- Excimer Emission in Protonated Pyridine Systems. 2. Excimer Emission of Protonated Dipyridylalkanes in Solution at Room Temperature and 77 K
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Emission properties of (2-pyridyl)-(CH2)n-(2-pyridyl) (n = 2, 3, 5, and 7) and (4-pyridyl)-(CH2)n-(4-pyridyl) (n = 2, 3, and 5) were studied in solution in the presence of trifluoroacetic acid at room temperature and 77 K.At room temperature, only 1,3-di(2-pyridyl)propane exhibits a very weak fluorescence at approximately 6900 cm-1 to the red of the normal fluorescence.This band is ascribed to an intramolecular excimer fluorescence between the protonated pyridine moieties.However, 4,4'-dipyridylalkanes do not fluoresce.At 77 K, being specific to a mixed solvent of tetrahydrofuran, methanol, and methyltetrahydrofuran (4:3:1 by volume), the protonated 2,2'-dipyridylalkanes exhibit a structureless band around around 325 nm besides the normal fluorescence band, but they exhibit no excimer fluorescence.On the other hand, the protonated 4,4'-dipyridylalkanes apparently exhibit only a structureless band around 325 nm.The 325-nm fluorescence band comes from a dimerlike excimer in which the protonated pyridine moieties interact intermolecularly in the excited state.The efficiency of the dimerlike excimer formation is independent of the length of methylene chain.From studies on the effects of solvent and temperature on the dimerlike excimer emission, it is found that the formation of the dimerlike excimer is strongly related to a solvent cage effect.
- Handa, Takashi,Utena, Yoshio,Yajima, Hirofumi
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- Gemini pyridinium surfactants: Synthesis and conductometric study of a novel class of amphiphiles
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A new series of pyridinium cationic gemini surfactants was prepared by quaternization of the 2,2′-(α,ω-alkanediyl)bispyridines with N-alkylating agents, whose reactivity is briefly discussed. Particularly useful was the use of long-chain alkyl triflates (trifluoromethanesulfonates) for both overcoming the sterical hindrance in the pyridines and obtaining higher synthetic yields. Well-known 4,4′-(α,ω -alkanediyl)bis(1-alkylpyridinium) structures showed narrow temperature ranges for practical applications, due to their high Krafft points, while the new 2,2′-(α,ω)-alkanediyl)bis-(1-alkylpyridinium) series, accounted for good surface active properties. Due to the Krafft points below 0 °C, they could be exploited as solutions in water at any temperature. The characterization of the behavior of the series was performed by conductivity measurements. Some of the proposed structures exhibited unusual surface active behavior, which was interpreted in terms of particular conformational arrangements.
- Quagliotto, Pierluigi,Viscardi, Guido,Barolo, Claudia,Barni, Ermanno,Bellinvia, Silvia,Fisicaro, Emilia,Compari, Carlotta
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- Synthesis, physicochemical characterization, and interaction with DNA of long-alkyl-chain gemini pyridinium surfactants
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Abstract Pyridinium gemini surfactants with hexadecyl chains linked to nitrogen atoms and a tuned aliphatic spacer that bridges the two pyridinium polar heads in 2,2′-positions have been synthesized and characterized. A multitechnique approach allowed us to study the aggregation behavior, using conductivity, surface tension, and fluorescence. Graphs of the specific conductivity (κ) versus the surfactant molar concentration (C), and graphs of the molar conductivity (Λ) versus C0.5 suggest pre-aggregation phenomena of these amphiphiles at very low concentration. The trends of Amin as a function of the spacer length confirm the hypothesis of a conformational change of the molecule with four methylene groups as spacer owing to stacking interactions between the two pyridinium rings mediated by the counterion. Moreover, the trends of Amin and counterion binding (β) suggest that the spacer must be longer than eight carbon atoms to fold efficiently toward the micellar core. The opportunity to tune the surfactant structure and aggregation properties make those surfactants - particularly the long-chain ones for which the DNA complexing ability was shown by means of atomic force microscopy (AFM) imaging - desirable candidates for gene-delivery experiments. Bringing it all together: This study on gemini pyridinium surfactants (see figure) contributes to the knowledge about the aggregation behavior of these compounds and their interactions with biological molecules. Structure-activity relationships were found in the context of the physico-chemical properties of these compounds and DNA compaction. These insights should improve the understanding of surfactant-based gene delivery.
- Barbero, Nadia,Magistris, Claudio,Quagliotto, Pierluigi,Bonandini, Luca,Barolo, Claudia,Buscaino, Roberto,Compari, Carlotta,Contardi, Laura,Fisicaro, Emilia,Viscardi, Guido
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- Metal Acetylide Elimination: The Key Step in the Cascade Decomposition and Transformation of Metalated Propargylamines
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Metal acetylide elimination facilitates a novel one-pot cascade metalation and elimination/addition route to a series of unsymmetrical secondary amines from the reaction of secondary propargylamines with organometallic reagents. Spectroscopic evidence suggests a dimetalated amido intermediate rather than an allene.
- Flynn, Matthew T.,Blair, Victoria L.,Andrews, Philip C.
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p. 1225 - 1228
(2018/04/30)
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- NOVEL MICROBIOCIDES
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The present invention relates to methods of controlling or preventing phytopathogenic diseases on useful plants or on propagation material thereof comprising applying to useful plants, the locus thereof or propagation material thereof a compound of formula (I) wherein Q, Q', L1, L2, L3, L4, L5, L6 and X are as defined in claim 1. The invention also relates to novel compounds that may be used in said methods, as well as intermediates useful for the preparation of the novel compounds.
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Page/Page column 158
(2013/03/26)
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- HOMOLYTIC PYRIDYLETHYLATION OF CYCLOHEXANE AND TETRALIN
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The homolytic pyridylethylation of cyclohexene and tetraline with 2-vinylpyridine under conditions of peroxide and thermal initiation was investigated.In addition to the main reaction products, i.e., cycloalkylethylpyridines (1 : 1 adducts), compounds indicating rearrangement of the radicals with H migration were also isolated and identified.
- Il'yasov, E.A.,Galust'yan, G.G.
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p. 326 - 330
(2007/10/02)
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- FREE-RADICAL PYRIDYLETHYLATION OF ARYLALKANES
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2-(3-Arylpropyl)pyridines were synthesized in 30-54percent yields by the free-radical addition of toluene, o-, m-, and p-xylenes, and mesitylene to 2-vinylpyridine at 250-350 deg C.The products of rearrangement of the intermediate adduct radical with 1,3-H migration were isolated and identified.
- Galust'yan, G. G.,Il'yasov, E. A.,Kadyrov, Ch. Sh.
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p. 307 - 310
(2007/10/02)
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