Synthesis and Electrochemical Studies of Ruthenium(II) Dicarbonyl Bis(ferrocenyl-β-diketonates)

The reaction of [Ru₃(CO)₁₂] ( 1 ) with six equiv. of FcC(O)CH₂C(O)R ( 2a , R = Me; 2b , R = Fc; Fc = Fe(η⁵-C₅H₄)(η⁵-C₅H₅)) produced the Ru^II compounds [Ru(CO)₂(FcC(O)CHC(O)R)₂] ( 3a , R = Me; 3b , R = Fc) in moderate yields. IR studies and single-crystal X-ray analysis ( 3a ) confirmed that the CO ligands are cis-oriented and that the respective β-diketonates O,O'-chelate-bonded setting-up an octahedral surrounding at Ru^II. Electrochemical (cyclic and square-wave voltammetry) and spectroelectrochemical (UV/Vis-NIR, IR) measurements were additionally carried out. Compounds 3a , b display two ( 3a : E₁^o' = 140; E₂^o' = 255 mV; ΔE^o' = 115 mV for [ 3a ]⁺/[ 3a ]²⁺) or four ( 3b : E₁^o' = 80 mV, E₂^o' 190 mV (ΔE^o' = 110 mV, [ 3b ]⁺/[ 3b ]²⁺), E₃^o' = 355 mV (ΔE^o' = 165 mV, [ 3b ]²⁺/[ 3b ]³⁺), E₄^o' = 490 mV (ΔE^o' = 135 mV, [ 3b ]³⁺/[ 3b ]⁴⁺)) electrochemical reversible one-electron redox processes indicating electrostatic interactions among the ferrocenyl groups as oxidation progresses, which was confirmed by UV/Vis-NIR and in situ IR spectroscopy. One ferrocenyl group on each β-diketonate ligand is by this means 1^st oxidized before the 2^nd ferrocenyl group of the same β-diketonate building block follows.     

Tetraanions of acepleiadylene and pyrene? An electrochemical study

Acepleiadylene can be electrochemically reduced to its tetraanion at -57°C using THF as solvent and LiBPh₄ as supporting electrolyte.(E₁^o = ?1.85V, E₂^o = ?2.51V, E₃^o = ?3.11V, E₄^o = 3.14V vs. Ag/AgCl).All attemps to generate the tetraanion of the isoelectronic pyrene under different conditions failed.     

The thermodynamic stability of P8, A CBS‐Q study

The thermodynamic stabilities of P₂, P₄, and three P₈ cage structure were investigated through high‐precision CBS‐Q calculations. The CBS‐Q values for the bond energy of P₂ (ΔE_o: +115.7 kcal mol⁻¹) and the formation of P₄ from P₂ (Δ E_o:‐56.6 kcal mol⁻¹) were in excellent agreement with the experimental values (E_o: +117 and ‐56.4 kcal mol⁻¹ respectively). Among the P₈ cages, the cubane structure was the least stable (Δ E_o +37 kcal vs. 2×P₄). The most stable P₈ isomer adopts a cuneane structure resembling S₄N₄, and is more stable than white phosphorus at T = 0 K (Δ E_o −3.3 kcal mol⁻¹), but still unstable under standard conditions for entropic reasons (Δ G^o of +8.1 kcal mol⁻¹ vs. 2×P₄). The CBS‐Q energies represent significant revisions (6–20 kcal mol⁻¹) of previous computational predictions obtained by high‐level single method calculations. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:453–457, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20119     

Temperature and composition dependence of viscosity. II. Temperature dependence of viscosity of propylene carbonate-dimethoxyethane mixtures

The application of the currently used equations for the reproduction of the temperature dependence of viscosity η of binary solvent mixtures of propylene carbonate (PC) and dimethoxyethane (DME) favors the choice of the Vogel-Fulcher-Tammann (VFT) equation using the ideal glass transition point as the reference temperature T_o for the estimation of free and blocked (inaccessible) volumes. Reduced plots show that the free volumes as obtained from the VFT equation mainly determine the viscosities of the liquid mixtures; the blocked volumes V_x(T_o)≡V_o (x: mole fraction of PC) show ideal behavior. The effect of negative excess volumes V ^E on viscosity, studied in the preceding paper, is examined in comparison with the effect of a temperature decrease. The equal signs of η ^E and V ^E can be explained by referring the viscosities to the reference temperature T_o.     

Characterization of Heterogeneous Interaction Behavior in Ternary Mixtures by a Dielectric Analysis: Equi-Molar H–bonded Binary Polar Mixtures in Aqueous Solutions

The heterogeneous associating behavior of the aqueous binary mixtures of ethyl alcohol, ethylene glycol, glycerol and mono alkyl ethers of ethylene glycol, and aqueous ternary mixtures of equi-molar binary systems (i.e., mono alkyl ethers of ethylene glycol with ethyl alcohol, ethylene glycol and glycerol) have been investigated over the entire concentration range using accurately measured dielectric constants at 25 ^∘C. The concentration dependent values of the excess dielectric parameter ε^E and effective Kirkwood correlation factor g ^eff were determined using the measured values of the static dielectric constant, ε_o, at 1 MHz and the high frequency limiting dielectric constant ε_∞ = n _D ². The observed ε^E values in aqueous binary and ternary mixtures are negative over the entire concentration range, which implies the formation of heterogeneous complexes between these molecules that reduces the effective number of dipoles. The stoichiometric ratio corresponding to the maximum interaction in alcohol + water mixtures increases with an increase in the number of hydroxyl groups of the alcohol molecules, but for mono alkyl ethers of ethylene glycol + water mixtures it decreases with the increase in the molecular size of the mono alkyl ethers. In aqueous ternary mixtures the stoichiometric ratio for the maximum extent of heterogeneous interaction is governed by the molecular size of the mono alkyl ethers. It was also found that the strength of the heterogeneous H–bond connectivities in the water + alcohol systems decrease with an increase in the number of hydroxyl groups of the alcohol molecules. However in the case of water + mono alkyl ether binary mixtures and in ternary mixtures, the strength of H–bond connectivities increases with the increase in the molecular size of the mono alkyl ether. An analysis of the g ^eff values confirms that the heterogeneous interaction involves the orientation of molecular dipoles in the studied systems.     

Anion induced regulation of the absorption maximum of the twenty two carbon analog of the N-retinylidene-n-butylammonium cation.

Abstract— This study was undertaken to further investigate the way in which the counter anion controls the Λ_max of the absorption spectrum of compounds similar to N-retinylidene-n-butylammonium salts (NRBA). The following relationship had been found: ΔE =ΔE^o -F d₀e²/εd²; here ΔE is the observed excitation energy, e the charge on the electron, ε the dielectric constant, d₀ a constant and d the distance between centers of opposite charge as estimated from crystallographic radii. Resonance theory implies that ΔE^o should be of the same numerical value as the corresponding carbonium ion which can be generated readily from the corresponding alcohol. The C₂₂SB analog of NRBA was prepared and then converted to the halide salts. The Δ_max of these salts was determined in several halohydrocar-bon solvents, and ΔE^o was determined by least squares for each solvent. The average value of ΔE^o was found to be 653 nm, while the Λ_max, for the carbonium ion was previously found to be 644 nm. The results are supportive of previous work.     

Theoretical investigation of carboranylpyrrole structures and the thermal resistance and conducting properties of carboranylpyrrole polymers

The carboranylpyrrole polymers are functional materials with superior thermal resistance and conducting performances. The carboranylpyrrole structures and Laplacian bond order (LBO) of carborane moiety, as well as the thermal resistance and conducting properties of carboranylpyrrole dimers or polymers, were investigated theoretically. The ¹¹B NMR chemical shifts of 3-(2-methyl-o-carboranyl)alkyl-1H-pyrrole monomers (CP-1 to CP-5) were calculated and analyzed. The average LBO values of some characteristic chemical bonds in the carborane cages of CP-1 to CP-5 molecules were calculated. It is found that the average LBO values of carborane moieties change slightly with the increase in alkyl chain length. The temperature resulting in about 15–20 % weight loss for CP-1, CP-3, CP-4 and CP-5 polymers is predicted to be more than 700 °C. Apart from the C–C bonds in carborane moieties of 3-(2-R-o-carboranyl)propyl-1H-pyrrole (R = CH₂OH, CH₂OCH₃, CN, COCl, Ph) substituents, the LBO values of other bonds in these cages change slightly relative to that in the molecule of 3-(2-methyl-o-carboranyl)propyl-1H-pyrrole (CP-3). The C–C bond LBO values in the carborane cages of these substituents with electron-donating groups (R = CH₂OH, CH₂OCH₃) are bigger than that in CP-3, while those values in those substituents with electron-withdrawing groups (R = CN, COCl, Ph) are smaller than that in CP-3. The polymerization activity calculated for CP-1 to CP-5 monomers increases with the increase in alkyl chain length. The calculated orbital energy gap (?E _LUMO?HOMO) of CP-1 to CP-5 dimers decreases with the increase in alkyl chain length, and accordingly, the electronic conductivity has the potential to increase. In addition, the calculated band gaps of CP-1 to CP-5 dimers cell models also decrease with the increase in alkyl chain length.     

Synthesis and mass spectrum of 3-(3′-pyridinyloxymethyl)pyridine and polarography of its dialkyl diquaternary salts

3-(3′-Pyridinyloxymethyl)pyridine is prepared by reaction of 3-hydroxymethylpyridine with 3-bromopyridine and converted to the 1,1′-dimethyl and 1,1′-diethyl diquaternary salts with alkyl iodides. The salts are reduced polarographically at a potential (E_o) of about - 1.02 to - 1.10 V in the pH range of 5.5-8.5.     

Thermodynamics of Adsorption and Micellization of Triblock Copolymers of Oxyethylene and Oxybutylene in Aqueous Medium Using Surface Tensiometry

The aqueous solutions of three triblock copolymers based on polyoxyethylene and polyoxybutylene of the type E_mB₁₀E_m have been analyzed by surface tension measurements. Surface activity of these triblock copolymers was studied by measuring surface parameters, like surface excess concentration, Γ₂, area per molecule of polymer and standard Gibb's free energy of adsorption, Δ^oG_ads, at various temperatures in the range of 20 to 50°C. The Effect of block length of hydrophilic portion of triblock copolymers on surface activity was investigated in this work. Miceller behavior of these triblock copolymers was also investigated using above technique. Critical micelle concentration (CMC) was determined from the plot of surface tension versus log of concentration in the range of temperature of 20–50°C. Thermodynamic parameters, standard free energy of micellization, Δ^oG_mic, standard enthalpy of micellization, Δ^oH_mic, and standard entropy of micellization, Δ^oS_mic were calculated from CMC value using closed association model in this range of temperature. Self assembly behavior of triblock copolymer E₂₀B₁₀E₂₀ was compared with E₃₀B₁₀E₃₀ and E₄₈B₁₀E₄₈ triblock copolymer. Effect of temperature on surface and miceller properties of the triblock copolymers was also studied.     

Coaction of sub-band and doped nitrogen on visible light photoactivity of N-doped TiO2

We found in our previous work that the high photoactivity of N-doped TiO₂ for the oxidation of propylene under visible light was attributed to the photoactive center V_o^•-NO-Ti and the formation of sub-band originated from a large amount of single-electron-trapped oxygen vacancies (denoted as V_o^•; C. X. Feng, Y. Wang, Z. S. Jin, J. W. Zhang, S. L. Zhang, Z. S. Wu, Z. J. Zhang [2008], New J. Chem. 32 , 1038). In the present study, the structure of the sub-band within E_g of a representative sample N-NTA-400 was investigated by means of photoluminescence (PL) spectrometry and ultraviolet-visible light-near infrared diffuse reflectance spectra. The coaction of the sub-band and doped nitrogen on visible light photocatalytic activity of N-doped TiO₂ was also investigated. The electron spin resonance spectra measured under laser irradiation (λ = 532 nm) indicate that the doped nitrogen may contribute to stabilize the trapping electron center, i.e. surface oxygen vacancy (V_o^••), and hence suppress the PL, enhancing the photocatalytic activity.     

The Partial Molar Heat Capacities and Expansions of Inosine, 2′-Deoxyinosine and 2′-Deoxyguanosine in Aqueous Solution at 298.15 K

Solution densities over the temperature range 288.15 to 313.15 K have been measured for aqueous solutions of the nucleosides inosine, 2′-deoxyinosine, and 2′-deoxyguanosine, from which the partial molar volumes of the solutes at infinite dilution, V ₂^o, were obtained. The partial molar expansions for the nucleosides at infinite dilution and 298.15 K, E ₂^o {E ₂^o=(∂ V ₂^o/∂ T) _p }, were derived from the V ₂^o results. The V ₂^o values at 298.15 K for the two sugars D-ribose and 2-deoxyribose also have been determined. The partial molar heat capacities at infinite dilution for all the solutes, C _p,2^o, have been determined at 298.15 K. These V ₂^o,E ₂^o, and C _p,2^o results are critically compared with all of the results available from the literature, and the use of group additivity to evaluate these solution thermodynamic properties for the sparingly soluble nucleoside guanosine is explored.     

Theoretical Study on the Mechanism of Ni‐Catalyzed Alkyl–Alkyl Suzuki Cross‐Coupling

Ni‐catalyzed cross‐coupling of unactivated secondary alkyl halides with alkylboranes provides an efficient way to construct alkyl–alkyl bonds. The mechanism of this reaction with the Ni/ L1 ( L1 =trans‐N,N′‐dimethyl‐1,2‐cyclohexanediamine) system was examined for the first time by using theoretical calculations. The feasible mechanism was found to involve a Ni^I–Ni^III catalytic cycle with three main steps: transmetalation of [Ni^I( L1 )X] (X=Cl, Br) with 9‐borabicyclo[3.3.1]nonane (9‐BBN)R₁ to produce [Ni^I( L1 )(R₁)], oxidative addition of R₂X with [Ni^I( L1 )(R₁)] to produce [Ni^III( L1 )(R₁)(R₂)X] through a radical pathway, and C? C reductive elimination to generate the product and [Ni^I( L1 )X]. The transmetalation step is rate‐determining for both primary and secondary alkyl bromides. KOiBu decreases the activation barrier of the transmetalation step by forming a potassium alkyl boronate salt with alkyl borane. Tertiary alkyl halides are not reactive because the activation barrier of reductive elimination is too high (+34.7 kcal mol^?1). On the other hand, the cross‐coupling of alkyl chlorides can be catalyzed by Ni/ L2 ( L2 =trans‐N,N′‐dimethyl‐1,2‐diphenylethane‐1,2‐diamine) because the activation barrier of transmetalation with L2 is lower than that with L1 . Importantly, the Ni⁰–Ni^II catalytic cycle is not favored in the present systems because reductive elimination from both singlet and triplet [Ni^II( L1 )(R₁)(R₂)] is very difficult.     

An oxyluminescence investigation of the auto-oxidation of nylon 66

The kinetics of the thermal oxidation of stabilised and unstabilised nylon 66 fibres and films have been studied by photon counting oxyluminescence methods from 50°C to 150°C. The activation energies for initiation (E₁), propagation (E₃) and termination (E₅) over this temperature range are: E₁ = 16 kcal mol^?1, E₃ = 17·5 kcal mol^?1 and E₅ ≈ 12 kcal mol^?1. The extent of orientation of the polymer does not change the nature of the oxyluminescence curve or E₃ and E₅ above 110°C.Significant losses of critical mechanical properties of the fibres occur in the induction period at 100°C and non-stationary kinetics are described to enable this region to be studied by oxyluminescence. The oxidation rate in the induction period and the limiting rate region in air is one-third the rate in oxygen at atmospheric pressure. Non-stationary methods show that alkyl radical reactions are competitive with alkyl peroxy radical formation in air over the temperature range 100°C to 140°C. This affects the course of the oxidation reaction and the stabiliser efficiency and explains the observation of unsaturated oxidation products by phosphorescence spectroscopy.     

Probing the role of the linker in ferrocene-ATP conjugates: monitoring protein kinase catalyzed phosphorylations electrochemically

The synthesis and electrochemical properties of ferrocene conjugates are presented for the purpose of investigating adenosine 5′‐[γ‐ferrocenoylalkyl] triphosphate ( 1 a – 4 a , ferrocene (Fc)–ATP) as co‐substrates for phosphorylation reactions. Compounds 1 a – 4 a were synthesized, purified by HPLC, and characterized by NMR spectroscopy and mass spectrometry. In solution, all Fc–ATP bioconjugates exhibit a reversible one‐electron redox process with a half‐wave potential (E_1/2) in the 390–430 mV range, peak separations (ΔE_p) in the 40–70 mV range, and the peak current ratio (i_pa/i_pc) near unity. The peptide‐modified surface Glu‐Gly‐Ile‐Tyr‐Asp‐Val‐Pro was used to study the sarcoma‐related protein (Src) kinase activity by employing the Fc–ATP bioconjugates as co‐substrates. Subsequent kinase‐catalyzed transfer of the γ‐Fc‐phosphate group to the tyrosine residues of the surface‐bound peptides was characterized by a formal potential (E^o) ≈390 mV (vs. Ag/AgCl). The Fc‐coverage, estimated by time‐of‐flight secondary‐ion mass spectrometry (TOF‐SIMS) and cyclic voltammetry (CV), suggested validity of Fc–ATP conjugates as kinase co‐substrates. Depending on the length of the alkyl spacer of the Fc–ATP conjugate, different current densities were obtained, pointing to a direct correlation between the two. Molecular modeling revealed that the structural constraint imposed by the short alkyl spacer ( 1 a ) causes a steric congestion and negatively affects the outcome of phosphorylation reaction. An optimal analytical response was obtained with the Fc–ATP conjugates with linker lengths longer than six CH₂ groups.     

29Si and 13C NMR Studies of organofunctional di- and trisilanes

A series of di- and trisilanes of general structure Ph₃SiSiMe₂R and (Ph₃Si)₂SiR′R″ were synthesized, and the ²⁹Si and ¹³C chemical shifts and one-bond siliconsilicon coupling constants (¹J_SiSi) were measured. The coupling constants of the disilanes were found to be primarily dependent upon the inductive effect of the alkyl group, R, as measured by the Taft o^★ constant. In both series of compounds, increasing alkyl substitution at silicon led to a decrease in ¹J_SiSi.     

Thermal analysis study of some transition metal complexes by TG and DSC methods

The thermodynamic and thermal properties of [Cu(L)₂·Cl₂], [Ni(L)₂]·Cl₂, [Co(L)₂·Cl₂]; L=1,2-bis(o-aminophenoxy)ethane (BAFE), complexes have been investigated. The thermal decomposition of the complexes took place in two distinct steps in endothermic reaction up to 700°C. The activation energy E, the entropy change S ^#, enthalpy H change and Gibbs free energy change G ^# were calculated from the results of thermogravimetry analysis (TG) and heat capacity from the results of differential scanning calorimetry (DSC). It was found that the thermal stabilities and activation energies of the complexes follow the order Ni(II)>Cu(II)>Co(II) and E _Co<E _Ni<E _Cu, respectively.This revised version was published online in November 2005 with corrections to the Cover Date.     

Synthesis and Application of a Perfluorinated Ammoniumyl Radical Cation as a Very Strong Deelectronator

The perfluorinated dihydrophenazine derivative (perfluoro‐5,10‐bis(perfluorophenyl)‐5,10‐dihydrophenazine) (“phenazine^F”) can be easily transformed to a stable and weighable radical cation salt by deelectronation (i.e. oxidation) with Ag[Al(OR^F)₄]/ Br₂ mixtures (R^F=C(CF₃)₃). As an innocent deelectronator it has a strong and fully reversible half‐wave potential versus Fc⁺/Fc in the coordinating solvent MeCN (E°′=1.21 V), but also in almost non‐coordinating oDFB (=1,2‐F₂C₆H₄; E°′=1.29 V). It allows for the deelectronation of [Fe^IIICp*₂]⁺ to [Fe^IV(CO)Cp*₂]²⁺ and [Fe^IV(CN‐^tBu)Cp*₂]²⁺ in common laboratory solvents and is compatible with good σ‐donor ligands, such as L=trispyrazolylmethane, to generate novel [M(L)_x]ⁿ⁺ complex salts from the respective elemental metals.     

Molecular structure and conformation of gaseous chloroacetyl chloride as determined by electron diffraction

Chloroacetyl chloride is studied by gas-phase electron diffraction at nozzle-tip tempera- tures of 18, 110 and 215°C. The molecules exist as a mixture of anti and gauche confor- mers with the anti form the more stable. The composition (mole fraction) of the vapor with uncertainties estimated at 2σ is found to be 0.770 (0.070), 0.673 (0.086) and 0.572 (0.086) at 18, 110 and 215°C, respectively. These values correspond to an energy difference with estimated standard deviation ΔE^o = E^o_g -E^o_a = 1.3 ± 0.4 kcal mol^?1 and an entropy difference ΔS^o = S^o_g -S^o_a = 0.7 ± 1.1 cal mol^?1 K^?1. Certain of the diffraction results permit the evaluation of an approximate torsional potential function of the form 2V = V₁(1 - cos φ) + V₂(1 - cos 2φ) + V₃(1 - cos 3φ); the results are V₁ = 1.19 ± 0.33, V₂ = 0.56 ± 0.20 and V₃ = 0.94 ± 0.12, all in kcal mol^?1. The results for the distance (r_a), angle (_∠α) and r.m.s. amplitude parameters obtained at the three temperatures are entirely consistent. At 18°C the more important parameters are, with estimated uncertainties of 2σ, r(C-H) = 1.062(0.030) Å, r(CO) = 1.182(0.004) Å, r(C-C) = 1.521(0.009) Å. r(CO-Cl) = 1.772(0.016) Å, r(CH₂-Cl) = 1.782(0.018) Å, ∠C-C-0 = 126.9(0.9)°, ∠CH₂-CO-C1 = 110.0(0.7)°,∠CO-CH₂-C1 = 112.9(1–7)°, ∠H-C-H = 109.5° (assumed), ∠φ (gauche torsion angle relative to 0° for the anti form) = 116.4(7.7)°, δ (r.m.s. amplitude of torsional vibration in the anti conformer) == 17.5(4.2)°.     

铀(Ⅵ)与不对称希夫碱配合物的合成和热分解反应动力学

邻苯二胺与5－氯－2－羟基二苯酮、邻香草醛作用合成了一种不对称希夫碱配体C₂₇H₂₁N₂O₃Cl（H₂L）。在正丁醇和甲醇体系中硝酸铀酰与该配体反应合成了一种固体希夫碱配合物[UO₂(HL)(NO₃)(H₂O)]·H₂O。通过元素分析、IR、UV、¹H NMR、TG-DTG及摩尔电导率分析等手段对合成的配合物进行了表征,用非等温热重法研究了铀(Ⅵ)配合物的热分解反应动力学,推断出第三步热分解的动力学方程为：d α /d t = A · e^{- E/RT} ·3/2[(1- α )^-1/3-1]^-1,得到了动力学参数E和A。并计算出了活化熵△S^¹和活化吉布斯自由能△G^¹。