Reactions of ozone with olefins: Ethylene,allene, 1,3-butadiene,and trans- 1,3-pentadiene

The reactions of O₃ with ethylene, allene, 1,3-butadiene, and trans-1,3-pentadiene have been studied in the presence of excess O₂ over the temperature range 232 to 298 K. The initial O₃ pressure was varied from 4–18 mtorr, and the olefin pressure was varied from 0.1 to 4.5 torr (ethylene), 2.8 to 39.6 torr (allene), 52.7 to 600 mtorr (1,3-butadiene) or 26.2 to 106 mtorr (trans-1,3-pentadiene). The O₃ decay was monitored by ultraviolet absorption. The reactions are first order in both O₃ and olefin, and the rate coefficients are independent of the O₂ pressure. For the O₃-ethylene system, various diluent gases (O₂, N₂, air) were used and the rate coefficients were found to be independent of the nature of the diluent gas. The various rate coefficients fit the Arrhenius expressions (k in cm³ s^?1): where the reported uncertainties are one standard deviation and R is in cal/mol K.     

2D-layered structure of coordination polymer,zinc trifluoroacetate-1,3-bis(4-pyridyl)propane

Compound [Zn(CF₃CO₂)₂(Bpp)₂], where Bpp is 1,3-bis(4-pyridyl)propane, was synthesized and its structure and luminescent properties were determined. Crystals are monoclinic, space group C2/c, a = 21.261(1) Å, b = 17.642(1) Å, c = 18.632(1) Å, β = 115.85(1)°, V = 6289.3(6) ų, ρ_calcd = 1.453 g/cm³, Z = 8. The structure comprises 2D neutral layers of conjugated multiunit rings composed of four Zn²⁺ ions united by four bridging Bpp ligands. Each of two crystallographically nonequivalent Zn atoms is coordinated at the octahedra apices to four nitrogen atoms of two Bpp ligands and two O(CF₃CO₂) atoms. Trifluoroacetate anions are coordinated to Zn²⁺ ions in monodentate manner. The compound exhibits photoluminescence in solid state.     

Crystal structures of 2-ferrocenylmethylidenehydrazono-1,3-dithiane and 2-ferrocenylmethylidenehydrazono-1,3-dithiepane

Two compounds of 2-ferrocenylmethylidenehydrazono-1,3-dithiane (1) and 2-ferrocenylmethylidenehydrazono-1,3-dithiepane (2) are synthesized and their single crystal structures are determined by the X-ray diffraction method. Compound 1 belongs to the orthorhombic Pca2₁ space group with the cell parameters: a = 13.989(4) Å, b = 5.785(2) Å, c = 18.231(5) Å, V = 1475.4(7) ų; while compound 2 crystallizes in a monoclinic symmetry, P2₁/c space group with a = 15.320(2) Å, b = 5.8028(6) Å, c = 36.584(4) Å, β = 91.932(1)° and V = 3250.4(6) ų.     

Induced circular dichroism spectra of 2-(2,4,6-cycloheptatrien-1-ylidene)-4-cyclopentene-1,3-dione included inβ-cyclodextrin

The assignment of the absorption spectra of 2-(2,4,6-cycloheptatrien-1-ylidene)-4-cyclopentene-1,3-dione (1) is reported by measuring the induced circular dichroism spectra of the β-cyclodextrin complex with1. It is concluded from the signs of the induced circular dichroism bands that the first absorption band (17.1×10³–34.3×10³ cm^?1) is composed of three electronic transitions having perpendicular, parallel and perpendicular polarizations with respect to the long axis (z) of1. The second absorption band (34.3×10³–42.8×10³ cm^?1) is composed of two electronic transitions having parallel polarizations with respect to the long axis of1 and the third absorption band (42.8×10³–47.1×10³ cm^?1) has the transition dipole moment perpendicular to the long axis of1. Our experimental assignments are supported by CNDO/S CI calculations.     

Synthesis and crystal structure of [Na(H<Subscript>2</Subscript>O)<Subscript>4</Subscript>][EuL<Subscript>4</Subscript>] · 0.775CH<Subscript>2</Subscript>Cl<Subscript>2</Subscript> (HL = 1,3-bis(1,3-dimethyl-1H-pyrazol-4-yl)-1,3-propanedione)

[Na(H₂O)₄][EuL₄] · 0.775CH₂Cl₂ (I) has been synthesized by the reaction of Eu(NO₃)₃ · 6H₂O with 1,3-bis(1,3-dimethyl-1H-pyrasol-4-yl)-1,3-propanedione (HL) in the presence of NaOH. Its crystal structure has been solved by X-ray diffraction analysis. Crystals are tetragonal; a = 16.2401(5) Å, c = 11.9113(4) Å, V= 3141.50(17) ų, ρ_calcd = 1.427 g/cm³, μ(MoK _α) = 1.140 mm^?1, space group P4/n, Z = 2. The structural units forming a crystal of compound I are [EuL₄]^? complex anions, [Na(H₂O)₄]⁺ cations, and CH₂Cl₂ molecules. The coordination polyhedron of the Eu atom is an Archimedean antiprism formed by the O atoms of four bidentate chelate ligands L^?.     

Syntheses and coordination behaviour of 2-(ortho-phosphinophenyl)-functionalised 1,3-dioxolanes and 1,3-dioxanes towards a [(COD)Rh]-complex fragment - models for immobilised complexes

The syntheses are reported of the ether-phosphine ligands: 2-(ortho-diphenylphosphinophenyl)-1,3-dioxolane (1a), 2-(ortho-diisopropylphosphinophenyl)-1,3-dioxolane (1b), 2-(ortho-diphenylphosphinophenyl)-1,3-dioxane (1c), 2-(ortho-diisopropylphosphinophenyl)-1,3-dioxane (1d). Their reaction with [(COD)RhCl]₂ (COD: 1,5-cyclooctadiene) results in the formation of the mononuclear complexes: {chloro(COD)[2-(ortho-diphenylphosphinophenyl)-1,3-dioxolane]rhodium(I)} (2a), {chloro(COD)[2-(ortho-diisopropylphosphinophenyl)-1,3-dioxolane]rhodium(I)} (2b), {chloro(COD)[2-(ortho-diphenylphosphinophenyl)-1,3-dioxane]rhodium(I)} (2c), and {chloro(COD)[2-(ortho-diisopropylphosphinophenyl)-1,3-dioxane]rhodium(I)} (2d). The chloride ligands of compounds 2a and 2b were abstracted with TlPF₆, with accompanied insertion of an acetal oxygen atom of the ligands 1a and 1b into the coordination sphere of the metal centre, producing {(COD)[η²-P,O-2-(ortho-diphenylphosphinophenyl)-1,3-dioxolane]rhodium(I)}PF₆ (3a∗PF₆) and {(COD)[η²-P,O-2-(ortho-diisopropylphosphinophenyl)-1,3-dioxolane]rhodium(I)}PF₆ (3b∗PF₆). In contrast the dioxane analogues of 3, 3c∗BF₄ and 3d∗BF₄, were formed by reacting the ligands 1c, 1d with [Rh(COD)₂]BF₄. The ligands 1 and the complexes 2 serve as model compounds for their via acetalation to a polyvinylalcohol resin bound analogues. The complexes synthesised were employed as pre-catalysts in the hydroformylation reaction of 1-octene.     

A spectroscopic determination of the methyl radical recombination rate constant in shock waves

The reactions CH₃ +

and CD₃ +

have been studied in shoch waves at 1200–1500 K and densities of 2 × 10^?6 ?2 × 10^?4 mol cm^?3 using UV absorption near 216 nm. The rate constants at the highest densities: k_H = (1.7 ± 0.6) × 10^?11 cm³ s^?1 and k_D = (2.2 ± 0.9) × 10^?11 cm³ s^?1 are close to the second order limit. At the lowest densities the rates are lower by a factor of 5. The experimental results agree well with theoretical predictions based on the statistical adiabatic channel model but differ from those of conventional RRKM calculations. A direct observation of the equilibrium C₂H₆ ? 2CH₃ favours the “high” value for ΔH⁰₀ (87.76 kcal/mol).     

Cobalt(II) complex with 4,4,4-trifluoro-1-thienylbutane-1,3-dione and dimethyl sulfoxide: Molecular and crystal structures

The crystal structure of a cobalt(II) complex with 4,4,4-trifluoro-1-thienylbutane-1,3-dione (Tfa) and dimethyl sulfoxide (DMSO) was determined using X-ray diffraction. The crystals are monoclinic: a = 7.590(3) Å, b = 17.996(8) Å, c = 10.440(4) Å, β = 106.263(8)°, V = 1368.9(10) ų, space group P2 ₁, Z = 2, ρ_calcd = 1.595 g/cm³, R = 0.0364. The coordination polyhedron of the cobalt atom is an octahedron made up of four O atoms of two Tfa ligands and two O atoms of two DMSO molecules. The deviation of the cobalt atom from the plane of 4O(Tfa) is 0.037 Å. The average Co-O(DMSO) and Co-O(Tfa) bond lengths are 2.122 and 2.052 Å, respectively.     

Allosteric bindings of thiacalix[4]arene-based receptors with 1,3-alternate conformation having two different side arms

A novel ditopic receptor possessing two complexation sites such as crown ether and 2-pyridylmethyl groups bearing 1,3-alternate conformation based on thiacalix[4]arene was prepared. The binding behaviors with Li⁺ and Ag⁺ have been examined by ¹H NMR titration experiment. The exclusive formation of mononuclear complexes of 1,3-alternate-5 with Li⁺ and Ag⁺ was observed even though the formation of the heterogeneous dinuclear complexes was expected. The decomplexation of Li⁺ from the crown moiety of 1:1 complex 1,3-alternate-5?Li⁺ to form the Ag⁺?1,3-alternate-5 complex by addition of AgSO₃CF₃ clearly shows that pyridyl moiety works as an efficient switch-off of the recognition ability of the crown moiety. We have also developed the construction of hydrogen-bonding self-assembly heterodimeric systems based on bis(4-pyridyl) and dicarboxylic acid thiacalix[4]arene derivatives in 1,3-alternate conformation. Their supramolecular behaviors are studied by ¹H NMR titration experiments with K⁺ and Ag⁺ ions. Although the values of the dimerization constants are relatively small, the stability of the dimers is strong enough to overcome only small conformational changes upon complex formation.     

The electronic structure of 5-methylhexa-1,2,4-triene-1,3-diyl, the first representative of highly delocalized triplet ethynylvinylcarbenes, from ESR spectroscopy data and quantum chemical calculations

The ESR spectrum of the first representative of highly conjugated triplet ethynylvinylcarbenes, 5-methylhexa-1,2,4-triene-1,3-diyl (1), was recorded in solid argon matrix. The zero-field splitting (ZFS) parameters of carbene 1 (D = 0.5054±0.0006 cm^?1 and E = 0.0045±0.0002 cm^?1) determined from the experimental ESR spectrum are in between the corresponding parameters of ethynylcarbene C3H2 (2) and vinylcarbene C₃H₄ (3): D(3) < D(1) < D(2) and E(2) < E(1) < E(3). Quantum chemical calculations of the ZFS parameters of 1, 2, and 3 have been carried out for the first time using two DFT-based approaches, RODFT and UDFT. An analysis of the experimental and theoretical ZFS parameters shows that carbene 1 is characterized by a greater extent of delocalization of the spin density of unpaired electrons than carbenes 2 and 3. The characteristic structural fragments of carbene 1 possess the principal features of the electronic structure of both ethynylcarbene (2) and vinylcarbene (3), respectively. Magnetic spin-spin interactions are identical in carbenes 1 and 2. The dominant contribution to D in 1 and 2 results from the one-center spin-spin interactions on carbon atoms in the propynylidene group, which are subjected to strong spin polarization.     

Synthesis,properties and X‐ray structure of 5‐azido‐2‐methoxy‐1,3‐xylyl‐18‐crown‐5

5‐Azido‐2‐methoxy‐1,3‐xylyl‐18‐crown‐5 has been prepared by reacting p‐toluenesulfonyl azide with the carbanion generated from the reaction of 5‐bromo‐2‐methoxy‐1,3‐xylyl‐18‐crown‐5 with n‐butyl lithium. The asymmetric N₃ stretch of this product has been observed as a single band at 2110 cm^?1 in dichloromethane solution. Addition of solid NaSCN, KSCN and CsSCN shifts this band to 2115, 2113 and 2112 cm^?1, respectively. Computational studies of this azide at the B3LYP‐6‐31G* level in the presence and absence of Na⁺ predicted these bands to be at 2173 cm^?1 and 2184 cm^?1. For the salt‐containing solutions, additional bands were observed at 2066 cm^?1, 2056 cm^?1 and 2055 cm^?1, respectively, which are in the range expected for CN stretches. The X‐ray structure of this azide has been determined. The terminal and internal N? N bond lengths were found to be 1.127(2) and 1.245(2) Δ, respectively, which is the usual pattern for aromatic azides. The crown ether is looped over the face of the aromatic ring resulting in an angle of 38.94° between the plane defined by the aromatic ring and that defined by the five ring oxygen atoms. In addition, the CH₃ group is rotated out of the plane of the phenyl ring with C1‐C18‐O181‐C182 and C17‐C18‐O181‐C182 dihedral angles of 93.81(14)° and ‐90.54(14)°, respectively.     

The lowest triplet state of tetramethyl-1,3-cyclobutanedithione. II. Calculation of spin-orbit coupling

A calculation of the spin-orbit coupling in the lowest excited triplet state of tetramethyl-1,3-cyclobutanedithione (TMCBDT) has been performed. The results show the following. (1) In the TMCBDT crystal the ground singlet-to-lowest triplet transition moment is predicted to be exclusively ? c polarized, as observed. (2) The assignment of the lowest triplet state should be ³A_u as found earlier for the oxygen analog. TMCBD. (3) The two largest contributions (～ 60%) to the isolated-molecule T₁ → S₀ transition moment come from the two triplet-triplet transitions.

and

, both of which are polarized along the CS bonds. (4) The total contribution to the transition moment parallel to the CS bonds is 76% from the T_l ← T₁ transitions and 24% from the S_γ ← S₀ transitions. And, finally, (5) the calculated oscillator strength of 2 × 10^?4 for the largest T₁ ← S₀ component (along y) falls within the range of typical spin-allowed, singlet-singlet n-⁼ transitions.     

Structure of tetrakis((1,3-diethyl-2-thiobarbiturato)(butanol-1))dicobalt(II)

The structure of the dimeric complex [Co₂(BuOH)₄(Detba)₄] (I), where НDetba is 1,3-diethyl-2-thiobarbituric acid, and BuOH is butanol-1, is determined (CIF file CCDC 1475273), and its IR spectrum is studied. The crystals are monoclinic: a = 10.7185(5), b = 21.985(1), c = 12.7235(7) Å, β = 92.196(2)°, V = 2996.1(3) ų, space group P2₁/c, Z = 2. The Co²⁺ ions in compound I are joined in pairs by bridging ligands μ₂-Detba^–?O,O'. In addition, each of them is linked through the O atoms to one terminal Detba–ion and two BuOH molecules to form a trigonal bipyramid СоО₅. Hydrogen bonds O–H···O formed by BuOH and Detba^– join the binuclear complexes into an infinite chain. The data of IR spectroscopy are consistent with the results of X-ray diffraction analysis.     

Synthesis, crystal structures and properties of four manganese coordination polymers with 4,4-bipyridine-derived ligands

Four new coordination polymers, namely Mn₂(4,4-bpy)₂(o-tol)₄ 1, Mn₂(4,4-bpy)₂(m-tol)₄ 2, Mn₂(bpp)₂(m-tol)₄ 3 and {[Mn₂(4,4-bpy)₂(p-tol)₄][Mn(4,4-bpy)₂(H₂O)₂(p-tol)₂]}·6H₂O 4 have been synthesized from 4,4′-bipyridine (4,4-bpy), 1,3-bis(4-pyridyl)-propane (bpp), o-toluic acid (o-Htol), m-toluic acid (m-Htol) and p-toluic acid (p-Htol). All four complexes feature dinuclear Mn₂(tol)₄ moieties, which are bridged by 4,4-bpy or bpp ligands to form 1D double-chain structures. The resulted 1D double-chains are assembled via hydrogen bonding or π···π stacking into 2D supramolecular layers. The complexes were characterized by physico-chemical (thermal behavior) and infrared spectroscopy. Variable temperature magnetic characterization suggest weak antiferromagnetic coupling exchange between dimeric Mn(II) centers (J = ?0.46 cm^?1 for 1, ?0.56 cm^?1 for 2, ?1.28 cm^?1 for 3 and ?0.59 cm^?1 for 4).     

Expression and Characterization of a Novel 1,3-Propanediol Dehydrogenase from <Emphasis Type="Italic">Lactobacillus brevis</Emphasis>

1,3-Propanediol dehydrogenase (PDOR) is important in the biosynthesis of 1,3-propanediol. In the present study, the dhaT gene encoding PDOR was cloned from Lactobacillus brevis 6239 and expressed in Escherichia coli for the first time. Sequence analysis revealed that PDOR containing two Fe²⁺-binding motifs and a cofactor motif belongs to the type III alcohol dehydrogenase. The purified recombinant PDOR exhibited a single band of 42 kDa according to SDS-PAGE. Optimal temperatures and pH values of this dehydrogenase are 37 °C, 7.5 for reduction and 25 °C, 9.5 for oxidation, respectively. We found that PDOR was more stable in acid buffer than in alkaline condition, and 60 % of its relative activity still remained after a 2-h incubation at 37 °C. The activity of PDOR can be enhanced in the presence of Mn²⁺ or Fe²⁺ iron and inhibited by EDTA or PMSF by different degrees. The K _m and V _max of this dehydrogenase are 1.25 mM, 64.02 μM min^?1 mg^?1 for propionaldehyde and 2.26 mM, 35.05 μM min^?1 mg^?1 for 1,3-PD, respectively. Substrate specificity analysis showed that PDOR has a broad range of substrate specificities. The modeling superposition indicated that the structural differences may account for the diversity of PDORs’ properties. Thus, our PDOR is a potential candidate for facilitating the 1,3-PD biosynthesis.     

Sequence Ion Structures and Dissociation Chemistry of Deprotonated Sucrose Anions

We investigate the tandem mass spectrometry of regiospecifically labeled, deprotonated sucrose analytes. We utilize density functional theory calculations to model the pertinent gas-phase fragmentation chemistry of the prevalent glycosidic bond cleavages (B₁-Y₁ and C₁-Z₁ reactions) and compare these predictions to infrared spectroscopy experiments on the resulting B₁ and C₁ product anions. For the C₁ anions, barriers to interconversion of the pyranose [α-glucose-H]^?, C₁ anions to entropically favorable ring-open aldehyde-terminated forms were modest (41 kJ mol^?1) consistent with the observation of a band assigned to a carbonyl stretch at ~?1680–1720 cm^?1. For the B₁ anions, our transition structure calculations predict the presence of both deprotonated 1,6-anhydroglucose and carbon 2-ketone ((4S,5S,6R)-4,5-dihydroxy-6-(hydroxymethyl)dihydro-2H-pyran-3(4H)-one) anion structures, with the latter predominating. This hypothesis is supported by our spectroscopic data which show diagnostic bands at 1600, 1674, and 1699 cm^?1 (deprotonated carbon 2-ketone structures), and at ~?1541 cm^?1 (both types of structure) and RRKM rate calculations. The deprotonated carbon 2-ketone structures are also the lowest energy product B₁ anions.

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Graphical Abstract ?

     

Nickel(II) complex with 1,4,7-tris(2-aminoethyl)-1,4,7-triazacyclononane

A nickel(II) complex, [Ni(taetacn)](ClO₄)₂ ? H₂O, where taetacn = 1,4,7-tris(2-aminoethyl)-1,4,7-triazacyclononane was synthesized. The crystal structure was determined by the single-crystal X-ray diffraction method at 293 K. The complex crystallizes in the orthorhombic space group Pna2₁ with a = 16.004(2) Å, b = 10.186(1) Å, c = 13.937(2) Å, V = 2271.9(5) ų, D_x = 1.56 g cm^?3, D_m = 1.59 g cm^?3 (floatation method), and Z = 4. The R₁ [I > 2σ(I)] and wR₂ (all data) values are 0.0636 and 0.1672, respectively, for all 4845 independent reflections. The compound is composed of octahedral nickel(II) cation with three 2-aminoethyl pendant groups of taetacn, tetrahedral ClO ₄ ^? anion, and a water molecule of crystallization. Electronic spectra are consistent with the octahedral geometry. Temperature dependence of the magnetic susceptibility (4.5–300 K) can be interpreted considering the zero-field splitting of the nickel(II) ion (g = 2.14, D = 3.72 cm^?1, and Nα = 300 × 10^?6 cm³ mol^?1). Cyclic voltammetry in DMF showed quasi-reversible and irreversible oxidation waves (E_pa = 0.54 V, E_pc = 0.45 V; E_pa = 1.16 V, E_pc = 0.71 V vs. Ag/Ag⁺).