Structure and Spectral Properties of Pyrazine Ligand Assisted Self-Assembly of a Coordination Polymer Containing Copper-Cyanide Building Blocks

The metal–organic framework $ ^{3}_{\infty } \left[ {{\text{Cu}}_{3} \left( {\text{CN}} \right)_{3} \cdot \left( {\text{pyz}} \right)_{ 2} } \right] $ ∞ 3 [ Cu 3 ( CN ) 3 · ( pyz ) 2 ] , 1, (pyz pyrazine) was prepared in water/acetonitrile solvent at ambient temperature from the adducts K₃[Cu(CN)₄], pyrazine and Me₂SnCl₂. The structure of 1 consists of four-coordinate Cu(1) sites exhibiting a distorted tetrahedral geometry and the linear two-coordinate Cu(2) sites. Notably distorted cages, [Cu₈(CN)₄(pyz)₄], [Cu₈(CN)₆(pyz)₂] and [Cu₆(CN)₂(pyz)₄], can be considered as the basic building blocks of the structure of 1. Box-like structures create inextricably interpenetrated equivalent 3D-frameworks. The structure and spectroscopic properties of 1 were also investigated by thermal analysis and IR, mass, UV/Vis and fluorescence spectra.     

New Organotin/CuCN/Quinazoline 3D-Supramolecular Coordination Polymers Having Catalytic and Luminescence Activities

The new bimetallic supramolecular coordination polymers (SCP); ³ _∞[Cu(CN)₂·Me₃Sn·qaz], 1 and ³ _∞[Cu₂(CN)₄·(Ph₃Sn)₂·qaz], 2 (qaz?=?quinazoline), are prepared in water/acetonitrile solvent at room temperature. The structure of 1 consists of the anionic Cu(CN)₂ building blocks connected by the Me₃Sn cations to form zigzag chains which are bridged by qaz creating 2D-sheets. The interwoven infinite sheets are arranged in parallel A···A···A fashion developing 3D-network structure via H-bonds, π–π stacking, and Cu–C contacts. The network structure of 2 exhibits two different copper sites forming two Cu(CN)₂ building blocks which are connected by the Ph₃Sn groups constructing elongated corrugated chains. The qaz ligand connects these chains forming 3D-network structure containing the rhombic [Cu₂(μ₃-CN)₂] motif. 1 and 2 are luminescent materials which can be used in applications as molecular sensing systems. Also, the catalytic activity of 1 and 2 was investigated towards the degradation of Metanil Yellow (MY) dye by dilute solution of hydrogen peroxide as oxidant.     

New host–guest supramolecular coordination polymers based on [(Me3Sn)3Fe(CN)6]n with alkali metal iodides and their applications as electrode materials in batteries

The metal iodides reduce partially the host coordination polymer of the type $ ^{ 3}_{\infty } \left[ {\left( {{\text{Me}}_{ 3} {\text{Sn}}} \right)_{ 3} {\text{Fe}}\left( {\text{CN}} \right)_{ 6} } \right] $ , I, to give new host–guest supramolecular coordination polymers (SCP). The physical and chemical characteristics of the new products were studied by elemental analyses, X-ray powder diffraction, IR, UV/Vis, and solid state NMR spectra. The host–guest SCP are [M_x(Me₃Sn)₃Fe_(1–x)^IIIFe _x ^II (CN)₆]_n M = Li⁺·2H₂O, 1; Li⁺, 2; Na⁺, 3; K⁺, 4; Cu⁺, 5, [Li(Me₃Sn)₃Fe^II(CN)₆]_n, 6 and [(LiDEE)_0.9(Me₃Sn)₃Fe _o.1 ^III Fe _o.9 ^II (CN)₆]_n, 7. The stoichiometry and nature of the guest depend on the type of the metal iodide and the reaction conditions. The polymeric nature of these SCP is due to the presence of trigonal bipyramidal configured structure which bridges between the single d-transition metal ions. The host–guest SCP containing the Li ions have been tested as electrodes to construct four different lithium-ion batteries.     

Linear Coordination Polymers Assembled from Dinuclear Cu(I) Units: Interchain π–π and CH–π Interactions in Controlling Alignments of Polymeric Chains in Solid State

An axial substitution of the coordinated acetonitrile molecules in dinuclear Cu(I) compound, [Cu₂(μ-PhPPy₂)₂(CH₃CN)₂](ClO₄)₂ (1) (PhPPy₂ = bis(2-pyridyl)phenylphosphine) by various dicarboxylates (isophthalate, terephthalate and naphthalene-2,6-dicarboxylate) led to a class of new linear coordination polymers, {[Cu₂(μ-PhPPy₂)₂](μ-1,3-C₆H₄(CO₂)₂)}_∞ (2), {[Cu₂(μ-PhPPy₂)₂](μ-1,4-C₆H₄(CO₂)₂)}_∞ (3) and {[Cu₂(μ-PhPPy₂)₂](μ-2,6-C₁₂H₆(CO₂)₂)}_∞ (4). X-ray crystallographic studies reveals that all the polymers adopt almost linear structures, where the dicarboxylate groups connect dinuclear Cu(I) units as linkers. In 2 and 4, polymeric chains are parallel to each other. However the chains in 3 are arranged layer by layer, where polymeric chains are parallel in one layer, but chains in the neighboring layers are aligned with the angle (42°). The detailed structural analyses demonstrate that in solid state, the polymeric chains display different orientations which are controlled by interchain π–π and CH–π interactions. In solid state, all the coordination polymers are highly emissive at room temperature, which exhibit phosphorescence characteristics and are assigned as metal to ligand charge transfer.     

Assembly and Fluorescence Properties of 3D-Copper(I) Cyanide Coordination Polymers Based on Methylpyrazine and Tetramethylpyrazine in Presence of Me<Subscript>3</Subscript>SnCl

The reactions of K₃[Cu(CN)₄], Me₃SnCl and methylpyrazine (Me-pyz) or tetramethylpyrazine (Me₄-pyz) in water/dioxane system afforded two new coordination polymers (CP); [{Cu(μ-CN)}₂(μ-Me₄-pyz)·dioxane] _n , 1, and [Cu{μ-Mepyz}{μ-CNSn(Me₃)NC–}], 2. X-ray single crystal analysis shows that 1 contains two crystallographically different copper(I) ions which acquire trigonal planar geometry. The structure of 1 contains non-linear (CuCN)_∞ chains that are interconnected by the Me₄-pyz ligands forming 3D-network structure. The structure of 1 has two-fold interpenetrating 3D-networks with dioxane molecules encapsulated in the voids of the structure. The structures of these CP were also investigated by FTIR and mass spectroscopy, thermal analysis and compared with the prototype compounds. Spectroscopic analyses of 2 confirm the presence of all components (Me₃Sn⁺, Cu(CN)₂ ^? and Me-pyz) and support the composition predicted by elemental analysis. 1 and 2 display strong fluorescence in the solid state at room temperature.     

Two Supramolecular Microporous Metal–Organic Frameworks Templated by Keggin Polyoxometalates

Two new Keggin polyoxometalates (POM)-templated supramolecular metal–organic frameworks (MOF) with micropores, Cu₃(L)₆[H₃(PMo₁₂O₄₀)₂]·6H₂O (1) and Cu₃(L)₆[H₅(SiW₁₂O₄₀)₂]·6H₂O (2) (L?=?1,2-bis(imidazol-1-ylmethyl)ethane), have been prepared under hydrothermal conditions and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra and cyclic voltammetry. These two isostructural compounds are constructed by two distinct moieties, a Keggin polyanion and a linear [Cu(L)₂]⁺ subunit. The [Cu(L)₂]⁺ subunits further form a microporous MOF through supramolecular interactions. The Keggin polyanions act as templates inducing the micropores. The electrochemical and electrocatalytic behavior of compounds 1 and 2 bulk-modified carbon paste electrodes (1-, 2-CPE) was studied.     

Effect of an Ionic Liquid on the Catalytic Performance of Thiocyanatodioxomolybdenum(VI) Complexes for the Oxidation of Cyclooctene and Benzyl Alcohol

The complexes (PPh₄)₂[Mo^VIO₂(NCS)₄] (1), Mo^VIO₂(NCS)₂(di-tBu-bipy) (2) and Mo ₂ ^VI O₅(NCS)₂(di-tBu-bipy)₂ (3) (di-tBu-bipy = 4,4′-di-tert-butyl-2,2′-bipyridine) were studied as catalyst precursors for the oxidation of cyclooctene (Cy8) and benzyl alcohol (BzOH), using either dimethyl sulfoxide (DMSO) or tert-butyl hydroperoxide (TBHP) as oxidant. By dissolving complex 2 in the room temperature ionic liquid 1-butyl-3-methylpyridinium tetrafluoroborate, the catalytic performance with TBHP was improved (higher selectivity to the aldehyde and higher Cy8 conversions). For Cy8 oxidation, the unreacted substrate and products were easily extracted with n-hexane, and the ionic phase containing the catalyst could be reused without loss of catalytic performance.     

The Inclusion of Organometallic Derivatives of Cyclotriphosphazenes Inside SiO2 Matrix and Their Conversion to Nanostructured Metal-Oxides and Phosphates

Organometallic derivatives of the cyclotriphosphazene N₃P₃[OC₆H₄CH₂CN·TiClCp₂]₆ (1), N₃P₃(O₆H₅)₅[OC₆H₄N·W(CO)₅] (2), N₃P₃[OC₆H₄CH₂CN·Mo(CO)₅]₆ (3), [N₃P₃(O₆H₅)₅(OC₅H₄N·CpRu(PPh₃)₂)][PF₆] (4), [N₃P₃(O₂C₁₂H₈)₂OC₅H₄N·Ag(PPh₃)][OSO₂CF₃] (5), N₃P₃[OC₆H₅]₅ [OC₅H₄N·Cu][PF₆] (6) and N₃P₃[OC₆H₄CH₂CN·CuCl]₆[PF₆]₆ (7),were incorporated inside SiO₂ through the sol–gel method. The metal–organic nanocomposites of the general formula N₃P₃[OC₆H₄CH₂CN·TiClCp₂]₆·nSiO₂ (G ₁ ), N₃P₃[OC₆H₄N·W(CO)₅]·nSiO₂ (G ₂ ), N₃P₃[OC₆H₄CH₂CN·Mo(CO)₅]₆·nSiO₂ (G ₃ ), N₃P₃(O₆H₅)₅OC₅H₄N·CpRu(PPh₃)₂][PF₆]·nSiO₂ (G ₄ ), [N₃P₃(O₂C₁₂H₈)₂OC₅H₄N·Ag(PPh₃)][OSO₂CF₃]·nSiO₂ (G ₅ ), N₃P₃[OC₆H₅]₅[OC₅H₄N·Cu][PF₆]·(SiO₂) _n (G ₆ ), and N₃P₃[OC₆H₄CH₂CN·CuCl]₆[PF₆]₆·(SiO₂) _n (G ₇ ), were characterized by IR spectroscopy; ¹²C, ³¹ P and ²⁹Si MAS NMR measurements as well as UV–Visible diffuse reflectance spectra, indicating the presence of the respective organometallic derivatives of the cyclotriphosphazene incorporated into SiO₂. Pyrolysis of these nanocomposites under air at 800 °C gives rise to nanostructured metal-oxides and metal phosphates incorporated into amorphous SiO₂, with the presence in some cases of complexes phase mixtures. From some precursors, we obtained metal-oxides/phosphates nanoparticles separated from the SiO₂ nanoparticles instead the oxides/phosphates nanoparticles inside the SiO₂ matrix. Additionally and for comparison purposes, we used the compound N₃P₃[NH(CH₂)₃Si(OEt)₃]₆ as gelator. Nanocomposites (G′ ₁ ), (G′ ₂ ) and (G′ ₃ ) exhibited mainly morphological differences while in some cases composition differences when using TEOS as gelator. Some simple metal-containing compounds as (O₃SCF₃)Ag(PPh₃)(HOC₅H₄N), [CuCl₂·NC₅H₄OH] and [CuCl₂·NCCH₂C₆H₄OH]—which are useful models of the most complexes (G ₅ ), (G ₆ ) and (G ₇ ) were also prepared and incorporated in amorphous silica. Their pyrolytic products were compared with those of more complex cyclotriphosphazene analogous. Interestingly, the pyrolysis of the nanocomposite [(O₃SCF₃)Ag(PPh₃)(HOC₅H₄N)][SiO₂] _n affords the firstly-reported materials containing Ag₂O along with SiO₂ nanoparticles.     

Structure,Luminescence, and Vapochromism of Bridged Cationic Copper(I) Dimers and Polymers

The dimeric complex of Cu(I) [Cu₂(PPh₃)₄(MeCN)₂(Bpy)](BF₄)₂ (1a, Bpy = 4,4′-dipyridyl) self-assembles in CH₂Cl₂ or acetone and shows intense photoluminescence (excitation λ_max = 356 nm, emission λ_max = 486 nm, ? = 0.47). The MeCN ligands are readily removed from 1a, producing [Cu₂(PPh₃)₄(Bpy)](BF₄)₂ (1b) and altering the photophysical behavior (excitation λ_max = 336 nm, emission λ_max = 568 nm, ? = 0.07). The desolvated compound 1b reversibly absorbs many vapor phase nucleophiles, as revealed by thermogravimetry. Intense luminescence emission is restored for 1b/Nu, Nu = MeCN (1a), acetone, tetrahydrothiophene (THT), and Et₂S. Films of 1b are produced when CH₂Cl₂ solutions of 1a are cast onto glass. The films also react with Nu vapor, again producing intense emission. The pyrazine-bridged dimer [Cu₂(PPh₃)₄(MeCN)₂(Pyz)](BF₄)₂ (2a) is produced in CH₂Cl₂, while [Cu₂(PPh₃)₄(MeCN)(acetone)(Pyz)](BF₄)₂?½[Cu₂(PPh₃)₄(MeCN)₂(Pyz)](BF₄)₂ (2b) is formed in acetone. The crystal structure of the polymer {[Cu(PPh₃)₂(Bpy)](BF₄)?acetone} _n (3) is reported, as is the mixed polymer/dimer structure {[Cu(PPh₃)₂(Pyz)](BF₄)} _n ?½n[Cu₂(PPh₃)₄(BF₄)₂(Pyz)] (4b) in which the dimer units show Cu–FBF₃ coordination. The Pyz dimer and the Pyz and Bpy polymers show much weaker luminescence behavior than that of Bpy dimers 1a and the related 1b/Nu adducts. Nucleophile adduct structures [Cu₂(PPh₃)₄(THT)₂(Bpy)](BF₄)₂?½ethyl ether (5) and [Cu₂(PPh₃)₄(Py)₂(Bpy)](BF₄)₂?CH₂Cl₂ (6) confirmed the coordination of one Nu per Cu to 1b.     

Hydrothermal Syntheses and Crystal Structures of Three Zn(II) Coordination Compounds Constructed with 3,5-Pyrazoledicarboxylic Acid

Three novel metal–organic coordination compounds, [Zn(Hdcp)(H₂O)₄]·1.5H₂O (1), [Zn(Hdcp)(H₂O)₂]_∞ (2) and [Zn₃(dcp)₂(H₂O)₅]_∞ (3) with the ligand 3,5-pyrazoledicarboxylic acid were prepared by the hydrothermal method. The complexes were structurally characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. Compound 1 is a mononuclear molecule that is linked into a 3D supramolecular framework via N–H···O and O–H···O hydrogen bonds. In 2, two types of carboxylic bridges were found between Zn^II ions to form a 1D double-chain. The 1D chains were further construct into a 3D structure by hydrogen bonds. Trinuclear 3 consists of 1D bi-infinite parallelogram chains of [Zn₃(dcp)₂(H₂O)₃] trimers. In the basic trinuclear unit a further bridging mode of the ligand is seen where two dcp^3? ligands chelate three Zn^II ions by utilizing five donors of the dcp^3? ligand. The photoluminescent properties of 1, 2 and 3 were investigated.     

Theoretical study of the reactive intermediate Si2Me4[(η5-C5H4) Fe(CO)2] 2 2−

In two previous papers (Kinget al., J. Organomet. Chem. 19, 327, 1969; Pannellet al., Organometallics 9, 859, 1990), the synthesis and X-ray structure of the two tetramethyl disilyl complexes [(η⁵-C₅H₅) Fe(CO)₂]₂Si₂Me₄ (I) and Si₂Me₄[(η⁵-C₅H₄) Fe(CO)₂CH₃]₂ (II) were reported. ComplexII is obtained fromI [2]. However, attempts to form other derivatives fromI have generally failed. In the chemical process to getII fromI, an intermediate complex, Si₂Me₄[(η⁵-C₅H₄) Fe(CO)₂] ₂ ^2? (III), is probably formed. This is similar to complexII without the two methyl groups bonded to the Fe atoms. Therefore, a theoretical study that may shed some light on the intermediate structure, stability, and reactivity is justified. We have developed theoretical studies consisting of extended Huckel electronic structure calculations on the simulated intermediate geometry. The results obtained from these calculations suggest that it might be stable enough to form during reactions of complexI. The more reactive sites, which suggest reaction alternatives, are pointed out.     

A Luminescent Rod-Packing Organic–Inorganic Hybrid Framework Based on Copper(I) Cyanide Ribbon and 5-(4-Pyridine)tetrazole Ligand

The hydrothermal reaction of CuCN, K₃Fe(CN)₆ and 5-(4-pyridine)tetrazole generated a novel three-dimensional organic–inorganic hybrid framework, namely, {Cu₃(5PyTAZ)(CN)₂} _n (1) (5PyTAZ = 5-(4-pyridine)tetrazole). X-ray single-crystal diffraction shows that two independent Cu(I) centers are four-coordinate tetrahedral and three-coordinate trigonal geometries, which are connected by μ ₃-CN groups to form a 1D [Cu₃(CN)₂] _n inorganic ribbon along the c-axis direction. Each 5PyTAZ ligand links four adjacent inorganic ribbons via its five N-atoms to generate a complex 3D hybrid structure. If the 1D copper(I) cyanide ribbon was regarded as rod-shape building block, 1 exhibits a simple rod-packing topological framework. Furthermore, 1 is characterized by X-ray powder diffraction, elemental analysis, FT-IR, Raman spectra and TG/DTA. Notably, solid-state luminescence measurements indicate that 1 is a potential photoluminescence material.     

Three-Dimensional Structure of Barium–Cupric Nitrilotriacetate and One-Dimensional Structure of Cobalt–Cupric Nitrilotriacetate: Template Effect of Cations on the Formation of Coordination Polymers

Three mixed-metal nitrilotriacetates [Ba(H₂O)₃Co(nta)Cl]_n (1), [Ba(H₂O)₃Ni(nta)Cl]_n (2), and [Ba(H₂O)₃Cu(nta)Cl]_n (3) (H₃nta = nitrilotriacetic acid) were prepared by the reaction of M²⁺ ions (M = Co, Ni, and Cu), K₃nta, and Ba²⁺ ions in water. The reaction of complexes 1 and 2 with CuSO₄·5H₂O afforded [Co(H₂O)₆]_n[Cu₂(nta)₂]_n·2nH₂O (4) and [Ni(H₂O)₆]_n[Cu₂(nta)₂]_n·2nH₂O (5), respectively. The reaction mechanism was elucidated. The crystal structure analyses indicate that the Ba²⁺ ions formed one-dimensional (1D) zigzag chains in complex 3, and the chains were connected by Cu(nta)^? anions to form a three-dimensional network. On the other hand, in complexes 4 and 5, the Cu(nta)^? anions formed 1D zigzag chains, and the [Co(H₂O)₆]²⁺ (or [Ni(H₂O)₆]²⁺) cations existed as isolated units.     

Influence of ruthenium alkylidene complexes bearing tricyclohexylphosphine or 3-bromopyridine ligand on the properties of fluorine containing polymers

The catalytic performance of ruthenium alkylidene complexes bearing tricyclohexylphosphine or 3-bromopyridine ligand in the ring opening metathesis polymerization (ROMP) of fluorine containing monomers, exo-N-4-fluorophenyl-7-oxanorbornene-5,6-dicarboximide (FPhONDI) and exo-N-4-fluorophenyl-norbornene-5,6-dicarboximide (FPhNDI) was investigated. Pure monomers were subjected to ROMP with RuCl₂(PCy₃)₂(CHPh) (I), RuCl₂(PCy₃)(H₂IMes)(CHPh) (II), RuCl₂(3-Br-py)₂(PCy₃)(CHPh) (III) and RuCl₂(3-Br-py)₂(H₂IMes)(CHPh) (IV). The polymers were fully characterized using NMR, DSC, SEM and GPC. Catalysts I–IV displayed significant ROMP activity, allowing for the synthesis of the corresponding polymers with polydispersity indices (PDIs) in the range of 1.4–4.0. High molecular weight polymers (Mw up to 4.95 x10⁵) were prepared in yields up to 90 %, depending on the initiator and monomer used.     

Syntheses and Structural Analytical Studies of Two Co(II) Complexes Based on 1,4-Di(benzimidazole-1-yl)benzene

Two new Co(II) complexes of 1,4-di(benzimidazole-1-yl)benzene ligand (L) with the formulas [(CoLCl₂)(CHCl₃)(DMF)]_∞ (1) and [CoL(NO₃)₂]_∞ (2) have been synthesized by anion-directed self-assembly. Both complexes have been characterized by elemental analyses, IR, and X-ray single crystal diffraction. Complexes 1 and 2 exhibit 1D chain structures. In 1, Co(II) ions possess a distorted tetrahedral coordination environment composed of N₂Cl₂ donors from two L ligands and two chloride ions, while the Co(II) ions in 2 reveal a distorted octahedral structure defined by the N₂O₄ donors from two L ligands and two nitrate anions. These results illustrate that the anions play an important role in the self-assembly of metal–organic materials.     

Uranyl Coordination Polymers Incorporating η5-Cyclopentadienyliron-Functionalized η6-Phthalate Metalloligands: Syntheses,Structures and Photophysical Properties

The reaction of two η⁵-cyclopentadienyliron(II)-functionalized terephthalate and phthalate metalloligands, namely [(η⁵-C₅H₅)Fe^II(η⁶-1,4-HO₂CC₆H₄CO₂H)][(η⁵-C₅H₅)Fe^II(η⁶-1,4-HO₂CC₆H₄CO₂)][PF₆] and [(η⁵-C₅H₅)Fe^II(η⁶-1,2-HO₂CC₆H₄CO₂H)][(η⁵-C₅H₅)Fe^II(η⁶-1,2-HO₂CC₆H₄CO₂)][PF₆]—hereafter [H₂ CpFeTP][HCpFeTP][PF₆] and [H₂ CpFeP][HCpFeP][PF₆], respectively—with [UO₂(NO₃)₂]·6H₂O under hydrothermal conditions yielded four new coordination polymers; (1) [(UO₂)F(HCpFeTP)(PO₄H₂)]·2H₂O, (2) [(UO₂)₂(CpFeTP)₄]·5H₂O, (3) [(UO₂)₂F₃(H₂O)(CpFeP)], and (4) [H₂ CpFeP][UO₂F₃]. The use of metalloligands has proven to be a viable route towards the incorporation of a secondary metal center into uranyl bearing materials. Depending upon the protonation state, the iron sandwich metalloligands may vary from zwitterionic neutral or monoanionic coordinating species as observed in compounds 1–3, or a positively charged species that hydrogen bonds with anionic [UO₂F₃]^? chains as observed in 4. Further, the hydrolysis of the charge balancing PF₆ ^? anion increases the diversity of UO₂ ²⁺ coordinating species by contributing both F^? and PO₄ ^3? anions (1, 3, 4). The luminescent properties of 1–4 were also studied and revealed the absence of uranyl emission, suggestive of a possible energy transfer from the uranyl cation to the iron(II) metal center.     

Crystal Structure and Physicochemical Properties of Two Supramolecular Compounds: (C4H8NH2)4[Mo8O26] and (NH4)Na2[AsIIIMo6O21(O2CCH2NH3)3]·8H2O

Two inorganic–organic hybrid supramolecular compounds based on polyoxometalates formulated as (C₄H₈NH₂)₄[Mo₈O₂₆] (1) and (NH₄)Na₂[As^IIIMo₆O₂₁(O₂CCH₂NH₃)₃]·8H₂O (2) have been synthesized by conventional solution method and characterized by infrared, UV–Vis and single-crystal X-ray diffraction analyses. Thermal analysis was performed to study their thermal stability. The atomic arrangement in compound (1) can be described as inorganic layers built by [Mo₈O₂₆]^4?, pyrrolidinium cations are embedded into layers. The fascinating structural feature of compound (2) is that the glycine molecules are bounded to two edge-sharing Mo centers via their carboxylate functionality leading to functionalized heteropolymolybdate [As^IIIMo₆O₂₁(O₂CCH₂NH₃)₃]^3?, extensive net hydrogen bonds between cations and anions contribute to the crystal packing. The electrochemical behavior of compound (2) has been studied.     

Synthesis and Crystal Structures of a Lanthanum(III) 1D Polymer and a Mixed-Ligand Cerium(III) Binuclear Complex Derived from Pyridine-2,6-dicaboxylic Acid

Lanthanum(III) and cerium(III) complexes of pyridine-2,6-dicaboxylic acid (H₂Pydc) have been prepared and their crystal structures were determined by X-ray crystallography. The single crystal analysis reveals that the lanthanum(III) complex, 1 is polymeric consisting of {[La(Pydc)₂(H₂O)₂]·4H₂O} _n units linked through carboxylate oxygen atoms and exhibiting nine coordination number. Intermolecular O–H···O hydrogen bonds produce R ₁ ¹ (6), R ₄ ⁴ (16) and R ₄ ⁴ (20) rings, which lead to three-dimensional polymeric chains. The crystal structure of the cerium(III) complex, 2 [{Ce(Pydc)₃}{Ce(Pydc)(HO–CH₂CH₂–OH)(H₂O)₃}·6H₂O)] shows that the complex is a mixed-ligand binuclear system in which one cerium coordinated to three Pydc molecules, while the other cerium is bound to one Pydc, one oxygen atom of the other Pydc, one ethylene glycol and three water molecules. Each of the two Ce(III) ions is nine coordinated. Intermolecular O–H···O hydrogen bonds produce R ₂ ² (8) and R ₂ ² (20) rings, which lead to three-dimensional polymeric chains. The complexes were further investigated using elemental analysis, FTIR spectroscopy and thermogravimetric analysis.     

Synthesis and characterization of new poly(amide)s derived from bis(4-(4-aminophenoxy)phenyl)methylphenylsilane and bis(4-carboxyphenyl)R1R2 silane acids

This study describes the synthesis and characterization of a new diamine; bis(4-(4-aminophenoxy)phenyl)methylphenylsilane, which by reaction with bis(4-carboxyphenyl)R₁R₂ silane derivatives, and following the methodology of the direct polycondensation, allowed the preparation of three new poly(amide)s (PAs). These polymers contain two diphenylsilane (Ph–Si–Ph) and oxyether moieties in their repetitive unit. The reaction to obtain the diamine starting from the respective diphenol was developed in two steps. The first step consisted on obtaining the dinitro derivative, bis(4-(4-nitrophenoxy)phenyl)methylphenylsilane, with a yield of 83 %. Then, this compound was reduced by reaction with hydrazine and Pd-activated carbon, with a yield of 67 % in the diamine. Both compounds were characterized by spectroscopic techniques (FT-IR, ¹H, ¹³C and ²⁹Si NMR). The synthesis of the PAs (PA-I, PA-II and PA-III) presented a yield of 35–79 %, glass transition temperature between 136 and 149 °C and inherent viscosities in the range 0.08–0.16 g/dL. PA-I and PA-III presented a transmittance value (at 400 nm) of 91 and 87 %, respectively, while PA-II only reached a value of 70 %. All these results were analysed in accordance with structural details of each repetitive unit and were also compared with those obtained from poly(amides) series not containing flexible elements in their chains. The TGA analyses demonstrated that the new polymers still maintain a high thermal resistance, despite the incorporation of the flexible units.     

Structural, Theoretical and Multinuclear NMR Study of a New Polymeric Mercury(II) Complex with an Ambidentate Phosphorus Ylide

The reactions of phosphorus ylides of the type Ph₃P=C(H)C(O)R [R = 2,4-dichlorophenyl (L ¹ ) and 4-isopropylphenyl (L ² )] with HgX₂ [X = Cl (1, 4), Br (2, 5) and I (3, 6)] salts using methanol as a solvent are reported. Single crystal X-ray analysis carried out on L ¹ , 2 and 3 and reveals the presence of a novel polymeric structure for 2 and a centrosymmeteric dimeric structure for 3. The complexes have been studied by elemental analyses, IR, ¹H and ³¹P NMR spectroscopy. On the basis of DFT calculations, the formation of [Hg₂Br₆]^2? anions in 2 has a key role in the formation of the polymeric structure; and, the formation of [Hg₂L₂I₄] molecule thermodynamically is about 25 kcal/mol more favorable than the corresponding [Hg₂L₂Br₄] molecule.