Synthesis, Rotational Dynamics, and Photophysical Characterization of a Crystalline Linearly Conjugated Phenyleneethynylene Molecular Dirotor

We report the synthesis, crystal structure, solid-state dynamics, and photophysical properties of 6,13-bis­((4-(3-(3-methoxyphenyl)-3,3-diphenylprop-1-yn-1-yl)­phenyl)­ethynyl)-5,7,12,14-tetrahydro-5,14:7,12-bis­([1,2]­benzeno)­pentacene (<b>1</b>), a molecular dirotor with a 1,4-bis­((4-ethynylphenyl)­ethynyl)­benzene (BEPEB) chromophore. The incorporation of a pentiptycene into the molecular dirotor provides a central stator and a fixed phenylene ring relative to which the two flanking ethynylphenylene rotators can explore various torsion angles; this allows the BEPEB fluorophore dynamics to persist in the solid state. X-ray diffraction studies have shown that molecular dirotor <b>1</b> is packed so that all the BEPEB fluorophores adopt a parallel alignment, this is ideal for the development of functional materials. Variable temperature, quadrupolar echo ²H NMR studies have shown that phenylene rotator flipping has an activation energy of 9.0 kcal/mol and a room temperature flipping frequency of ∼2.6 MHz. Lastly, with measurements in solution, glasses, and crystals, we obtained evidence that the fluorescence excitation and emission spectra of the phenyleneethynylene chromophores is dependent on the extent of conjugation between the phenylene rings, as determined by their relative dihedral angles. This work provides a promising starting point for the development of molecular dirotors with polar groups whose amphidynamic nature will allow for the rapid shifting of solid-state absorption, fluorescence, and birefringence, in response to external electric fields

Synthesis, Rotational Dynamics, and Photophysical Characterization of a Crystalline Linearly Conjugated Phenyleneethynylene Molecular Dirotor

We report the synthesis, crystal structure, solid-state dynamics, and photophysical properties of 6,13-bis­((4-(3-(3-methoxyphenyl)-3,3-diphenylprop-1-yn-1-yl)­phenyl)­ethynyl)-5,7,12,14-tetrahydro-5,14:7,12-bis­([1,2]­benzeno)­pentacene (<b>1</b>), a molecular dirotor with a 1,4-bis­((4-ethynylphenyl)­ethynyl)­benzene (BEPEB) chromophore. The incorporation of a pentiptycene into the molecular dirotor provides a central stator and a fixed phenylene ring relative to which the two flanking ethynylphenylene rotators can explore various torsion angles; this allows the BEPEB fluorophore dynamics to persist in the solid state. X-ray diffraction studies have shown that molecular dirotor <b>1</b> is packed so that all the BEPEB fluorophores adopt a parallel alignment, this is ideal for the development of functional materials. Variable temperature, quadrupolar echo ²H NMR studies have shown that phenylene rotator flipping has an activation energy of 9.0 kcal/mol and a room temperature flipping frequency of ∼2.6 MHz. Lastly, with measurements in solution, glasses, and crystals, we obtained evidence that the fluorescence excitation and emission spectra of the phenyleneethynylene chromophores is dependent on the extent of conjugation between the phenylene rings, as determined by their relative dihedral angles. This work provides a promising starting point for the development of molecular dirotors with polar groups whose amphidynamic nature will allow for the rapid shifting of solid-state absorption, fluorescence, and birefringence, in response to external electric fields

Analysis of Responsive Polymer Films Using Surface Acoustic Waves

The Surface Acoustic Wave (SAW) technique is applied for the first time to quantify the properties of a responsive polymer brush layer. Using a single SAW chip, the response of five different brush compositions to several pH changes was monitored in parallel in a single run. These results were compared with QCM-D studies on the same system. SAW exhibited two remarkable advantages against QCM-D: (i) multiplexing capability, which allowed considerable reduction in experimental time and expenses (1/8 reduction of experimental time, 1/5 in the number of chips, and 1/10 in solvent consumption in our case), and (ii) higher sensitivity in both mass and viscosity change than QCM-D (4–5 times higher in our systems). Our results demonstrate the suitability and advantages of the SAW technology for application in polymer science, in particular for the study of the compositional effects in responsive thin layers

Additional file 1: of Cholera diagnosis in human stool and detection in water: protocol for a systematic review of available technologies

Template for data extraction. (XLSX 22KB

Additional file 2: of Cholera diagnosis in human stool and detection in water: protocol for a systematic review of available technologies

PRISMA-P (Preferred Reporting Items for Systematic review and Meta-Analysis Protocols) 2015 checklist: recommended items to address in a systematic review protocol. (DOCX 17 kb

Selective Access to Trisubstituted Macrocyclic <i>E</i>- and <i>Z</i>‑Alkenes from the Ring-Closing Metathesis of Vinylsiloxanes

Macrocyclic (<i>E</i>)-alkenylsiloxanes, obtained from <i>E</i>-selective ring-closing metathesis reactions, can be converted to the corresponding (<i>Z</i>)-alkenyl bromides and (<i>E</i>)-alkenyl iodides allowing access to both <i>E-</i> and <i>Z</i>-trisubstituted macrocyclic alkenes. The reaction conditions and substrate scope of these stereoselective transformations are explored