Laser flash photolysis of [3,n]paracyclophan-2-ones. Direct observation and chemical behavior of 4,4'-(1,n-alkanediyl)bisbenzyl biradicals

The 4,4'-(1,n-alkanediyl)bisbenzyl biradicals (2b-d) have been generated from the Norrish type-I reaction of [3,n]paracyclophan-2-ones (1b-d) giving the paracyclophanes 3b-d as the only reaction products. The behavior of biradicals 2b-d has been studied in detail and compared with the previously reported biradical 2a. The lifetimes increase as the chain length decreases and are affected by the solvent viscosity, thus showing the effect of the length of the chain on the conformations of the biradicals. Quenching with persistent radicals such as TEMPO resulted in length-dependent rate constants. Finally, the study of the magnetic field effects on the biradical lifetimes suggest that ISC control determines biradical lifetimes for long-chain systems.     

Carboxylate complexation by 1,1'-(1,2-phenylene)bis(3-phenylurea) in solution and the solid state

A simple bis-urea containing anion receptor, synthesised from ortho-phenylenediamine, has been shown to have excellent selectivity for carboxylates in solution, with a crystal structure elucidation of the benzoate complex showing four hydrogen bonds between the receptor and anion in the solid state.     

On-line chemical generation of tris(2,2'-bipyridyl)ruthenium(III) and its application in CE with chemiluminescence detection

A novel tris(2,2'-bipyridyl)ruthenium(III) [Ru(bipy)(3) (3+)]-based chemiluminescence (CL) detection in CE using an on-line chemical generation scheme has been demonstrated. Two continuous streams respectively containing solutions of Ru(bipy)(3) (2+) and acidic cerium(IV) used as a homogeneous chemical oxidant are employed to generate Ru(bipy)(3) (3+), which is delivered into the reaction capillary of a coaxial flow interface and then reacted with analytes at the end of the separation capillary to yield light. The important operational parameters for separation and detection are identified and optimized. Four alpha-ketocarboxylic acids used as models, outside of the amine-containing compounds, are successfully separated and detected to evaluate the feasibility of the approach. The excellent resolution and detection sensitivity was achieved by using 50 mmol/L phosphate running buffer (pH 9.5) with 0.7 mmol/L CTAB, and CL reagent solution streams containing 0.15 mmol/L Ru(bipy)(3) (2+) and 0.8 mmol/L cerium(IV) (0.25 mol/L H(2)SO(4)), respectively. The concentration detection limits for alpha-ketocarboxylic acids were below 3.7x10(-8) mol/L (S/N = 3). The proposed method was applied to the determination of alpha-ketocarboxylic acids in five different honey samples with satisfactory results.     

Azanone (HNO): generation,stabilization and detection

HNO (nitroxyl, azanone), joined the ‘biologically relevant reactive nitrogen species’ family in the 2000s. Azanone is impossible to store due to its high reactivity and inherent low stability. Consequently, its chemistry and effects are studied using donor compounds, which release this molecule in solution and in the gas phase upon stimulation. Researchers have also tried to stabilize this elusive species and its conjugate base by coordination to metal centers using several ligands, like metalloporphyrins and pincer ligands. Given HNO''s high reactivity and short lifetime, several different strategies have been proposed for its detection in chemical and biological systems, such as colorimetric methods, EPR, HPLC, mass spectrometry, fluorescent probes, and electrochemical analysis. These approaches are described and critically compared. Finally, in the last ten years, several advances regarding the possibility of endogenous HNO generation were made; some of them are also revised in the present work.

HNO (nitroxyl, azanone), joined the ‘biologically relevant reactive nitrogen species’ family in the 2000s.     

Syntheses and Crystal Structures of Two Coordination Polymers of Cobalt and Cadmium Assembled by 4,4ˊ-(Ethane-1,2-diyldioxy)dibenzoic Acid

Two new metal-organic coordination polymers [Co0.5（Heoba）（bib）0.5]2n（1） and [Cd（eoba）（phen）]n（2）（H2eoba = 4,4-（ethane-1,2-diyldioxy）dibenzoic acid, bib = 1,4-bis（imidazol-1-yl）-butane, phen = 1,10-phenanthroline） have been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectrum, TG and single-crystal X-ray diffraction. Complex 1 is a 2D network structure, and complex 2 exhibits a 3D network structure. Moreover, the luminescent property of complex 2 has been investigated in the solid state.     

Electrochemical and ferromagnetic couplings in 4,4',4' '-(1,3,5-benzenetriyl)tris(phenoxyl) radical formation

4,4',4' '-(1,3,5-Benzenetriyl)tris(2,6-di-tert-butylphenol) was prepared by the cross-coupling of 1,3,5-tribromobenzene and [4-(trimethylsiloxy)phenyl]magnesium bromide. X-ray analysis of the single crystal showed a propeller-like structure with a mean dihedral angle of 39 degrees between the hydroxyphenyl and the core benzene. The phenoxyl mono-, di-, and triradicals were generated by the electrochemical oxidation of the trianion. A stepwise radical formation was revealed by a differential pulse voltammogram, electrolytic ESR spectroscopy, and a comproportionation reaction between the radicals, which was discussed as an effect of the pi-conjugated but non-Kekulé-type coupler. The quartet and triplet ground state for the tri- and diradical, respectively, were confirmed by a SQUID measurement.     

High-yielding, regiospecific synthesis of cis(4,4')-di(carbomethoxybenzo)-30-crown-10, its conversion to a pyridyl cryptand and strong complexation of 2,2'- and 4,4'-bipyridinium derivatives

A high yielding (93%), regiospecific synthesis of cis(4,4')-di(carbomethoxybenzo)-30-crown-10 (1c) is reported. The derived crown ether diol 1d was converted to pyridyl cryptand 12 in 44% yield by reaction with pyridine-2,6-dicarbonyl chloride. Binding of two different 4,4'-bipyridinium (paraquat) species (3) and 2,2'-bipyridinium (diquat) 4 by 12 was explored via (1)H NMR spectroscopy, NOE experiments, mass spectrometry, X-ray crystallographic analyses, and isothermal titration calorimetry. Cryptand 12 exhibits the highest association constant for diquat ever reported (Ka = 1.9 x 10(6) M(-1)) and very high association constants for paraquats (Ka > 10(5) M(-1)) in acetone at 22 degrees C. The binding constant of diquat 4 by cryptand 12 is nearly 6-times higher than any other reported host.     

Controllable preparation, network structures and properties of unusual metal-organic frameworks constructed from 4,4'-(hexafluoroisopropylidene)diphthalic acid and 4,4'-bipyridyl

Three novel 3D metal-organic frameworks of [Ni(2)(hfpdpt)(bpy)(2)(H(2)O)(2)](H(2)O)(8) (1), [Ni(3)(Hhfpdpt)(2)(bpy)(4)](H(2)O)(2) (2), and [Mn(2)(hfpdpt)(H(2)O)(2)] (3) have been synthesized by the hydrothermal reaction of Ni(II) or Mn(II) nitrate, 4,4'-(hexafluoroisopropylidene)diphthalic acid (H(4)hfpdpt), and 4,4'-bipyridyl (bpy). Complex 1 self-assembles into a 3D framework with unconventional 4-connected network topology, while 2 and 3 exhibit two kinds of unusual (4,8)-connected topological networks. Notably, in 1 and 2, the bpy coligand participates in the construction of their 3D frameworks, and the pH value also plays an important role to tune their space arrangements, while in 3, the bpy coligand is not involved in the final crystalline lattice. Furthermore, a detailed investigation on their magnetic and adsorptive properties is carried out.     

The solution behavior of poly(vinylpyrrolidone): its clouding in salt solution, solvation by water and isopropanol, and interaction with sodium dodecyl sulfate

This article deals with the solution properties of poly(vinylpyrrolidone) (PVP) in salt and surfactant environment. The cloud point (CP) of PVP has been found to be induced by the salts NaCl, KCl, KBr, Na2SO4, MgSO4, and Na3PO4. On the basis of CP values for a salt at different [PVP], the energetics of the clouding process have been estimated. The effect of the surfactant, sodium dodecyl sulfate (SDS), on the salt-induced CP has also been studied, and reduction in CP at low [SDS] and increase in CP at high [SDS] have been observed. The water vapor adsorption of PVP has been determined by isopiestic method. The results display a BET Type III isotherm whose analysis has helped to obtain the monolayer capacity of PVP and formation of multilayer on it. The solvation of PVP in a solution of water and a water-isopropanol mixture has been determined by conductometry from which contribution of the individual components were estimated. The interaction of PVP with SDS in solution led to formation of a complex entity, which has been studied also by conductometry adopting a binding-equilibrium scheme. SDS has been found to undergo two types of binding as monomers in the pre- critical aggregation concentration (CAC) range and as small clusters in the post CAC region. The stoichiometries of binding and binding constant were evaluated.     

Investigation of solution and solid-state properties of poly(R,R,4,4-cyclohexylidene diphenylene diphenyl-4,4-disulfonate)

Solution and solid-state properties of poly(R,R^′,4,4^′-cyclohexylidene diphenylene diphenyl-4,4^′-disulfonate) (PS-6: R=R^′=H; PS-7: R=CH₃, R^′=H; PS-8: R=R^′=Cl; PS-9: R=CH₃, R^′=Cl and PS-10: R=R^′=Br) have been determined and discussed in terms of nature of the substituents. Ultrasonic velocity (2 MHz) and acoustical parameters of PS-7 and PS-9 solutions in chloroform, 1,2-dichloroethane and tetrahydrofuran (THF) at 30, 35 and 40 °C have been evaluated to understand the effect of methyl and chlorine groups, concentration, and temperature on molecular interactions. The data are interpreted in light of solvent-polymer and polymer-polymer interactions. Predominant solvation is observed in THF system and the least in chloroform system at all three temperatures. The structural change is observed above 2%. Both the polymers possess structure-forming tendency and it is supported by positive values of S_n.The densities of PS-7 and PS-9 determined by floatation method are in excellent agreement with calculated values but those determined by specific volume method differ remarkably from calculated values due to solvation effect. PS-7 and PS-9 possess respectively tensile strength of 38.4 and 1.1 N/mm²; electric strength of 16.2 and 25.0 kV/mm and volume resistivity of 5.7×10¹⁶ and 1.0×1017Ωcm. The low tensile strength of PS-9 is due to low molecular weight, rigid and brittle nature of the polymer chains. PS-6 to PS-9 are thermally stable up to about 349-379 °C while PS-10 up to about 279 °C and involved two-step degradation. DTA thermograms indicated T_g at about 204-226 °C. High activation energy indicated rigid nature of the polymer chains and the positive magnitudes of ΔS* indicated less ordered transition state. The nature of the substituents (CH₃, Cl and Br) affected thermal, mechanical and electrical properties.     

2-溴-4,4'-二硝基-3'-二甲基锍-2'-联苯酚内盐的合成、结构及性质的研究

在胺存在下,3,7-二硝基二苯并溴五环硫酸氢盐与二甲基亚砜反应生成2-溴-4,4'-二硝基-3'-二甲基锍-2'-联苯酚内盐(3).3的X射线晶体结构分析数据表明其分子具有内盐结构但酚氧负离子的负电荷是部分离域的,分子内两苯环所成的两面角为117.3°.3在熔解时发生重排及热分解分别生成2-溴-2'-甲氧基-3'-甲硫基-4,4'-二硝基联苯(6)及3,7-二硝基-4-甲硫基-二苯并呋喃(7).3与盐酸反应生成相应的锍盐(8).     

Polycrystalline and solution Raman spectra of t-1,2-bis(4-pyridyl)ethylene,its dihydrochloride and its dideuterochloride

The normal Raman spectra of trans-1,2-bis(4-pyridyl)ethylene and its dihydrochloride and dideuterochloride salts are reported. Frequency shifts observed upon salt formation and deuteration are utilized in the assignment of vibrational modes. Additional assignments are made by comparisons to other pyridine-containing molecules and trans-stilbene. Assignment of the normal Raman spectrum of trans-1,2-bis(4-pyridyl)ethylene is essential to interpretation of the surface Raman spectrum of this molecule reported elsewhere[1].     

Application of 4,4＇-（2-Carboxypropane-1,3-diyl）dibenzoic Acid in Coordination Metal Complexes： Synthesis,Characterization, and Theoretical Studies①

[Pb(HL)(phen)]n(1) and [Cd3L2(phen)]n(2), where phen = 1,10-phenanthroline and L = 4,4'-(2-carboxylatopropane-1,3-diyl)dibenzoate, were hydrothermally prepared and fully characterized by X-ray single-crystal diffraction, infrared spectroscopy and thermogravimetric analyses. The decomposition temperature of 1 and 2 was measured to be ca. 304 and 416 ℃, respectively. The charge transfer transition based absorption of 1 and 2 was also verified by the powder scattering spectra and theoretical analyses.     

Li-biphenyl-1,2-dimethoxyethane solution: calculation and its application

Metallic lithium reacts with biphenyl in 1,2-dimethoxyethane (DME) solvent at room temperature. This reaction has been studied using density functional theory (DFT) at the B3LYP level together with the 6-311++G (d,p) basis set. From the energy results of the corresponding optimized geometries for intermediate complexes, the reaction can be interpreted as a charge-transfer process between lithium and biphenyl followed by Li+ coordination with ether oxygens in DME. In addition, the experimentally observed vibrational bands can be unambiguously assigned and interpreted according to the normal modes calculated for the biphenyl-Li-DME complex. This organic complex solution has been demonstrated as a very effective chemical lithiation agent. V2O5 can be lithiated up to 1.45 lithium ions per formula. The lithiated V2O5 shows a high Li-extraction capacity of 173 mAh/g as cathode material for lithium ion batteries.