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Alejandro Bugarin - One of the best experts on this subject based on the ideXlab platform.
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π-Conjugated Triazenes: Intermediates That Undergo Oxidation and Substitution Reactions.
The Journal of organic chemistry, 2017Co-Authors: Enrique Barragan, Alejandro BugarinAbstract:Novel reactivity for π-conjugated Triazenes is herein reported. This observed and unprecedented Triazene reactivity gave access to oxidation and substitution reactions. These transformations include successful synthesis of aldehydes, ketones, ethers, and sulfides from readily available organic azides via π-conjugated Triazene intermediates. Notably, the afforded adducts were obtained in good yields, at room temperature, and in the absence of added metal catalysts.
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π‑Conjugated Triazenes: Intermediates That Undergo Oxidation and Substitution Reactions
2017Co-Authors: Enrique Barragan, Alejandro BugarinAbstract:Novel reactivity for π-conjugated Triazenes is herein reported. This observed and unprecedented Triazene reactivity gave access to oxidation and substitution reactions. These transformations include successful synthesis of aldehydes, ketones, ethers, and sulfides from readily available organic azides via π-conjugated Triazene intermediates. Notably, the afforded adducts were obtained in good yields, at room temperature, and in the absence of added metal catalysts
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novel Triazene dyes from n heterocyclic carbenes and azides syntheses stability and spectroscopic properties
Tetrahedron Letters, 2014Co-Authors: Siddappa A Patil, Kana White, Alejandro BugarinAbstract:abstract A series of substituted Triazene dyes were synthesized by coupling functionalized imidazol-2-ylideneswith various azides (alkyl, vinyl, aryl, and heteroaryl), in moderate to excellent yields. Their structureswere confirmed by spectroscopic studies (IR, NMR, UV–vis, and HRMS). Additionally, the solid-statestructure of Triazene dye 7 was secured by single crystal X-ray diffraction. Electron delocalizationbetween the two coupled components was studied using UV–vis spectroscopy. The respective Triazeneswere found to exhibit k max values ranging between 294 and 450 nm. 2014 Elsevier Ltd. All rights reserved. Triazenes are very useful and versatile tools in organic synthesisandhavebeenusedbroadlyinmultipleapplications,includingpro-tecting groups for diazonium salts and amines, 1 halide-maskinggroups in the synthesis of small molecules, 2 macro-molecules, 3 and photoactive substrates. 4 Triazenes can also be converted intodifferent reactive and functional groups with the correct set ofreagents, depending on the anticipated application.
Zahary Raikov - One of the best experts on this subject based on the ideXlab platform.
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Superoxide scavenging activity of spin-labeled nitrosourea and Triazene derivatives.
Free Radical Research, 1994Co-Authors: Vesselina Gadzheva, Kohji Ichimori, Hiroe Nakazawa, Zahary RaikovAbstract:Superoxide scavenging activities (SSA) of newly synthesized spin-labeled nitrosourea and Triazene derivatives, and their precursor nitroxides were investigated by the ESR/spin-trapping method using the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and hypoxanthine/xanthine oxidase as the superoxide-generating system. The spin-labeled nitrosoureas, Triazenes and their precursor nitroxides exhibited excellent SSA, whereas clinically used nitrosourea and Triazene, which do not contain the nitroxide moiety, did not show any SSA. Furthermore, it was deduced that these nitroxides scavenge superoxide by redox cycling between nitroxide and corresponding hydroxylamine.
Alexander Wokaun - One of the best experts on this subject based on the ideXlab platform.
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Laser-Induced Forward Transfer Using Triazene Polymer Dynamic Releaser Layer
2010Co-Authors: James Shaw Stewart, Thomas Lippert, Matthias Nagel, Frank Nüesch, Alexander WokaunAbstract:This article presents a short review of the use of Triazene polymer as a dynamic release layer (DRL) for laser-induced forward transfer (LIFT), before looking at the latest research in more detail. The field of Triazene polymer ablation only started around 20 years ago and has grown rapidly into a number of different application areas. Most promisingly, Triazene ablation has been refined as a method for propulsion, bringing the benefits of LIFT to the deposition of sensitive transfer materials. The key to understanding LIFT with a Triazene DRL is to understand the more fundamental nature of Triazene polymer ablation in both frontside and backside orientations. This article focuses on the most recent experimental results on LIFT with a Triazene DRL: the effect of picosecond pulse lengths compared with nanosecond pulse lengths; the effect of reduced air pressure; and the improvements in transfer in terms of range of transfer materials, and transfer across a gap. The results all help improve fundamental understanding of Triazene-based LIFT, and the transfer of functioning OLEDs demonstrates the capability of the technique.
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laser ablation of polymers studied by ns interferometry and ns shadowgraphy measurements
Applied Surface Science, 2003Co-Authors: Michelle Hauer, D J Funk, Thomas Lippert, Alexander WokaunAbstract:Abstract The dynamic processes during ablation are studied by nanosecond-interferometry and shadowgraphy. Most commercial polymers exhibit poor laser ablation properties, therefore special Triazene polymers, with superior ablation properties were developed. The photochemical active Triazene group absorbs around 330 nm whereas the absorption around 200 nm is due to the photostable aromatic groups. The ns-interferometry shows that the etching of the Triazene polymer starts and ends with the laser beam after irradiation at 193 and 308 nm. Shadowgraphy of the Triazene polymer and polyimide reveal that the speed of the aerial shockwave increases with fluence and is higher for irradiation at 193 nm than for 308 nm. Shockwaves with equal or higher velocities are observed for the Triazene polymer compared to polyimide.
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Excimer laser ablation of Triazene-containing polyesters with different topologies
Acta Polymerica, 1998Co-Authors: O. Nuyken, Alexander Wokaun, U. Dahn, Th. Kunz, C. Hahn, Volker Hessel, J. LandsiedelAbstract:We report on excimer laser polymer ablation experiments on polymers with Triazene groups (Ph-N=N-NR 2 ) as well as their photolytical behavior. Two polyesters incorporating the photosensitive Triazene group and their main chain (PEla,b) are compared with one that contains this group as a pendant unit (PE2). With respect to the characteristic ablation parameters, there is no significant difference between these species but in comparison to a triazeno-polysulfide we observe increased efficiency in terms of the saturation depth d max . In contrast, the quality of the patterns depends on the topology of the Triazene-containing polyester: the main-chain polyester displays ablation micropatterns of improved quality. The photolysis in solution occurs faster for the main-chain polymers built up from cyclic monomers than for open ring structures. Polymeric Triazenes are photolyzed slower than the corresponding monomeric diols.
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Photolysis, thermolysis, and protolytic decomposition of a Triazene polymer in solution
Macromolecular Chemistry and Physics, 1995Co-Authors: Oskar Nuyken, Alexander Wokaun, Thomas Lippert, Jürgen Stebani, Andrej StaškoAbstract:The depolymerization of a triazeno-group containing photopolymer, poly[oxy-1,4-phenyleneazo(methylimino)hexamethylene(methylimino)azo-1,4-phenylene], is investigated in a tetrahydrofuran (THF) solution. Irradiation of the material leads to a clean decomposition of the photolabile polymer, as monitored by UV spectroscopy and gel-permeation chromatography (GPC). As compared to the photolysis in THF solution, the light-induced decomposition rate of a polymer in a polymer film is shown to be much slower. The highly photosensitive triazeno group also decomposes thermally at temperatures above approx. 220°C. The kinetics of thermal degradation of the polymer in substance was investigated at a temperature of 256°C, and monitored by GPC measurements. During this decomposition, one first observes the development of higher molar-mass fractions, which result from grafting reactions of primary radicals. Upon further thermolysis the Triazene polymer is completely degraded to low-molar-mass products. The volatile decomposition products were identified by gas chromatography/mass spectrometry (GC/MS) analysis. The protolytic decomposition, which represents the retrosynthesis of the Triazene polymer, was studied in a 9:1 mixture of tetrahydrofuran and an aqueous citrate buffer solution. Although the decomposition rate in this solvent mixture is slow, as compared to the depolymerization in diluted hydrochloric acid, a clean decomposition of the Triazene polymer is obtained.
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Synthesis and characterization of a novel photosensitive Triazene polymer
Die Makromolekulare Chemie Rapid Communications, 1993Co-Authors: Jiirgen Stebani, Thomas Lippert, Oskar Nuyken, Alexander WokaunAbstract:Triazene compounds have recently attracted attention due to a variety of interesting properties. The cytostatic activity discovered for several substituted Triazenes *) has stimulated intense research efforts directed towards the development of Triazene-based drugs3). In view of the importance of this field, several reviews on the synthesis of Triazenes are available4-’). A second class of applications is based on the fact that the triazeno group is comparatively stable with respect to thermal decomposition, but undergoes facile photo-chemical cleavage releasing nitrogen. This property, which may lead to novel applications in photolithography and photoreproduction, is the motivation for the present study. Photopolymers which can be structured by light are important materials in the microelectronics industry. Laser ablation of polymers ‘3 ’) has been intensively investigated in this context; the laser treatment represents a dry processing technique, without the need for wet processing steps. Powerful XeC1*-excimer lasers emitting at 308 nm are available for reliable large-scale industrial operation, making it desirable to use this wavelength in polymer ablation. However, many polymers suitable for application in microelectronics do not absorb at this wavelength. Therefore, progress has been made recently in sensitizing these polymers for ablation at 308 nm, by the addition of low-molecular-weight chromophors. Acridine lo), benzophenone ‘ I ) , pyrene 12), porphyrines 1 3 ) and 1,3-diphenylTriazenes 143 15) have been tested for this purpose. Recently, we have successfully used and characterized several l-phenyl-3,3-dialkylTriazenes as dopants for the ablation of poly(methy1 methacrylate) (PMMA) at 308 nm 16). An attractive alternative to physical doping is the incorporation of the triazeno group into the polymer itself. Recently, polymer-analogous reactions have been used to synthesize a PMMA copolymer containing ca. 0,3 mol-Vo of Triazene side chains ”). In the present communication, we are investigating the synthesis of another novel type of photopolymer which contains two triazeno groups per repeating unit. Synthesis is carried out by a polycondensation reaction in which a bis-diazonium salt and a
Stefan Bräse - One of the best experts on this subject based on the ideXlab platform.
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ortho-Perfluoroalkylation and ethoxycarbonyldifluoromethylation of aromatic Triazenes.
The Journal of organic chemistry, 2013Co-Authors: Andreas Hafner, Angela Bihlmeier, Martin Nieger, Wim Klopper, Stefan BräseAbstract:A robust protocol for perfluoroalkylation and ethoxycarbonyldifluoromethylation of functionalized aromatic Triazenes is described. Using silver(I)-fluoride and different fluorinated (trimethyl)silyl substituted species, it was possible to synthesize various ortho-fluorinated Triazenes in good yields via simple CH-substitution. Initial reactions under solvent-free (neat) conditions indicate a stabilizing interaction between “AgRf” and the Triazene moiety, which may be responsible for the good yields and regioselectivity. The transformation possibilities of the Triazene moiety make these reactions interesting for the synthesis of fluorinated building blocks. In addition, quantum chemical calculations suggest that the stabilization of the radical intermediate in the ortho-position is distinctly more favored for aromatic Triazenes than for other aromatic substrates.
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the virtue of the multifunctional Triazene linkers in the efficient solid phase synthesis of heterocycle libraries
Accounts of Chemical Research, 2004Co-Authors: Stefan BräseAbstract:With the implementation of combinatorial chemistry into the modern drug discovery process, the approach to novel diverse heterocycle libraries is an indispensable requirement. Triazenes, which are concealed diazonium salts, can be used to link functionalized arenes and amines to generate various heterocyclic structures, namely, benzoannelated nitrogen heterocycles, upon cleavage from the resin. Since Triazene anchors are stable toward various reagents and perform well under a range of reaction conditions, these multifunctional linkers are well suited for automated solid-phase syntheses and the syntheses of complex organic molecules, such as natural products, on solid supports.
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Multifunctional Linkers as an Efficient Tool for the Synthesis of Diverse Small Molecule Libraries: The Triazene Anchors
Methods in enzymology, 2003Co-Authors: Stefan Bräse, Stefan Dahmen, Matthias LormannAbstract:Publisher Summary Triazenes provide new possibilities for the activation of the ortho-position of arenes by coordination of metal ions and/or by lowering the electron density of the arene ring, they are also ideal synthons for diazonium salts. This chapter discusses two linkers based on the Triazene chemistry, T 1 and T 2, used for the synthesis of diverse small molecule libraries. While the T 1 linker system consists of 3,3-dialkyl-1 aryl Triazene bound to the support via the alkyl chain, the T 2 linker family is based on immobilized aryl diazonium salts. The Triazene T 1 linker has been successfully used as a linker for arenes. While the T 1 linker involves an immobilization of a diazonium salt on an amine resin, the T 2 linker represents the reversal of this concept. The T2 linker has recently been shown to be a versatile backbone amide anchor. Immobilized disubstituted Triazenes were acylated with carboxylic acid anhydrides or chlorides to give amide derivatives. These amides were cleaved under very mild conditions using trimethyl chlorosilane. This sequence thus, employs the T 2 system as backbone amine linker and was demonstrated in the automated library synthesis of substituted amide derivatives.
Thomas Lippert - One of the best experts on this subject based on the ideXlab platform.
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Laser-Induced Forward Transfer Using Triazene Polymer Dynamic Releaser Layer
2010Co-Authors: James Shaw Stewart, Thomas Lippert, Matthias Nagel, Frank Nüesch, Alexander WokaunAbstract:This article presents a short review of the use of Triazene polymer as a dynamic release layer (DRL) for laser-induced forward transfer (LIFT), before looking at the latest research in more detail. The field of Triazene polymer ablation only started around 20 years ago and has grown rapidly into a number of different application areas. Most promisingly, Triazene ablation has been refined as a method for propulsion, bringing the benefits of LIFT to the deposition of sensitive transfer materials. The key to understanding LIFT with a Triazene DRL is to understand the more fundamental nature of Triazene polymer ablation in both frontside and backside orientations. This article focuses on the most recent experimental results on LIFT with a Triazene DRL: the effect of picosecond pulse lengths compared with nanosecond pulse lengths; the effect of reduced air pressure; and the improvements in transfer in terms of range of transfer materials, and transfer across a gap. The results all help improve fundamental understanding of Triazene-based LIFT, and the transfer of functioning OLEDs demonstrates the capability of the technique.
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Synthesis and characterisation of new hard polyurethanes with Triazene pendants
Journal of Photochemistry and Photobiology A: Chemistry, 2005Co-Authors: Emil C. Buruiana, Thomas Lippert, Tinca Buruiana, Violeta Melinte, Hiroshi Yoshikawa, Hiroshi MashuharaAbstract:Abstract Three new hard type polyurethanes based on 2,4-toluene diisocyanate (2,4-TDI) and different Triazene diols, namely 1-phenyl-3,3′-di(2-hydroxyethyl) Triazene (PT-D), 1-naphthyl-3,3′-di(2-hydroxyethyl) Triazene (NT-D) and 1-(4-nitro)-phenyl-3,3′-di(2-hydroxyethyl) Triazene (NOT-D) were synthesized and characterized. The photosensitivity of these polymers was evaluated by UV irradiation, in DMF solution and as films by following the disappearance of the π–π* absorption band corresponding to the Triazene group. The polyurethane containing the NOT-D monomer revealed no decrease of its absorption bands even during prolonged irradiation, but could be structured with high quality using 308 nm laser irradiation. The ablation results revealed that the etching depth could be controlled by varying the laser fluence and number of laser pulses.
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laser ablation of polymers studied by ns interferometry and ns shadowgraphy measurements
Applied Surface Science, 2003Co-Authors: Michelle Hauer, D J Funk, Thomas Lippert, Alexander WokaunAbstract:Abstract The dynamic processes during ablation are studied by nanosecond-interferometry and shadowgraphy. Most commercial polymers exhibit poor laser ablation properties, therefore special Triazene polymers, with superior ablation properties were developed. The photochemical active Triazene group absorbs around 330 nm whereas the absorption around 200 nm is due to the photostable aromatic groups. The ns-interferometry shows that the etching of the Triazene polymer starts and ends with the laser beam after irradiation at 193 and 308 nm. Shadowgraphy of the Triazene polymer and polyimide reveal that the speed of the aerial shockwave increases with fluence and is higher for irradiation at 193 nm than for 308 nm. Shockwaves with equal or higher velocities are observed for the Triazene polymer compared to polyimide.
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Photolysis, thermolysis, and protolytic decomposition of a Triazene polymer in solution
Macromolecular Chemistry and Physics, 1995Co-Authors: Oskar Nuyken, Alexander Wokaun, Thomas Lippert, Jürgen Stebani, Andrej StaškoAbstract:The depolymerization of a triazeno-group containing photopolymer, poly[oxy-1,4-phenyleneazo(methylimino)hexamethylene(methylimino)azo-1,4-phenylene], is investigated in a tetrahydrofuran (THF) solution. Irradiation of the material leads to a clean decomposition of the photolabile polymer, as monitored by UV spectroscopy and gel-permeation chromatography (GPC). As compared to the photolysis in THF solution, the light-induced decomposition rate of a polymer in a polymer film is shown to be much slower. The highly photosensitive triazeno group also decomposes thermally at temperatures above approx. 220°C. The kinetics of thermal degradation of the polymer in substance was investigated at a temperature of 256°C, and monitored by GPC measurements. During this decomposition, one first observes the development of higher molar-mass fractions, which result from grafting reactions of primary radicals. Upon further thermolysis the Triazene polymer is completely degraded to low-molar-mass products. The volatile decomposition products were identified by gas chromatography/mass spectrometry (GC/MS) analysis. The protolytic decomposition, which represents the retrosynthesis of the Triazene polymer, was studied in a 9:1 mixture of tetrahydrofuran and an aqueous citrate buffer solution. Although the decomposition rate in this solvent mixture is slow, as compared to the depolymerization in diluted hydrochloric acid, a clean decomposition of the Triazene polymer is obtained.
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Synthesis and characterization of a novel photosensitive Triazene polymer
Die Makromolekulare Chemie Rapid Communications, 1993Co-Authors: Jiirgen Stebani, Thomas Lippert, Oskar Nuyken, Alexander WokaunAbstract:Triazene compounds have recently attracted attention due to a variety of interesting properties. The cytostatic activity discovered for several substituted Triazenes *) has stimulated intense research efforts directed towards the development of Triazene-based drugs3). In view of the importance of this field, several reviews on the synthesis of Triazenes are available4-’). A second class of applications is based on the fact that the triazeno group is comparatively stable with respect to thermal decomposition, but undergoes facile photo-chemical cleavage releasing nitrogen. This property, which may lead to novel applications in photolithography and photoreproduction, is the motivation for the present study. Photopolymers which can be structured by light are important materials in the microelectronics industry. Laser ablation of polymers ‘3 ’) has been intensively investigated in this context; the laser treatment represents a dry processing technique, without the need for wet processing steps. Powerful XeC1*-excimer lasers emitting at 308 nm are available for reliable large-scale industrial operation, making it desirable to use this wavelength in polymer ablation. However, many polymers suitable for application in microelectronics do not absorb at this wavelength. Therefore, progress has been made recently in sensitizing these polymers for ablation at 308 nm, by the addition of low-molecular-weight chromophors. Acridine lo), benzophenone ‘ I ) , pyrene 12), porphyrines 1 3 ) and 1,3-diphenylTriazenes 143 15) have been tested for this purpose. Recently, we have successfully used and characterized several l-phenyl-3,3-dialkylTriazenes as dopants for the ablation of poly(methy1 methacrylate) (PMMA) at 308 nm 16). An attractive alternative to physical doping is the incorporation of the triazeno group into the polymer itself. Recently, polymer-analogous reactions have been used to synthesize a PMMA copolymer containing ca. 0,3 mol-Vo of Triazene side chains ”). In the present communication, we are investigating the synthesis of another novel type of photopolymer which contains two triazeno groups per repeating unit. Synthesis is carried out by a polycondensation reaction in which a bis-diazonium salt and a
