catena‐Poly­[[di‐μ‐benzoato‐κ4O:O′‐disilver(I)]‐μ‐N,N′‐bis(2‐fluoro­benzyl­idene)­butane‐1,4‐di­amine‐κ2N:N′]

The title complex, [Ag₂(C₇H₅O₂)₂(C₁₈H₁₈F₂N₂)]_n, is a dinuclear silver(I) compound with one inversion centre between pairs of Ag atoms and another at the mid‐point of the central C—C bond in the butane‐1,4‐diamine moiety. Each of the smallest repeat units consists of two silver(I) cations, two benzoate anions and one N,N′‐bis(2‐fluorobenzyl­idene)­butane‐1,4‐di­amine Schiff base ligand. Each Ag^I ion is three‐coordinated in a trigonal configuration by two O atoms from two benzoate anions and one N atom from a Schiff base ligand. The di‐μ‐benzoato‐disilver(I) moieties are linked by the bridging Schiff base ligand, giving zigzag polymeric chains with an [–Ag⋯Ag—N—C—C—C—C—N–]_n backbone running along the b axis.     

The stability of water‐ and fat‐soluble vitamin in dentifrices according to pH level and storage type

The purpose of this study is to evaluate the vitamin stabilities in dentifrices by analyzing various vitamins according to the level and storage temperature. The stabilities of water‐ and fat‐soluble vitamins were investigated in buffer solution at different pH values (4, 7, 8, 10 and 11) for 14 days and in dentifrices at different pH (7 and 10) for 5 months at two temperature conditions (room and refrigeration temperature) by analyzing the remaining amounts using HPLC methods. In the buffer solution, the stability of vitamins B₁, B₆ and C was increased as the pH values increased. Vitamins E and K showed poor stability at pH 4, and vitamin B₃ showed poor stability at pH 11. In dentifrices, the storage temperature highly influenced vitamin stability, especially vitamins C and E, but the stabilities of vitamins B₁ and C according to pH values did not correspond to the buffer solution tests. Vitamin B group was relatively stable in dentifrices, but vitamin C completely disappeared after 5 months. Vitamin K showed the least initial preservation rates. Vitamins were not detected in commercial dentifrices for adults and detected amounts were less than the advertised contents in dentifrices for children. Copyright © 2015 John Wiley & Sons, Ltd.     

Homo‐ and copolymerization of norbornene derivatives with ethene by ansa‐fluorenylamidodimethyltitanium activated with methylaluminoxane

(t‐BuNSiMe₂Flu)TiMe₂ ( 1 ) activated with Me₃Al‐free methylaluminoxane (dried MAO) which conducts vinyl addition polymerization of norbornene (N) with very high activity was applied for homopolymerization of N derivatives (i.e., 5‐vinyl‐2‐norbornene (5V2N), 5‐ethylidene‐2‐norbornene (5E2N), dicyclopentadiene (DCPD)) at 40 °C. The activities for the N derivatives were about two orders of magnitude lower than that for N and decreased in the following order: 5E2N ? 5V2N ? DCPD. Copolymerization of ethene (E) and 5E2N under an atmospheric pressure of E was then conducted by 1 ‐dried MAO. The copolymerization proceeded with better activity than the homopolymerization of 5E2N and gave poly(E‐co‐5E2N) with narrow molecular weight distribution. The content of the ethylidene group in poly(E‐co‐5E2N) was controlled by the feed ratio of 5E2N/E. The T_g value of the copolymer changed from 70 °C to 155 °C according to the 5E2N content from 27 mol % to 68 mol %. The addition of N as a third monomer to the E‐5E2N copolymerization improved the activity and raised the T_g values of the terpolymer above 200 °C. The content of 5E2N was controlled by the 5E2N/N ratio with keeping the high T_g values. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4581–4587, 2007     

Mixed‐valence class I transition and electrochemistry of bis(triphenylamine)‐based aramids containing isolated ether‐linkage

A series of solution‐processable electrochromic (EC) aromatic polyamides with bis(triphenylamine)ether (TPAO) units in the backbone were prepared by the phosphorylation polyamidation from a newly synthesized diamine monomer, bis(N‐4‐aminophenyl‐N‐4‐methoxyphenyl‐4‐aminophenyl)ether, and various dicarboxylic acids. These polymers were highly soluble in many organic solvents and showed useful levels of thermal stability associated with high glass‐transition temperatures and high char yields (higher than 50 at 800 °C in nitrogen). The polymer films showed reversible electrochemical oxidation and electrochromism with high contrast ratio in the visible range, which also exhibited moderate coloration efficiency (CE), low switching time, and good stability. Especially, the polyamides with two electroactive nitrogen centers only showed one‐stage oxidative coloring (no intervalence charge‐transfer [IV‐CT] band was detected), implying the two electrons are simultaneously removed from the TPAO units on account of the ether‐linkage definitely isolated the two redox centers. The mixed‐valence (MV) Class I/II/III transition and electrochemistry of the synthesized model compounds were investigated for the bridged triarylamine system with various N? N distances and intramolecular electron transfer (ET) capability. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Poly[2,7‐(9,9‐dihexylfluorene)‐alt‐pyridine] with donor‐acceptor architectures: A new series of blue‐light‐emitting alternating copolymers

A novel series of well‐defined alternating poly[2,7‐(9,9‐dihexylfluorenyl)‐alt‐pyridinyl] (PDHFP) with donor‐acceptor repeat units were synthesized using palladium (0)‐catalyzed Suzuki cross‐coupling reactions in good to high yields. In this series of alternating polymers, 2, 7‐(9,9‐dihexylfluorenyl) was used as the light emitting unit, and the electron deficient pyridinyl unit was employed to provide improved electron transportation. These polymers were characterized by ¹H‐NMR and ¹³C‐NMR, gel permeation chromatography (GPC), thermal analyses, and UV‐vis and fluorescence spectroscopy. The glass transition temperature of copolymers in nitrogen ranged from 110 to 148 °C, and the copolymers showed high thermal stabilities with high decomposition temperatures in the range of 350 to 390 °C in air. The difference in linkage position of pyridinyl unit in the polymer backbone has significant effects on the electronic and optical properties of polymers in solution and in film phases. Meta‐linkage (3,5‐ and 2,6‐linkage) of pyridinyl units in the polymer backbone is more favorable to polymer for pure blue emission and prevention of aggregation of polymer chain than para‐linkage (2,5‐linkage) of the pyridinyl units. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4792–4801, 2004     

From N‐Nitro to N‐Nitroamino: Preparation of High‐Performance Energetic Materials by Introducing Nitrogen‐Containing Ions

In the design of energetic materials, high energetic performance and good molecular stability are two main goals. Energetic functionalization which strives for maximum energy often results in unstable chemical bonds and causes safety problems in practical production and storage operations. In this work, N‐nitro‐ and N‐nitroamino‐functionalized mono‐ and bis(1,2,4‐triazoles) were synthesized and characterized by infrared, and multinuclear NMR spectra, and elemental analyses. The N‐nitroamino‐functionalization strategy was employed for bis(imidazole), leading to high density compound 14 (2.007 g cm^?3 at 100 K; 1.94 g cm^?3 at room temperature) and energetic salt 15 . While N‐nitro‐functionalized products are thermally unstable and highly moisture sensitive, N‐nitroamino‐functionalized energetic salts, which are comprised of additional nitrogen‐containing ions, exhibit good density, moderate to excellent structural stabilities, and high performance.     

Two different products from the reaction of 1‐aryl‐5‐chloro‐3‐methyl‐1H‐pyrazole‐4‐carbaldehyde with cyclohexylamine when the aryl substituent is phenyl or pyridin‐2‐yl: hydrogen‐bonded sheets versus dimers

Cyclohexylamine reacts with 5‐chloro‐3‐methyl‐1‐(pyridin‐2‐yl)‐1H‐pyrazole‐4‐carbaldehyde to give 5‐cyclohexylamino‐3‐methyl‐1‐(pyridin‐2‐yl)‐1H‐pyrazole‐4‐carbaldehyde, C₁₆H₂₀N₄O, (I), formed by nucleophilic substitution, but with 5‐chloro‐3‐methyl‐1‐phenyl‐1H‐pyrazole‐4‐carbaldehyde the product is (Z)‐4‐[(cyclohexylamino)methylidene]‐3‐methyl‐1‐phenyl‐1H‐pyrazol‐5(4H)‐one, C₁₇H₂₁N₃O, (II), formed by condensation followed by hydrolysis. Compound (II) crystallizes with Z′ = 2, and in one of the two independent molecular types the cyclohexylamine unit is disordered over two sets of atomic sites having occupancies of 0.65 (3) and 0.35 (3). The vinylogous amide portion in each compound shows evidence of electronic polarization, such that in each the O atom carries a partial negative charge and the N atom of the cyclohexylamine portion carries a partial positive charge. The molecules of (I) contain an intramolecular N—H...N hydrogen bond, and they are linked by C—H...O hydrogen bonds to form sheets. Each of the two independent molecules of (II) contains an intramolecular N—H...O hydrogen bond and each molecular type forms a centrosymmetric dimer containing one R₂²(4) ring and two inversion‐related S(6) rings.     

Synthese und Molekülstrukturen von N‐substituierten Diethylgallium‐2‐pyridylmethylamiden

Synthesis and Molekular Structures of N‐substituted Diethylgallium‐2‐pyridylmethylamides (2‐Pyridylmethyl)(tert‐butyldimethylsilyl)amine ( 1a ) and (2‐pyridylmethyl)‐di(tert‐butyl)silylamine ( 1b ) form with triethylgallane the corresponding red adducts 2a and 2b via an additional nitrogen‐gallium bond. These oily compounds decompose during distillation. Heating under reflux in toluene leads to the elimination of ethane and the formation of the red oils of [(2‐pyridylmethyl)(tert‐butyldimethylsilyl)amido]diethylgallane ( 3a ) and [(2‐pyridylmethyl)‐di(tert‐butyl)silylamido]diethylgallane ( 3b ). In order to investigate the thermal stability solvent‐free 3a is heated up to 400 °C. The elimination of ethane is observed again and the C‐C coupling product N, N′‐Bis(diethylgallyl)‐1, 2‐dipyridyl‐1, 2‐bis(tert‐butyldimethylsilyl)amido]ethan ( 4 ) is found in the residue. Substitution of the silyl substituents by another 2‐pyridylmethyl group and the reaction of this bis(2‐pyridylmethyl)amine with GaEt₃ yield triethylgallane‐diethylgallium‐bis(2‐pyridylmethyl)amide ( 5 ). The metalation product adds immediately another equivalent of triethylgallane regardless of the stoichiometry. The reaction of GaEt₃ with 2‐pyridylmethanol gives quantitatively colorless 2‐pyridylmethanolato diethylgallane ( 6 ).     

Syntheses,Structure, Electrochemistry,and Optical Properties of 1,3‐Diethyl‐2,3‐dihydro‐1‐H‐1,3,2‐pyrido‐[4,5‐b]‐diazaboroles

Reaction of 2,5‐bis(dibromoboryl)thiophene ( 4 ) or 1,4‐bis(dibromoboryl)benzene ( 6 ) with two equivalents of N,N′‐dilithiated 2,3‐diaminopyridine ( 3 ) led to the generation of the pyridodiazaboroles 5 and 7 in which the two diazaborole rings are linked by 2,5‐thiophen‐diyl or 1,4‐phenylene units via the boron atom. The novel compounds were characterized by elemental analyses and spectroscopy (¹H‐, ¹¹B‐, ¹³C‐NMR, MS, and UV‐VIS). The molecular structure of 5 was elucidated by X‐ray diffraction. Cyclovoltammograms of 5 and 7 show two irreversible oxidation waves at 0.76 and 0.73 V, respectively vs Fc/Fc⁺. The novel compounds display intense blue luminescence with Stokes shifts of 76 and 74 nm and relative quantum yields of 39 and 43 % vs Coumarin 120 (Φ = 50 %).     

Nitrogen‐Rich Amino‐triazolium Salts Based on Binary 4,5‐Dicyano‐1,2,3‐triazolate (C4N5–) Anion

A series of amino‐triazolium salts based on 4,5‐dicyano‐1,2,3‐triazolate (C₄N₅^–) anion were synthesized for first time by means of facile deprotonation reactions. The ionic compounds were characterized by single‐crystal X‐ray diffraction, vibrational spectroscopy, and elemental analysis. The thermal stability of the salts was assessed by differential scanning calorimetry, which showed good thermal stabilities up to above 180 °C. The heats of formation of these salts were computed using the methods of isodesmic reactions. In addition, the sensitivities of the studied salts toward impact and friction were determined, and all salts were found to be neither impact (> 40 J) nor friction sensitive (> 360 N).     

Insensitive and Thermostable Energetic Materials Based on 3‐Ureido‐4‐tetrazole‐furazan: Synthesis,Characterization, and Properties

Energetic salts composed of ureido, furazan, and tetrazole were prepared by simple and efficient chemical routes to explore new insensitive and thermostable energetic materials. 3‐Ureido‐4‐tetrazole‐furazan ( 3 ) and its ammonium salt ( 5 ) and hydrazinium salt ( 6 ) were confirmed by single‐crystal X‐ray diffraction. The thermal stabilities of the synthesized salts were studied using differential scanning calorimetry, and the detonation performances of these salts were calculated using EXPLO 5 V6.01. All the salts exhibit good thermal stability (Td: 148–259 °C) and mechanical sensitivities (IS > 40 J, FS > 360 N), and their detonation velocities range from 7316 to 8655 m · s^–1. Compounds 6 and 10 are potential candidates as novel insensitive and heat‐resistant explosives because of their high detonation temperatures of 247 and 256 °C, good detonation velocities of 8432 and 8523 m · s^–1, and good detonation pressures of 25.6 and 26.8 GPa.     

1‐(4,6‐Diethoxy­pyrimidin‐2‐yl)‐2‐thioxo‐2,3‐dihydro­pyrido[2,3‐d]pyrimidin‐4(1H)‐one

In the title compound, C₁₅H₁₅N₅O₃S, two parallel inter­molecular N—H⋯S hydrogen bonds, forming an eight‐membered ring, link two mol­ecules into a dimer unit; these dimer units linked into a chain of edge‐fused rings by weak C—H⋯O hydrogen bonds.     

The first crystal structures of six‐ and seven‐membered tellurium‐ and nitrogen‐containing (Te—N) heterocycles: 2H‐1,4‐benzotellurazin‐3(4H)‐one and 2,3‐dihydro‐1,5‐benzotellurazepin‐4(5H)‐one

There is a paucity of data concerning the structures of six‐ and seven‐membered tellurium‐ and nitrogen‐containing (Te—N) heterocycles. The title compounds, C₈H₇NOTe, (I), and C₉H₉NOTe, (II), represent the first structurally characterized members of their respective classes. Both crystallize with two independent molecules in the asymmetric unit. When compared to their sulfur analogs, they exhibit slightly greater deviations from planarity to accommodate the larger chalcogenide atom, with (II) adopting a pronounced twist‐boat conformation. The C—Te—C angles of 85.49 (15) and 85.89 (15)° for the two independent molecules of (I) were found to be somewhat smaller than those of 97.4 (2) and 97.77 (19)° for the two independent molecules of (II). The C—Te bond lengths [2.109 (4)–2.158 (5) Å] are in good agreement with those predicted by the covalent radii. Intermolecular N—H...O hydrogen bonding in (I) forms centrosymmetric R₂²(8) dimers, while that in (II) forms chains. In addition, intermolecular Te...O contacts [3.159 (3)–3.200 (3) Å] exist in (I).     

Silyl‐Terminated Ethylene‐co‐Norbornene Copolymers by Organotitanium‐Based Catalysts

Ethylene (E) and norbornene (N) were copolymerized in the presence of PhSiH₃ as chain‐transfer agent with [Ti(η⁵:η¹‐C₅Me₄SiMe₂NBu^t)(η¹‐Me)₂] precatalyst combined with [Ph₃C][B(C₆F₅)₄]. The silane was introduced at chain‐ends of E‐co‐N copolymers with concomitant reinitiation of the growing polymer chain. The concentrations of the silane and polymer molecular weight are inversely correlated. The characteristic signals of  SiH₂Ph chain‐ends were observed by ¹H NMR. The Si heteroatom is predominantly adjacent to ethylene units in E‐co‐N copolymers with high N content.

     

Quantum chemistry aspects of the solvent effects on the ene reaction of 1‐Phenyl‐1,3,4‐triazolin‐2,5‐dione and 2‐methyl‐2‐butene

A density functional theory study was used to investigate the quantum aspects of the solvent effects on the kinetic and mechanism of the ene reaction of 1‐phenyl‐1,3,4‐triazolin‐2,5‐dione and 2‐methyl‐2‐butene. Using the B3LYP/6–311++ G(d,p) level of the theory, reaction rates have been calculated in the various solvents and good agreement with the experimental data has been obtained. Natural bond orbital analysis has been applied to calculate the stabilization energy of N18? H19 bond during the reaction. Topological analysis of quantum theory of atom in molecule (QTAIM) studies for the electron charge density in the bond critical point (BCP) of N18? H19 bond of the transition states (TSs) in different solvents shows a linear correlation with the interaction energy. It is also seen form the QTAIM analysis that increase in the electron density in the BCP of N18? H19, raises the corresponding vibrational frequency. Average calculated ratio of 0.37 for kinetic energy density to local potential energy density at the BCPs as functions of N18? H19 bond length in different media confirmed covalent nature of this bond. Using the concepts of the global electrophilicity index, chemical hardness and electronic chemical potentials, some correlations with the rate constants and interaction energy have been established. Mechanism and kinetic studies on 1‐phenyl‐1,3,4‐triazolin‐2,5‐dione and 2‐methyl‐2‐butene ene reaction suggests that the reaction rate will boost with interaction energy enhancement. Interaction energy of the TS depends on the solvent nature and is directly related to electron density of the bonds involved in the reaction proceeding, global electrophilicity index and electronic chemical potential. However, the chemical hardness relationship is reversed. Finally, an interesting and direct correlation between the imaginary vibrational frequency of the N18? H19 critical bond and its electron density at the TS has been obtained. © 2014 Wiley Periodicals, Inc.     

5α‐Androst‐3‐en‐17‐one oxime

The title compound, C₁₉H₂₉NO, is a C17‐oxime derivative of a potent aromatase inhibitor, which surprisingly has been found to have no inhibitory power. It crystallizes with two independent molecules in the asymmetric unit. C=N—O—H...N hydrogen bonds link pairs of molecules to form dimers almost parallel to the bc plane. Cohesion of the structure is also due to another three C—H...O hydrogen bonds directed along the a axis. This hydrogen‐bonding scheme can be correlated to the almost complete loss of inhibitory power of the title compound.     

5′‐Allyl‐2′‐benzoyloxy‐3′‐methoxy‐4‐nitroazobenzene

The structure of the title compound, 4‐allyl‐2‐methoxy‐6‐[(4‐nitrophenyl)diazenyl]phenyl benzoate, C₂₃H₁₉N₃O₅, displays the characteristic features of azobenzene derivatives. The azobenzene moiety of the molecule has a trans configuration and in this moiety, average C—N and N=N bond lengths are 1.441 (3) and 1.241 (3) Å, respectively.     

N,N′‐Bis(2‐pyridyl)benzene‐1,2‐diamine

Hindered rotation about the partial double C—N bonds between the amine and pyridine moieties in the title mol­ecule, C₁₆H₁₄N₄, results in two different conformations of the N‐aryl‐2‐amino­pyridine units. One, assuming an E conformation, is involved in a pair of N—H⋯N hydrogen bonds that generate a centrosymmetric (8) motif. The second, adopting a Z conformation, is not engaged in any hydrogen bonding and is flattened, the dihedral angle between the benzene and pyridine rings being 12.07 (7)°. This conformation is stabilized by an intramolecular C—H⋯N interaction [C⋯N = 2.9126 (19) Å, H⋯N = 2.31 Å and C—H⋯N = 120°].     

Synthesis and characterization of new aromatic polyamides bearing crown ethers or their dipodal counterparts in the pendant structure. I. Benzo‐12‐crown‐4 and ortho‐bis(2‐ethoxyethoxy)benzene

Two novel isophthalic diacid‐based monomers have been synthesized by inclusion in ring position 5 of a functionalized benzoylamine moiety. The functionalization includes a 12‐crown‐4 ether group fused with the benzene subunit and a dipodand substructure, formally a disubstitution of the benzene ring, with two sequences of ethyl‐terminated ethylene oxide units, which represent the open‐chain counterpart of the alicylic crown moiety. The polycondensation of the two diacids with five aromatic diamines yielded 10 new polyamides with crown or podand pendant substructures. The polyamides had previously been chemically characterized by NMR, IR, and elemental analysis. The polymers showed high glass transition temperatures of up to 349 °C, good thermal stability (T_{donset, N2} ≈ 400 °C), and improved solubility in organic solvents. The presence of acyclic or alicyclic oxyethylene sequences as crown ether or podand substructures and an additional amide side group per repeat unit made the polymers essentially amorphous and improved their water absorption ability in comparison with nonsubstituted polyamides. Water uptake values as high as 12% were observed at 65% relative humidity. All the polyamides showed a good film‐forming ability, and the mechanical properties of these films are considered to be satisfactory for experimental aromatic polyamides. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2270–2281, 2006     

2‐Diazo‐2H‐indoles

2‐Diazo‐2H‐indoles were prepared by diazotization of the corresponding 1H‐indol‐2‐amines and subsequent neutralization. On the basis of NMR data and ab initio and semiempirical calculations, we suggest that the zwitterionic form A is the most representative structure for 2‐diazo‐2H‐indoles. In fact, spectral data are compatible with a 1H‐indole structure, and the fully optimized molecules gave distances in agreement with those reported for the anion obtained from 1H‐indole. The calculated charges are compatible with a zwitterionic structure in which the negative charge is mainly located at the ring N‐atom at variance with the case of diazopyrroles and 3‐diazo‐3H‐indoles where the negative charge is essentially located on the ipso C‐atom.