Dinuclear Subunits Research Articles

Modelling the Binding of Cytotoxic Dinuclear Copper Complexes to two Neighboring Phosphate Esters of DNA Using Glutarate: A Tetranuclear Metallo‐Macrocycle vs a Dinuclear Model

AbstractA family of dinuclear complexes was rationally designed to bind to two neighboring phosphate diesters of DNA by molecular recognition. Although these complexes bind strongly and irreversibly to DNA and induce apoptosis in cancer cells, a direct proof of the intended binding mode is missing. To mimic two neighboring phosphate diesters of DNA, we use here the dicarboxylate glutarate as a difunctional ligand. Starting from the acetate‐bound CuII2 complex, protonation results in the de‐coordination of acetate and allows the synthesis of the glutarate‐bound complex. Instead of bridging two CuII ions of one dinuclear complex, two glutarates bridge two dinuclear complexes resulting in a tetranuclear metallo‐macrocycle. The molecular structures of two different salts differ in the square‐pyramidal coordination to the CuII ions. The carboxylate stretching modes, the d‐d and the CT transtitions are not sensitive enough to resolve these differences. The exchange coupling is weakly antiferromagnetic between the CuII ions in the dinuclear subunits and negligible between the subunits via the glutarates. The consequences for suited ligands to model the binding to two neighboring phosphate diesters in the DNA backbone is discussed.

Structural characterization of the 1-metallo-2-t-butyl-1,2-dihydropyridyl rubidium and caesium complexes

With recent reports of alkali metal amides used in homogeneous catalytic chemistry where the reactivity down group one is dependent on the metal identity, esoteric rubidium and caesium amides are finding new admirers amongst chemists who usually study lithium, sodium, and potassium utility amides. Here, as a forerunner to their exploitation in catalysis, we report the X-ray crystallographic and NMR solution structures of the 1-metallo-2-t-butyl-1,2-dihydropyridyl (DHP) complexes of rubidium and caesium, thereby completing the homologous alkali metal series. Crystallized as monosolvated {[Rb(tBuDHP)·THF]2}∞ and hemisolvated {[Cs(tBuDHP)]2·THF}∞, both form spectacular supramolecular structures. While each shares a plethora of metallo-π-contacts with the DHP anion, their subunits differ. The former dimerizes in a ‘slipped’ fashion via interactions between the symmetrically-equivalent Rb centres and the π-system of the adjacent DHP ring, but the latter has distinct Cs centres within its dinuclear subunit, with one Cs engaging in σ-bonding to two tBuDHP anions, whereas the other Cs binds in a more side-on fashion to the π-system of the ring.

RETRACTED: Two new mixed ligand coordination polymers: Photo-catalytic properties, treatment and nursing application values on puerperal infection

• Two new mixed-ligand coordination polymers have been prepared. • Their photo-catalytic activities were explored through the MB photo-degradation. • Their application values on the puerperal infection were explored. Two coordination polymers based on mixed ligand, namely [Cu(L)(phen)(H 2 O)] n (1) and [Co(L)(4,4’-bipy)] (2) (4,4’-bipy is 4,4’-bipyridine, phen is 1,10-phenanthroline, H 2 L is 5-(benzyloxy)benzene-1,3-dicarboxylic acid), were produced hydrothermally, and their structures were characterized through X-ray diffraction. Results show that complex 1 features a 1D chain-like structure, which is further extended into a 3D supra-molecular network via H-bond interactions, while complex 2 reveals a 2D layered network based on the di-nuclear subunit of [Co 2 (COO) 2 ]. Their photo-catalytic activities were explored through methylene blue photo-degradation under UV light irradiation. Their application values on the puerperal infection were explored, and the specific mechanism was investigated. First, the inflammatory cytokines released into the plasma during bacterial infection was determined via enzyme linked immuno-sorbent assay. Afterward, the bacterial survival genes relative expression levels were determined with real-time reverse transcription polymerase chain reaction.

Homologous series of coordination polymers based on semi-rigid tricarboxylato-bridged Co2+/Ni2+: Syntheses, structures, and magnetic properties

Hydrothermal reactions of Ni2+ or Co2+ with 5-((4-carboxyphenoxy)-methyl)isophthalic acid (H3L) and KOH in the absence or presence of the auxiliary N donors 1,10-phenanthroline (1,10-phen) and 2,2′-bipyridyl (2,2′-bpy) resulted in the coordination polymers [Ni2(μ3-HL2−)(μ4-HL2−)(μ-OH2)(H2O)3]n (1), [Ni(μ-HL2−)(1,10-phen)(H2O)]n·3nH2O (2), [Ni(μ-HL2−)(2,2′-bpy)(H2O)]n (3), and [Co(μ-HL2−)(1,10-phen)(H2O)]n·3nH2O (4), [Co(μ-HL2−)(2,2′-bpy)(H2O)]n (5). The semi-rigid tricarboxylic ligand HL2− in part leads to predictably isomorphous, in part to unexpectedly different structures for the neighboring cations in the periodic table. Compound 1 crystallizes in an interpenetrated 3D network with hms 3,5-conn topology and is isomorphous to the corresponding Co compound (Y. Y. An, L. P. Lu and M. L. Zhu, Acta Crystallogr., Sect. C: Struct. Chem., 74 (2018) 418–423). 2 and 4 are also isostructural and form 1D zig-zag chains. In contrast, the dianionic linker HL2− adopts alternative conformations in the one-dimensional polymers 3 and 5; despite similar local environment about the cations, these structures are entirely different. The structural differences between the 3D networks in 1 and its Co congener on the one hand and the chain polymers 2–5 on the other hand are reflected in the magnetic properties: a carboxylato group bridges two cations in the former. Within these dinuclear subunits, significant magnetic interactions are observed. These interactions are ferromagnetic in 1; the susceptibility follows the Curie–Weiss law with C = 2.53(1) cm3 K mol−1 and θ = 1.92(3) K. In contrast, each coordinated carboxylato moiety in 2–5 binds to only one cation; the magnetic properties in these solids are dominated by single ion behavior and structural differences are negligible. χmT for the Ni2+ compounds 2 and 3 can be described by spin-only behavior and zero-field splitting, whereas orbital momentum is only partially quenched in the Co2+ derivatives 4 and 5.

Time-controlled synthesis of the 3D coordination polymer U(1,2,3-Hbtc)2 followed by the formation of molecular poly-oxo cluster {U14} containing hemimellitate uranium(iv).

Two coordination compounds bearing tetravalent uranium were synthesized in the presence of tritopic hemimellitic acid in acetonitrile with a controlled amount of water (H2O/U ≈ 8) and structurally characterized. Compound 1, [U(1,2,3-Hbtc)2]·0.5CH3CN is constructed around an eight-fold coordinated uranium cationic unit [UO8] linked by the poly-carboxylate ligands to form dimeric subunits, which are further connected to form infinite corrugated ribbons and a three-dimensional framework. Compound 2, [U14O8(OH)4Cl8(H2O)16(1,2,3-Hbtc)8(ox)4(ac)4] ({U14}) exhibits an unprecedented polynuclear {U14} poly-oxo uranium cluster surrounded by O-donor and chloride ligands. It is based on a central core of [U6O8] type surrounded by four dinuclear uranium-subunits {U2}. Compound 1 was synthesized by a direct reaction of hemimellitic acid with uranium tetrachloride in acetonitrile (+H2O), while the molecular species ({U14} (2)) crystallized from the supernatant solution after one month. The slow hydrolysis reaction together with the partial decomposition of the starting organic reactants into oxalate and acetate molecules induces the generation of such a large poly-oxo cluster with fourteen uranium centers. Structural comparisons with other closely related uranium-containing clusters, such as the {U12} cluster based on the association of inner core [U6O8] with three dinuclear sub-units {U2}, were performed.

Organic-inorganic hybrid materials from divalent metal cations and expanded N,N′-donor linkers

Abstract The rod-shaped linker (E,E)-N,N′-(3,3′-dimethyl-4,4′-biphenyldiyl)bis[1-(3-pyridinyl)methanimine] (L) is exploited for the first time in the synthesis of extended structures. Four new coordination polymers of composition {[ZnL(OAc)2]·EtOH}n (1), {[CdL(OAc)2]·MeOH}n (2), {[Cu2L(OAc)4]·CH2Cl2}n (3) and [MnL(N3)2]n (4) have been structurally characterized. The metal cations and the anionic ancillary ligands play pivotal roles for the topology of these compounds. In the crystalline reaction products of Zn(II), Cd(II) and Cu(II) acetate with the organic linker, the acetate anions connects two neighboring cations to dinuclear [M2(OAc)4] subunits. These secondary building units are further crosslinked by the N,N′-donor ligand, either perpendicular to the acetato bridges, leading to a ladder-like ribbon for 1 and 2, or in the direction of the metal···metal separation, resulting in a simple chain in the case of 3. Instead of dinuclear secondary building units, a different topology results from reaction of the N,N′ linker with Mn(ClO4)2 in the presence of azide anions: 1,3 bridging by the N3 − groups leads to infinite chains. These are crosslinked by L in perpendicular direction, and the layer structure 4 is obtained. Natural bond orbital (NBO) analyses revealed information on the basis of orbital interactions about the coordination environments of the metal ions. Thermogravimetric measurements indicate the highest thermal stability for 2. Strong antiferromagnetic coupling within the dinuclear subunits of 3 is observed as a consequence of superexchange via the acetato bridges.

Lanthanide Complexes with 2,3-Dimethoxybenzoic Acid and Terpyridine: Crystal Structures, Thermal Properties, and Antibacterial Activities

The lanthanide coordination complexes Er(2,3-DMOBA)3(terpy)(H2O) (1) and [Nd(2,3-DMOBA)3(terpy)(H2O)]2 (2) (2,3-DMOBA = 2,3-dimethoxybenzoate; terpy = 2,2′:6′,2′′-terpyridine) were synthesized and characterized by IR spectroscopy, powder X-ray diffraction (XRD), single-crystal X-ray diffraction, and thermogravimetric analysis. Complex 1 crystallizes in the triclinic system, space group P1, and the mononuclear subunits form a 1D chain structure along the a axis by hydrogen bonds. Complex 2 crystallizes in the monoclinic system, space group P21/c, and the dinuclear subunits are further linked via the offset face-to-face π···π weak stacking interactions to form a supramolecular 2D layered structure. Thermal analysis showed that the complexes have three decomposition steps. The first step is the loss of coordination water molecules. The neutral terpy ligands and partial 2,3-DMOBA ligands are lost in the second step. The remaining 2,3-DMOBA ligands are lost in the third step. The 3D stacked plots for the FT-IR spectra of the evolved gases are recorded and the gaseous products are identified by the typical IR spectra obtained at different temperatures from the 3D stacked plots. Meanwhile, the results of the antibacterial action tests show that 1 and 2 have better antibacterial activities to Candida albicans than to Escherichia coli or Staphylococcus aureus. In addition, complex 2 has better antibacterial action to Candida albicans than complex 1.

Self-assembly of lanthanide(iii) coordination polymers from a bifunctional 2-(pyridin-2-yl)-1H-imidazole-4,5-dicarboxylate ligand with the assistance of oxalate: syntheses, structures, luminescence, and magnetic properties

Based on a bifunctional 2-(pyridine-2-yl)-1H-4,5-imidazole-dicarboxylic acid ligand, a novel family of lanthanide coordination polymers with formulas [Ln(HPIDC)(C2O4)0.5(H2O)]n (Ln = La, 1; Ce, 2) and [Ln2(HPIDC)(C2O4)2(H2O)3]n·2nH2O (Ln = Pr, 3; Nd, 4; Sm, 5; Eu, 6; Gd, 7; Tb, 8; Dy, 9; Ho, 10; Er, 11), (H3PIDC = 2-(pyridine-2-yl)-1H-imidazole-4,5-dicarboxylic acid & H2C2O4 = oxalic acid) has been prepared under hydro-solvothermal conditions and characterized by single crystal X-ray diffraction, elemental analysis, IR spectroscopy, and thermogravimetric analysis. Notably, the ligands adopt the same μ3-kN,O:kO′,O′′:kO′′′ conformation in all compounds, which brings about two types of isostructural lanthanide coordination polymers. Namely, 1 and 2 crystallize in the monoclinic space group P21/n and are composed of [Ln2(COO)2] dinuclear subunits with networks having the symbol (63·82·10)2(63)2(8). Meanwhile, 3–11 crystallize in the monoclinic space group P21/c and are constructed with tetranuclear [Ln4(COO)4] subunits with networks having the symbol (103)2(104·122)(10)2. The photoluminescence measurement indicates that Eu(III) and Tb(III) coordination polymers show very strong reddish-orange and green emission bands with CIE chromaticity coordinates (0.612, 0.325) and (0.284, 0.523) and quantum yields of 54.3% & 34.7%, respectively. The magnetic properties of 3 and 7–11 are investigated, and the results indicate a ferromagnetic interaction between Gd(III) magnetic centers in complex 7 and antiferromagnetic interactions in other complexes.

Positional isomeric effect on CuII and CdII complexes based on perfluorinated dicarboxylate ligands and bipyridyl co-tectons

Five novel CuII and CdII complexes with the formula {[Cu2(HBDO-F4)2(BDO-F4)-(2,2′-bipy)2](CH3OH)} (1), [Cd2(BDO-F4)2(2,2′-bipy)2(H2O)2] (2), {[Cu(BDO-F4)(4,4′-bipy)(H2O)2](CH3OH)2}n (3), {[Cd(BDO-F4)(4,4′-bipy)(H2O)2](CH3OH)2}n (4) and {[Cd(BDC-F4)-(2,2′-bipy)](H2O)2}n (5) have been prepared by reaction of metal perchlorates with H2BDO-F4 (tetrafluorophthalic acid) or H2BDC-F4 (tetrafluoroterephthalic acid) in the presence of different bipyridyl co-ligands (2,2′-bipy=2,2′-bipyridine and 4,4′-bipy=4,4′-bipyridine). All these complexes were characterized by elemental analysis, IR spectra and X-ray single crystal diffraction. Complexes 1 and 2 show binuclear structures, and further connected by hydrogen bonding to result in the final supramolecular 3-D framework and 1-D box-like chain, respectively. Polymers 3 and 4 are isostructural, where the metal centers are connected by BDO-F42− and 4,4′-bipy ligands to generate a 2-D grid-like (4,4) network. These layers are interlinked through hydrogen bonds to form a 3-D architecture. Complex 5 exhibits a distinct (4,4) coordination layer constructed by paddle-wheel [Cd2(COO)4] dinuclear subunits. The results reveal that the diverse structure of 1–5 can be adapted by the different positions of carboxylate groups of perfluorinated ligands, as well as the metal centers and auxiliary ligands. Moreover, their thermal stability and fluorescent properties have also been investigated.

Alkoxide bridged Copper(II) Hinokitiolato and Tropolonato Complexes: Polymorphism, Reconstructive Phase Transition, and Magnetic Properties

AbstractPolymorphism and an unexpected reconstructive phase transition in [Cu(trop)(μ‐OMe)]2 (trop = tropolonate) were studied by single crystal and powder X‐ray diffraction; the phase transition is associated with a huge hysteresis of ca. 200 °C. In the readily reproducible crystal form, the methoxide‐bridged dinuclear subunits aggregate to infinite chains by longer bonds in the Jahn‐Teller distorted coordination sphere. Analogous alkoxide‐bridged derivatives with the substituted ligand hinokitiol (hino), [Cu(hino)(μ‐OR)]2 (R = Me, Et, iPr) form pairs of dinuclear complexes and aggregate to discrete tetranuclear molecules. The inter‐cation distance patterns are reflected in the magnetic properties of these two structure types: Strong antiferromagnetic coupling within the dinuclear subunits is observed in either case, but susceptibility measurements confirm differences in exchange coupling between neighboring central CuII atoms.

Three Isostructural 4‐Sulfophthalate‐Based Lanthanide Complexes: Syntheses, Crystal Structures, and Luminescent Properties

AbstractThree lanthanide complexes with the ligand 4‐sulfophthalate (sp3–), [Ln(H2O)2(sp)]n [Ln = Dy (1), Tb (2), and Er (3)], were solvo‐/hydrothermally synthesized by changing the rare earth cations, and were characterized structurally and photophysically. Complexes 1–3 are isostructural, exhibiting a two‐dimensional layered structure with centrosymmetric dinuclear subunits infinitely extended by 4‐connected sp3– connectors. Photoluminescence spectra of 1–3 demonstrate that anionic sp3– ligand can serve as a functionalized chromophore to sensitize the luminescent emission of the lanthanide ion, suggesting that the sp3–‐involved lanthanide complexes can be used as novel optical materials.

Syntheses, Structures, and Photoluminescent Properties of Lanthanide Coordination Polymers Based on a Zwitterionic Aromatic Polycarboxylate Ligand

Three series of lanthanide coordination polymers, {[Ln(L)(H2O)2]·NO3·2H2O }n (Ln = La 1, Pr 2), {[Ln2(L)2(NO3)(H2O)2]·Cl·6H2O}n (Ln = Nd 3), {[Ln(L)(H2O)2]·Cl·3H2O}n (Ln = Sm 4, Eu 5, Gd 6, Tb 7, Dy 8, Ho 9, Er 10, Tm 11, Yb 12, and Lu 13) (H3L = 4-carboxy-1-(3,5-dicarboxy-benzyl)-pyridinium chloride), have been successfully synthesized under hydro(solvo)thermally conditions. Single-crystal X-ray diffraction analyses revealed that compounds 1–3 all crystallize in triclinic space group P1̅, but they display different three-dimensional structures with diverse dinuclear subunits. In contrast, compounds 4–13 display the same layer structures in the triclinic space group P1̅. The structural difference of these two classes of compounds is derived from the effect of lanthanide contraction. Powder X-ray diffraction (PXRD) and thermogravimetric analyses of compounds 1–13 have also been investigated and discussed in detail. The solid-state luminescent properties of compounds 4, 5, 7, and 8 were characterized, and the results revealed that they exhibit characteristic Sm(III), Eu(III), Tb(III), and Dy(III) emissions in the pink, red, green, and yellow light regions, respectively. More interestingly, the luminescence colors of the Tb(1–x)(L):xEu can easily be tuned from green to green-yellow, yellow, orange, and red-orange due to the energy transfer from Tb3+ to Eu3+ ions by adjusting the doping concentration of Eu3+ ions.

Ferric Ammonium Citrate – What's in It?

AbstractFerric ammonium citrate (FAC) is administered to humans in drugs or food supplements, but its exact composition and structural features are not known. We report that the major component in commercial FAC‐brown and FAC‐green is a trinuclear ferric citrate complex, namely [Fe3(cit)4H]6– (1). Complex 1 comprises a dinuclear subunit in which two ferric ions with a 3.122(1) Å separation are bridged by two alkoxido oxygen atoms from two citrate ligands. Two other alkoxido oxygen atoms form a bridge to a third ferric ion completing an Fe3O4 inner core. The compound [Cr(urea)6]2·1·14.5H2O exhibits paramagnetic behavior that corresponds to three magnetically independent high‐spin (HS) d5 and two d3 centers. In addition to complex 1, FAC‐green also contains a dinuclear ferric citrate complex, namely [Fe2(Hcit)3]3–, in an approximate ratio of 1:1.

3D Heterometallic 3d–4f coordination polymers based on organodisulfonate ligand with isonicotinic acid as a co-ligand: synthesis, crystal structures, photoluminescent and magnetic properties

The hydrothermal reaction of rare earth nitrates, CuCN, 2,7-naphthalenedisulfonate (2,7-nds), and isonicotinic acid (Hina) affords a new family of 3-D heterometallic 3d–4f coordination polymers, [Ln2Cu(2,7-nds)2(ina)4(H2O)4]·4H2O (Ln = Nd (1), Sm (2), Eu (3), Gd (4); 2,7-nds = 2,7-naphthalenedisulfonate, Hina = isonicotinic acid). Complexes 1–4 are structurally characterized by single crystal X-ray diffraction, elemental analysis, FT-IR spectroscopy (IR), powder X-ray diffraction, and thermogravimetric analyses. X-ray crystal structure analyses reveal that 1–4 are isomorphous with dinuclear subunit [Sm2(ina)4] binding Cu ions to generate 2-D networks. Such 2-D networks are pillared by linking 2,7-nds ligands to result in the 3-D layer-pillared Ln(III)–Cu(II) coordination architectures. The valence of Cu salts changed in the reaction. In addition, the luminescence properties of 1–3 and the magnetic properties of 3 and 4 have also been investigated.

Syntheses, crystal structures, and properties of new metal--5-bromonicotinate coordination polymers

Four metal–5-bromonicotinate (Brnic) coordination polymers [Fe(Brnic)2(H2O)2]n (1), [Ni(Brnic)2]n (2), [Ni(Brnic)(bpy)(H2O)2]n·n(Brnic)·4.5nH2O (3), and [Co2(Brnic)3(bpy)2(OH)]n·nH2O (4) have been synthesized and structurally characterized (bpy=4,4′-bipyridine). Complex 1 has corrugated (4,4) sheets formed by μ-Brnic ligands and planar nodes Fe(II). As for 2–4, they all built up from Brnic-bridged dinuclear subunits, but have very different structure features. Complex 2 is a twin-like polymer with (4,4) layers formed by twin paddle-wheel [Ni2(Brnic)4] subunits. Through the bridge coordination of bpy ligands with dinuclear rings [Ni2(Brnic)2] and trigons [Co2(Brnic)3(OH)], 63-topological cationic layers with nanosized grids of 3 and chiral ladder-type double chains of 4 formed, respectively. Notably, halogen-related interactions play an important role in the formation of 3D metallosupermolecules 1–4. The thermostabilities of all compounds have been discussed in detail. Moreover, the magnetic investigations of 2 and 4 indicate that there exist antiferromagnetic interactions in the paddle-wheel [Ni2(Brnic)4] and trigon [Co2(Brnic)3(OH)] cores, respectively.

Synthesis and Crystal Structure of a New Aluminum(III) Oxalate Complex, (C2H10N2)2 [Al2(μ-O2)(C2O4)4].2H2O

A new Al(III) oxalate complex, (C2H10N2)2.[Al2(μ-O2)(C2O4)4]·2H2O (1), has been synthesized by hydrothermal technique. Single-crystal X-ray diffraction analysis reveals that the compound crystallizes in triclinic space group P-1 (2) with cell parameters a = 7.5297 (5) Å, b = 8.1418 (6) Å, c = 9.8279 (8) Å, α = 107.48 (1)°, β = 99.96 (1)°, γ = 95.09 (1)°. Four oxalate ligands binds with two metal centers in bidentate fashion and creates a rare μ-oxo bridged Al(III) dimer. Further, these dinuclear subunits, [Al2(μ-O2)(C2O4)4]4−, are linked by ethylene diamine [(NH3CH2CH2NH3)2+] and water molecules via hydrogen bonding through ab-planes making a two-dimensional supramolecular layered structure.

Dinuclear copper(II) complexes bridged by imidazole-4,5-dicarboxylate

ObjectiveTwo novel dinuclear Cu(II) complexes bridged by imidazole-4,5-dicarboxylate (HImdc) that derived from the tridentate amines N,N-bis(2-pyridylmethyl)methylamine (MeDPA) and 2,6-[bis(pyrazol-1H-yl)methyl]pyridine (bpzpy) are reported: [Cu2(MeDPA)2(μ4-HImdc)(H2O)(ClO4)] ClO4·3H2O (1) and [Cu2(bpzpy)2(μ4-HImdc)(H2O)2](ClO4)2·2 1/2 H2O (2). MethodsThe complexes were characterized by single crystal structure determination, and spectral and magnetic measurements. ResultsIn both single crystal structures, 4+2 geometries of the Cu(II) centers and bis-N,O chelate μ4-HImdc bridges in the dinuclear subunits are observed. Complexes 1 and 2 reveal moderate to strong antiferromagnetic coupling. ConclusionThe coupling parameters J=−67.9cm−1 (1) and J=−89.6cm−1 (2) correlate with the CuN⋯N(Imdc) angle α.

Synthesis, Crystal Structures, and Solid-State Luminescent Properties of Diverse Ln–Pyridine-3,5-Dicarboxylate Coordination Polymers Modulated by the Ancillary Ligand

Nine members of the novel Ln–pyridine-3,5-dicarboxylate coordination polymer family, namely, [Ln(PDC)(GA)]n (Ln = Gd (1), Tb (2), Dy (3), Er (4)), [Ln(PDC)(OAc)(H2O)]n·nH2O (Ln = Sm (5), Eu (6), Gd (7)), [Gd(PDC)(OAc)(H2O)2]n·nH2O (8), and [Tb(PDC)1.5(H2O)]n (9) (PDC = pyridine-3,5-dicarboxylate, GA = glycolate, OAc = acetate), have been successfully obtained by carefully regulating the ancillary ligand or reaction temperatures. Complexes 1–4 are isomorphous two-dimensional networks generated by Ln–glycolate chains and bridging PDC ligands. When the HOAc was utilized instead of glycolic acid, isomorphic three-dimensional compounds 5–7 were isolated. The Ln3+ atoms are first bridged by acetate anions to give dinuclear clusters, which are extended by nearby six PDC ligands forming a 3D (3,6)-connected flu-topological framework. Notably, the increase of reaction temperature from 160 to 180 °C during the synthesis of compound 7 led to compound 8, the other 3D (3,6)-connected structure on the base of dinuclear subunits with rtl topology. Furthermore, the absence of HOAc introduced the formation of compound 9, in which each binuclear cluster links adjacent eight PDC anions to give a 3D (3,8)-connected tfz-d topological structure. The elemental analyses, XRPD, FT-IR, and TGA were also investigated to characterize compounds 1–9. Furthermore, solid-state photoluminescence measurements show that these Ln–pyridine-3,5-dicarboxylate coordination polymers produce strong emissions at room temperature.

Two New Organic‐Inorganic Hybrid Compounds using Bi‐ and Mono‐Nuclear Cu‐H2biim Subunits to modify Keggin Anions

Abstract Two new Keggin‐based organic‐inorganic hybrid compounds, namely [Cu8(H2biim)8(SiW12O40)2]·7H2O (1) and [Cu2(H2biim)4(H2O)2(SiMo12O40)] (2) (H2biim = 2,2′‐biimidazole), were hydrothermally synthesized by using the bi‐imidazole ligand and Keggin anions, and characterized by single‐crystal X‐ray diffraction, elemental analyses, IR spectra, and cyclic voltammetry. In compound 1, two H2biim ligands are fused by two Cu+ ions to form a dinuclear [Cu2(H2biim)2]4+ subunit. The Cu3‐based dinuclear subunits are further connected by [SiW12O40]4– anions to construct a 1D chain. The other Cu1‐based dimer acts as a supporting unit of the anion. Through changing [SiW12O40]4– to [SiMo12O40]4–, compound 2 was obtained, including discrete anions and mononuclear subunits [Cu(H2biim)2(H2O)]2+. The electrochemical behaviors of compounds 1 and 2 bulk‐modified carbon paste electrodes (1‐ and 2‐CPE) were studied.

Tetranuclear Lanthanide (III) Complexes Containing Dimeric Subunits: Single-Molecule Magnet Behavior for the Dy4 Analogue

The reaction of the lanthanide(III) salts [Dy(III), Tb(III), and Gd (III)] with a hetero donor chelating ligand N'-(2-hydroxy-3-methoxybenzylidene)-6-(hydroxymethyl) picolinohydrazide (LH3) and pivalic acid (PivH) in the presence of tetra-n-butylammonium hydroxide (TBAH) afforded the tetranuclear Ln(III) coordination compounds, [Ln4(LH)2(LH2)2(μ2-η(1)η(1)Piv)2(η(1)Piv)4]·2CHCl3 [Ln = Dy(1), Tb(2), and Gd(3)]. The molecular structure of these complexes reveals that the tetranuclear derivatives are composed of two dinuclear subunits which are interconnected through the coordination action of the picolinoyl hydrazine ligand. Within each subunit two different types of Ln(III) ions are present. One of these is eight-coordinate in a distorted triangular dodecahedral geometry while the other is nine-coordinate in a distorted spherical capped square antiprism geometry. Alternating current (ac) susceptibility measurements of complex 1 reveal a frequency- and temperature-dependent two step out-of-phase signals under 1kOe DC field which is characteristic of a single-molecule magnet (SMM) behavior. Analysis of the magnetic data afforded the anisotropic barriers and relaxation times: Δ/kB = 62.6 K, τ0 = 8.7 × 10(-7) s; Δ/kB = 26.3 K, τ0 = 1.26 × 10(-6) s for the slow and fast relaxations respectively.