Activation of sp3Carbon−Hydrogen Bonds by Cobalt and Iron Complexes and Subsequent C−C Bond Formation

2009 ◽  
Vol 28 (20) ◽  
pp. 6090-6095 ◽  
Author(s):  
Guoqiang Xu ◽  
Hongjian Sun ◽  
Xiaoyan Li
Keyword(s):  
Hydrogen Bonds ◽  
Bond Formation ◽  
Iron Complexes

1H -NMRInvestigations on the Hydrogen Bond Formation between the Tranquilizers Diazepam and Nitrazepam and Some Nucleobases

1978 ◽  
Vol 33 (11-12) ◽  
pp. 870-875 ◽  
Author(s):  
Hans-Helmut Paul ◽  
Helmut Sapper ◽  
Wolfgang Lohmann
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Binding Sites ◽  
Spectroscopic Data ◽  
Proton Magnetic Resonance ◽  
Proton Magnetic Resonance Spectroscopy ◽  
Bond Formation ◽  
Resonance Spectroscopy ◽  
Hydrogen Bond Formation ◽  
Dimer Model

The formation of hydrogen bonds between the minor tranquilizers diazepam and nitrazepam and a few nucleobases was studied in deuterochloroform solution by means of proton magnetic resonance spectroscopy. The thermodynamic and spectroscopic data of the associations were evaluated on the basis of a dimer model, using the concentration dependent shifts of the protons involved in hydrogen bonds. The interactions of nitrazepam (ΔH0= -10 to -21 k J/mol; ΔG250 - 0.2 to -7.4 kJ/mol) were found to be stronger than those of diazepam (ΔH0 = - 10 to - 13 kJ/mol; ΔG250 = 6.0 to 6.4 k j/mol). The various binding sites of the benzodiazepines for hydrogen bonds are discussed.

scholarly journals Polarisable Hydrogen Bond Formation and Ionic Interactions in Model Phospholipid Polar Head Molecules

1973 ◽  
Vol 28 (5-6) ◽  
pp. 323-330 ◽  
Author(s):  
Georg Papakostidis ◽  
Georg Zundel
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Phosphoric Acid ◽  
Bond Formation ◽  
Ion Pairs ◽  
Water Soluble ◽  
Ionic Interactions ◽  
Hydrogen Bond Formation ◽  
Continuous Absorption ◽  
Phosphate Groups

The serine phosphoric acid P-methylester (SPM) and the ethanol-amine phosphoric acid P-methylester (EPM) were synthesized as water soluble models for the functional groups of the corresponding phospholipids. Investigations were made of the aqueous solutions of these molecules as a function of deprotonation and protonation. An intramolecular, easily polarisable hydrogen bond occurs in the zwitterion of the SPM. The solutions of different salts of SPM were studied as well as the influence of counter ion pairs. Counterion pairs hardly influence these bonds. At about 50% deprotonation extremely easily polarisable intermolecular bonds form. At about 100% deprotonation of the zwitterion the hydrogen bonds observed are affected by the presence of CO2. The above is indicated by changes of the bands of the carboxylic and phosphate groups, and in particular by a continuous absorption in the infrared spectrum. During protonation of the EPM easily polarisable intermolecular POH+ ... OP hydrogen bonds form at first, but as protonation increases the solutions become acidic, that is, H5O2+ groupings form.

ChemInform Abstract: Silicon-Nitrogen Bond Formation by Nucleophilic Activation of Silicon- Hydrogen Bonds.

ChemInform ◽  
2010 ◽  
Vol 22 (26) ◽  
pp. no-no
Author(s):  
R. J. P. CORRIU ◽  
D. LECLERCQ ◽  
P. H. MUTIN ◽  
J. M. PLANEIX ◽  
A. VIOUX
Keyword(s):  
Hydrogen Bonds ◽  
Bond Formation ◽  
Nitrogen Bond

Reversible C–C Bond Formation between Redox-Active Pyridine Ligands in Iron Complexes

2012 ◽  
Vol 134 (50) ◽  
pp. 20352-20364 ◽  
Author(s):  
Thomas R. Dugan ◽  
Eckhard Bill ◽  
K. Cory MacLeod ◽  
Gemma J. Christian ◽  
Ryan E. Cowley ◽  
...  
Keyword(s):  
Bond Formation ◽  
Iron Complexes ◽  
Pyridine Ligands ◽  
Redox Active

AFM Research in Catalysis and Medicine

2020 ◽  
Vol 7 (3) ◽  
pp. 248-255
Author(s):  
Ludmila Matienko ◽  
Mil Elena Mickhailovna ◽  
Binyukov Vladimir Ivanovich ◽  
Goloshchapov Alexandr Nikolaevich
Keyword(s):  
Hydrogen Bonds ◽  
Active Sites ◽  
Morphological Changes ◽  
Iron Complexes ◽  
Supramolecular Structures ◽  
Intermolecular Hydrogen Bonds ◽  
Force Microscopy ◽  
Atomic Force ◽  
Non Covalent Interactions ◽  
Covalent Interactions

Background: In this study, we show that the AFM method not only allows monitoring the morphological changes in biological structures fixed on the surface due to H-bonds, but also makes it possible to study the self-organization of metal complexes by simulating the active center of enzymes due to intermolecular H-bonds into stable nanostructures; the sizes of which are much smaller than the studied biological objects. The possible role of intermolecular hydrogen bonds in the formation of stable supramolecular metal complexes, which are effective catalysts for the oxidation of alkyl arenes to hydroperoxides by molecular oxygen and mimic the selective active sites of enzymes, was first studied by AFM. Methods and Results: The formation of supramolecular structures due to intermolecular hydrogen bonds and, possibly, other non-covalent interactions, based on homogenous catalysts and models of active centers enzymes, heteroligand nickel and iron complexes, was proven by AFM-technique. AFM studies of supramolecular structures were carried out using NSG30 cantilever with a radius of curvature of 2 nm, in the tapping mode. To form nanostructures on the surface of a hydrophobic, chemically modified silicon surface as a substrate, the sample was prepared using a spin-coating process from solutions of the nickel and iron complexes. The composition and the structure of the complex Ni2(acac)(OAc)3·NMP·2H2O were determined in earlier works using various methods: mass spectrometry, UV- and IR-spectroscopy, elemental analysis, and polarography. Self-assembly of supramolecular structures is due to intermolecular interactions with a certain coordination of these interactions, which may be a consequence of the properties of the components themselves, the participation of hydrogen bonds and other non-covalent interactions, as well as the balance of the interaction of these components with the surface. Using AFM, approaches have been developed for fixing on the surface and quantifying parameters of cells. Conclusion: This study summarizes the authors' achievements in using the atomic force microscopy (AFM) method to study the role of intermolecular hydrogen bonds (and other non-covalent interactions) and supramolecular structures in the mechanisms of catalysis. The data obtained from AFM based on nickel and iron complexes, which are effective catalysts and models of active sites of enzymes, indicate a high probability of the formation of supramolecular structures in real conditions of catalytic oxidation, and can bring us closer to understanding enzymes activity. With a sensitive AFM method, it is possible to observe the self-organization of model systems into stable nanostructures due to H-bonds and possibly other non-covalent interactions, which can be considered as a step towards modeling the active sites of enzymes. Methodical approaches of atomic force microscopy for the study of morphological changes of cells have been developed.

Autoxidative Carbon-Carbon Bond Formation from Carbon-Hydrogen Bonds

2010 ◽  
Vol 49 (29) ◽  
pp. 5004-5007 ◽  
Author(s):  
Áron Pintér ◽  
Abhishek Sud ◽  
Devarajulu Sureshkumar ◽  
Martin Klussmann
Keyword(s):  
Hydrogen Bonds ◽  
Bond Formation ◽  
Carbon Bond ◽  
Carbon Carbon Bond ◽  
Carbon Hydrogen Bonds

scholarly journals Iron complexes of tetramine ligands catalyse allylic hydroxyamination via a nitroso–ene mechanism

2015 ◽  
Vol 11 ◽  
pp. 2549-2556 ◽  
Author(s):  
David Porter ◽  
Belinda M-L Poon ◽  
Peter J Rutledge
Keyword(s):  
Bond Formation ◽  
Iron Complexes ◽  
Spectroscopic Studies ◽  
Asymmetric Induction ◽  
Allylic Amination ◽  
Reaction Proceeds ◽  
Hydrocarbon Substrates

Iron(II) complexes of the tetradentate amines tris(2-pyridylmethyl)amine (TPA) and N,N′-bis(2-pyridylmethyl)-N,N′-dimethylethane-1,2-diamine (BPMEN) are established catalysts of C–O bond formation, oxidising hydrocarbon substrates via hydroxylation, epoxidation and dihydroxylation pathways. Herein we report the capacity of these catalysts to promote C–N bond formation, via allylic amination of alkenes. The combination of N-Boc-hydroxylamine with either FeTPA (1 mol %) or FeBPMEN (10 mol %) converts cyclohexene to the allylic hydroxylamine (tert-butyl cyclohex-2-en-1-yl(hydroxy)carbamate) in moderate yields. Spectroscopic studies and trapping experiments suggest the reaction proceeds via a nitroso–ene mechanism, with involvement of a free N-Boc-nitroso intermediate. Asymmetric induction is not observed using the chiral tetramine ligand (+)-(2R,2′R)-1,1′-bis(2-pyridylmethyl)-2,2′-bipyrrolidine ((R,R′)-PDP).

scholarly journals Microscopic Structural Features of Water in Aqueous-Reline Mixture of Varying Composition

2020 ◽  
Author(s):  
Soham Sarkar ◽  
Atanu Maity ◽  
Rajarshi Chakrabarti
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Choline Chloride ◽  
Bond Formation ◽  
Orientational Order ◽  
Water Structure ◽  
Structural Features ◽  
Water Molecules ◽  
Hydrogen Bond Formation ◽  
Hydrogen Bonded

Reline, a mixture of urea and choline chloride in 2:1 molar ratio, is one of the most frequently used deep eutectic solvents. Pure reline and its aqueous solution have large scale industrial use. Owing to the presence of active hydrogen bond formation sites, urea and choline cation can disrupt the hydrogen-bonded network in water. However, a quantitative understanding of the microscopic structural features of water in the presence of reline is still lacking. We use extensive all-atom molecular dynamics simulations to elucidate the effect of the gradual addition of co-solvents on microscopic arrangements of water molecules. We consider four aqueous solutions of reline, between the wt% 26.3 to 91.4. A disruption of the local hydrogen-bonded water structure is observed on inclusion of urea and choline chloride. The extent of deviation of water structure from tetrahedrality is quantified using the orientational order parameter. Our analyses show a monotonic increase in structural disorder as the co-solvents are added. Increment in the values are observed when highly electro-negative hetero-atoms like Nitrogen, Oxygen of urea and choline cations are counted as the partners of the central water molecules. Further insights are drawn from the characterization of the hydrogen-bonded network of the water and we observe gradual rupturing of water-water hydrogen bonds and its subsequent replacement by the water-urea hydrogen bonds. A negligible contribution from the hydrogen bonds between water and bulky choline cation has also been found. Considering all the constituents as the hydrogen bond partner we calculate the possibility of successful hydrogen bond formation with a central water molecule. This gives a clear picture of the underlying mechanism of water replacement by urea.

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