Showing papers on "Triazene published in 2012"

Rhodium(III)-catalyzed C-H activation of arenes using a versatile and removable triazene directing group.

Abstract: Diverse opportunities: A Rhodium(III)-catalyzed ortho-selective olefination of arenes using a novel triazene as a directing group is reported. This method exhibits substantial post-functionalization synthetic versatility, overcoming a vital limitation in C sp 2-H activation/functionalization products: restricted structural diversity.

Tuning nonlinear optical and optoelectronic properties of vinyl coupled triazene chromophores: a density functional theory and time-dependent density functional theory investigation

Abstract: Triazenes are a unique class of polyazo compounds containing three consecutive nitrogen atoms in an acyclic arrangement and are promising NLO candidates. In the present work, a series of 15 donor-π-acceptor type vinyl coupled triazene derivatives (VCTDs) with different acceptors (−NO2, −CN, and −COOH) have been designed, and their structure, nonlinear response, and optoelectronic properties have been studied using density functional theory and time-dependent density functional theory methods. B3LYP/6-311g(d,p) optimized geometries of the designed candidates show delocalization from the acceptor to donor through a π-bridge. Molecular orbital composition analysis reveals that HOMO is stabilized by the π-bridge, whereas acceptors play a major role in the stabilization of LUMO. Among the three acceptors, nitro derivatives are found to be efficient NLO candidates, and tri- and di-substituted cyano and carboxylic acid derivatives also show reasonably good NLO response. The effect of solvation on these propertie...

Novel one-pot synthesis of thiophenols from related triazenes under mild conditions

Abstract: In this work, at first, triazenes were synthesized from primary aryl amines. Afterwards, triazenes were converted into the corresponding thiophenols in one-pot using sodium sulfide in acidic media, by in situ generation of diazonium counterion beside hydrogen sulfide as anionic sulfur nucleophile at room temperature. The procedure can be a convenient shortcut for the preparation of thiophenols from primary aryl amines.

5-(1-(4-phenyl)-3-(4-nitrophenyl)triazene)-10,15,20-triphenylporphyrin: a new triazene-porphyrin dye and its spectroelectrochemical properties

Abstract: The new triazene-porphyrin dye 5-(1-(4-phenyl)-3-(4-nitrophenyl)triazene)-10,15,20-triphenylporphyrin, encompassing a reactive protonated triazene moiety, was prepared starting from meso-tetraphenylporphyrin (H2TPP), first converting it to the 5-(4-nitrophenyl)-10,15,20-triphenylporphyrin, then reducing to the 5-(4-aminophenyl)-10,15,20-tri(phenyl)porphyrin intermediate, and reacting with the diazonium salt of 4-nitroaniline; and characterized by spectroscopic and electrochemical methods. The absorption spectrum of the neutral species resembled the sum of H2TPP and of 1,3-bis(4-nitrophenyl)triazene spectrum, but the deprotonated anionic species showed more delocalized frontier orbitals, behaving as a push-pull system exhibiting triazenide-to-porphyrin charge-transfer transitions.

Synthesis, Structure, and Solution Study of a Mercury(II) Complex with the Ligand [1‐(2‐Methoxyphenyl)‐3‐(4‐chlorophenyl)]triazene

Abstract: The title ligand, [1-(2-methoxyphenyl)-3-(4-chlorophenyl)]triazene, HL (1), was prepared. In a reaction with Hg(NO3)2 it forms the complex [Hg(C26H22Cl2N6O2)], [HgL2] (2). Both compounds were characterized by means of X-ray crystallography, CHN analysis, FT-IR, 1H NMR, and 13C NMR spectroscopy. In the structure of compound 1, two independent fragments are present in the unit cell. They exhibit trans arrangement about the –N=N– double bond. The dihedral angles between two benzene rings in both fragments are 4.36 and 18.79 A, respectively. Non-classic C–H···N hydrogen bonding and C–H···π interactions form a layer structure along the crystallographic ab plane [110]. In compound 2, the HgII atom is hexacoordinated by two tridentate [1-(2-methoxyphenyl)-3-(4-chlorophenyl)]triazenide ligands through a N2O2 set. In addition, in the structure of 2, monomeric complexes are connected to each other by C–H···π stacking interactions, resulting in a 2D architecture. These C–H···π edge-to-face interactions are present with H···π distances of 3.156 and 3.027 A. The results of studies of the stoichiometry and formation of complex 2 in methanol solution were found to support its solid state stoichiometry.

Isolation and Properties of a Chain of Cyano-Bridged Complex {LCuII(μ-CN)}n With Triazenido Ligand and a Cyano-Bridged Mixed-Valence Complex {CuIICuI(μ-CN)3}n

Abstract: One reaction of 1-[(2-carboxymethyl) benzene]-3-[2-pyridine] triazene (HL) with CuCl2·2H2O, and NaCN gives a chain of cyano-bridged complex {LCuII(μ-CN)}n 1 and a cyano-bridged mixed-valence complex {CuIICuI(μ-CN)3}n 2, respectively. The X-ray crystal structures of both complexes have been obtained. Magnetic studies indicate significant antiferromagnetic coupling between the copper(II) centers for complex 1, with coupling constants (J) of –129.6 cm−1.

Photocatalytic cleavage of hydroxytriazenes: a solid-state synthesis of azo-dyes under sunlight irradiation

Abstract: Sunlight-induced decomposition of hydroxytriazenes, and green photochemical synthesis of azo-dyes is described. Three substituted hydroxytriazenes, viz: 3-hydroxy-3-(2-methylphenyl)-1-(3-chloro-4-fluorophenyl)triazene (o-CFHT), 3-hydroxy-3-(3-methylphenyl)-1-(3-chloro-4-fluorophenyl)triazene (m-CFHT), and 3-hydroxy-3-(4-methylphenyl)-1-(3-chloro-4-fluorophenyl)triazene (p-CFHT) were co-crystallized with β-naphthol in equimolar ratio and exposed to sunlight for 9–10 h. The reaction resulted in formation of azo-dyes which were identified by comparison with the products obtained by the conventional method (standard azo-dye), by use of HPLC. A probable mechanism has been suggested. This is first eco-friendly synthesis of azo-dyes using hydroxytriazenes.

Solid-Phase Synthesis of Phenylalanine Containing Peptides Using a Traceless Triazene Linker

Abstract: The use of a triazene function to anchor phenylalanine to a polymeric support through its side chain is reported. To prove the usefulness of this strategy in solid-phase peptide synthesis, several bioactive peptides have been prepared including cyclic, C-modified, and protected peptides. The triazene linkage is formed by coupling the diazonium salt of Fmoc-Phe(pNH2)-OAllyl to a MBHA-polystyrene resin previously functionalized with isonipecotic acid (90%). Further assembly of the peptide chain, cleavage from the resin using 2–5% TFA in DCM, and reduction of the resulting diazonium salt of the peptide with FeSO4·7H2O in DMF afforded the desired products in high purities (73–94%).

Study of Cyclyzation of o-(1-Alkynyl)- and o-(1,3-Butadiynyl)aryltriazenes under the Action of Acids

Abstract: The investigation of Richter cyclization of o-(1-alkynyl)- and o-(1,3-butadiynyl)arenediazonium salts generated by acid cleavage of triazenes was carried out by the methods of NMR and ESI MS (Electrospray Ionization Mass Spectrometry). The effect was shown of the substituents at the carbon atom of the triple bond and in the aromatic ring, of the solvent, temperature, and the reagents ratio on the rate of the cyclization and the yield of its products, 4-bromo-3-alkyl- and 4-bromo-3-ethynylcinnolines; the conditions of their synthesis were optimized. The possibility to use 4-bromo-3-ethynylcinnolines as substrates of electrophilic cyclization was demonstrated.

Structural and Solution Studies of two Mercury(II) Complexes with [1,3‐Bis(2‐ethoxy)benzene]triazene

Abstract: The reaction of [1,3-bis(2-ethoxy)benzene]triazene, [HL], with Hg(SCN)2 and Hg(CH3COO)2, resulted in the formation of the complexes [HgL(SCN)] (1) and [HgL2]·CH3OH (2). They were characterized by means of X-ray crystallography, CHN analysis, FT-IR, 1H NMR, and 13C NMR spectroscopy. The structure of compound 1 consists of two independent complexes in which the HgII atoms are stacked along the crystallographic a axis to form infinite chains. Each HgII atom is chelated by one L ligand and one SCN ligand, whereas in compound 2, the HgII atom is surrounded by two L ligands. In addition, 1D chains formed by metal–π interactions are connected to each other by C–H···π stacking interactions in the structure of 1, which results in a 2D architecture. An interesting feature of compound 2 is the presence of C–H···π edge-to-face interactions.

Synthesis and Structures of Dinuclear Copper(I) and Silver(I) 1, 3-Bis[(2-chloro)benzene]triazenide Complexes†

Abstract: In the presence of Et3N, the reaction of 1, 3-bis[(2-chloro)benzene]triazene (HL) with CuCl or AgNO3 gives the triazenide complexes {Cu2(L)2} (1) and {Ag2(L)2} (2), respectively. The X-ray crystal structures of both complexes were obtained. The metal–metal distances (Cu···Cu and Ag···Ag) are 2.4974(5) and 2.7208(5) A, respectively.

Synthesis and Reactivity of 1-[(2-methoxy)benzene]- 3-[benzothiazole]Triazene With Copper(II) or Cobalt(II) Chloride

Abstract: A new triazene, 1-[(2-methoxy)benzene]-3-[benzothiazole] triazene (HL), has been synthesized and charaterized In the presence of Et3N, the reaction of HL and CuCl2·2H2O or CoCl2·6H2O gives the triazenide complexes [Cu4L′4(μ-OMe)4] 1 (L′ 1-[benzothiazole]triazene ion) and [Co2L4] 2, respectively The X-ray crystal structures of both complexes have been obtained Magnetic studies indicate significant antiferromagnetic coupling between the copper(II) centers or cobalt(II) centers for complexes 1 and 2, with coupling constants (J) of –587 cm−1 for 1 and –147 cm−1 for 2 Complex 2 shows one reversible one-electron redox wave at –0835 V, and one irreversible oxidation at –0193 V, which are in accord with the redox potentials of [CoIII-CoII]/[CoII-CoII] and [CoIII-CoIII]/[CoII-CoII] couples, respectively

Grafting of 'push-pull' systems on germanium: towards the electric passivation

Abstract: Despite its excellent electronic properties, germanium is limited by the low passivation of its oxide. Therefore, new dielectrics must be developed. Furthermore, germanium sensitivity requires the creation of a passivation layer on the surface. Even if numerous studies were carried out on new inorganic dielectrics, this research project concerns the design, the realization and the development of thin passivating organic dielectric films on germanium for nanoelectronics applications. This work principally involves the synthesis of new push-pull molecules (π-conjugated systems bearing a donor and an acceptor part) and germanium functionalization. New donor-acceptor systems and π-conjugated linear systems containing an anchoring group were synthesized through new ways. In particular, a series of azobenzene derivatives with different acceptors (fluorinated groups, pyridinium, nitro) and donors (amines, alkoxyl) and various anchoring groups (thiol, carboxylic acid, diazonium salt, triazene) was obtained. Meanwhile, preparation and functionalization of germanium surfaces was studied. A new process to etch the native oxide and obtain halogenated surfaces with low roughness was developed. Germanium substrates were then functionalized with thiol but also with diazonium salts. This new spontaneous grafting process considerably decreased the reaction time (15 minutes spontaneous grafting of diazonium salts against 3 days for self-assembled monolayers of thiol formation) in mild conditions. Thin films obtained present stability similar to the one of thiol monolayers. Π-conjugated linear systems were grafted both as thiol and diazonium salt to probe the influence of the aromatic core on the film formation and properties. Finally, push-pull systems were also grafted. Electronic studies on gold with π-conjugated systems were realized. These studies were extended to germanium and allow expecting significant results with push-pull molecules.

Diaryl phosphine compounds

Abstract: A method for making diazo-compounds, diazonium salts thereof and other protected forms of these compounds. Diazo-compounds are prepared by reaction of a tertiary phosphine reagent carrying a reactive carbonyl group with an azide. The reaction can also generate an acyl triazene which can be converted thermally or by addition of base to form the diazo-compound or the acyl triazene can be isolated. The method is particularly useful for conversion of azides carrying one or more electron withdrawing groups to diazo-compounds. The method can be carried out in aqueous medium under mild conditions and is particularly useful for conversion of azido sugars to diazo-compounds and diazonium salts thereof under physiological conditions. Tertiary phosphine reagents, particularly those that are water-soluble, and precursors for preparation of the reagents are provided.

Rhodium(III)‐Catalyzed C—H Activation of Arenes Using a Versatile and Removable Triazene Directing Group.

Abstract: Arenes are selectively olefinated by acrylates or acrylonitrile at the ortho-position to the piperidine-, pyrrolidine-, or dibenzylamine-derived triazene directing group.