Study on the Mechanism of the Radiation-Induced Chain Oxidation of N,N,N,N-Tetramethyl-4,4′-diaminodiphenylmethane by Tetrabromomethane in Poly(vinyl chloride) Films

Kinetics and mechanism of the radiation-induced chain oxidation of N,N,N,N-tetramethyl-4,4-diaminodiphenylmethane (Am) by tetrabromomethane in poly(vinyl chloride) (PVC) films were studied by ESR and optical spectroscopy. The quantitative analysis of the ESR spectra of PVC films containing Am and CBr₄ irradiated with -rays at 77 K was performed. The nature of radical species involved in the chain process was established. It was shown that the heating of the films after their irradiation at 77 K resulted in the formation of free radicals Am^·, which initiated the chain oxidation of amine with a chain length of 100. The kinetic features of the chain oxidation–reduction reactions occurring in vacuum and in the presence of oxygen were compared.     

Study on the extraction of trivalent lanthanide ions with N,N′-dimethyl-N,N′-diphenyl-malonamide and diglycolamide

The extraction of trivalent lanthanide (Ln(III) ions with two diamides: (1) N,N′-dimethyl-N,N′-diphenyl-malonamide (MA) and (2) N,N′-dimethyl-N,N′-diphenyl-diglycolamide (DGA) from nitric acid solution was studied. Chemical bond properties of extracted complexes were investigated by UV-VIS and FT-IR spectroscopies. The chemical bond strength between Ln(III) ions and the ligands in extracted complexes was closely related with the magnitude of the distribution ratios of Ln(III) ions: the extracted complex having a stronger bond between Ln(III) ion and the ligand showed a higher magnitude of the distribution ratio of Ln(III) ion.     

Preparation,crystal structure and luminescence of lanthanide coordination polymers with 2,2′-dimethyl-4,4′-bipyridine-N,N′-dioxide

Four coordination polymers of the bidentate ligand 2,2′-dimethyl-4,4′-bipyridine-N,N′-dioxide (L), [La(L)(NO₃)₃(H₂O)] _n (1), {[Gd₂(L)₃(NO₃)₆]·6H₂O} _n (2), {[Sm(L)₂(H₂O)₄]·3ClO₄·2L·4H₂O} _n (3) and {[Nd(L)₂(H₂O)₄]·3ClO₄·2L·4H₂O} _n (4) have been synthesized by the diffusing solvent mixture method. Results of X-ray diffraction analysis reveal that 1, with a Ln/L stoichiometry of 1:1, displays a rare 3-D three-fold interpenetrating diamondoid framework, while 2 has a Ln/L stoichiometry of 1:1.5 and exhibits a polycatenane network with a {8²,10} topology and large channels accommodated by water. Complexes 3 and 4, with Ln/L stoichiometry of 1:2, have 3-D two-fold interpenetrating diamondoid structures and large voids. Nonlinear optical property of 2 and luminescence of 3 were also investigated.     

Synthesis and Crystal Structure of 4,4′-Diamino-N,N′-diethyl Bisbenzenesulfamide

A new compound of 4,4′-diamino-N,N′-diethyl bisbenzenesulfamide (C18H26N4O4S2, Fw = 426.55) has been synthesized and its structure was determined by X-ray crystallography method. The crystal belongs to the monoclinic system, space group P21/c with a = 10.0623(9), b = 13.6759(13), c =15.5309(14) , β = 100.482(2)o, V = 2101.6(3) 3, Dc = 1.348 g/cm3, F(000) = 904, μ = 0.285 mm–1, Z = 4, the final R = 0.0512 and wR = 0.1363 for 3485 observed reflections with I > 2σ(I). The structure of the title compound is pseudo secondary axisymmetric, and the two sulfamide-groups show distorted tetrahedral configurations.     

Curing of N,N′-diglycidylimides with polyfunctional compounds

This paper describes the curing reactions of new N,N′-diglycidylimides containing trimellitimide units. Reactions were carried out using several polyfunctional curing agents, viz. aromatic primary diamines and phthalic anhydride. Spectroscopic techniques were used to study the curing process. The course of reaction was followed by i.r. spectroscopy. Some intermediate species were detected by recording ¹³C-NMR spectra until the products became insoluble in the usual deuterated solvents.     

Complexation of amine free radicals during the radiation-induced chain oxidation reaction of <Emphasis Type="Italic">N,N,N′,N′</Emphasis>-tetramethyl-4,4′-diaminodiphenylmethane

Complexation of free radicals derived from the amine in the chain redox reaction in γ-irradiated solid PVC films doped with N,N,N′-N′-tetramethyl-4,4′-diaminodiphenylmethane (Am) and CBr₄ was studied by means of the ESR and luminescence techniques. The effect of concentration of the additives Am and CBr₄ on the quenching of fluorescence of Am^· radicals was examined. The data were rationalized in terms of the Stern-Volmer formalism for static quenching, which results from the formation of nonfluorescing ground-state charge-transfer complexes between the radical Am^·, as well as its dimeric form Am ₂ ^· , and CBr₄. The association constants of the complexes were determined. The mechanism of radiation-induced chain oxidation of Am involving these complexes is discussed.     

Synthesis, Structure, Photoluminescence and Theoretical Study of (N,N′-Dimethyl-4,4′-bipyridinium)[Cd2(μ 2-Cl)4Cl2]n with N,N′-Dimethyl-4,4′-bipyridinium Generated in Situ

The title complex, (N,N′-dimethyl-4,4′-bipyridinium)[Cd₂(μ ₂-Cl)₄Cl₂]_n (1), in which the N,N′-dimethyl-4,4′-bipyridinium was generated in situ, was synthesized via hydrothermal reaction. X-Ray diffraction analysis revealed that the structure of 1 consisted of MV ²⁺ (MV ²⁺ = N,N′-dimethyl-4,4′-bipyridinium) cationic moieties and infinite [Cd2(μ ₂-Cl)₄Cl₂]_n anionic chains. The cadmium atom was bound by one terminal chlorine atom and four μ ₂-bridging chlorine atoms, yielding a slightly distorted triangular bipyramid. Photoluminescent investigation revealed that the complex displayed an emission in greenish blue region.     

Study on the influence of ageing on chemical and mechanical properties of N,N′-dimethyl-N,N′-diphenylcarbamide stabilized propellants

Double-base propellants undergo chemical, physical and mechanical changes upon ageing, leading to changes in ballistic performance and presenting explosive hazards. This report studies the variation of chemical and mechanical properties of aged N,N′-dimethyl-N,N′-diphenylcarbamide (methyl centralite) stabilized propellants in order to simulate and evaluate the natural ageing throughout the artificial one. Therefore, a comparative study of stabilizer depletion, plasticizers content, heat of combustion and mechanical properties such as storage modulus, loss modulus and damping of naturally and artificially aged propellants has been carried out by the following techniques: high-performance liquid chromatography (HPLC), thermogravimetric analyzer (TG), calorimeter of combustion and dynamic mechanical analyzer (DMA), respectively. The results obtained show that all properties are closely connected. In addition, the determination of stabilizer depletion, plasticizers evaporation, decrease of heat of combustion and mechanical properties are very useful for a better understanding of the decomposition and ageing behaviour of propellants. The HPLC investigation of stabilizer has shown good stability of the propellants. The results obtained for DMA have shown that some considerable changes of the mechanical and viscoelastic properties of the propellants occurred during ageing. These results confirm the results obtained by TG for the reduction of the nitroglycerine amount and the decrease of the heat of combustion.     

Sensitive Spectrophotometric Determination of Benzoylperoxide with N,N,N′,N′-Tetramethyl-p-phenylenediamine

Abstract

A highly sensitive spectrophotometric determination of benzoylperoxide (BPO) based on the color developing reaction between N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) and BPO in the presence of cerium(IV) in weakly acidic media is proposed. The calibration graph is linear in the range 0–6000 ng BPO per 10 ml with an apparent molar absorptivity of 4.73 × 10⁵ 1 mol^?1 cm-1 at 612 nm. The proposed method is about 50-fold more sensitive than N-ethyl-2-naphthylamine (NENA), and application to assays of flour is described.     

Synthesis,Crystal Structure and Spectroscopic Properties of N,N′-Diphenyl-N,N′-bis(2-fluorophenyl)-1,1′-biphenyl-4,4′-diamine

A fluorinated tetraphenylbenzidine derivative, N,N′-diphenyl-N,N′-bis(2-fluorophenyl)-1,1′-biphenyl-4,4′-diamine (C36H26F2N2, Mr = 524.59) was synthesized via the palladiumcatalyzed Buchwald-Hartwig reaction of N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine with 2-fluoroiodobenzene (yield: 75%) and structurally characterized. It crystallizes in monoclinic, space group P21/n with a = 9.820(7), b = 14.305(11), c = 10.233(8) , β = 108.973(9)o, V = 1359.3(18) 3, Z = 2, Dc = 1.282 g/cm3, μ(MoKα) = 0.084 mm-1, F(000) = 548, S = 1.018, the final R = 0.0439 and wR = 0.0928. It presents a linear centrosymmetric framework constituted by a linkage of biphenyl as a bridge and two fluorinated diphenylamine moieties. The UV-Vis absorption and fluorescence spectra of the title compound were also investigated. This compound emits intense blue fluorescence with a peak wavelength of 406 nm in film.     

Features of condensation of 4,4′-Dihydroxybiphenyl with phenylphosphonous tetraethyldiamide

4,4′-Dihydroxybiphenyl was condensed with phenylphosphonous tetraethyldiamide. The moleccular mass, chemical composition, and structural features of the product, oligo(4,4′-biphenylene phenylphosphonite), were elucidated using the method of matrix-activated laser desorption/ionization, with a time-of-flight (TOF) mass analyzer. The oligophenylphosphites containing labile P-N bond, which are unstable under conditions of recording mass spectra, were stabilized by conversion into oligophenylphosphonates. 1H-Tetrazole catalyzes the reaction of phenylphosphonous tetraethyldiamide with 4,4′-dihydroxybiphenyl. Cross-linking in the solid state of the oligo(4,4′-biphenylene phenylphosphonite) containing terminal phosphonamidite group leads to gradual increase in the molecular weight and is accompanied by redox processes.     

Experimental and theoretical study of the charge transport property of 4,4′-N,N′-dicarbazole-biphenyl

The hole and electron mobilities of the amorphous films of the organic semiconductor 4,4′-N,N′-dicarbazole-biphenyl (CBP) at different electric fields were measured through the time of flight (TOF) method. Based on its crystalline structure, the hole and electron mobilities of CBP were calculated. A detailed comparison between experimental and theoretical results is necessary for further understanding its charge transport properties. In order to do this, charge mobilities at zero electric field, μ(0), were deduced from experimental data as a link between experimental and theoretical data. It was found that the electron transport of CBP is less affected by traps compared with its hole transport. This unusual phenomenon can be understood through the distributions of frontier molecular orbitals. We showed that designing materials with frontier molecular orbitals localized at the center of the molecule has the potency to reduce the influence of traps on charge transport and provide new insights into designing high mobility charge transport materials.     

Structure influence of chiral 1,1′-biscarboline-N,N′-dioxide on the enantioselective allylation of aldehydes with allyltrichlorosilanes

A series of new axially chiral 1,1′-biscarboline-N,N′-dioxide Lewis base organocatalysts were examined in the asymmetric allylation of aldehydes with allyltrichlorosilane. The chiral catalysts (R)-1a–e bearing ester groups in 3,3′ position provided good yields of the homoallyl alcohols with excellent enantioselectivities up to 99% for a broad substrate scope that covers aliphatic, aromatic, heteroaromatic, and α,β-unsaturated aldehydes. Solvent effects on the conversion and enantioselectivity were elucidated, and CH₂Cl₂ proved to be the optimal solvent for the reactions. In addition, the allylation with crotyltrichlorosilane was explored and the result showed that anti-isomer was favored from (E)-crotyltrichlorosilane with complete diastereoselectivity.     

Reactions of N-Allyl- and N-Propargyltriflimides with N,N′-Disubstituted Carbodiimides

The alkylating activity of N-allyl- and N-propargyltriflimides toward N,N′-dicyclohexyl- and N,N′-diphenylcarbodiimides has been studied. Activation of the nitrogen atom by two electron-withdrawing trifluoromethanesulfonyl groups favors cleavage of the C–N bond in the absence of a catalyst with the formation of N-substituted unsaturated ureas.

     

Cyclopalladated complexes of 2-phenylbenzothiazole with 4,4′-bipyridyl

Complexes [Pd(bt)(4,4′-bpy)OOCCH₃], [Pd(bt)NO₃]₂(m-4,4′-bpy), [Pd(bt)(m-4,4′-bpy)]₄(NO₃)₄ (bt⁻ is deprotonated form of 2-phenylbenzothiazole, bpy is 4,4′-bipyridyl) are prepared and characterized by ¹H NMR, electron absorption and emission spectroscopy, as well as by voltammetry. The upfield shift of the signal of proton in the ortho-position to the donor carbon atom of the cyclopalladated ligand in the complexes [(Δδ = −(1.1–1.5) ppm] is assigned to the anisotropic effect of the ring current of the pyridine rings of the 4,4′-bipyridyl moiety, which are orthogonal to the coordination plane. Characteristic longwave absorption bands λ = (387±4) nm and the low-temperature phosphorescence bands λ = (512±3) nm in the complexes are assigned to the chromophore {Pd(bt)} metal complex fragment. The reduction waves in the complexes [E _1/2 = −(1.54±0.04) and E _p = −(1.83±0.03) V] are assigned to the ligand-centered processes of the successive electron transfer to the π* orbitals localized predominantly on the coordinated pyridine components of the 4,4′-bipyridyl moiety.     

Electronic structure and electro-optical properties of ion radicals formed during the reduction of N,N′-dialkylsubstituted salts of 4,4′-bipyridyl

Symmetric N,N′-disubstituted salts of 4,4′-bipyridyl (viologens) are synthesized and described. It is shown by cyclic voltammetry that disubstituted salts of 4,4′-bipyridyl have a tendency toward reversible two-electron reduction. Normal first and second step oxidation-reduction potentials with respect to saturated silver chloride electrodes at various potential scan rates are found. The spectra of the high-resolution electron paramagnetic resonance of viologen cation radicals formed during the reduction of N,N′-disubstituted salts of 4,4′-bipyridyl are obtained and interpreted. It is established that the nature of substitutes and counterions in a viologen molecule considerably influences the distribution of its spin density, voltammetric curves, and electro-optical properties.     

2,7-Dibromonaphthalene and 4,4′-dibromobiphenyl in the synthesis of oxadiamine N,N, N′, N′-tetraaryl derivatives and studies of formation of bismacrocyclic compounds from them

Russian Chemical Bulletin - The Pd-catalyzed tetraarylation of diamines and oxadiamines with 2,7-dibromonaphthalenes and 4,4′-dibromobiphenyl was studied. These reactions gave the...     

Cyclopalladation of N,N,N′,N′-tetramethylisophthalthioamide

Summary N,N,N,N-Tetramethylisophthalthioamide (Hmpt) was cyclopalladated with PdCl₂ in hot dimethylsulphoxide to give [PdCl(mpt)]. The structure was determined by X-ray analysis. The thioamide is metallated at C(2) to act as an S528-01C528-02S tridentate anionic ligand. There is appreciable steric repulsion between the benzene ring H(4, 6) and the dimethylamino groups. The hydrogens and the methyl groups mutually deviate from the coordination plane in opposite directions. The stability of the fused 5,5-membered chelate ring formed by the S528-03C528-04S ligand seems to overcome the steric hindrance. Derivatives were prepared by replacement of the chloride ion with iodide, diethyldithiocarbamate, 4-tert-butylpyridine, or tri-n-butylphosphine, and characterized spectroscopically. The S528-05C528-06S-fused chelate ring was maintained in these derivatives.