Synthesis of co-ordination networks from flexible bis-(4-pyridyl) ligands and cadmium salts.

Crystallisation of flexible dipyridyl ligands with Cd(NO₃)₂·4H₂O, Cd(ClO₄)₂·xH₂O or Cd(NO₃)₂·4H₂O and KSCN gives co-ordination networks of composition [Cd(ClO₄)₂(Py₂C₃H₆)₂(H₂O)₂]·Py₂C₃H₆ 1 (Py₂C₃H₆ =1,3-bis(4-pyridyl)propane); [Cd(ClO₄)₂(Py₂C₂H₄)₃] 2 (Py₂C₂H₄ =1,2-bis(4-pyridyl)ethane); [Cd(NCS)₂(Py₂C₃H₆)] 3; [Cd₂(NO₃)₄(o-C₆H₄(CH₂CH₂4-Py)₂)₄] 4 (o-C₆H₄(CH₂CH₂Py)₂ =1,2-bis[2-(4-pyridyl)ethyl] benzene and [Cd(NO₃)₂(PyCH₂CH₂CH=CHCH₂CH₂Py)₃] 5 (PyCH₂CH₂CH=CHCH₂CH₂Py =1,6-bis(4-pyridyl)hex-3-ene). The compounds were characterised by X-ray single crystal diffraction studies which revealed the presence of different polymeric motifs. Structures 1 and 5 consist of 1-D polymeric chains, structure 4 consists of a 2-D polymeric network and structure 3 is a 3-D polymeric network. None of these exhibit lattice interpenetration. However structure 2 consists of three identical but independent interpenetrating 3-D lattice networks.     

Molecular cubes with high-spin ground states

Reactions of Schiff bases with copper(II), nickel(II), iron(II) and manganese(II) sources yielded tetranuclear complexes of [Cu₄(Hhsae)₄]·2H₂O·4CH₃CN (1), [Ni₄(sae)₄(MeOH)₄] (2), [Fe₄(Hsapd)₄]·2H₂O·4MeOH (3) and [Mn₄(sap)₄(MeOH)₄]·H₂O (4), (H₃hsae=2-(4-hydroxysalicylideneamino)-1-ethanol, H₂sae=2-salicylideneamino-1-ethanol, H₃sapd=2-salicylideneaminopropane-2-methyl-1,3-propanediol, and H₂sap=3-salicylideneamino-1-propanol), respectively. Complexes 1–4 have cubane core structures, in which four metal ions are bridged by alkoxides. Magnetic susceptibility measurements revealed that 1–3 have high-spin ground states of S=2, 4 and 8, respectively, while 4 has a diamagnetic ground state.     

A facile organometallic-induced cross-linking of copolymers of phosphazene

Incorporation of the organometallic fragments ML_n=CpFe(dppe)I and CpRu(PPh₃)₂Cl to the random copolymers [{NP(O₂C₁₂H₈)}_0.8{NP(OC₆H₄CH₂CN)₂}_0.15{NP(OC₆H₄CH₂CN)(OC₆H₅)}_0.05]_n (1) [{NP(O₂C₁₂H₈)}_0.55{NP(OC₆H₄CH₂CN)₂}_0.2{NP(OC₆H₄CH₂CN)(OC₆H₅)}_0.25]_n (2) produce the new compounds of the approximate composition: [{NP(O₂C₁₂H₈)}_x{NP(OC₆H₄CH₂CN·ML_n)₂}_y{NP(OC₆H₄CH₂CN·ML_n)(OC₆H₅)}_z]_n. The iron derivatives in solution undergo deprotonation of the dppe, probably caused by a polymeric matrix, which in turn causes a spontaneous cross-linking affording sparingly, soluble materials. Thermal analysis of the compounds using DSC and DTA techniques indicates that the incorporation of the organometallic fragment in the copolymer produces materials, which leave an amount of residue depending on the metal, as well as on the functionalization degree of the cyanide groups. Incorporation of the organometallic fragments to the polymer does not produce an improved conductivity in comparison to the insulator polymer without the organometallic fragment.     

Synthesis and characterisation of infinite coordination networks with 1,6-bis(4-pyridyl)hexane and copper nitrate

Crystallisation of 1,6-bis(4-pyridyl)hexane (Py₂C₆H₁₂) with copper nitrate gives two different phases. Phase 1 of composition [Cu(Py₂C₆H₁₂)₃(NO₃)₂]·2[Cu(Py₂C₆H₁₂)₂(H₂O)(NO₃)]·2(NO₃)·EtOH consists of two different infinite chains in a 1:2 ratio that are interlocked. Hydrogen bonds link chains I to II and chains II to II. In contrast phase 2 of composition [Cu₂(Py₂C₆H₁₂)₄(H₂O)₂]·(NO₃)₄·(Py₂C₆H₁₂)·(EtOH)·2(H₂O) is based upon an infinite 3D framework. It consists of four interpenetrating 3D networks that are crystallographically equivalent.     

Novel inclusion compounds consolidated by host-host and host-guest hydrogen bonding: Complexes of thiourea with (2-hydroxyethyl)trimethylammonium carbonate and oxalate

New inclusion complexes [(CH₃)₃N⁺CH₂CH₂OH]₂CO₃^2-·6(NH₂)₂CS (1) and [(CH₃)₃N⁺CH₂CH₂OH]₂C₂O₄^2-·2(NH₂)₂CS (2) have been prepared and characterized by X-ray crystallography. In the crystal structure of 1, the choline ions are accommodated within an open channel-type host lattice built of urea molecules and carbonate ions. In complex 2, the choline ions are sandwiched between pleated sheets constructed from the parallel arrangement of thiourea-oxalate ribbons. In both inclusion compounds the guest choline ions form O-H⋯O donor hydrogen bonds with anionic O atoms in the host lattices.     

Geometric isomerism of layered complexes of uranyl selenates: Synthesis and structure of (H3O)[C5H14N]2[(UO2)3(SeO4)4(HSeO4)(H2O)] and (H3O)[C5H14N]2[(UO2)3(SeO4)4(HSeO4)(H2O)](H2O)

New uranyl selenates with organic cations (H₃O)[C₅H₁₄N]₂[(UO₂)₃(SeO₄)₄(HSeO₄)(H₂O)] (I) and (H₃O)[C₅H₁₄N]₂[(UO₂)₃(SeO₄)₄(HSeO₄)(H₂O)](H₂O) (II) were synthesized by evaporation of aqueous solutions and studied. Compound I has monoclinic symmetry, space group C2/c, a = 16.7572(13), b = 11.7239(12), c = 19.0490(13) Å, β = 98.875(6)°, V = 3697.6(5) ų, Z = 4. The crystal structure was solved by the direct method and refined to R ₁ = 0.085 for 2868 reflections with |F _hkl | ≥ 4σ|F _hkl |. Compound II has monoclinic symmetry, space group P2₁/n, a = 10.8252(10), b = 19.0007(10), c = 18.6463(15) Å, β = 100.324(7)°, V = 3773.2(5) ų, Z = 4. The crystal structure was solved by the direct method and refined to R ₁ = 0.084 for 5721 reflections with |F _hkl | ≥ 4σ|F _khl |. The structures of I and II are based on layered complexes [(UO₂)₃(SeO₄)₄(HSeO₄)(H₂O)]^3? formed by combination of uranyl pentagonal bipyramids and selenate tetrahedra. H₃O⁺ cations, water molecules, and protonated methylbutylamine cations are located in the interlayer space. Geometric isomerism of two-dimensional complexes [(UO₂)₃(SeO₄)₅(H₂O)] in the structures of uranyl selenates was found and described.     

Blue luminescence of poly[1-phenyl-5-(α-naphthoxy)pentyne]

A disubstituted polyacetylene with naphthalene pendant (–{(C₆H₅)CC[(CH₂)₃ONap]}_n–), Nap=1-napthyl; (1) was synthesized. Upon photoexcitation, THF solutions of (1) emitted strong blue light of 460 nm, whose quantum efficiency is comparable to that of poly(1-phenyl-1-octyne), a well-known highly emissive disubstituted polyacetylene. Little shift was observed in the luminescence spectra of the thin solid films of (1). An electroluminescence device with a configuration of ITO/(1):PVK/bathocuproine/Alq₃/LiF/Al was constructed, which emitted blue light of 468 nm with a maximum brightness of 955 cd/m² and a power efficiency of 0.18 lm/W.     

Synthesis and structure of Cs3[UO2(CH3COO)3]2(NCS)·H2O

The compound Cs₃[UO₂(CH₃COO)₃]₂(NCS)·H₂O (I) was synthesized and studied by IR spectroscopy and single crystal X-ray diffraction. Compound I crystallizes in the monoclinic system with the following unit cell parameters: a = 7.8286(9), b = 19.892(2), c = 20.050(2) Å, β = 94.527(2)°, space group P2₁/c, Z = 4, R = 0.0387. The uranium-containing structural units in crystals of I are mononuclear complexes [UO₂(CH₃COO)₃]^? belonging to crystal-chemical group AB ₃ ⁰¹ (A = UO ₂ ²⁺ , B⁰¹ = CH₃COO^?) of uranyl complexes.     

Conglomerate crystallization behavior of racemic [Co(N4)(aminoacidato)]2+ complexes

Crystal structures, absolute configurations, and crystalline packing features of nine complexes, namely, cis-α-Λ-(RR)(δλδ)-[Co(trien)(D-histidinato)](ClO₄)₂·2H₂O 1, cis-β₁-Δ-(RR)(λδδ)- [Co(trien)(L-asparaginato)](ClO₄)₂ 2, cis-β₂-Λ(SS)(λλδ)-[Co(trien)(L-valinato)](ClO₄)₂·H₂O 3, cis-β₂-Δ-(RR)(δδλ)[Co(trien)(D-methioninato)](ClO₄)₂ and its enantiomer 4, trans(N,t-N)-[Co(tren)(DL-leucinato)]X₂, (X=ClO₄⁻ 5, BF₄⁻ 6, PF₆⁻ 7), and trans(N,t-N)-[Co(tren)(DL- methioninato)]X₂ (X=Br⁻ 8, Cl⁻(BF₄⁻) 9) (trien=triethylenetetramine, tren=tris(2-aminoethyl)amine), have been determined. All compounds were prepared from racemic DL-amino acid. 1–3 crystallize as conglomerates. 5–7 are isomorphous and crystallize as the so-called conglomeratic solids. While 4, 8 and 9 undergo racemic crystallization. In 1–7, the carboxylic oxygen of the amino acid forms double hydrogen bonds with the amino hydrogen atoms of N4 and/or amino acidato of an adjacent cation. By these hydrogen bonds, cations having the same chirality are linked together into helical string. In the isomorphous 8 and 9, the cation containing L-methionine interacts with a cation containing D-methioninine, through hydrogen bonds, to form a racemic pair, and no spiral string arrangements are observed.     

Importance of H2 gas for growth of hot-wire CVD nanocrystalline 3C-SiC from SiH4/CH4/H2

Silicon carbide (SiC) thin films were prepared by hot-wire chemical vapor deposition from SiH₄/CH₄/H₂ and the influence of H₂ gas flow rate (F(H₂)) on the film properties was investigated. The SiH₄ gas flow rate was 1 sccm. At the CH₄ gas flow rate (F(CH₄)) of 1 sccm, nanocrystalline cubic SiC (nc-3C-SiC) grew even without H₂. On the other hand, at F(CH₄) = 2 sccm, amorphous SiC grew without H₂ and nc-3C-SiC grew above F(H₂) = 50 sccm. As F(H₂) was increased, the crystallinity improved both at F(CH₄) = 1 and 2 sccm. However, the mean crystallite size decreased at F(CH₄) = 1 sccm and increased at F(CH₄) = 2 sccm. We discuss growth mechanisms of nc-3C-SiC.     

Enhanced optoelectronics properties of europium(III) complexes with β-diketone and nitrogen heterocyclic ligands

Preparation and photoluminescence behavior of six new europium complexes with β-diketone 1-(2-hydroxy phenyl)-3-phenylpropane-1,3-dione (HPPP) and bathophenanthroline (batho), 2,2′-bipyridyl (bipy), 2,2′-biquinoline (biq), neocuproin (neo) and 1,10-phenanthroline (phen) are reported in solid state. The ligand (HPPP) and complexes Eu(HPPP)₃·H₂O (1), Eu(HPPP)₃·phen (2), Eu(HPPP)₃·batho (3), Eu(HPPP)₃·bipy (4), Eu(HPPP)₃·biq (5) and Eu(HPPP)₃·neo (6) were characterized by means of elemental analysis, infrared spectroscopy, proton nuclear magnetic resonance (¹H-NMR). The optical properties, thermal stability and crystalline nature were investigated by photoluminescence spectroscopy, thermogravimetric analysis and XRD respectively. The emission spectra show narrow intense emission band of central europium (III) metal ion that arise from the high intense ⁵D₀ → ⁷F₀ transition. The introduction of ancillary ligands like batho, bipy, biq, neo, phen enlarged the π-conjugation system in complexes as a result higher luminescence intensity, longer life time (τ) and higher quantum efficiency (η) observed in europium ternary complexes in comparison to Eu(HPPP)₃·H₂O (1). Based on the emission spectra, the luminescence decay curve was measured which indicated that the transfer of energy from HPPP ligand to the europium metal is more efficient in complexes 2–6 than complex 1.     

Anionic NbO-type copper organic framework decorated with carboxylate groups for light hydrocarbons separation under ambient conditions

Light hydrocarbons are important raw materials for industrial products and fine chemicals. The storage and separation of C₁–C₃ hydrocarbons are vital to their practical use. Here, we report efficient C₁–C₃ hydrocarbon adsorption and separation with a NbO-type anionic copper metal–organic framework with uncoordinated –COO^? groups ([Cu₂(L)·(H₂O)₂]·2H₂O·3DMA·(CH₃)₂NH₂) (1). Complex 1 exhibited large C₂H₂ (190 cm³ g^?1), C₂H₄ (147 cm³ g^?1), C₂H₆ (156 cm³ g^?1), C₃H₆ (170 cm³ g^?1), and C₃H₈ (173 cm³ g^?1) uptakes and high selectivities for C₂H₂/CH₄ (32.3), C₃H₆/CH₄ (152), and C₃H₈/CH₄ (127) under ambient conditions. The excellent cycling performance of the material was reflected by only 9.2 and 10.9% losses of the C₂H₂ and C₃H₆ storage capacities even after ten cycles of adsorption–desorption tests. First-principles calculations and Grand canonical Monte Carlo simulations further revealed that not only the open metal sites but also the –COO^? groups played a key role in the high C₂–C₃ hydrocarbon uptakes. The results obtained in this study suggest that anionic 1 is a promising candidate for light hydrocarbon adsorption and natural gas purification at room temperature.     

Structure of hydrogeno bis (dihydrogeno diphosphonate) trithallium: T13H(H2CH2P2O6)2

T1₃H(H₂CH₂P₂O₆)₂ was found to be monoclinic B2/b, a = 10.736 (6) Å, b = 12.382 (7) Å, c = 11.527 (4) Å, γ = 106.11 (5)°, Z = 4. The structure was solved with MULTAN and refined to R(Fo) = 0.063 for 1500 reflections measured with MoKα radiation. This structure can be described as a succession, parallel to the (100) plane, of diphosphonate groups and thallium ions layers.Hydrogen bondings are found between the diphosphonate groups' layers. This bonding conduct to the formation of anionic group (H₂CH₂P₂O₆HH₂CH₂P₂O₆)³⁻ analogous to the (H₂P₂O₇HH₂P₂O₇)³⁻ complex anion.     

Double stranded chains and interwoven structures: the role of conformational isomerism in coordination polymers

The 1:3 and 1:1.5 coordination complexes of 1,3–bis(4–pyridyl)propane, 1, [Ni(1)₂(H₂O)₂][NO₃]₂⋅(1)⋅(H₂O), 2 and [Cd₄(1)₆(NO₃)₈], 3 form a double stranded chain and four-fold interwoven structures, respectively. Complex 2 is an unusual coordination complex where the ligand not only coordinates with the metal salt but also cocrystallizes with the coordination complex. The double stranded linear chains in 2 have 24 membered rings with a Ni···Ni intra-chain distance of 11.53 Å and close-pack to form a two dimensional layered structure. The anions, non-coordinating ligands, and the solvated water molecules sandwich between the layers in a bilayer fashion. Complex 3 forms an open network owing to its T-shaped geometry but the conformational flexibility of the ligand blurs the difference between the expected brick wall pattern and the distorted hexagonal network. The internal dimensions between opposite Cd metal centers in the distorted non-planar network are ca 18.3×23.2×28.5 Å. These open networks readily undergo four-fold parallel interpenetration and result in a carpet like structure.     

Synthesis and photocatalytic properties of HTaWO6/(Pt,TiO2) and HTaWO6/(Pt,Fe2O3) nanocomposites

HTaWO₆/(Pt,TiO₂) and HTaWO₆/(Pt,Fe₂O₃) nanocomposites were synthesized by successive intercalation reactions of HTaWO₆ with [Pt(NH₃)₄]Cl₂ aqueous solution, n-C₃H₇NH₂/n-heptane mixed solution and acidic TiO₂ colloid solution or [Fe₃(CH₃CO₂)₇(OH)(H₂O)₂]NO₃ aqueous solution followed by UV light irradiation. The gallery heights of HTaWO₆/(Pt,TiO₂), HTaWO₆/TiO₂, HTaWO₆/(Pt,Fe₂O₃) and HTaWO₆/Fe₂O₃ was less than 0.51 nm. The host HTaWO₆ was white possessing band gap energy of 3.1 eV, whereas HTaWO₆/Pt, HTaWO₆/(Pt,TiO₂), HTaWO₆/Fe₂O₃ and HTaWO₆/(Pt,Fe₂O₃) were yellow and showed broad reflection over 400–600 nm together with that corresponding to the host layer. Photocatalytic activities of HTaWO₆/TiO₂ and HTaWO₆/Fe₂O₃ were superior to those of unsupported TiO₂ and Fe₂O₃ and were greatly enhanced by co-incorporation of Pt. HTaWO₆/Pt, HTaWO₆/(Pt,TiO₂), HTaWO₆/Fe₂O₃ and HTaWO₆/(Pt,Fe₂O₃) showed photocatalytic activity.     

Near-infrared luminescent polymer thin films containing Yb(III) complex and photosensitized dye

Polymethylmethacrylate (PMMA) thin films containing Yb(pms)₃(H₂O)₈ (pms: bis(perfluoromethanesulfonyl)imide) and dipyridophenazine with DMSO and DMSO-d₆ were fabricated on the glass substrates. The films show photosensitized near-IR luminescence under UV light irradiation of 370 nm in wavelength. The emission quantum yields of Yb(III) complex in PMMA (film 1), PMMA containing DMSO (film 2), and PMMA containing DMSO-d₆ (film 3) thin films are 0.18, 0.26, and 0.26%, respectively. The emission quantum yields of films 1 and 2 were considerably enhanced after the annealing at 80 °C.     

Extrinsic luminescence centers in CdI2 crystals doped with PbI2 (10−4 to 1 mol %)

We have studied the luminescence properties of PbI₂ doped (10^?4 to 1 mol %) CdI₂ crystals in the temperature range 4.2–90 K and those of 2H- and 4H-PbI₂ crystals at 90 K. The results demonstrate that the Pb atoms produce impurity centers in the form of isolated Pb²⁺ ions and 4H-PbI₂ nanocrystals located in the plane of the layers or along linear structural defects of CdI₂. The formation of PbI₂ nanocrystals was confirmed by atomic force microscopy. We discuss excitonic and electron-hole mechanisms of energy transfer to luminescence centers.     

Aerosol assisted chemical vapour deposition of germanium thin films using organogermanium carboxylates as precursors and formation of germania films

Diethyl germanium bis-picolinate, [Et₂Ge(O₂CC₅H₄N)₂], and trimethyl germanium quinaldate, [Me₃Ge(O₂CC₉H₆N)], have been used as precursors for deposition of thin films of germanium by aerosol assisted chemical vapour deposition (AACVD). The thermogravimetric analysis revealed complete volatilization of complexes under nitrogen atmosphere. Germanium thin films were deposited on silicon wafers at 700°C employing AACVD method. These films on oxidation under an oxygen atmosphere at 600°C yield GeO₂. Both Ge and GeO₂ films were characterized by XRD, SEM and EDS measurements. Their electrical properties were assessed by current?Cvoltage (I?CV) characterization.     

The effects of divalent and trivalent dopants on the luminescence properties of ZnO fine particle with oxygen vacancies

The engineering, various factors, and mechanism responsible for emission and high intensity of ZnO luminescence are well developed. Only a few researchers investigate the role of oxygen vacancy on the luminescence properties of doped ZnO. The objective of this research is to synthesize the ZnO fine particle with tailored oxygen vacancy by doping with 5 at.% of divalent and trivalent dopants, i.e., magnesium (ZnO:Mg²⁺), calcium (ZnO:Ca²⁺), gadolinium (ZnO:Gd³⁺), and lanthanum (ZnO:La³⁺) using spray pyrolysis method. The samples prepared at 700 °C with 5 l/min carrier gas flow characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectroscopy. The oxygen vacancy was successfully tuned by introducing various doping into ZnO fine particles. It is found that the oxygen vacancy responsible for the increase of DLE intensity (I_DLE) on the deconvoluted of PL spectra. When the ZnO fine particle doped with trivalent ions (Gd³⁺, La³⁺), the contribution of NBE intensity (I_NBE) is higher than I_DLE. Important phenomena also observed when the excitation wavelength was tuned. The contribution of I_DLE and I_NBE changes, lead to control the luminescence properties.