• Energy Research
• Restricted close
• Open Source close
• chemical sciences close
• CH close
• FR close

AbstractWe have investigated the spectroscopic properties (absorption spectra, emission spectra, emission lifetimes) of three triads in CH2Cl2: C2‐M‐C2, C343‐M‐C343, and C2‐M‐C343, in which M is a shape‐persistent macrocyclic hexagonal backbone composed of two 2,2′‐bipyridine (bpy) units embedded in opposing sides, and C2 and C343 are coumarin 2 and coumarin 343, respectively. All the components are strongly fluorescent species (Φ=0.90, 0.79, and 0.93 for M, C2, and C343, respectively, as established by investigating suitable model compounds). In each triad excitation of M leads to almost quantitative energy transfer to the lowest coumarin‐localised excited state. Upon addition of acid, the two bpy units of the M component undergo independent protonation leading to monoprotonated (e.g., C2‐M⋅H+‐C2) and diprotonated (e.g., C2‐M⋅2 H+‐C2) species. Further addition of acid leads to protonation of the coumarin component so that each triad is involved in four protonation equilibria. Protonation causes strong (and reversible, upon addition of base) changes in the absorption and fluorescence properties of the triads because of inversion of the excited‐state order and/or the occurrence of electron‐transfer quenching processes.

AbstractWe have investigated the spectroscopic properties (absorption spectra, emission spectra, emission lifetimes) of three triads in CH2Cl2: C2‐M‐C2, C343‐M‐C343, and C2‐M‐C343, in which M is a shape‐persistent macrocyclic hexagonal backbone composed of two 2,2′‐bipyridine (bpy) units embedded in opposing sides, and C2 and C343 are coumarin 2 and coumarin 343, respectively. All the components are strongly fluorescent species (Φ=0.90, 0.79, and 0.93 for M, C2, and C343, respectively, as established by investigating suitable model compounds). In each triad excitation of M leads to almost quantitative energy transfer to the lowest coumarin‐localised excited state. Upon addition of acid, the two bpy units of the M component undergo independent protonation leading to monoprotonated (e.g., C2‐M⋅H+‐C2) and diprotonated (e.g., C2‐M⋅2 H+‐C2) species. Further addition of acid leads to protonation of the coumarin component so that each triad is involved in four protonation equilibria. Protonation causes strong (and reversible, upon addition of base) changes in the absorption and fluorescence properties of the triads because of inversion of the excited‐state order and/or the occurrence of electron‐transfer quenching processes.

AbstractWe report the design, synthesis and evaluation of dynamic “octopus” amphiphiles with emphasis on their efficiency as activators in synthetic membrane‐based sensing systems. Previously, we found that the in situ treatment of charged hydrazides with hydrophobic aldehydes or ketones gives amphiphilic counterion activators of polyion transporters in lipid bilayers, and that their efficiency increases with the number of their hydrophobic tails. Herein, we expand this series to amphiphiles with one cationic head (guanidinium or ammonium) and four exchangeable hydrophobic tails. These results, with the highest number of tails reported to date, confirm that dynamic octopus amphiphiles provide access to maximal activity and selectivity. Odorants, such as muscone, carvone, or anisaldehyde are used to outline their usefulness in differential sensing systems that operate based on counterion‐activated DNA transporters in fluorogenic vesicles. The enhanced ability of octopus amphiphiles to enable the discrimination of enantiomers as well as that of otherwise intractable ortho, meta, and para isomers and short cyclo‐/alkyl tails is demonstrated. These findings identify dynamic octopus amphiphiles as being promising for application to differential sensing, “fragrant” cellular uptake, and slow release.

AbstractWe report the design, synthesis and evaluation of dynamic “octopus” amphiphiles with emphasis on their efficiency as activators in synthetic membrane‐based sensing systems. Previously, we found that the in situ treatment of charged hydrazides with hydrophobic aldehydes or ketones gives amphiphilic counterion activators of polyion transporters in lipid bilayers, and that their efficiency increases with the number of their hydrophobic tails. Herein, we expand this series to amphiphiles with one cationic head (guanidinium or ammonium) and four exchangeable hydrophobic tails. These results, with the highest number of tails reported to date, confirm that dynamic octopus amphiphiles provide access to maximal activity and selectivity. Odorants, such as muscone, carvone, or anisaldehyde are used to outline their usefulness in differential sensing systems that operate based on counterion‐activated DNA transporters in fluorogenic vesicles. The enhanced ability of octopus amphiphiles to enable the discrimination of enantiomers as well as that of otherwise intractable ortho, meta, and para isomers and short cyclo‐/alkyl tails is demonstrated. These findings identify dynamic octopus amphiphiles as being promising for application to differential sensing, “fragrant” cellular uptake, and slow release.

Abstract This study considers effects of pressure of up to 110 kbar on line position and fluorescence lifetime τ for 4 T 1 → 6 A 1 transition in LMA:Mn 2+ and LMA:Mn 2+ , Nd 3+ . Energy transfer between Mn 2+ and Nd 3+ in LMA:Mn 2+ , Nd 3+ has also been considered. Results indicate pressure induced line shift towards longer wavelengths, a red-shift in both crystals with the same rate of 0.182 nm kbar −1 . Pressure influences fluorescence lifetime τ in the considered crystals differently; whereas for LMA:Mn 2+ increasing pressure causes slow linear decrease of τ , and for LMA:Mn 2+ , Nd 3+ τ increases linearly as pressure raises. Energy transfer efficiencies decrease with pressure. High pressure induced red-shift can be explained by a simple model.

Abstract This study considers effects of pressure of up to 110 kbar on line position and fluorescence lifetime τ for 4 T 1 → 6 A 1 transition in LMA:Mn 2+ and LMA:Mn 2+ , Nd 3+ . Energy transfer between Mn 2+ and Nd 3+ in LMA:Mn 2+ , Nd 3+ has also been considered. Results indicate pressure induced line shift towards longer wavelengths, a red-shift in both crystals with the same rate of 0.182 nm kbar −1 . Pressure influences fluorescence lifetime τ in the considered crystals differently; whereas for LMA:Mn 2+ increasing pressure causes slow linear decrease of τ , and for LMA:Mn 2+ , Nd 3+ τ increases linearly as pressure raises. Energy transfer efficiencies decrease with pressure. High pressure induced red-shift can be explained by a simple model.

Abstract Thermal cross-linking in presence of residual solvent dimethylsulfoxide without any addition of cross-linker molecules is described. This elegant method increases spectacularly the mechanical and hydrolytic stability of sulfonated aromatic polymers (SAP), making them suitable for use in liquid water also at 145 °C. Data on water uptake, mechanical properties and proton conductivity are presented and discussed from a bond energy point of view. The developed method is also inexpensive, being incorporated in the normal membrane casting procedure. This opens new horizons and hitherto conventionally disregarded SAP membranes should be reconsidered as fuel cell membranes.

Abstract Thermal cross-linking in presence of residual solvent dimethylsulfoxide without any addition of cross-linker molecules is described. This elegant method increases spectacularly the mechanical and hydrolytic stability of sulfonated aromatic polymers (SAP), making them suitable for use in liquid water also at 145 °C. Data on water uptake, mechanical properties and proton conductivity are presented and discussed from a bond energy point of view. The developed method is also inexpensive, being incorporated in the normal membrane casting procedure. This opens new horizons and hitherto conventionally disregarded SAP membranes should be reconsidered as fuel cell membranes.