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Jean-pierre Dutasta - One of the best experts on this subject based on the ideXlab platform.
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Restricted Guest Tumbling in Phosphorylated Self-Assembled Capsules
Journal of the American Chemical Society, 2010Co-Authors: Steven Harthong, Béatrice Dubessy, Christophe Aronica, Jérôme Vachon, Jean-christophe Mulatier, Jean-pierre DutastaAbstract:ABii diphosphonatocavitands self-assemble in chloroform solution to form dimeric molecular capsules. The molecular capsules can incarcerate an N-Methylpyridinium or N-methylpicolinium guest. We have demonstrated that the supramolecular assembly acts as a molecular rotor as a result of the restricted motion of the guest inside the molecular cavity. In the solid state, X-ray diffraction analysis of the free host showed that two cavitands interact through strong hydrogen bonds to give the supramolecular self-assembled capsule. The solid-state structure of the N-methylpicolinium complex is comparable to that of the free host and indicates that the guest is not a prerequisite for the formation of the capsule. DOSY NMR studies provided a definitive argument for the formation of the free and complexed supramolecular capsule in CDCl3 solution. In solution, the tumbling of the N-Methylpyridinium and N-methylpicolinium guests about the equatorial axes of the host can be frozen and differs by the respective energy barriers, with the larger picolinium substrate having a larger value (ΔG⧧ = 69.7 kJ mol−1) than the shorter pyridinium guest (ΔG⧧ = 44.8 kJ mol−1). This behavior corresponds to the restricted rotation of a rotator in a supramolecular rotor.
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Self-Complementary Phosphonate Cavitands
Journal of Organic Chemistry, 2009Co-Authors: Béatrice Dubessy, Steven Harthong, Christophe Aronica, Denis Bouchu, Marco Busi, Enrico Dalcanale, Jean-pierre DutastaAbstract:iii-Phosphorylated cavitands incorporating an N-Methylpyridinium guest moiety as the fourth bridging unit form supramolecular associations by inclusion of the charged CH3N+-pyridinium head into a neighboring host cavity. The dimeric association is favored in solution and was characterized by NMR, mass spectrometry, DOSY experiments, and single crystal X-ray analysis.
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Structure of a 4:1:4 supramolecular assembly of neutral TiiiiPO cavitands and tetrakis(N-Methylpyridinium)porphyrin iodide.
Journal of Organic Chemistry, 2007Co-Authors: Rita De Zorzi, Jean-christophe Mulatier, Béatrice Dubessy, Silvano Geremia, Lucio Randaccio, Jean-pierre DutastaAbstract:Four tetraphosphorylated TiiiiPO cavitands 1 encapsulate the pyridinium heads of a tetrakis(N-Methylpyridinium)porphyrin iodide to form a 4:1:4 (host)4/guest4+/4I- complex. The single-crystal X-ray diffraction analysis shows the arrangement of the four cavities bound to the CH3N+ groups of the porphyrin moiety and the four iodide anions nested between the phenethyl substituents of the hosts. 1H NMR investigations show that the structure is preserved in chloroform solution and underscore the effect of the counteranions.
Narmin Noorani - One of the best experts on this subject based on the ideXlab platform.
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Dissociation Behavior of l(+)-Lactic Acid in Aqueous Solutions of (1-Alkyl-4-methylpyridinium bromide + Poly (ethyleneglycol)) at T = (288.15–318.15) K
Journal of Solution Chemistry, 2018Co-Authors: Hemayat Shekaari, Abbas Mehrdad, Narmin NooraniAbstract:The effect of 1-alkyl-4-methylpyridinium based ionic liquids on the conductivity behavior of l (+)-lactic acid (LaH) was studied in Poly(ethylene glycol) (PEG) aqueous solutions. The molar conductivities of LaH in the aqueous solutions of PEG, (PEG + 1-hexyl-4-methylpyridinium bromide) and (PEG + 1-octyl-4-methylpyridinium bromide) were measured over the temperature ranges of 288.15–318.15 K. The molar conductivity data were analyzed by applying the Quint–Viallard (QV) conductivity equation to determine the limiting molar conductivities ( Λ ^0) and dissociation constants ( $$ K_{\text{D}} $$ K D ). The results show that the values of limiting molar conductivity increased as the temperature increased, which indicates that the dissociation process is endothermic. The $$ K_{\text{D}} $$ K D values were also used to calculate the dissociation standard thermodynamic functions ( $$ \Delta G_{\text{D}}^{0} $$ Δ G D 0 , $$ \Delta S_{\text{D}}^{0} $$ Δ S D 0 and $$ \Delta H_{\text{D}}^{0} $$ Δ H D 0 ). The results revealed that the dissociation process of LaH is controlled by entropy at all temperatures.
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Dissociation Behavior of l (+)-Lactic Acid in Aqueous Solutions of (1-Alkyl-4-methylpyridinium bromide + Poly (ethyleneglycol)) at T = (288.15–318.15) K
Journal of Solution Chemistry, 2017Co-Authors: Hemayat Shekaari, Abbas Mehrdad, Narmin NooraniAbstract:The effect of 1-alkyl-4-methylpyridinium based ionic liquids on the conductivity behavior of l(+)-lactic acid (LaH) was studied in Poly(ethylene glycol) (PEG) aqueous solutions. The molar conductivities of LaH in the aqueous solutions of PEG, (PEG + 1-hexyl-4-methylpyridinium bromide) and (PEG + 1-octyl-4-methylpyridinium bromide) were measured over the temperature ranges of 288.15–318.15 K. The molar conductivity data were analyzed by applying the Quint–Viallard (QV) conductivity equation to determine the limiting molar conductivities (Λ 0) and dissociation constants ( $$ K_{\text{D}} $$ ). The results show that the values of limiting molar conductivity increased as the temperature increased, which indicates that the dissociation process is endothermic. The $$ K_{\text{D}} $$ values were also used to calculate the dissociation standard thermodynamic functions ( $$ \Delta G_{\text{D}}^{0} $$ , $$ \Delta S_{\text{D}}^{0} $$ and $$ \Delta H_{\text{D}}^{0} $$ ). The results revealed that the dissociation process of LaH is controlled by entropy at all temperatures.
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Conductivity and dissociation behavior of l(+)-lactic acid in the aqueous solutions of (1-butyl-4-methylpyridinium halide, 1-butyl-3-methylimidazolium halide + polyethylene glycol) at different temperatures
Journal of Molecular Liquids, 2017Co-Authors: Hemayat Shekaari, Abbas Mehrdad, Narmin NooraniAbstract:Abstract In this paper, the effect of some ionic liquids on the conductivity behavior of l (+)–lactic acid was studied in polyethylene glycol aqueous solutions. The molar conductivities of l (+)–lactic acid in the aqueous solutions of polyethylene glycol, polyethylene glycol + 1–butyl–3–methylimidazolium bromide, polyethylene glycol + 1–butyl–3–methylimidazolium chloride, polyethylene glycol + 1–butyl–4–methylpyridinium bromide, and polyethylene glycol + 1–butyl–4–methylpyridinium chloride were measured at the temperature ranges of (288.15–318.15) K. The molar conductivity data were correlated using Quint–Viallard (QV) conductivity equation to calculate the limiting molar conductivities (Λ 0 ) and dissociation constants ( K D ). The results show that limiting molar conductivity increase by increasing both of the anion size and acidic power of ILs cation. The K D values were also used to calculate the dissociation standard thermodynamic functions (Δ G D 0 , Δ S D 0 , and Δ H D 0 ). The values of Δ G D 0 are positive and become more positive at higher temperatures. This implies that the dissociation of the acid is controlled by entropy term.
David R Mcmillin - One of the best experts on this subject based on the ideXlab platform.
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a pared down version of 5 10 15 20 tetra n methylpyridinium 4 yl porphyrin intercalates into b form dna regardless of base composition binding studies of tri n methylpyridinium 4 yl porphyrins
Biochemistry, 2008Co-Authors: Kim Andrews, David R McmillinAbstract:Positively charged N-Methylpyridinium-4-yl substituents promote the binding of a porphyrin to DNA, but they also impose steric constraints. To clarify when intercalative binding is most feasible, this report describes syntheses and binding studies of two tricationic ligands: 5,10,15-tri(N-Methylpyridinium-4-yl)porphyrin (H 2 Tri4) and 5-methyl-10,15,20-tri(N-Methylpyridinium-4-yl)porphyrin (H 2 MeTri4). Techniques used to characterize the binding interactions include viscometry and spectroscopic studies of the absorption, emission, and circular dichroism. The striking observation is that intercalation is the only detectable binding motif when the trisubstituted porphyrin H 2 Tri4 combines with [poly(dA-dT)] 2 , [poly-(dG-dC)] 2 , or salmon testes DNA. H 2 Tri4 is, however, a limiting case. Parallel studies of H 2 MeTri4 and the copper(II) derivative Cu(MeTri4) reveal that external binding to [poly(dA-dT)] 2 becomes important when a fourth meso substituent is present, even one as small as the methyl group. Intercalation of H 2 Tri4 is sterically feasible because two N-Methylpyridinium-4-yl substituents can reside in the major groove, though the charge alignment is not optimal. However, the presence of the fourth substituent on H 2 MeTri4 further destabilizes the intercalated form, and external binding becomes competitive for a flexible host like [poly(dA-dT)] 2 .
Matthew F Woodward - One of the best experts on this subject based on the ideXlab platform.
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transition metal halide salts of 2 amino 3 methylpyridine synthesis crystal structures and magnetic properties of 3 map 2cux4 3 map 2 amino 3 methylpyridinium x cl br
Inorganica Chimica Acta, 2000Co-Authors: Thomas J Coffey, Christopher P Landee, Ward T Robinson, Mark M Turnbull, Mon Winn, Matthew F WoodwardAbstract:Abstract The reaction of CuX2·nH2O with HX [X=Cl, Br] and 2-amino-3-methylpyridine in aqueous solution gave compounds of the formula (3-MAP)2(CuX4) [3-MAP=2-amino-3-methylpyridinium]. The compounds have been characterized by single-crystal X-ray diffraction. The complexes crystallize as salts with the 3-MAP cations separating layers of tetrahalometallate anions. Both compounds have two independent molecules in their asymmetric units. Weak antiferromagnetic interactions are observed, which suggest a primarily low-dimensional magnetic exchange network.
Hemayat Shekaari - One of the best experts on this subject based on the ideXlab platform.
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Dissociation Behavior of l(+)-Lactic Acid in Aqueous Solutions of (1-Alkyl-4-methylpyridinium bromide + Poly (ethyleneglycol)) at T = (288.15–318.15) K
Journal of Solution Chemistry, 2018Co-Authors: Hemayat Shekaari, Abbas Mehrdad, Narmin NooraniAbstract:The effect of 1-alkyl-4-methylpyridinium based ionic liquids on the conductivity behavior of l (+)-lactic acid (LaH) was studied in Poly(ethylene glycol) (PEG) aqueous solutions. The molar conductivities of LaH in the aqueous solutions of PEG, (PEG + 1-hexyl-4-methylpyridinium bromide) and (PEG + 1-octyl-4-methylpyridinium bromide) were measured over the temperature ranges of 288.15–318.15 K. The molar conductivity data were analyzed by applying the Quint–Viallard (QV) conductivity equation to determine the limiting molar conductivities ( Λ ^0) and dissociation constants ( $$ K_{\text{D}} $$ K D ). The results show that the values of limiting molar conductivity increased as the temperature increased, which indicates that the dissociation process is endothermic. The $$ K_{\text{D}} $$ K D values were also used to calculate the dissociation standard thermodynamic functions ( $$ \Delta G_{\text{D}}^{0} $$ Δ G D 0 , $$ \Delta S_{\text{D}}^{0} $$ Δ S D 0 and $$ \Delta H_{\text{D}}^{0} $$ Δ H D 0 ). The results revealed that the dissociation process of LaH is controlled by entropy at all temperatures.
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Dissociation Behavior of l (+)-Lactic Acid in Aqueous Solutions of (1-Alkyl-4-methylpyridinium bromide + Poly (ethyleneglycol)) at T = (288.15–318.15) K
Journal of Solution Chemistry, 2017Co-Authors: Hemayat Shekaari, Abbas Mehrdad, Narmin NooraniAbstract:The effect of 1-alkyl-4-methylpyridinium based ionic liquids on the conductivity behavior of l(+)-lactic acid (LaH) was studied in Poly(ethylene glycol) (PEG) aqueous solutions. The molar conductivities of LaH in the aqueous solutions of PEG, (PEG + 1-hexyl-4-methylpyridinium bromide) and (PEG + 1-octyl-4-methylpyridinium bromide) were measured over the temperature ranges of 288.15–318.15 K. The molar conductivity data were analyzed by applying the Quint–Viallard (QV) conductivity equation to determine the limiting molar conductivities (Λ 0) and dissociation constants ( $$ K_{\text{D}} $$ ). The results show that the values of limiting molar conductivity increased as the temperature increased, which indicates that the dissociation process is endothermic. The $$ K_{\text{D}} $$ values were also used to calculate the dissociation standard thermodynamic functions ( $$ \Delta G_{\text{D}}^{0} $$ , $$ \Delta S_{\text{D}}^{0} $$ and $$ \Delta H_{\text{D}}^{0} $$ ). The results revealed that the dissociation process of LaH is controlled by entropy at all temperatures.
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Conductivity and dissociation behavior of l(+)-lactic acid in the aqueous solutions of (1-butyl-4-methylpyridinium halide, 1-butyl-3-methylimidazolium halide + polyethylene glycol) at different temperatures
Journal of Molecular Liquids, 2017Co-Authors: Hemayat Shekaari, Abbas Mehrdad, Narmin NooraniAbstract:Abstract In this paper, the effect of some ionic liquids on the conductivity behavior of l (+)–lactic acid was studied in polyethylene glycol aqueous solutions. The molar conductivities of l (+)–lactic acid in the aqueous solutions of polyethylene glycol, polyethylene glycol + 1–butyl–3–methylimidazolium bromide, polyethylene glycol + 1–butyl–3–methylimidazolium chloride, polyethylene glycol + 1–butyl–4–methylpyridinium bromide, and polyethylene glycol + 1–butyl–4–methylpyridinium chloride were measured at the temperature ranges of (288.15–318.15) K. The molar conductivity data were correlated using Quint–Viallard (QV) conductivity equation to calculate the limiting molar conductivities (Λ 0 ) and dissociation constants ( K D ). The results show that limiting molar conductivity increase by increasing both of the anion size and acidic power of ILs cation. The K D values were also used to calculate the dissociation standard thermodynamic functions (Δ G D 0 , Δ S D 0 , and Δ H D 0 ). The values of Δ G D 0 are positive and become more positive at higher temperatures. This implies that the dissociation of the acid is controlled by entropy term.
