N-BF2-O

Carbazole modified salicylaldimines and their difluoroboron complexes: effect of the tert-butyl and trifluoromethyl terminal groups on organogelation and piezofluorochromism

Jiabao Sun, Jingbo Sun, Wenhua Mi, Pengchong Xue, Jinyu Zhao, Lu Zhai and Ran Lu  

New J. Chem., 2017, 41, 763-772
DOI: 10.1039/C6NJ03063G

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Luminescent nanofibers were generated from nontraditional π-gelators based on salicylaldimines and their difluoroboron complex bearing tert-butyl carbazole and trifluoromethylbenzene.

 

naphthyridine

10.1021/acs.orglett.6b00311

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Borys Osmialowski, Ph.D. D.Sc.

UTP University of Science and Technology
Faculty of Chemical Technology and Engineering
Department of Organic Chemistry
Seminaryjna 3, PL-85-326, Bydgoszcz, Poland

http://kcho.utp.edu.pl/BO

pH-Regulated Selectivity in Supramolecular Polymerizations: Switching between Co- and Homopolymers [feedly]

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pH-Regulated Selectivity in Supramolecular Polymerizations: Switching between Co- and Homopolymers
// ChemEurJ

Abstract

A strategy is presented to regulate the selectivity in aqueous supramolecular polymerizations by changes in pH. In neutral buffered conditions, oppositely charged phenylalanine-based dendritic peptide amphiphiles self-assemble into (AB)_n alternating copolymers of low polydispersity when mixed in a 1:1 comonomer feed ratio. Via pH switch of the glutamic acid and lysine side chains, attractive Coulomb interactions in the coassembled materials are screened and selective polymerization occurs to form (A)_n homopolymers of the acidic comonomer at low pH and (B)_n homopolymers of the basic comonomer at high pH, while the complementary comonomer is released during the transition. Reversible switching is demonstrated between these three different polymeric states, which were characterized by CD and fluorescence spectroscopy, using a peptide based minimalistic fluorophore/quencher pair, and transmission electron microscopy.

Switchcraft: A strategy to regulate the selectivity in aqueous supramolecular polymerizations is presented. In neutral buffer, oppositely charged dendritic peptide amphiphiles selectively self-assemble into alternating copolymers. At high and low pH, the formation of either the basic or acidic homopolymer occurs while the complementary comonomer is released. The transition between these three different polymeric states is fully reversible and can be switched multiple times.

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Frontispiece: Anionic CH⋅⋅⋅X− Hydrogen Bonds: Origin of Their Strength, Geometry, and Other Properties [feedly]

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Frontispiece: Anionic CH⋅⋅⋅X− Hydrogen Bonds: Origin of Their Strength, Geometry, and Other Properties
// ChemEurJ

The Power of the H-Bond Because of its importance and widespread occurrence, the phenomenon of H-bonding has motivated an enormous amount of investigative effort over the years. In their Full Paper on page 1474 ff., B. Nepal and S. Scheiner describe the various sources of binding in the CH⋅⋅⋅X⁻ⁿ H-bond between F₃CH and various anions. The top figure in the highlight graphic shows the charge transfer from a F lone pair into the σ*(CH) antibonding orbital. The Coulombic attraction between the F⁻ anion and the most positive region of F₃CH is displayed in the middle section. The lower segment illustrates the redistribution of electron density that occurs when the two subunits interact, increases in purple and losses in blue.

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Thermochromic and Mechanochromic Luminescence Umpolung in Isostructural Metal–Organic Frameworks Based on Cu6I6 Clusters [feedly]

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Thermochromic and Mechanochromic Luminescence Umpolung in Isostructural Metal–Organic Frameworks Based on Cu6I6 Clusters
// InorgChem

Inorganic Chemistry

DOI: 10.1021/ic502207f

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Cobalt-Catalyzed Oxidative Isocyanide Insertion to Amine-Based Bisnucleophiles: Diverse Synthesis of Substituted 2-Aminobenzimidazoles, 2-Aminobenzothiazoles, and 2-Aminobenzoxazoles

Cobalt catalysis: Synthesis of substituted 2-aminobenzimidazoles, 2-aminobenzothiazoles, and 2-aminobenzoxazoles was achieved by using cobalt(II) acetate catalyzed isocyanide insertion to o-diaminobenzene, 2-aminobenzenethiol, and 2-aminophenol derivatives in 1,4-dioxane (see scheme). It was found that the reaction proceeded efficiently to give the desired products in up to 95 % isolated yields by CN and CS (O, N) formation in a single step.

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Original Page: http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fchem.201300239

Supramolecular Control of Hetero-multinuclear Polytopic Binding of Metal Ions (ZnII, CuI) at a Single Calix[6]arene-Based Scaffold

Przesłano za pośrednictwem Czytnika Google

Supramolecular Control
of Hetero-multinuclear Polytopic
Binding of Metal Ions (ZnII, CuI) at a Single
Calix[6]arene-Based Scaffold

Inorganic Chemistry

DOI: 10.1021/ic300632q

B.Osmialowski

Antiaromaticity Proved by the Anisotropic Effect in 1H NMR Spectra

 

 

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Antiaromaticity Proved by the Anisotropic Effect in 1H NMR Spectra

przez The Journal of Physical Chemistry A: Latest Articles (ACS Publications) autor: Erich Kleinpeter and Andreas Koch dnia 12-05-03

The Journal of Physical Chemistry A

DOI: 10.1021/jp300860q

 

 

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Tautomeric Switching and Metal-Cation Sensing of Ligand-Equipped 4-Hydroxy-/...

 

 

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Tautomeric Switching and Metal-Cation Sensing of Ligand-Equipped 4-Hydroxy-/4-oxo-1,4-dihydroquinolines

przez Chemistry - A European Journal autor: Aleksandar R. Todorov, Martin Nieger, Juho Helaja dnia 12-04-19

Abstract

Novel 4-hydroxyquinoline (4HQ) based tautomeric switches are reported. 4HQs equipped with coordinative side arms (8-arylimino and 3-piperidin-1-ylmethyl groups) were synthesized to access O- or N-selective chelation of Zn²⁺ and Cd²⁺ ions by 4HQ. In the case of the monodentate arylimino group, O chelation of metal ions induces concomitant switching of phenol tautomer to the keto form in nonpolar or aprotic media. This change is accompanied by selective and highly sensitive fluorometric sensing of Zn²⁺ ions. In the case of the bidentate 8-(quinolin-8-ylimino)methyl side arm, NMR studies in CD₃OD indicated that both Cd²⁺ and Zn²⁺ ions afford N chelation for 4HQ, coexisting with tautomeric switching from quinolin-4(1H)-one to quinolin-4-olate. In corroboration, UV/Vis-monitored metal-ion titrations in toluene and methanol implied similar structural changes. Additionally, fluorescence measurements indicated that the metal-triggered tautomeric switching is associated with compound signaling properties. The results are supported by DFT calculations at the B3LYP 6-31G* level. Several X-ray structures of metal-free and metal-chelating 4HQ are presented to support the solution studies.

Switching tautomers: Transformation of 4-hydroxyquinolines (4HQ) into novel tautomeric switches is described. 4HQ are equipped with ligand moieties at C-8 and C-3 positions to achieve metal ion adjustable control of keto-phenol tautomerism. In the case of the 8-(quinolin-8-ylimino)methyl side arm, metal ion induced tautomeric switching from keto to phenolate form was observed in nonpolar and polar media (see figure). Both O- and N-site-directed chelation resulted in selective Zn²⁺ fluorescence sensing.

 

 

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