Bridging Anions Research Articles

Synthesis, Crystal Structure, and Luminescent Property of One-Dimensional Chain Coordination Polymer [Cu(1,6-nds)(py)4]n·2.5nH2O

The copper coordination polymer [Cu(1,6-nds)(py)4]n·2.5nH2O (1,6-nds = 1,6-naphthalenedisulfonate anion, py = pyridine) was synthesized in water by the reflux method. The characterization results of X-ray single crystal diffraction show that the coordination polymer has a one-dimensional chain structure, the two sulfonate groups of 1,6-naphthalenedisulfonate anion bridge with two copper ions by coordination bonds. The copper ion also coordinates with four pyridine molecules. The uncoordinated water molecules interconnect with each other, and also connect to the complex molecules via hydrogen bonds. The coordination polymer displays a strong fluorescence emission peak centered at 462 nm.

Crystal structure of CdSO4(H2O): a redetermination.

The crystal structure of the title compound, cadmium sulfate monohydrate or poly[(μ2-aqua)(μ4-sulfato)­cadmium], was redetermined based on modern CMOS (complementary metal oxide silicon) data. In comparison with the previous study [Bregeault & Herpin (1970 ▸). Bull. Soc. Fr. Mineral. Cristallogr. 93, 37–42], all non-H atoms were refined with anisotropic displacement parameters and the hydrogen-bonding pattern unambiguously established due to location of the hydrogen atoms. In addition, a significant improvement in terms of precision and accuracy was achieved. In the crystal, the Cd2+ cation is coordinated by four O atoms of four sulfate anions and two O atoms of water mol­ecules, forming a distorted octa­hedral trans-[CdO6] polyhedron. Each sulfate anion bridges four Cd2+ cations and each water mol­ecule bridges two Cd2+ cations, leading to the formation of a three-dimensional framework, with Cd⋯Cd separations in the range 4.0757 (2)–6.4462 (3) Å. O—H⋯O hydrogen-bonding inter­actions of medium strength between the coordinating water mol­ecules and sulfate anions consolidate the crystal packing.

Crystal structure and photoluminescence of a new two-dimensional Cd(II) coordination polymer based on 3-(carboxymethoxy)-2-naphthoic acid

Abstract A new Cd(II) coordination polymer, [Cd(CNA)] n (1) (H2CNA = 3-(carboxymethoxy)-2-naphthoic acid), was hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. The crystals are monoclinic, space group P21/c with a = 16.9698(18), b = 7.8314(8), c = 8.9553(10) Å, β = 100.657(2)°, V = 1169.6(2) Å3, Z = 4, D calcd. = 2.03 g cm−3, μ(MoK α ) = 1.9 mm−1, F(000) = 696 e, R = 0.0305, wR = 0.0784 for 172 refined parameters and 2285 data. Each CNA anion bridges three Cd(II) cations to give rise to a two-dimensional network structure. Topologically, if each CNA anion is regarded as a linker, and each Cd(II) atom considered as a 4-conencted node, the structure is simplified as a 4-connected (4,4) network. The solid state photoluminescent properties of the compound were also studied at room temperature.

Crystal structure of NH4[La(SO4)2(H2O)

The principal building units in the crystal structure of ammonium aqua-bis(sulfato)-lanthanate(III) are slightly distorted SO4 tetra-hedra, LaO9 polyhedra in the form of distorted tricapped trigonal prisms, and NH4 (+) ions. The La(3+) cation is coordinated by eight O atoms from six different sulfate tetra-hedra, two of which are bidentate coordinating and four monodentate, as well as one O atom from a water mol-ecule; each sulfate anion bridges three La(3+) cations. These bridging modes result in the formation of a three-dimensional anionic [La(SO4)2(H2O)](-) framework that is stabilized by O-H⋯O hydrogen-bonding inter-actions. The disordered ammonium cations are situated in the cavities of this framework and are hydrogen-bonded to six surrounding O atoms.

Two new tetrazamacrocycle based Cu(II) complexes with 2D → 0D single-crystal to single-crystal transformation

Two new tetrazamacrocycle based compounds, namely, [Cu6L3(SO4)2]·SO4·8H2O (1) and [Cu2L(SO4)(H2O)].2H2O (2), have been prepared at different temperatures (H2L=10,21-dimethyl-3,6,14,17-tetraazatricyclo[17.3.18,12]tetracosa-1(23),8,10,12(24),19,21-hexaene-23,24-diolate). In 1, each SO42− anion bridges three [Cu2L]2+ cations to yield a hexagonal network, whereas in 2 each SO42− anion only links one [Cu2L]2+ cation to afford a discrete binuclear structure. Remarkably, the 2D network structure of 1 was transformed into the 0D structure of 2 in a single-crystal to single-crystal (SC–SC) fashion at room temperature.

Two heterometallic-organic frameworks composed of iron(III)-salen-based ligands and d(10) metals: gas sorption and visible-light photocatalytic degradation of 2-chlorophenol.

Two examples of heterometallic-organic frameworks (HMOFs) composed of dicarboxyl-functionalized Fe(III)-salen complexes and d(10) metals (Zn, Cd), [Zn2(Fe-L)2(μ2-O)(H2O)2]⋅4 DMF⋅4 H2O (1) and [Cd2(Fe-L)2(μ2-O)(H2O)2]⋅2 DMF⋅H2O (2) (H4L = 1,2-cyclohexanediamino-N,N'-bis(3-methyl-5-carboxysalicylidene), have been synthesized and structurally characterized. In 1 and 2, each square-pyramidal Fe(III) atom is embedded in the [N2O2] pocket of an L(4-) anion, and these units are further bridged by a μ2-O anion to give an (Fe-L)2(μ2-O) dimer. The two carboxylate groups of each L(4-) anion bridge Zn(II) or Cd(II) atoms to afford a 3D porous HMOF. The gas sorption and magnetic properties of 1 and 2 have been studied. Remarkably, 1 and 2 show activity for the photocatalytic degradation of 2-chlorophenol (2-CP) under visible-light irradiation, which, to the best of our knowledge, is the first time that this has been observed for Fe(III)-salen-based HMOFs.

Synthesis and characterization of decanuclear Ln(III) cluster of mixed calix[8]arene-phosphonate ligands (Ln = Pr, Nd)

Two novel decanuclear Ln(III) compounds (Ln=Pr for 1, Nd for 2) have been solvothermally obtained by using p-tert-butylcalix[8]arene (H8TBC8A) and phenylphosphonate (PhPO3H2) as ligands. Single crystal X-ray diffraction studies reveal that both compounds are stacked by dumbbell-like Ln10 clusters, which are capped by two TBC8A8− supports and linked by four complementary PhPO32− ligands as well as other bridging anions. In addition, the self-assembly behavior of both compounds is interesting: the cationic Ln10 cluster layers are separated by the layers of H6TBC8A2− ligands. Moreover, the luminescent and magnetic properties of both compounds were examined.

The construction of supramolecular polymers through anion bridging: from frustrated hydrogen-bonding networks to well-ordered linear arrays

The construction of supramolecular polymers has been realized by converting random hydrogen-bonding networks into well-ordered linear hydrogen-bonding arrays through an anion-bridging strategy.

Utilization of Pure Silica Extracted from Rice Husk and FTIR Structural Analysis of the Prepared Glasses

Egyptian rice husk was subjected to different chemical and thermal treatment methods, aiming to extract high pure silica. Three samples (S1, S2 and S3) were prepared applying three different chemical treatment methods. Two sets of the obtained samples were prepared, where the first set was calcinated at 600oC and the other set was calcinated at 750 oC by slow heating (starting at RT and ending at the desired calcinations temperature for 2 h).XRF was applied to identify the chemical composition and purity of the extracted silica, while XRD was applied to confirm the amorphous nature and the presence of some induced carbon black in the obtained silica. It was found that S3 slowly heated at 750 oC presents the highest silica content (98.6 %). Such sample was fed directly to the calcinations furnace at 750 oC (sudden heating for comparison) where it presents only 90.6% silica, and 3.74 % residual carbon black. However, the extracted silica from sample S3 was used to prepare glasses obeying the composition (75-x) mol% RH-silica, x mol% Bi2O3, 25 mol% Na2O, (where 0 ≤ x ≤ 20).FTIR spectroscopic analysis was applied to investigate the internal structure of the prepared glasses, where the glass networks were found to contain mainly SiO4, BiO3 and BiO6 structural groups, as well as some bridging and non-bridging oxygen anions. Also, some O-H and H-O-H groups were also detected which may be due to the used KBr disk technique.

Dinuclear iridium and rhodium complexes with bridging arylimidazolide-N(3),C(2) ligands: synthetic, structural, reactivity, electrochemical and spectroscopic studies.

Deprotonation of 1-arylimidazoles (aryl = mesityl (Mes), 2,6-diisopropylphenyl (Dipp)), with n-butyl lithium afforded the corresponding derivatives (1-aryl-1H-imidazol-2-yl)lithium (1a, Ar = Mes; 1b, Ar = Dipp) in good yield. Reaction of 1a with 0.5 equiv. of [Ir(cod)(μ-Cl)]2 yielded two geometrical isomers of a doubly C2,N3-bridged dinuclear complex [Ir(cod){μ-C3H2N2(Mes)-κC2,κN3}]2 (3), 3H-H, a head-to-head (H-H) isomer of CS symmetry, and 3H-T, the thermodynamically preferred head-to-tail (H-T) isomer of C2 symmetry. The metallated carbon of the 4 electron donor anionic bridging ligands has some carbene character, reminiscent of the situation in N-metallated protic NHC complexes. Displacement of cod ligands from 3H-H and 3H-T afforded the tetracarbonyl complexes [Ir(CO)2{μ-C3H2N2(Mes)-κC2,κN3}]24H-H and 4H-T, respectively. The reaction with PMe3, which gave only one complex, [Ir(CO)(PMe3){μ-C3H2N2(Mes)-κC2,κN3}]2 (5), demonstrates that the isomerization of the central core Ir[μ-C3H2N2(Mes)-κC2,κN3]2Ir from H-H to H-T on going from 4H-H to 5 is readily triggered by phosphine substitution under mild conditions. Oxidative-addition of MeI to 5 afforded the formally metal-metal bonded d(7)-d(7) complex [Ir2(CO)2(PMe3)2(Me)I{μ-C3H2N2(Mes)-κC2,κN3}2] (6). The blue [Ir(C2H4)2{μ-C3H2N2(Mes)-κC2,κN3}]2 (7) and purple [Rh(C2H4)2{μ-C3H2N2(Dipp)-κC2,κN3}]2 (9) tetraethylene complexes were also obtained with only a H-T arrangement of the bridging ligands. Although only modestly efficient in alkane dehydrogenation, complex 7 was found to be a more active pre-catalyst than 3H-T, 4H-T and 5, probably because of the favorable lability of the ethylene ligands. From cyclic voltammetry, exhaustive coulometry and spectroelectrochemistry studies, it was concluded that 3H-T undergoes a metal-based one electron oxidation to generate the mixed-valent Ir(i)/Ir(ii) system. The energy of the intervalence band for the orange dirhodium complex [Rh(cod){μ-C3H2N2(Mes)-κC2,κN3}]2 (8) is shifted toward lower energies in comparison with 3H-T, reflecting the decrease of the energy with the intermetallic distance. It was concluded from the EPR study that the Ir and Rh centres contribute substantially to the experimental magnetic anisotropy and thus to the singly occupied molecular orbital (SOMO) in the mixed-valent Ir(i)/Ir(ii) and Rh(i)/Rh(ii) systems. The molecular structures of 3H-H, 3H-T, 8 and 9 have been determined by X-ray diffraction.

Effect of Nitrogen on Properties of Na2O–CaO–SrO–ZnO–SiO2 Glasses

Glasses in the Na2O–CaO–SrO–ZnO–SiO2 system have previously been investigated for suitability as a reagent in Al‐free glass polyalkenoate cements (GPCs). These materials have many properties that offer potential in orthopedics. However, their applicability has been limited, to date, because of their poor strength. This study was undertaken with the aim of increasing the mechanical properties of a series of these Zn‐based GPC glasses by doping with nitrogen to give overall compositions of: 10Na2O–10CaO–20SrO–20ZnO–(40−3x)SiO2–xSi3N4 (x is the no. of moles of Si3N4). The density, glass‐transition temperature, hardness, and elastic modulus of each glass were found to increase fairly linearly with nitrogen content. Indentation fracture resistance also increases with nitrogen content according to a power law relationship. These increases are consistent with the incorporation of N into the glass structure in threefold coordination with silicon resulting in extra cross‐linking of the glass network. This was confirmed using 29Si MAS‐NMR which showed that an increasing number of Q2 units and some Q3 units with extra bridging anions are formed as nitrogen content increases at the expense of Q1 units. A small proportion of Zn ions are found to be in tetrahedral coordination in the base oxide glass and the proportion of these increases with the presence of nitrogen.

Synthesis, structures and luminescent properties of two zinc(II) complexes from flexible bis(tetrazolate) ligands

Two Zn(II) coordination polymers, [Zn2H(dte)2(HCOO)·(H2O)·(CH3OH)]n (1) and [Zn2(dtp)(OH)2]n (2), with flexible 1,2-di(1H-tetrazol-5-yl)ethane (H2dte) and 1,2-di(1H-tetrazol-5-yl)propane (H2dtp) have been prepared. The dte2− and dtp2− ligands adopt chelating and bridging coordination, and link three Zn(II) ions into a 2-D layer and a 1-D chain, respectively. The anionic formate and hydroxyl bridges are formed in situ, which further extend the 2-D layer and the 1-D chain into 3-D and 2-D networks, respectively. Complexes 1 and 2 showed a maximum fluorescent emission at 403 and 422 nm, respectively.

Dual emission and excited-state mixed-valence in a quasi-symmetric dinuclear Ru-Ru complex.

The synthesis and characterization of the new dinuclear dipeptide [(EtOOC-tpy)Ru(tpy-NHCO-tpy)Ru(tpy-NHCOCH3)](4+) 3(4+) of the bis(terpyridine)ruthenium amino acid [(HOOC-tpy)Ru(tpy-NH2)](2+) 1(2+) are described, and the properties of the dipeptide are compared to those of the mononuclear complex [(EtOOC-tpy)Ru(tpy-NHCOCH3)](2+) 4(2+) carrying the same functional groups. 3(4+) is designed to serve a high electronic similarity of the two ruthenium sites despite the intrinsic asymmetry arising from the amide bridge. This is confirmed via UV-vis absorption and NMR spectroscopy as well as cyclic voltammetry. 4(2+) and 3(4+) are emissive at room temperature, as expected. Moreover, 3(4+) exhibits dual emission from two different triplet states with different energies and lifetimes at room temperature. This is ascribed to the presence of a unique thermal equilibrium between coexisting [Ru(II)(tpy-NHCO-tpy(·-))Ru(III)] and [Ru(III)(tpy-NHCO-tpy(·-))Ru(II)] states leading to an unprecedented excited-state Ru(II)Ru(III) mixed-valent system via the radical anion bridge tpy-NHCO-tpy(·-). The mixed-valent cation 3(5+), on the other hand, shows no measurable interaction of the Ru(II)Ru(III) centers via the neutral bridge tpy-NHCO-tpy (Robin-Day class I). Reduction of 3(4+) to the radical cation 3(3+) by decamethylcobaltocene is bridge-centered as evidenced by rapid-freeze electron paramagnetic resonance spectroscopy. Interestingly, all attempts to observe 3(3+) via NMR and UV-vis absorption spectroscopy only led to the detection of the diamagnetic complex 3-H(3+) in which the bridging amide is deprotonated. Hence 3-H(3+) (and 4-H(+)) appear to reduce protons to dihydrogen. The ease of single and double deprotonation of 4(2+) and 3(4+) to 4-H(+), 3-H(3+), and 3-2H(2+) was demonstrated using a strong base and was studied using NMR and UV-vis absorption spectroscopies. The equilibrating excited triplet states of 3(4+) are reductively quenched by N,N-dimethylaniline assisted by hydrogen bonding to the bridging amide.

Effect of Axial Ligands on the Spectroscopic and Electrochemical Properties of Diruthenium Compounds

Three related diruthenium complexes containing four symmetrical anionic bridging ligands were synthesized and characterized as to their electrochemical and spectroscopic properties. The examined compounds are represented as Ru2(dpb)4Cl, Ru2(dpb)4(CO), and Ru2(dpb)4(NO) in the solid state, where dpb = diphenylbenzamidinate anion. Different forms of Ru2(dpb)4Cl are observed in solution depending on the utilized solvent and the counteranion added to solution. Each Ru2(5+) form of the compound undergoes multiple redox processes involving the dimetal unit. The reversibility as well as potentials of these diruthenium-centered electrode reactions depends upon the solvent and the bound axial ligand. The Ru2(5+/4+) and Ru2(5+/6+) processes of Ru2(dpb)4Cl were monitored by UV-vis spectroscopy in both CH2Cl2 and PhCN. A conversion of Ru2(dpb)4Cl to [Ru2(dpb)4(CO)](+) was also carried out by simply bubbling CO gas through a CH2Cl2 solution of Ru2(dpb)4Cl at room temperature. The chemically generated [Ru2(dpb)4(CO)](+) complex undergoes several electron transfer processes in CH2Cl2 containing 0.1 M TBAClO4 under a CO atmosphere, and the same reactions were seen for a chemically synthesized sample of Ru2(dpf)4(CO) in CH2Cl2, 0.1 M TBAClO4 under a N2 atmosphere, where dpf = N,N'-diphenylformamidinate anion. Ru2(dpb)4(NO) undergoes two successive one-electron reductions and a single one-electron oxidation, all of which involve the diruthenium unit. The CO and NO adducts of Ru2(dpb)4 were further characterized by FTIR spectroelectrochemistry, and the IR spectral data of these compounds are discussed in light of results for previously characterized Ru2(dpf)4(CO) and Ru2(dpf)4(NO) derivatives under similar solution conditions.

Effects of Anion and Bipyridyl Bridging Ligand Identity on the Co(II) Coordination Networks

Five new coordination polymers, {[Co(OAc)2(bpe)(H2O)]·0.5(dmf)}n (1), {[Co(bpy)2(H2O)4][Co(tfa)(bpy)2(H2O)3](tfa)3·1.5(bpy)}n (2), [Co(tfa)2(dps)4]n (3), {[Co(tfa)2(bpe)4]·H2O}n (4), and [Co(tfa)2(bpp)4]n (5) (where AcO– = CH3CO2–; tfa– = CF3CO2–; bpy = 4,4′-bipyridine; bpe = 1,2-bis(4-pyridyl)ethane; bpp = 1,3-bis(4-pyridyl)propane; dps = 4,4′-dipyridyl sulfide; dmf = N,N′-dimethylformamide) were synthesized by the reactions of Co(OAc)2·4H2O and Co(tfa)2·4H2O with different dipyridyl ligands and characterized by elemental analysis, IR spectra, and X-ray single-crystal diffraction. Compound 1 exhibits extended two-dimensional (2D) networks through the bridging AcO– and bpe ligands. The polymeric motifs in 2–5 are exclusively based on bipyridine-type ligands and results in 1D cationic chains in 2, similar charge-neutral double tapes in 3 and 4, and a 2D polymeric network in 5. In 2–5, the tfa anions coordinate to the Co(II) center in a monodentate mode. An impact of the anion’s fluorination on coordination modes and supramolecular architectures is registered. Magnetic measurements reveal almost vanishing exchange interactions in the layered materials 1 and 5. The correlation of mechanical properties and crystal structure has been demonstrated for 1.

Poly[(μ3-3,5-diisopropyl-4H-1,2,4-triazolato-κ3N:N′:N′′)silver(I)

In the polymeric title compound, [Ag(C8H14N3)]n, the AgI cation is coordinated by three N atoms from three 3,5-diisopropyl-1,2,4-triazolate anions in a T-shaped geometry. The AgI cation deviates from the coordination plane by 0.014 (1) Å and the N—Ag—N bond angles are 96.85 (11), 97.72 (10) and 165.39 (12)°. The triazolate anion bridges three AgI cations, forming a three-dimensional polymeric network.

A family of double-layered coordination polymers containing Cd2+, N,O-chelating ligands, and bridging SCN− and Cl−

The syntheses, structures, and characterization (IR, TGA/DTA) of a family of layered coordination polymers containing Cd2+, bridging anions (SCN− and Cl−), and chelating C2H6N2O2 methyl carbazate (mc) and C3H8N2O2 ethyl carbazate (ec) ligands are described, viz: Cd(SCN)2(C2H6N2O2), Cd(SCN)Cl(C2H6N2O2), Cd(SCN)2(C3H8N2O2), and Cd(SCN)Cl(C3H8N2O2). Single-crystal structures show them to contain distorted CdN3OS2 (for the thiocyanate) and CdN2OCl2S (for the thiocyanate/chloride) octahedra, in which the mc and ec ligands adopt an N,O-bidentate coordination mode, and the four anions bridge adjacent metal ions, which leads to polymeric sheets built up from double-octahedral layers propagating in the (1 0 0) plane. The topological linkage of the metal ions, which is the same in each structure, can be described as a distorted hexagonal grid. The crystal structures are completed by weak N–H⋯O, N–H⋯N, N–H⋯Cl, and N–H⋯S hydrogen bonds, which all occur within the (1 0 0) polyhedral layers.

Synthesis, crystal structure and thermal behavior of a new 1D polymeric strontium complex with tetrazole-1-acetic acid

A new 1D polymeric strontium compound (Sr(tza)2(H2O)2)n was synthesized by reaction of tetrazole-1-acetic acid (Htza) with strontium carbonate, and characterized by X-ray single crystal diffraction, elemental analysis and IR spectroscopy. The central Sr(II) atom is coordinated by eight O atoms from 4 tza − ions and two water molecules. A zigzag chain along the c-axis is constructed by the tridentate tza − anion bridging two Sr(II) atoms. Differential scanning calorimetry (DSC) and thermogravimetric-differential thermogravimetric (TG-DTG) analyses were applied to assess the thermal decomposition behav- ior. The kinetic parameters were obtained by non-isothermal reaction kinetics, and the Arrhenius equation can be expressed as lnk = 22.17-258.2 × 10 3 /RT. The critical temperature of thermal explosion values, �S / = , �H / = andG / = were obtained at 562 K as, −65.71 J mol −1 K −1 , 255.51 kJ mol −1 and 291.78 kJ mol −1 , respectively.

Effect of anion on Ag(i)meso-helical chains formed with 4,4′-dipyridyl ketone: solventversusanion bridging and anion effects on the strength of ligand binding

Related coordination polymers with varying Ag : L ratios produced a series (1 : 1) that was not sensitive to anion and another (1 : 2) that displayed sensitivity to the anion showing a transition from 1D chains to 2D nets.

Polar Alignment of Λ-Shaped Basic Building Units within Transition Metal Oxide Fluoride Materials

A series of pseudosymmetrical structures of formula K10(M2OnF11-n)3X (M = V and Nb, n = 2, X = (F2Cl)1/3, Br, Br4/2,I4/2; M = Mo, n = 4, X = Cl, Br4/2, I4/2) illustrates generation of polar structures with the use of Λ-shaped basic building units (BBUs). For a compound to belong to a polar space group, dipole moments of individual species must be partially aligned. Incorporation of d(0) early transition metal polyhedral BBUs into structures is a common method to create polar structures, owing to the second-order Jahn-Teller distortion these polyhedra contain. Less attention has been spent examining how to align the polar moments of BBUs. To address alignment, we present a study on previously reported bimetallic BBUs and synthesized compounds K10(M2OnF11-n)3X. These materials differ in their (non)centrosymmetry despite chemical and structural similarities. The vanadium compounds are centrosymmetric (space groups P3m1 or C2/m) while the niobium and molybdenum heterotypes are noncentrosymmetric (Pmn21). The difference in symmetry occurs owing to the presence of linear, bimetallic BBUs or Λ-shaped bimetallic BBUs and related packing effects. These Λ-shaped BBUs form as a consequence of the coordination environment around the bridging anion of the metal oxide fluoride BBUs.