Hydrogen-bonded liquid crystals. Novel mesogens incorporating nonmesogenic bipyridyl compounds through complexation between hydrogen-bond donor and acceptor moieties

1993 ◽  
Vol 5 (8) ◽  
pp. 1094-1100 ◽  
Author(s):  
Takashi Kato ◽  
Jean M. J. Frechet ◽  
Paul G. Wilson ◽  
Takeshi Saito ◽  
Toshiyuki Uryu ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Liquid Crystals ◽  
Hydrogen Bond Donor ◽  
Donor And Acceptor ◽  
Hydrogen Bonded

N-Tosyl-L-proline benzene hemisolvate: a rare example of a hydrogen-bonded carboxylic acid dimer with symmetrically disordered H atoms

2019 ◽  
Vol 75 (9) ◽  
pp. 1228-1233
Author(s):  
Joanna Wojnarska ◽  
Katarzyna Ostrowska ◽  
Marlena Gryl ◽  
Katarzyna Marta Stadnicka
Keyword(s):  
Hydrogen Bond ◽  
Carboxylic Acid ◽  
Self Assembly ◽  
Acid Group ◽  
Benzene Molecule ◽  
Noncovalent Interaction ◽  
Hydrogen Bond Donor ◽  
Donor And Acceptor ◽  
Carboxylic Acid Dimer ◽  
Hydrogen Bonded

The carboxylic acid group is an example of a functional group which possess a good hydrogen-bond donor (–OH) and acceptor (C=O). For this reason, carboxylic acids have a tendency to self-assembly by the formation of hydrogen bonds between the donor and acceptor sites. We present here the crystal structure of N-tosyl-L-proline (TPOH) benzene hemisolvate {systematic name: (2S)-1-[(4-methylbenzene)sulfonyl]pyrrolidine-2-carboxylic acid benzene hemisolvate}, C12H15NO4S·0.5C6H6, (I), in which a cyclic R 2 2(8) hydrogen-bonded carboxylic acid dimer with a strong O—(1 \over 2H)...(1 \over 2H)—O hydrogen bond is observed. The compound was characterized by single-crystal X-ray diffraction and NMR spectroscopy, and crystallizes in the space group I2 with half a benzene molecule and one TPOH molecule in the asymmetric unit. The H atom of the carboxyl OH group is disordered over a twofold axis. An analysis of the intermolecular interactions using the noncovalent interaction (NCI) index showed that the TPOH molecules form dimers due to the strong O—(1 \over 2H)...(1 \over 2H)—O hydrogen bond, while the packing of the benzene solvent molecules is governed by weak dispersive interactions. A search of the Cambridge Structural Database revealed that the disordered dimeric motif observed in (I) was found previously only in six crystal structures.

New supramolecular architectures using hydrogen bonding

1993 ◽  
Vol 345 (1674) ◽  
pp. 49-56 ◽  
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Hydrogen Bond Donor ◽  
Binding Strength ◽  
Supramolecular Architectures ◽  
Self Assembling ◽  
Donor And Acceptor ◽  
The Stability ◽  
Bonded Complexes ◽  
Hydrogen Bonded

Several new multiply hydrogen bonded complexes have been studied to determine their strength and the specificity with which they form. While many factors contribute to the stability of multiply hydrogen bonded complexes, it appears that the arrangement of the hydrogen bond donor and acceptor groups is a particularly good predictor of binding strength. The results are consistent with W. L. Jorgensen’s secondary electrostatic hypothesis. The heterocyclic recognition units that have been synthesized may serve as the basis for constructing new synthetic hosts or new self-assembling systems.

scholarly journals Machine learning models for hydrogen bond donor and acceptor strengths using large and diverse training data generated by first-principles interaction free energies

2019 ◽  
Vol 11 (1) ◽  
Author(s):  
Christoph A. Bauer ◽  
Gisbert Schneider ◽  
Andreas H. Göller
Keyword(s):  
Machine Learning ◽  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Training Data ◽  
Free Energies ◽  
Hydrogen Bond Donor ◽  
Chemical Application ◽  
Hydrogen Bond Acceptor ◽  
Donor And Acceptor ◽  
Target Values

Abstract We present machine learning (ML) models for hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD) strengths. Quantum chemical (QC) free energies in solution for 1:1 hydrogen-bonded complex formation to the reference molecules 4-fluorophenol and acetone serve as our target values. Our acceptor and donor databases are the largest on record with 4426 and 1036 data points, respectively. After scanning over radial atomic descriptors and ML methods, our final trained HBA and HBD ML models achieve RMSEs of 3.8 kJ mol−1 (acceptors), and 2.3 kJ mol−1 (donors) on experimental test sets, respectively. This performance is comparable with previous models that are trained on experimental hydrogen bonding free energies, indicating that molecular QC data can serve as substitute for experiment. The potential ramifications thereof could lead to a full replacement of wetlab chemistry for HBA/HBD strength determination by QC. As a possible chemical application of our ML models, we highlight our predicted HBA and HBD strengths as possible descriptors in two case studies on trends in intramolecular hydrogen bonding.

The hydrogen bond donor and acceptor ability of thioformic acid

2011 ◽  
Vol 22 (5) ◽  
pp. 1015-1030 ◽  
Author(s):  
Damanjit Kaur ◽  
Ritika Sharma ◽  
Darpandeep Aulakh
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bond Donor ◽  
Donor And Acceptor

Infrared spectroscopic characterization of hydrogen-bonded propylene oxide − ethanol and propylene oxide − 2-fluoroethanol complexes isolated in solid neon matrices

2013 ◽  
Vol 91 (12) ◽  
pp. 1292-1302 ◽  
Author(s):  
Osama Y. Ali ◽  
Elyse Jewer ◽  
Travis D. Fridgen
Keyword(s):  
Hydrogen Bond ◽  
Propylene Oxide ◽  
Spectroscopic Characterization ◽  
Hydrogen Bond Donor ◽  
Hydrogen Bond Acceptor ◽  
Reduced Frequency ◽  
Enthalpy Of Proton Transfer ◽  
The Difference ◽  
Bonded Complexes ◽  
Hydrogen Bonded

The infrared absorption spectra of hydrogen-bonded complexes of propylene oxide with either ethanol or 2-fluoroethanol have been recorded in neon matrices. Mixtures of propylene oxide and ethanol or propylene oxide and 2-fluoroethanol vapors were mixed with an excess of neon gas and deposited onto a KBr substrate at 4.2 K. The results indicate that hydrogen-bonded complexes were formed with propylene oxide as the hydrogen bond acceptor and either ethanol or 2-fluoroethanol as the hydrogen bond donors. The features assigned to the O−H stretch were red-shifted by 175 and 193 cm−1 for the ethanol- and 2-fluoroethanol-containing complexes, respectively. The difference in red shifts can be accounted for due to the greater acidity of 2-fluroethanol. Deuterium isotope experiments were conducted to help confirm the assignment of the O–H stretch for the complexes. As well, structures and infrared spectra were calculated using B3LYP/6-311++G(2d,2p) calculations and were used to compare with the experimental spectra. A “scaling equation” rather than a scaling factor was used and is shown to greatly increase the utility of the calculations when comparing with experimental spectra. An examination of the O–H stretching red shifts for many hydrogen-bound complexes reveals a relationship between the shift and the difference between the acidity of the hydrogen bond donor and the basicity of the hydrogen bond acceptor (the enthalpy of proton transfer). Both hydrogen-bonded complexes and proton-bound complexes appear to have a maximum in the reduced frequency value that corresponds to complexes where the hydrogen/proton are equally shared between the two bases.

Synthesis and preliminary bioactivity evaluation of new pregnane brassinosteroid-like compounds

2005 ◽  
Vol 83 (8) ◽  
pp. 1084-1092 ◽  
Author(s):  
Daniel G Rivera ◽  
Francisco Coll
Keyword(s):  
Hydrogen Bond ◽  
Plant Growth ◽  
Hypocotyl Elongation ◽  
Hydrogen Bond Donor ◽  
Donor And Acceptor ◽  
Plant Growth Promoting ◽  
Plant Growth Promoting Activity ◽  
Growth Promoting ◽  
Cotyledon Expansion

Seven new pregnane compounds bearing some representative A- and B-ring brassinosteroid functions, as well as hydrogen bond donor and acceptor ones on the D ring, were efficiently synthesized. The obtained compounds did not show remarkable plant growth-promoting activity in the radish hypocotyl elongation and cotyledon expansion bioassays, however, introducing oxygen and amino functions on the D ring led to an enhancement of the bioactivity. The 16β-functionalized pregnane brassinosteroid-like compounds were slightly more active than the 16α-functionalized ones.Key words: steroids, brassinosteroids, pregnane analogues.

The heterobifunctional ligand 5-[4-(1,2,4-triazol-4-yl)phenyl]-1H-tetrazole and its role in the construction of a CdIImetal–organic chain structure

2012 ◽  
Vol 68 (10) ◽  
pp. m291-m294
Author(s):  
Andrey B. Lysenko
Keyword(s):  
Hydrogen Bond ◽  
Three Dimensional ◽  
Organic Ligand ◽  
Chain Structure ◽  
Polar Space ◽  
Hydrogen Bond Donor ◽  
Donor Acceptor ◽  
A Chain ◽  
Water Ligands ◽  
Hydrogen Bonded

5-[4-(1,2,4-Triazol-4-yl)phenyl]-1H-tetrazole, C9H7N7, (I), an asymmetric heterobifunctional organic ligand containing triazole (tr) and tetrazole (tz) termini linked directly through a 1,4-phenylene spacer, crystallizes in the polar space groupPc. The heterocyclic functions, serving as single hydrogen-bond donor (tz) or acceptor (tr) units, afford hydrogen-bonded zigzag chains with no crystallographic centre of inversion. In the structure ofcatena-poly[[diaquacadmium(II)]bis{μ2-5-[4-(1,2,4-triazol-4-yl)phenyl]tetrazol-1-ido-κ2N1:N1′}], [Cd(C9H6N7)2(H2O)2]n, (II), the CdIIdication resides on a centre of inversion in an octahedral {N4O2} environment. In the equatorial plane, the CdIIpolyhedron is built up from four N atoms of two kinds, namely oftrans-coordinating tr and tz fragments [Cd—N = 2.2926 (17) and 2.3603 (18) Å], and the coordinating aqua ligands occupy the two apical sites. The metal centres are separated at a distance of 11.1006 (7) Å by means of the double-bridging tetrazolate anion,L−, forming a chain structure. The water ligands and tz fragments interact with one another, like a double hydrogen-bond donor–acceptor synthon, leading to a hydrogen-bonded three-dimensional array.

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