahedra along the b direction; Ba2Fe2F9 contained one-dimensional ∞[Fe2F9]4- double chains, consisting of cis corner-sharing octahedra along the chain (a-axis direction) and trans corner-sharing octahedra vertical to the chain, while BaFe2F7 revealed three-dimensional (3D) frameworks that consist of isolated edge-sharing dinuclear FeII2F10 units linked via corners by FeIIIF6 octahedra. Magnetization and Mössbauer spectroscopy measurements revealed that Ba7Fe7F34 exhibits an antiferromagnetic phase transition at ∼11 K, where ferrimagnetic ∞[FeIIFeIII6F34]14- double chains are arranged in a paralleling manner, while Ba2Fe2F9 shows canted antiferromagnetic ordering at ∼32.5 K, leading to noncollinear spin ordering.

Halo-bridged Cu(II) complexes with pyridine–pyrazole ligands: Influence of halogen and ligand lipophilicity on antimicrobial activity

A series of five coordinated, doubly halo bridged Cu(II) complexes [Cu2(μ-X)2(Ln)2×2] (X=Cl and Br; n = 1, 2 and 3), CuL1Cl, CuL1Br, CuL2Cl, CuL2Br, CuL3Cl and CuL3Br (where L1 = 2-((1H-pyrazol-1-yl)methyl)pyridine, L2 = 2-((3-methyl-1H-pyrazol-1-yl)methyl)pyridine, L3 = 2-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)pyridine) have been synthesized and structurally characterized using FT-IR and UV–Vis spectroscopy analysis. Moreover, CuL1Cl, CuL1Br and CuL3Cl structures have also been confirmed by single crystal X-ray structural analysis. Copper ion in CuL1Cl, CuL1Br and CuL3Cl displayed distorted squared pyramidal geometry and formed dimers via bridged μ‑chloro/μ‑bromo coordination in the crystal lattice. The intermolecular C–H···Cl hydrogen bonding interaction further connected the dimers of CuL1Cl and CuL3Cl with four neighboring dinuclear complex units. Copper complexes were evaluated for their antimicrobial activity against Gram-negative and Gram-positive bacteria. Interestingly, copper complexes exhibited selective antimicrobial activity against Gram-positive bacteria. Further the increasing ligand lipophilicity showed the increase of antibacterial activity of copper complexes. The lipophilicity of ligands was regulated by number of methyl substituents on the ligands. The chloro bridged copper complexes exhibited relatively higher antibacterial activity compared to the bromo bridged copper complexes. Thus, the present structure-activity of simple copper complexes might provide insight on the structural design of new antimicrobial agents based on coordination complexes.

Synthesis and crystal structure of structurally different cadmium selenocyanate and thiocyanate coordination compounds containing 3‐chloropyridine as ligand

AbstractFour compounds with the composition Cd(NCSe)2(3‐ClPy)4 (1), [Cd(NCSe)2(3‐ClPy)2] ⋅ 3‐ClPy (2), Cd(NCSe)2(3‐ClPy)2 (3) and Cd(NCSe)2(3‐ClPy) (4) with 3‐ClPy = 3‐chloropyridine were synthesized. In the structure of 1 discrete complexes are observed, whereas in 2 the Cd cations are linked by pairs of selenocyanato anions into chains and between the chains 3‐chloropyridine solvate molecules are embedded. In compound 3 each two Cd cations are linked by pairs of anionic ligands into dinuclear units, that are further connected into layers by μ‐1,3 single bridging selenocyanate anions. In compound 4, both, octahedrally and tetrahe‐ drally coordinated Cd cations are present, that are linked by μ‐1,3‐ bridging anionic ligands into a three‐.dimensional network.Thermoanalytical investigations prove that compound 1 loses the 3‐chloropyridine ligands stepwise upon heating and transforms into compound 4 via compound 3 as an intermediate. Further investigations show that the thiocyanate analogue Cd(NCS)2(3‐ClPy) 5 that is not reported in the literature can also be prepared. Since no single crystals were available, the structure was solved from PXRD data and refined using the Rietveld method, which revealed that this compound is an isomer of 4. In its crystal structure the Cd cations are linked by μ‐1,3(N,S) and μ‐1,3,3(N,S,S)‐bridging anionic ligands into chains that are further connected via Cd2S2 rings into double chains.

Synthesis, structure, and electrochemical potential of a 3d − 4f heterobimetallic polyoxometalate

A three-dimensional (3-D) 3d-4f polyoxometalate (POM), [Gd2Cu(SiW12O40)(Hpca)4(pca)4(H2O)3]·(Hpca)2·H2O (1) (Hpca = isonicotinic acid, abbreviated as Cu-Gd-CP), was synthesized by hydrothermal method and characterized by XRD, TG, IR, and Ultraviolet–visible (UV–vis) spectra. The Gd3+ ions have two different coordination modes, which correspond to distinct kinds of dinuclear secondary building units, ([Gd12(Hpca)4(pca)4(H2O)2] and [Gd22(Hpca)4(pca)4(H2O)4]). Thus, there are two different types of pores (pore A and pore B) filled by free Hpca molecules in Cu-Gd-CP. The Hpac molecules in pore A are oriented perpendicular to each other in pore B. The electrochemical potential of Cu-Gd-CP is explored.

Geometrical isomerism in Ru2Au heterometal assembly: cis-linking of tetracyanidoaurate to tetrakis(μ-butanoato)diruthenium

A heterometal assembled complex of tetrakis(μ-butanoato)diruthenium(II,III) and tetracyanidoaurate(III) [RuIIRuIII(n-C3H7COO)4AuIII(CN)4]n was synthesized and characterized by the elemental analysis and infrared spectroscopy. The single-crystal X-ray structure analysis revealed that the complex consists of zigzag chain molecules of alternating arrangement of the Ru2(n-C3H7COO)4+ and Au(CN)4– units with cis-bridging mode of the Au(CN)4– units. The temperature dependence of the magnetic susceptibility data (4.5—300 K) showed that the magnetic interaction between the dinuclear RuIIRuIII units (S= 3/2) is negligibly small with a zero-field splitting parameter D value of 60 cm-1.

Synthesis and Characterization of the 2-(-(2-(-2-hydroxy-3-methoxybenzylideneamino)propylimino)methyl)-6-methoxyphenol dimanganese(III) Complex containing μ(O,O’)-nitrito-aqua Ligands

Single crystal of new nitrito bridged Mn(III) dinuclear compound {[Mn(L)(H2O)](μ-NO2)[Mn(L)(H2O)]}.(ClO4) has been synthesized in the absence of nitrite source. The compound was characterized by elemental analysis, IR spectroscopy and single crystal X‑ray diffraction. The compound crystallizes in the triclinic system in the space group P‑1 with a = 12.4175(3)Å, b = 13.6360(4) Å, c = 12.8207(5) Å, α = 74.876(3)°, β = 89.064(2)°, γ = 85.361(2)°, V = 2159.39(11) Å3, Z = 9, Dc = 1.489 Mg m-3. Each of the two ligand molecules encapsulates one Mn(III) ion in tetradentate fashion through two phenolate oxygen atoms and two azomethine nitrogen atoms. The two methoxy oxygen atoms of each ligand molecule remain uncoordinated. In the structure, each manganese(III) ion is situated in a N2O4 inner. The environment around each Mn(III) cation is best described as a distorted square pyramidal geometry, in which the equatorial plane is occupied by the atoms from the ligand molecule and the axial positions are occupied by one oxygen atom of a coordinated water molecule and one nitrito oxygen atom. The two Mn(III) ions are bridged though one μ1,3-nitrito group. Numerous intermolecular hydrogen bonds, established between water molecules as donors and phenoxo or methoxy oxygen atoms as acceptors, connect the dinuclear units into three-dimensional network.

Synthesis, Characterization and The Effect of the Auxiliary Ligands on the Dimensionality of Two Cobalt(II)-Fumarate Coordination Polymers with Bis(imidazole) Ligands

Two new Co(II) coordination polymers, namely {[Co(m-fum)0.5(m-obix)2(H2O)](NO3)}n (1), {[Co(m-fum)0.5(m-mbix)2(H2O)](NO3)}n (2), (H2fum: fumaric acid, obix:1,2-bis(imidazol-1-yl-methyl)benzene, mbix: 1,3-bis(imidazol-1-yl-methyl)benzene), have been successfully synthesized under hydrothermal conditions. They have been structurally characterized by elemental analysis, IR spectra, single crystal X-ray diffraction, powder X-ray diffraction (PXRD), magnetic properties. Single-crystal X-ray analysis reveals that the asymmetric units of both CPs contain a Co(II) ion, half fumarate ligand, two bis(imidazole) ligands, one aqua ligand and a nitrate ion. While two symmetry-related Co1 ions are connected by one fumarate ligand to generate a dinuclear unit and obix ligand links adjacent dinuclear units through the nitrogen atoms to form a 1D double chains in 1, each mbix ligand links two Co1 ions to form 1D double chains, and the adjacent chains are further linked together by fumarate ligands to form a 2D network in 2. The effect of bis(imidazole) ligands, which are o- and m-isomers, on the dimensionality of the formed coordination polymer was investigated. The reason for this great effect of bis(imidazole) ligands is that adjustments in the framework occur result of the bending of the semi-rigid imidazole ligands. Thermal analysis shows that 1 and 2 possess similar thermal behaviors. The optical band gap energy values of 1 and 2 observed 3.24 eV and 3.21 eV, respectively. This small difference in the band gap energy may be due to the difference in structural arrangement.

Synthesis, structure, and characterisation of a ferromagnetically coupled dinuclear complex containing Co(II) ions in a high spin configuration and thiodiacetate and phenanthroline as ligands and of a series of isomorphous heterodinuclear complexes containing different Co : Zn ratios.

We report the synthesis, crystal structure, and characterisation of a dinuclear Co(II) compound with thiodiacetate (tda) and phenanthroline (phen) as ligands (1), and of a series of metal complexes isomorphous to 1 with different Co : Zn ratios (2, 4 : 1; 3, 1 : 1; 4, 1 : 4; 5, 1 : 10). General characterisation methodologies and X-ray data showed that all the synthesised complexes are isomorphous to Zn(II) and Cu(II) analogues (CSD codes: DUHXEL and BEBQII). 1 consists of centrosymmetric Co(II) ion dimers in which the ions are 3.214 Å apart, linked by two μ-O bridges. Each cobalt atom is in a distorted octahedral environment of the N2O3S type. UV-vis spectra of 1 and 5 are in line with high spin (S = 3/2) Co(II) ions in octahedral coordination and indicate that the electronic structure of both Co(II) ions in the dinuclear unit does not significantly change relative to that of the magnetically isolated Co(II) ion. EPR spectra of powder samples of 5 (Co : Zn ratio of 1 : 10) together with spectral simulation indicated high spin Co(II) ions with high rhombic distortion of the zfs [E/D = 0.31(1), D > 0]. DC magnetic susceptibility experiments on 1 and analysis of the data constraining the E/D value obtained by EPR yielded g = 2.595(7), |D| = 61(1) cm-1, and an intradimer ferromagnetic exchange coupling of J = 1.39(4) cm-1. EPR spectra as a function of Co : Zn ratio for both powder and single crystal samples confirmed that they result from two effective S' = 1/2 spins that interact through dipolar and isotropic exchange interactions to yield magnetically isolated S' = 1 centres and that interdimeric exchange interactions, putatively mediated by hydrophobic interactions between phen moieties, are negligible. The latter observation contrasts with that observed in the Cu(II) analogue, where a transition from S = 1 to S' = 1/2 was observed. Computational calculations indicated that the absence of the interdimeric exchange interaction in 1 is due to a lower Co(II) ion spin density delocalisation towards the metal ligands.

Evidence of symmetry breaking in a Gd2 di-nuclear molecular polymer.

A chiral 3D coordination compound, [Gd2(L)2(ox)2(H2O)2], arranged around a dinuclear Gd unit has been characterized by X-ray photoemission and X-ray absorption measurements in the context of density functional theory studies. Core level photoemission of the Gd 5p multiplet splittings indicates that spin orbit coupling dominates over j-J coupling evident in the 5p core level spectra of Gd metal. Indications of spin-orbit coupling are consistent with the absence of inversion symmetry due to the ligand field. Density functional theory predicts antiferromagnet alignment of the Gd2 dimers and a band gap of the compound consistent with optical absorption.

Solid state structures and solution behaviour of tetranuclear lanthanide(III) carbonate-bridged coordination compounds of chiral 3 + 3 amine macrocycle.

The linking of two dinuclear macrocyclic units of large triphenolic hexaazamine by two carbonate anions results in the formation of dimeric tetranuclear Sm(III), Eu(III) and Gd(III) complexes. These complexes were initially obtained serendipitously by fixation of atmospheric carbon dioxide and subsequently obtained in a rational way by the application of carbonate salts. The X-ray crystal structures of these isomorphic complexes show highly folded conformation of the macrocycle. This type of conformation is also confirmed by 2D NMR spectra of the Sm(III) complex. The ESI-MS and NMR spectra reveal also that these carbonate complexes exist in solution in two different forms that are in a concentration-dependent dynamic equilibrium.

Unexpected Solvent-Dependent Self-Assembly of Alkali Metal Complexes of Calix[6]-mono-crown-4: Dinuclear Bowls, a Pseudo-Capsule, and a One-Dimensional Polymer.

1,4-Bridged calix[6]-mono-crown-4 (H4L) capable of metal binding was employed, and the influence of solvent variations on the formation of alkali metal complexes (1-6) was investigated. In the crystal, the bowl-shaped H4L host contains one water molecule in a good-fit fashion via H-bonds. When the H4L host was reacted with alkali metal hydroxides (M = Na, K, Rb, and Cs) in chloroform/methanol (solvent A), anion-free dinuclear bowl-shaped complexes of type [M2(H2L)] were isolated regardless of the metal ions. In the dinuclear bowl complexes 1-4, two metal ions (M1 and M2) show different binding behaviors: one (M1) locates inside the pocket like an "egg-in-nest", and the other (M2) positions above the M1 interacting with the calix rim. When chloroform/acetonitrile (solvent B) was used in potassium(I) complexation, interestingly, an elegant pseudo-capsule-type quadrunuclear complex 5 was isolated. In 5, two dipotassium(I) bowls in a rim-to-rim arrangement are triply bridged by one water and two acetonitrile molecules like a magic glue. However, in dichloromethane/methanol (solvent C), cesium(I) yielded an infinite product 6 in which dicesium(I) bowls are linked by cation-π interactions, giving rise to a one-dimensional zigzag coordination polymer. Taken collectively, all products share a dinuclear bowl unit, some of which are further extended to the pseudo-capsule or polymeric array, depending on the solvents. The results suggest the solvent variation as a versatile engineering tool and present a perspective on the metallosupramolecules of calix[6]-mono-crowns with monomer, dimer (e.g., pseudo-capsule), and polymer topologies.

Two novel 3D Zn(II)/Cd(II) MOFs with tri- or di-nuclear cluster units for multifunctional sensing applications in aqueous media

With flexible 2-methylenesuccinate acid (H2MSA) and rigid 4, 4′-bipyridine (bpy) as mixed ligands, two three-dimensional (3D) metal−organic frameworks (MOFs), {[Zn3(μ2-OH)2(MSA)2(bpy)2]·4H2O}n (1) and {[Cd(MSA)(bpy)]·2H2O}n (2), were obtained solvothermally. Complexes 1 and 2 both have a 3D framework structures, which include respectively a linear trinuclear [Zn3] or a rare dinuclear [Cd2] cluster node that consisting of two seven-coordinated Cd(II) ions. The adjacent [Zn3] or [Cd2] nodes in 1 and 2 are firstly linked together by the MSA2− ligand to form a 1D chain or a 2D layer unit respectively, which are further bridged by the bpy linkers to produce the 3D framework structures. If treating the [Zn3] and [Cd2] cluster as 4- and 6-connected nodes, the 3D frameworks of 1 and 2 can be simplified into a CdSO4 topological network with a Schläfli symbol of (65.8) and a rob network with a Schläfli symbol of (48.66.8), respectively. The PXRD patterns suggest that 1 and 2 have good stability when soaked in water for at least 48 h. The fluorescence sensing properties of 1 and 2 toward different metal inorganic ions were investigated, and two complexes both could sense Fe3+, MnO4− and Cr2O72− in aqueous solution with high sensitivity and selectivity (the LODs were 3.20 μM, 1.54 μM and 1.95 μM for 1, 1.15 μM, 0.48 μM and 1.23 μM for 2, respectively) as well as good recircularity. In addition, the mechanism of the selective luminescence quenching response for Fe3+, MnO4− and Cr2O72− could be attributed to the energy competition between the excitation of complex 1/2 and the ultraviolet absorption of responsive substances.

Syntheses, structures and fluorescence properties of a Zn and a Cd(II) coordination polymer based on the mixed ligands

Two new compounds, [Zn(4-npa)(btmb)]n (1) and [Cd(4-npa)(btmb)0.5(H2O)2]n (2) (H24-npa = 4-nitrophthalic acid, btmb = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene) have been achieved under hydrothermal conditions and structurally characterized by elemental analysis, IR spectroscopy and single-crystal x-ray diffraction. The compound 1 crystallizes in monoclinic crystal system, space group P21/c and is characterized by a two-dimensional layer structure containing 1 D Zn-carboxylate chains. Wherein the central Zn(II) ion is coordinated by two carboxylate O atoms and two N atoms to give a distorted tetrahedral [ZnO2N2] geometry. In compound 2, The hexa-coordinated Cd(II) ion forms a slightly distorted octahedral [CdNO5] geometry. The two Cd(II) centers are bridged by pair 4-npa dianions adopting bidentate-bridging mode to form a dinuclear unit. The dinuclear units are linked together by 4-npa dianions to form a Cd-carboxylate layer, and further extend by btmb molecules to form a 3 D pillared-layer metal–organic framework. The thermogravimetric analyses and luminescent properties of two compounds are also investigated.

An Unprecedented Dodecanuclear Copper(II) Complex Derived from an Unsymmetrical Schiff‐Base Ligand

AbstractA novel discrete dodecanuclear Cu(II) complex, [Cu12L26(OH)6]⋅2CH3CN (1) has been synthesised using an N2O3 donor unsymmetrical Schiff base ligand derived from the condensation of 1,3‐diamino‐2‐propanol with salicylaldehyde and o‐hydroxyacetophenone. Single crystal X‐ray diffraction study indicates that each deprotonated ligand chelates two Cu(II) centres which are also bridged by alkoxo oxygen; six such dinuclear units are joined by alkoxo and phenoxo groups of the ligand as well as hydroxo bridges to form the dodecanuclear structure. Magnetic studies indicate predominating antiferromagnetic coupling interactions between the paramagnetic Cu(II) centres.