scholarly journals Enantioselective Michael Addition to Vinyl Phosphonates via Hydrogen Bond-Enhanced Halogen Bond Catalysis

2021 ◽  
Author(s):  
Mikk Kaasik ◽  
Jevgenija Martõnova ◽  
Kristin Erkman ◽  
Andrus Metsala ◽  
Ivar Järving ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
1H Nmr ◽  
Michael Addition ◽  
Halogen Bond ◽  
Halogen Bonding ◽  
Nmr Titration ◽  
1H Nmr Titration ◽  
Asymmetric Michael Addition ◽  
Vinyl Phosphonates

An asymmetric Michael addition of malononitrile to vinyl phosphonates was accomplished by hydrogen bond-enhanced bifunctional halogen bond (XB) catalysis. 1H NMR titration experiments were used to demonstrate that halogen bonding,...

scholarly journals Selective Colorimetric Sensors for Cyanide and Acetate Ion in Partially Aqueous Medium

2018 ◽  
Author(s):  
Divya Singhal ◽  
Neha Gupta ◽  
Ashok Kumar Singh
Keyword(s):  
Detection Limit ◽  
Aqueous Medium ◽  
1H Nmr ◽  
Binding Constant ◽  
High Selectivity ◽  
Good Sensitivity ◽  
Dft Studies ◽  
Nmr Titration ◽  
1H Nmr Titration ◽  
Nanomolar Detection

4-(thiazol-2-yldiazenyl)phenol (L1) and 2-((4-hydroxyphenyl) diazenyl)-5-nitrophenol (L2) based on azo phenol were synthesised and used as selective colorimetric sensor for CN- and AcO− ion in DMSO/H2O-HEPES (v/v; 1:1, pH–7.3 ± 0.2) and showed good sensitivity with large red shifts and nanomolar detection limit for CN- and AcO- ion. The stoichiometry of L1 with CN−/AcO− ion was found to be 1:1 and L2 with CN−/AcO− ion was found to be 1:2. Binding constant for L1+ CN−, L1 + AcO−, L2 + CN− and L2 + AcO− were calculated by B-H plot as 1.6 × 103, 8.0 × 102, 8.4 × 103 and 1.7 × 102 respectively. L2 showed high selectivity towards CN− ion with low detection limit of 81 nM and large binding constant. In addition, 1H NMR titration and DFT studies also supported the deprotonation mechanism of receptors in the presence of selective anions.

Halogen Bonding Organocatalysis Enhanced through Intramolecular Hydrogen Bonds

2022 ◽  
Author(s):  
Asia Marie S Riel ◽  
Daniel Adam Decato ◽  
Jiyu Sun ◽  
Orion Berryman
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Halogen Bond ◽  
Direct Interaction ◽  
Halogen Bonding ◽  
Intramolecular Hydrogen Bonds ◽  
Intramolecular Hydrogen

Recent results indicate a halogen bond donor is strengthened through direct interaction with a hydrogen bond to the electron-rich belt of the halogen. Here, this Hydrogen Bond enhanced Halogen Bond...

scholarly journals An Acylhydrazone-Based Fluorescent Sensor for Sequential Recognition of Al3+ and H2PO4−

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6392
Author(s):  
Donghwan Choe ◽  
Cheal Kim
Keyword(s):  
Fluorescence Quenching ◽  
Dft Calculations ◽  
1H Nmr ◽  
Fluorescent Sensor ◽  
Visible Spectroscopy ◽  
Nmr Titration ◽  
Esi Ms ◽  
1H Nmr Titration ◽  
Uv Visible ◽  
Sequential Recognition

A novel acylhydrazone-based fluorescent sensor NATB was designed and synthesized for consecutive sensing of Al3+ and H2PO4−. NATB displayed fluorometric sensing to Al3+ and could sequentially detect H2PO4− by fluorescence quenching. The limits of detection for Al3+ and H2PO4− were determined to be 0.83 and 1.7 μM, respectively. The binding ratios of NATB to Al3+ and NATB-Al3+ to H2PO4− were found to be 1:1. The sequential recognition of Al3+ and H2PO4− by NATB could be repeated consecutively. In addition, the practicality of NATB was confirmed with the application of test strips. The sensing mechanisms of Al3+ and H2PO4− by NATB were investigated through fluorescence and UV–Visible spectroscopy, Job plot, ESI-MS, 1H NMR titration, and DFT calculations.

scholarly journals A halogen-bonding-catalyzed Michael addition reaction

2017 ◽  
Vol 53 (88) ◽  
pp. 12052-12055 ◽  
Author(s):  
Jan-Philipp Gliese ◽  
Stefan H. Jungbauer ◽  
Stefan M. Huber
Keyword(s):  
Michael Addition ◽  
Addition Reaction ◽  
Halogen Bond ◽  
Halogen Bonding ◽  
Michael Addition Reaction

The first application of synthetic halogen bond donors as catalysts in a Michael addition reaction is described.

The15N NMR chemical shift in the characterization of weak halogen bonding in solution

2017 ◽  
Vol 203 ◽  
pp. 333-346 ◽  
Author(s):  
Sebastiaan B. Hakkert ◽  
Jürgen Gräfenstein ◽  
Mate Erdelyi
Keyword(s):  
Hydrogen Bond ◽  
Chemical Shift ◽  
Halogen Bond ◽  
Molar Fraction ◽  
Halogen Bonding ◽  
Relative Strength ◽  
Lewis Base ◽  
Halogen Bonds ◽  
Bonded Complexes

We have studied the applicability of15N NMR spectroscopy in the characterization of the very weak halogen bonds of nonfluorinated halogen bond donors with a nitrogenous Lewis base in solution. The ability of the technique to detect the relative strength of iodine-, bromine- and chlorine-centered halogen bonds, as well as solvent and substituent effects was evaluated. Whereas computations on the DFT level indicate that15N NMR chemical shifts reflect the diamagnetic deshielding associated with the formation of a weak halogen bond, the experimentally observed chemical shift differences were on the edge of detectability due to the low molar fraction of halogen-bonded complexes in solution. The formation of the analogous yet stronger hydrogen bond of phenols have induced approximately ten times larger chemical shift changes, and could be detected and correlated to the electronic properties of substituents of the hydrogen bond donors. Overall,15N NMR is shown to be a suitable tool for the characterization of comparably strong secondary interactions in solution, but not sufficiently accurate for the detection of the formation of thermodynamically labile, weak halogen bonded complexes.

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